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IFF FORM and Chunk Registry
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Contents
- 1 IFF FORM and Chunk Registry
- 1.1 Third party FORMs
- 1.1.1 Chunk for specifying character set
- 1.1.2 Chunk for 2.0 VERSION string of an IFF file
- 1.1.3 Stereo chunks for 8SVX form
- 1.1.4 Looping chunks for 8SVX form
- 1.1.5 Amiga Contiguous Bitmap
- 1.1.6 Audio Interchange File Format File
- 1.1.7 Animated bitmap
- 1.1.8 ANIM brush
- 1.1.9 Cel animation
- 1.1.10 2-D Object standard format
- 1.1.11 Fantavision movie format
- 1.1.12 Flow
- 1.1.13 Color Lookup Table
- 1.1.14 NewTek Dynamic HAM color
- 1.1.15 Dots per inch
- 1.1.16 DPaint perspective
- 1.1.17 DPaint IV enhanced color cycling
- 1.1.18 Encapsulated PostScript
- 1.1.19 Numerical data storage
- 1.1.20 Program traceback
- 1.1.21 DPaint IV perspective move
- 1.1.22 RGB image
- 1.1.23 Sampled sound
- 1.1.24 3-D rendering data
- 1.1.25 ProWrite document format
- 1.2 Additional documents
- 1.1 Third party FORMs
IFF FORM and Chunk Registry
This section contains the official list of registered FORM and Chunk names that are reserved and in use. This list is often referred to as the 3rd part registry since these are FORM and Chunk types created by application developers and not part of the original IFF specification created by Electronic Arts and Commodore.
For all FORM and Chunk types that are public, the official specifications from the third party company are listed (in alphabetical order). At the end of this section are additional documents describing how the ILBM FORM type works on the Amiga.
New chunks and FORMS should be registered with CATS US, IFF Registry, 1200 Wilson Drive, West Chester, PA. 19380. Please make all submissions on Amiga diskette and include your address, phone, and fax.
Third party FORMs
The following is an alphabetical list of registered FORMs, generic chunks (shown as (any).chunkname), and registered new chunks for existing FORMs (shown as formname.chunkname). The center column describes where additional information on the FORM or chunk may be found. Items marked “EA IFF” are described in the main chapters of the EA IFF specs. Those marked “IFF TP” are described in the third-party specications section. Items marked “propos” are proposals which have been submitted to CATS, some of which are private. And items marked with “—” are private or yet unreleased specifications.
lll
(any).ANNO
& EA IFF & EA IFF 85 Generic Annotation chunk
(any).AUTH & EA IFF & EA IFF 85 Generic Author chunk
(any).CHRS & EA IFF & EA IFF 85 Generic character string chunk
(any).CSET.doc & IFF TP & chunk for specifying character set
(any).FVER.doc & IFF TP & chunk for 2.0 VERSION string of an IFF file
(any).HLID.doc & — & HotLink IDentification (Contact CATS for info)
(any).NAME & EA IFF & EA IFF 85 Generic Name of art, music, etc. chunk
(any).TEXT & EA IFF & EA IFF 85 Generic unformatted ASCII text chunk
(any).(c) & EA IFF & EA IFF 85 Generic Copyright text chunk
8SVX & EA IFF & EA IFF 85 8-bit sound sample form
8SVX.CHAN.PAN.doc & IFF TP & Stereo chunks for 8SVX form
8SVX.SEQN.FADE.doc & IFF TP & Looping chunks for 8SVX form
ACBM.doc & IFF TP & Amiga Contiguous Bitmap form
AHAM & — & unregistered (???)
AIFF.doc & IFF TP & Audio 1-32 bit samples (Mac,AppleII,Synthia Pro)
ANBM.doc & IFF TP & Animated bitmap form (Framer, Deluxe Video)
ANIM.brush.doc & IFF TP & ANIM brush format
ANIM.doc & IFF TP & Cel animation form
ANIM.op6.doc & IFF TP & Stereo (3D) Animations
ARC.proposal & propos & archive format proposal (old)
ARES & — & unregistered (???)
ATXT & — & temporariliy reserved
AVCF & — & AmigaVision flow (format not yet released)
AVCF.doc & IFF TP
AVCO & — & AmigaVision commands (format not yet released)
AVEV & — & AmigaVision events (format not yet released)
BANK & — & Soundquest Editor/Librarian MIDI Sysex dump
BBSD & — & BBS Database, F.Patnaude,Jr., Phalanx Software
C100 & — & Cloanto Italia private format
CAT & EA IFF & EA IFF 85 group identifier
CHBM & — & Chunky bitmap (name reserved by Eric Lavitsky)
CLIP & — & CAT CLIP to hold various formats in clipboard
CPFM & — & Cloanto Personal FontMaker (doc in their manual)
DCCL & — & DCCL - DCTV paint clip
DCPA & — & DCPA - DCTV paint palette
DCTV & — & DCTV - DCTV raw picture file
DECK & — & private format for Inovatronics CanDo
DR2D.doc & IFF TP & 2-D Object standard format
DRAW & — & reserved by Jim Bayless, 12/90
FANT.doc & IFF TP & Fantavision movie format
FIGR & — & Deluxe Video - reserved
FNTR & EA IFF & EA IFF 85 reserved for raster font
FNTV & EA IFF & EA IFF 85 reserved for vector font
FORM & EA IFF & EA IFF 85 group identifier
| FTXT | EA IFF | EA IFF 85 formatted text form |
| GRYP.proposal | propos | byteplane storage proposal (copyrighted) |
| GSCR | EA IFF | EA IFF 85 reserved gen. music score |
| GUI.proposal | propos | user interface storage proposal (private) |
| HEAD.doc | IFF TP | Flow - New Horizons Software |
| ILBM | EA IFF | EA IFF 85 raster bitmap form |
| ILBM.3DCM | — | reserved by Haitex |
| ILBM.3DPA | — | reserved by Haitex |
| ILBM.ASDG | — | private ASDG application chunk |
| ILBM.BHBA | — | private Photon Paint chunk (brushes) |
| ILBM.BHCP | — | private Photon Paint chunk (screens) |
| ILBM.BHSM | — | private Photon Paint chunk |
| ILBM.CLUT.doc | IFF TP | Color Lookup Table chunk |
| ILBM.CMYK.doc | IFF TP | Cyan, Magenta, Yellow & Black cmap (Contact CATS) |
| ILBM.CNAM.doc | — | Color naming chunk (Soft-Logik) (Contact CATS) |
| ILBM.CTBL.DYCP.doc | IFF TP | Newtek Dynamic Ham color chunks |
| ILBM.DCTV | — | reserved |
| ILBM.DGVW | — | private Newtek DigiView chunk |
| ILBM.DPI.doc | IFF TP | Dots per inch chunk |
| ILBM.DPPV.doc | IFF TP | DPaint perspective chunk (EA) |
| ILBM.DRNG.doc | IFF TP | DPaint IV enhanced color cycle chunk (EA) |
| ILBM.EPSF.doc | IFF TP | Encapsulated Postscript chunk |
| ILBM.TMAP | — | Transparency map (temporarily reserved) |
| ILBM.VTAG.proposal | propos | Viewmode tags chunk suggestion |
| ILBM.XBMI.doc | IFF TP | eXtended BitMap Information (Contact CATS) |
| IOBJ | — | reserved by Seven Seas Software |
| ITRF | — | reserved |
| LIST | EA IFF | EA IFF 85 group identifier |
| MIDI | — | Circum Design |
| MOVI | — | LIST MOVI - private format |
| MSCX | — | private Music-X format |
| MSMP | — | temporarily reserved |
| MTRX.doc | IFF TP | Numerical data storage (MathVision - Seven Seas) |
| NSEQ | — | Numerical sequence (Stockhausen GmbH) |
| OCMP | EA IFF | EA IFF 85 reserved computer prop |
| OCPU | EA IFF | EA IFF 85 reserved processor prop |
| OPGM | EA IFF | EA IFF 85 reserved program prop |
| OSN | EA IFF | EA IFF 85 reserved serial num prop |
| PGTB.doc | IFF TP | Program traceback (SAS Institute) |
| PICS | EA IFF | EA IFF 85 reserved Macintosh picture |
| PLBM | EA IFF | EA IFF 85 reserved obsolete name |
| PROP | EA IFF | EA IFF 85 group identifier |
| PRSP.doc | IFF TP | DPaint IV perspective move form (EA) |
| PTCH | — | Patch file format (SAS Institute) |
| PTXT | — | temporarily reserved |
| RGB4 | — | 4-bit RGB (format not available) |
| RGBN-RGB8.doc | IFF TP | RGB image forms, Turbo Silver (Impulse) |
| RGBX | — | temporarily reserved |
| ROXN | — | private animation form |
| SAMP.doc | IFF TP | Sampled sound format |
| SC3D | — | private scene format (Sculpt-3D) |
| SHAK | — | private Shakespeare format |
| SHO1 | — | Reserved by Gary Bonham (private) |
| SHOW | — | Reserved by Gary Bonham (private) |
| SMUS | EA IFF | EA IFF 85 simple music score form |
| SYTH | — | SoundQuest Master Librarian MIDI System driver |
| TCDE | — | reserved by Merging Technologies |
| TDDD.doc | IFF TP | 3-D rendering data, Turbo Silver (Impulse) |
| UNAM | EA IFF | EA IFF 85 reserved user name prop |
| USCR | EA IFF | EA IFF 85 reserved Uhuru score |
| UVOX | EA IFF | EA IFF 85 reserved Uhuru Mac voice |
| VDEO | — | private Deluxe Video format |
| WORD.doc | IFF TP | ProWrite document format (New Horizons) |
Chunk for specifying character set
chunk for specifying character set
Registered by Martin Taillefer.
A chunk for use in any FORM, to specify character set used for
text in FORM.
struct CSet {
LONG CodeSet; /* 0=ECMA Latin 1 (std Amiga charset) */
/* CBM will define additional values */
LONG Reserved[7];
}
Chunk for 2.0 VERSION string of an IFF file
chunk for 2.0 VERSION string of an IFF file Registered by Martin Taillefer. A chunk for use in any FORM, to contain standard 2.0 version string. $VER: name ver.rev where "name" is the name or identifier of the file and ver.rev is a version/revision such as 37.1 Example: $VER: workbench.catalog 37.42
Stereo chunks for 8SVX form
SMUS.CHAN and SMUS.PAN Chunks
Stereo imaging in the "8SVX" IFF 8-bit Sample Voice
---------------------------------------------------
Registered by David Jones, Gold Disk Inc.
There are two ways to create stereo imaging when playing back a digitized
sound. The first relies on the original sound being created with a stereo
sampler: two different samples are digitized simultaneously, using right and
left inputs. To play back this type of sample while maintaining the
stereo imaging, both channels must be set to the same volume. The second type
of stereo sound plays the identical information on two different channels at
different volumes. This gives the sample an absolute position in the stereo
field. Unfortunately, there are currently a number of methods for doing this
currently implemented on the Amiga, none truly adhering to any type of
standard. What I have tried to to is provide a way of doing this
consistently, while retaining compatibility with existing (non-standard)
systems. Introduced below are two optional data chunks, CHAN and PAN. CHAN
deals with sounds sampled in stereo, and PAN with samples given stereo
characteristics after the fact.
Optional Data Chunk CHAN
________________________
This chunk is already written by the software for a popular stereo sampler. To
maintain the ability read these samples, its implementation here is
therefore limited to maintain compatability.
The optional data chunk CHAN gives the information neccessary to play a
sample on a specified channel, or combination of channels. This chunk
would be useful for programs employing stereo recording or playback of sampled
sounds.
#define RIGHT 4L
#define LEFT 2L
#define STEREO 6L
#define ID_CHAN MakeID('C','H','A','N')
typedef sampletype LONG;
If "sampletype" is RIGHT, the program reading the sample knows that it was
originally intended to play on a channel routed to the right speaker,
(channels 1 and 2 on the Amiga). If "sampletype" is LEFT, the left speaker
was intended (Amiga channels 0 and 3). It is left to the discretion of the
programmer to decide whether or not to play a sample when a channel on the
side designated by "sampletype" cannot be allocated.
If "sampletype" is STEREO, then the sample requires a pair of channels routed
to both speakers (Amiga pairs [0,1] and [2,3]). The BODY chunk for stereo
pairs contains both left and right information. To adhere to existing
conventions, sampling software should write first the LEFT information,
followed by the RIGHT. The LEFT and RIGHT information should be equal in
length.
Again, it is left to the programmer to decide what to do if a channel for
a stereo pair can't be allocated; wether to play the available channel only,
or to allocate another channels routed to the wrong speaker.
Optional Data Chunk PAN
_______________________
The optional data chunk PAN provides the neccessary information to create a
stereo sound using a single array of data. It is neccessary to replay the
sample simultaneously on two channels, at different volumes.
#define ID_PAN MakeID('P','A','N',' ')
typedef sposition Fixed; /* 0 <= sposition <= Unity */
/* Unity is elsewhere #defined as 10000L, and
* refers to the maximum possible volume.
* /
/* Please note that 'Fixed' (elsewhere #defined as LONG) is used to
* allow for compatabilty between audio hardware of different resolutions.
*/
The 'sposition' variable describes a position in the stereo field. The
numbers of discrete stereo positions available is equal to 1/2 the number of
discrete volumes for a single channel.
The sample must be played on both the right and left channels. The overall
volume of the sample is determined by the "volume" field in the Voice8Header
structure in the VHDR chunk.
The left channel volume = overall volume / (Unity / sposition).
" right " " = overall volume - left channel volume.
For example:
If sposition = Unity, the sample is panned all the way to the left.
If sposition = 0, the sample is panned all the way to the right.
If sposition = Unity/2, the sample is centered in the stereo field.
Looping chunks for 8SVX form
SEQN and FADE Chunks
Multiple Loop Sequencing in the "8SVX" IFF 8-bit Sample Voice
---------------------------------------------------
Registered by Peter Norman, RamScan Software Pty Ltd.
Sound samples are notorious for demanding huge amounts of memory.
While earlier uses of digital sound on the Amiga were mainly in the form of
short looping waveforms for use as musical instruments, many people today
wish to record several seconds (even minutes) of sound. This of course eats
memory.
Assuming that quite often the content of these recordings is music, and that
quite often music contains several passages which repeat at given times,
"verse1 .. chorus .. verse2 .. chorus .." etc, a useful extention has been
added to the 8SVX list of optional data chunks. It's purpose is to conserve
memory by having the computer repeat sections rather than having several
instances of a similar sound or musical passage taking up valuable sample
space.
The "SEQN" chunk has been created to define "Multiple" loops or sections
within a single octave 8SVX MONO or STEREO waveform.
It is intended that a sampled sound player program which supports this chunk
will play sections of the waveform sequentially in an order that the SEQN
chunk specifies. This means for example, if an identical chorus
repeats throughout a recording, rather than have this chorus stored several
times along the waveform, it is only necessary to have one copy of the chorus
stored in the waveform.
A "SEQeNce" of definitions can then be set up to have the computer loop back
and repeat the chorus at the required time. The remaining choruses
stored in the waveform will no longer be necessary and can be removed.
eg. If we had a recording of the following example, we would find that
there are several parts which simply repeat. Substantial savings can be made
by having the computer repeat sections rather than have them stored in memory.
EXAMPLE
"Haaaallelujah....Haaaallelujah...Hallelujah..Hallelujah..Halleeeelujaaaah."
Applying a sequence to the above recording would look as follows.
Haaaallelujah....Haaaallelujah...Hallelujah..Hallelujah..Halleeeelujaaaah.
[ Loop1 ]
[ Loop2 ]
[ Loop3 ]
[ Loop4 ]
[ Loop5 ]
[ Dead Space ] [ Dead Space ]
The DEAD SPACE can be removed. With careful editing of the multiple loop
positions, the passage can be made to sound exactly the same as the original
with far less memory required.
Chunk Definitions...
Optional Data Chunk SEQN
________________________
The optional data chunk SEQN gives the information necessary to play a
sample in a sequence of defined blocks. To have a segment repeat twice,
the definition occurs twice in the list.
This list consists of pairs of ULONG "loop start" and "end" definitions which
are offsets from the start of the waveform. The locations or values must be
LONGWORD aligned (divisable by 4).
To determine how many loop definitions in a given file, simply divide the
SEQN chunk size by 8.
eg if chunk size == 40 ... number of loops = (40 / 8) .. equals 5 loops.
The raw data in a file might look like this...
'S-E-Q-N' [ size ] [ Loop 1 ] [ Loop 2 ] [ Loop 3 ]
5345514E 00000028 00000000 00000C00 00000000 00000C00 00000C08 00002000
^
^ 'Haaaallelujah..' 'Haaaallelujah..' 'Hallelujah..'
^
^
40 bytes decimal / 8 = 5 loop or segments
[ Loop 4 ] [ Loop 5 ]'B-O-D-Y' Size Data
00000C08 00002000 00002008 00003000 424F4459 000BE974 010101010101010
'Hallelujah..' 'Halleeeelujah..'
In a waveform containing SEQN chunks, the oneShotHiSamples should be set to 0
and the repeatHiSamples should equal the BODY length (divided by 2 if STEREO).
Remember the locations of the start and end of each segment or loop should
be LONGWORD aligned.
If the waveform is Stereo, treat the values and locations in exactly the same
way. In other words, if a loop starts at location 400 within a Stereo
waveform, you start the sound at the 400th byte position in the left data
and the 400th byte position in the right data simultaneously.
#define ID_SEQN MakeID('S','E','Q','N')
Optional Data Chunk FADE
_______________________
The FADE chunk defines at what loop number the sound should begin to
fade away to silence. It is possible to finish a sample of music in much
the same way as commercial music does today. A FADE chunk consists of
one ULONG value which has a number in it. This number corresponds to the
loop number at which the fade should begin.
eg. You may have a waveform containing 50 loops. A FADE definition of 45 will
specify that once loop 45 is reached, fading to zero volume should begin.
The rate at which this fade takes place is determined by the length of time
left to play. The playing software should do a calculation based on the
following...
Length of all remaining sequences including current sequence (in bytes)
divided by
the current playback rate in samples per second
= time remaining.
Begin stepping the volume down at a rate which will hit zero volume just as
the waveform finishes.
The raw data in a file may look like this.
'F-A-D-E' [ Size ] Loop No. 'B-O-D-Y' Size Data..
46414445 00000004 0000002D 424F4459 000BE974 01010101 01010101 etc etc
^
Start fading when loop number 45 is reached.
#define ID_FADE MakeID('F','A','D','E')
Although order shouldn't make much difference, it is a general rule of thumb
that SEQN should come before FADE and FADE should be last before the BODY.
Stereo waveforms would have CHAN,SEQN,FADE,BODY in that order.
Amiga Contiguous Bitmap
Amiga Contiguous Bitmap form
IFF FORM / CHUNK DESCRIPTION
============================
Form/Chunk ID: FORM ACBM (Amiga Contiguous BitMap)
Chunk ABIT (Amiga BITplanes)
Date Submitted: 05/29/86
Submitted by: Carolyn Scheppner CBM
FORM
====
FORM ID: ACBM (Amiga Contiguous BitMap)
FORM Description:
FORM ACBM has the same format as FORM ILBM except the normal BODY
chunk (InterLeaved BitMap) is replaced by an ABIT chunk (Amiga BITplanes).
FORM Purpose:
To enable faster loading/saving of screens, especially from Basic,
while retaining the flexibility and portability of IFF format files.
CHUNKS
======
Chunk ID: ABIT (Amiga BITplanes)
Chunk Description:
The ABIT chunk contains contiguous bitplane data. The chunk contains
sequential data for bitplane 0 through bitplane n.
Chunk Purpose:
To enable loading/storing of bitmaps with one DOS Read/Write per
bitplane. Significant speed increases are realized when loading/saving
screens from Basic.
SUPPORTING SOFTWARE
===================
(Public Domain, available soon via Fish PD disk, various networks)
LoadILBM-SaveACBM (AmigaBasic)
Loads and displays an IFF ILBM pic file (Graphicraft, DPaint, Images).
Optionally saves the screen in ACBM format.
LoadACBM (AmigaBasic)
Loads and display an ACBM format pic file.
SaveILBM (AmigaBasic)
Saves a demo screen as an ILBM pic file which can be loaded into
Graphicraft, DPaint, Images.
Audio Interchange File Format File
Audio 1-32 bit samples (Mac,AppleII,Synthia Pro)
provided by Steve Milne and Matt Deatherage, Apple Computer, Inc.
AIFF: Audio Interchange File Format File
----------------------------------------
The Audio Interchange File Format (Audio IFF) provides a standard for storing
sampled sounds. The format is quite flexible, allowing the storage of
monaural or multichannel sampled sounds at a variety of sample rates and
sample widths.
Audio IFF conforms to the "`EA IFF 85' Standard for Interchange Format Files"
developed by Electronic Arts.
Audio IFF is primarily an interchange format, although application designers
should find it flexible enough to use as a data storage format as well. If an
application does choose to use a different storage format, it should be able
to convert to and from the format defined in this document. This ability to
convert will facilitate the sharing of sound data between applications.
Audio IFF is the result of several meetings held with music developers over a
period of ten months during 1987 and 1988. Apple Computer greatly appreciates
the comments and cooperation provided by all developers who helped define this
standard.
Another "EA IFF 85" sound storage format is "`8SVX' IFF 8-bit Sampled Voice",
by Electronic Arts. "8SVX," which handles eight-bit monaural samples, is
intended mainly for storing sound for playback on personal computers. Audio
IFF is intended for use with a larger variety of computers, sampled sound
instruments, sound software applications, and high fidelity recording devices.
Data Types
A C-like language will be used to describe the data structures in this document
The data types used are listed below.
char: 8 bits signed. A char can contain more than just ASCII
characters. It can contain any number from -128 to 127
(inclusive).
unsigned char: 8 bits signed. Contains any number from 0 to 255 (inclusive).
short: 16 bits signed. Contains any number from -32,768 to 32,767
(inclusive).
unsigned short: 16 bits unsigned. Contains any number from 0 to 65,535
(inclusive).
long: 32 bits signed. Contains any number from -2,147,483,648
to 2,147,483,647 (inclusive).
unsigned long: 32 bits unsigned. Contains any number from 0 to
4,294,967,295 (inclusive).
extended: 80 bit IEEE Standard 754 floating point number (Standard
Apple Numeric Environment [SANE] data type Extended)
pstring: Pascal-style string, a one-byte count followed by text
bytes. The total number of bytes in this data type should
be even. A pad byte can be added to the end of the text to
accomplish this. This pad byte is not reflected in the
count.
ID: 32 bits, the concatenation of four printable ASCII characters
in the range " " (space, 0x20) through "~" (tilde, 0x7E).
Leading spaces are not allowed in the ID but trailing spaces
are OK. Control characters are forbidden.
Constants
Decimal values are referred to as a string of digits, for example 123, 0, 100
are all decimal numbers. Hexadecimal values are preceded by a 0x - e.g., 0x0A,
0x1, 0x64.
Data Organization
All data is stored in Motorola 68000 format. The bytes of multiple-byte
values are stored with the high-order bytes first. Data is organized as
follows:
7 6 5 4 3 2 1 0
+-----------------------+
char: | msb lsb |
+-----------------------+
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
+-----------------------+-----------------------+
char: | msb byte 0 | byte 1 lsb |
+-----------------------+-----------------------+
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
+-----------------------+-----------------------+
char: | msb byte 0 | byte 1 |
+-----------------------+-----------------------+
char: | byte 2 | byte 3 lsb |
+-----------------------+-----------------------+
Figure 1: IFF data storage formats
Referring to Audio IFF
The official name for this standard is Audio Interchange File Format. If an
application program needs to present the name of this format to a user, such
as in a "Save As..." dialog box, the name can be abbreviated to Audio IFF.
Referring to Audio IFF files by a four-letter abbreviation (i.e., "AIFF") in
user-level documentation or program-generated messages should be avoided.
File Structure
The "`EA IFF 85' Standard for Interchange Format Files" defines an overall
structure for storing data in files. Audio IFF conforms to those portions
of "EA IFF 85" that are germane to Audio IFF. For a more complete discussion
of "EA IFF 85", please refer to the document "`EAIFF 85', Standard for
Interchange Format Files."
An "EA IFF 85" file is made up of a number of chunks of data. Chunks are the
building blocks of "EA IFF 85" files. A chunk consists of some header
information followed by data:
+--------------------+
| ckID |\
+--------------------+ } header info
| ckSize |/
+--------------------+
| |
| |
| data |
| |
| |
+--------------------+
Figure 2: IFF Chunk structure
A chunk can be represented using our C-like language in the following manner:
typedef struct {
ID ckID; /* chunk ID */
long ckSize; /* chunk Size */
char ckData[]; /* data */
} Chunk;
The ckID describes the format of the data portion of a chunk. A program can
determine how to interpret the chunk data by examining ckID.
The ckSize is the size of the data portion of the chunk, in bytes. It does
not include the 8 bytes used by ckID and ckSize.
The ckData contains the data stored in the chunk. The format of this data is
determined by ckID. If the data is an odd number of bytes in length, a zero pad
byte must be added at the end. The pad byte is not included in ckSize.
Note that an array with no size specification (e.g., char ckData[];) indicates a
variable-sized array in our C-like language. This differs from standard C.
An Audio IFF file is a collection of a number of different types of chunks.
There is a Common Chunk which contains important parameters describing the
sampled sound, such as its length and sample rate. There is a Sound Data
Chunk which contains the actual audio samples. There are several other
optional chunks which define markers, list instrument parameters, store
application-specific information, etc. All of these chunks are described in
detail in later sections of this document.
The chunks in an Audio IFF file are grouped together in a container chunk.
"EA IFF 85" Standard for Interchange Format Files defines a number of
container chunks, but the one used by Audio IFF is called a FORM. A FORM has
the following format:
typedef struct {
ID ckID;
long ckSize;
ID formType;
char chunks[];
}
The ckID is always 'FORM'. This indicates that this is a FORM chunk.
The ckSize contains the size of data portion of the 'FORM' chunk. Note that
the data portion has been broken into two parts, formType and chunks[].
The formType field describes what's in the 'FORM' chunk. For Audio IFF files,
formType is always 'AIFF'. This indicates that the chunks within the FORM
pertain to sampled sound. A FORM chunk of formType 'AIFF' is called a FORM
AIFF.
The chunks field are the chunks contained within the FORM. These chunks are
called local chunks. A FORM AIFF along with its local chunks make up an
Audio IFF file.
Here is an example of a simple Audio IFF file. It consists of a file containing
single FORM AIFF which contains two local chunks, a Common Chunk and a Sound
Data Chunk.
__________________________
| FORM AIFF Chunk |
| ckID = 'FORM' |
| formType = 'AIFF' |
| __________________ |
| | Common Chunk | |
| | ckID = 'COMM' | |
| |__________________| |
| __________________ |
| | Sound Data Chunk | |
| | ckID = 'SSND' | |
| |__________________| |
|__________________________|
Figure 3: Simple Audio IFF File
There are no restrictions on the ordering of local chunks within a FORM AIFF.
A more detailed example of an Audio IFF file can be found in Appendix A. Please
refer to this example as often as necessary while reading the remainder of this
document.
Storage of AIFF on Apple and Other Platforms
On a Macintosh, the FORM AIFF, is stored in the data fork of an Audio IFF file.
The Macintosh file type of an Audio IFF file is 'AIFF'. This is the same as
the formType of the FORM AIFF. Macintosh applications should not store any
information in Audio IFF file's resource fork, as this information may not be
preserved by all applications. Applications can use the Application Specific
Chunk, defined later in this document, to store extra information specific to
their application.
Audio IFF files may be identified in other Apple file systems as well. On a
Macintosh under MFS or HFS, the FORM AIFF is stored in the data fork of a file
with file type "AIFF." This is the same as the formType of the FORM AIFF.
On an operating system such as MS-DOS or UNIX, where it is customary to use a
file name extension, it is recommended that Audio IFF file names use ".AIF"
for the extension.
On an Apple II, FORM AIFF is stored in a file with file type $D8 and auxiliary
type $0000. Versions 1.2 and earlier of the Audio IFF standard used file type
$CB and auxiliary type $0000. This is incorrect; the assignment listed in
this document is the correct assignment.
On the Apple IIGS stereo data is stored with right data on even channels and
left data on odd channels. Some portions of AIFF do not follow this
convention. Even where it does follow the convention, AIFF usually uses
channel two for right data instead of channel zero as most Apple IIGS
standards do. Be prepared to interpret data accordingly.
Local Chunk Types
The formats of the different local chunk types found within a FORM AIFF are
described in the following sections, as are their ckIDs.
There are two types of chunks: required and optional. The Common Chunk is
required. The Sound Data chunk is required if the sampled sound has a length
greater than zero. All other chunks are optional. All applications that use
FORM AIFF must be able to read the required chunks and can choose to
selectively ignore the optional chunks. A program that copies a FORM AIFF
should copy all the chunks in the FORM AIFF, even those it chooses not to
interpret.
The Common Chunk
The Common Chunk describes fundamental parameters of the sampled sound.
#define CommonID 'COMM' /* ckID for Common Chunk */
typedef struct {
ID ckID;
long ckSize;
short numChannels;
unsigned long numSampleFrames;
short sampleSize;
extended sampleRate;
} CommonChunk;
The ckID is always 'COMM'. The ckSize is the size of the data portion of the
chunk, in bytes. It does not include the 8 bytes used by ckID and ckSize.
For the Common Chunk, ckSize is always 18.
The numChannels field contains the number of audio channels for the sound.
A value of 1 means monophonic sound, 2 means stereo, and 4 means four channel
sound, etc. Any number of audio channels may be represented. For
multichannel sounds, single sample points from each channel are interleaved.
A set of interleaved sample points is called a sample frame.
The actual sound samples are stored in another chunk, the Sound Data Chunk,
which will be described shortly.
Single sample points from each channel are interleaved such that each
sample frame is a sample point from the same moment in time for each channel
available.
The numSampleFrames field contains the number of sample frames. This is not
necessarily the same as the number of bytes nor the number of samplepoints in
the Sound Data Chunk. The total number of sample points in the file is
numSampleFrames times numChannels.
The sampleSize is the number of bits in each sample point. It can be any
number from 1 to 32. The format of a sample point will be described in the
next section.
The sampleRate field is the sample rate at which the sound is to be played
back in sample frames per second.
One, and only one, Common Chunk is required in every FORM AIFF.
Sound Data Chunk
The Sound Data Chunk contains the actual sample frames.
#define SoundDataID 'SSND' /* ckID for Sound Data Chunk */
typedef struct {
ID ckID;
long ckSize;
unsigned long offset;
unsigned long blockSize;
unsigned char SoundData [];
} SoundDataChunk;
The ckID is always 'SSND'. The ckSize is the size of the data portion of the
chunk, in bytes. It does not include the 8 bytes used by ckID and ckSize.
The offset field determines where the first sample frame in the soundData
starts. The offset is in bytes. Most applications won't use offset and
should set it to zero. Use for a non-zero offset is explained in the
Block-Aligning Sound Data section below.
The blockSize is used in conjunction with offset for block-aligning sound
data. It contains the size in bytes of the blocks that sound data is aligned
to. As with offset, most applications won't use blockSize and should set it
to zero. More information on blockSize is in the Block-Aligning Sound Data
section below.
The soundData field contains the sample frames that make up the sound. The
number of sample frames in the soundData is determined by the numSampleFrames
field in the Common Chunk. Sample points and sample frames are explained in
detail in the next section.
The Sound Data Chunk is required unless the numSampleFrames field in the
Common Chunk is zero. A maximum of one Sound Data Chunk may appear in a FORM
AIFF.
Sample Points and Sample Frames
A large part of interpreting Audio IFF files revolves around the two concepts
of sample points and sample frames.
A sample point is a value representing a sample of a sound at a given point in
time. Each sample point is stored as a linear, 2's-complement value which may
be from 1 to 32 bits wide, as determined by sampleSize in the Common Chunk.
Sample points are stored in an integral number of contiguous bytes. One- to
eight-bit wide sample points are stored in one byte, 9- to 16-bit wide sample
points are stored in two bytes, 17- to 24-bit wide sample points are stored
in three bytes, and 25- to 32-bit wide sample points are stored in four bytes
(most significant byte first). When the width of a sample point is not a
multiple of eight bits, the sample point data is left justified, with the
remaining bits zeroed. An example case is illustrated in Figure 4. A 12-bit
sample point, binary 101000010111, is stored left justified in two bytes.
The remaining bits are set to zero.
___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___
| | | | | | | | | | | | | | | | |
| 1 0 1 0 0 0 0 1 | 0 1 1 1 0 0 0 0 |
|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|
<---------------------------------------------> <------------->
12 bit sample point is left justified rightmost
4 bits are
zero padded
Figure 4: 12-Bit Sample Point
For multichannel sounds, single sample points from each channel are
interleaved. A set of interleaved sample points is called a sample frame.
Single sample points from each channel are interleaved such that each
sample frame is a sample point from the same moment in time for each channel
available. This is illustrated in Figure 5 for the stereo (two channel) case.
sample sample sample
frame 0 frame 1 frame N
_____ _____ _____ _____ _____ _____
| ch1 | ch2 | ch1 | ch2 | . . . | ch1 | ch2 |
|_____|_____|_____|_____| |_____|_____|
_____
| | = one sample point
|_____|
Figure 5: Sample Frames for Multichannel Sound
For monophonic sound, a sample frame is a single sample point. For
multichannel sounds, you should follow the conventions in Figure 6.
channel
1 2 3 4 5 6
_________ _________ _________ _________ _________ _________
| left | right | | | | |
stereo | | | | | | |
|_________|_________|_________|_________|_________|_________|
| left | right | center | | | |
3 channel | | | | | | |
|_________|_________|_________|_________|_________|_________|
| front | front | rear | rear | | |
quad | left | right | left | right | | |
|_________|_________|_________|_________|_________|_________|
| left | center | right | surround| | |
4 channel | | | | | | |
|_________|_________|_________|_________|_________|_________|
| left | left | center | right | right |surround |
6 channel | | center | | | center | |
|_________|_________|_________|_________|_________|_________|
Figure 6: Sample Frame Conventions for Multichannel Sound
Sample frames are stored contiguously in order of increasing time. The sample
points within a sample frame are packed together; there are no unused bytes
between them. Likewise, the sample frames are packed together with no pad
bytes.
Block-Aligning Sound Data
There may be some applications that, to ensure real time recording and
playback of audio, wish to align sampled sound data with fixed-size blocks.
This alignment can be accomplished with the offset and blockSize parameters of
the Sound Data Chunk, as shown in Figure 7.
____________ __________________________________ ____________
|\\ unused \\| sample frames |\\ unused \\|
|____________|__________________________________|____________|
<-- offset --><- numSampleFrames sample frames ->
| blockSize | | | |
|<- bytes ->| | | |
|_______________|_______________|_______________|_______________|
block N-1 block N block N+1 block N+2
Figure 7: Block-Aligned Sound Data
In Figure 7, the first sample frame starts at the beginning of block N. This
is accomplished by skipping the first offset bytes of the soundData. Note
too, that the soundData bytes can extend beyond valid sample frames, allowing
the soundData bytes to end on a block boundary as well.
The blockSize specifies the size in bytes of the block to which you would
align the sound data. A blockSize of zero indicates that the sound data does
not need to be block-aligned. Applications that don't care about block
alignment should set the blockSize and offset to zero when creating Audio IFF
files. Applications that write block-aligned sound data should set blockSize
to the appropriate block size. Applications that modify an existing Audio IFF
file should try to preserve alignment of the sound data, although this is not
required. If an application does not preserve alignment, it should set the
blockSize and offset to zero. If an application needs to realign sound data
to a different sized block, it should update blockSize and offset accordingly.
The Marker Chunk
The Marker Chunk contains markers that point to positions in the sound data.
Markers can be used for whatever purposes an application desires. The
Instrument Chunk, defined later in this Note, uses markers to mark loop
beginning and end points.
Markers
A marker has the following format.
typedef short MarkerId;
typedef struct {
MarkerID id;
unsigned long position;
pstring markerName;
} Marker;
The id is a number that uniquely identifies that marker within a FORM AIFF.
The id can be any positive non-zero integer, as long as no other marker
within the same FORM AIFF has the same id.
The marker's position in the sound data is determined by the position field.
Markers conceptually fall between two sample frames. A marker that falls
before the first sample frame in the sound data is at position zero, while a
marker that falls between the first and second sample frame in the sound data
is at position 1. Note that the units for position are sample frames, not
bytes nor sample points.
Sample Frames
___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___
| | | | | | | | | | | | |
|___|___|___|___|___|___|___|___|___|___|___|___|
^ ^ ^
position 0 position 5 position 12
Figure 8: Sample Frame Marker Positions
The markerName field is a Pascal-style text string containing the name of the
mark.
Note: Some "EA IFF 85" files store strings a C-strings (text bytes followed by
a null terminating character) instead of Pascal-style strings. Audio IFF uses
pstrings because they are more efficiently skipped over when scanning through
chunks. Using pstrings, a program can skip over a string by adding the string
count to the address of the first character. C strings require that each
character in the string be examined for the null terminator.
Marker Chunk Format
The format for the data within a Marker Chunk is shown below.
#define MarkerID 'MARK' /* ckID for Marker Chunk */
typedef struct {
ID ckID;
long ckSize;
unsigned short numMarkers;
Marker Markers [];
} MarkerChunk;
The ckID is always 'MARK'. The ckSize is the size of the data portion of the
chunk in bytes. It does not include the 8 bytes used by ckID and ckSize.
The numMarkers field is the number of markers in the Marker Chunk. If
numMarkers is non-zero, it is followed by the markers themselves. Because
all fields in a marker are an even number of bytes, the length of any marker
will always be even. Thus, markers are packed together with no unused bytes
between them. The markers need not be ordered in any particular manner.
The Marker Chunk is optional. No more than one Marker Chunk can appear in a
FORM AIFF.
The Instrument Chunk
The Instrument Chunk defines basic parameters that an instrument, such as a
sample, could use to play the sound data.
Looping
Sound data can be looped, allowing a portion of the sound to be repeated in
order to lengthen the sound. The structure below describes a loop.
typedef struct {
short PlayMode;
MarkerId beginLoop;
MarkerId endLoop;
} Loop;
A loop is marked with two points, a begin position and an end position. There
are two ways to play a loop, forward looping and forward/backward looping.
In the case of forward looping, playback begins at the beginning of the sound,
continues past the begin position and continues to the end position, at which
point playback starts again at the begin position. The segment between the
begin and end positions, called the loop segment, is played repeatedly until
interrupted by a user action, such as the release of a key on a sampling
instrument.
___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___
sample frames | | | |<--- loop segment ---->| | | |
|___|___|___|___|___|___|___|___|___|___|___|___|
^ ^
begin position end position
Figure 9: Sample Frame Looping
With forward/backward looping, the loop segment is first played from the begin
position to the end position, and then played backwards from the end position
to the begin position. This flip-flop pattern is repeated over and over again
until interrupted.
The playMode specifies which type of looping is to be performed:
#define NoLooping 0
#define ForwardLooping 1
#define ForwardBackwardLooping 2
If NoLooping is specified, then the loop points are ignored during playback.
The beginLoop is a marker id that marks the begin position of the loop segment.
The endLoop marks the end position of a loop. The begin position must be
less than the end position. If this is not the case, then the loop segment
has zero or negative length and no looping takes place.
The Instrument Chunk Format
The format of the data within an Instrument Chunk is described below.
#define InstrumentID 'INST' /*ckID for Instruments Chunk */
typedef struct {
ID ckID;
long ckSize;
char baseNote;
char detune;
char lowNote;
char highNote;
char lowvelocity;
char highvelocity;
short gain;
Loop sustainLoop;
Loop releaseLoop;
} InstrumentChunk;
The ckID is always 'INST'. ckSize is the size of the data portion of the
chunk, in bytes. For the Instrument Chunk, ckSize is always 20.
The baseNote is the note at which the instrument plays back the sound data
without pitch modification. Units are MIDI (MIDI is an acronym for Musical
Instrument Digital Interface) note numbers, and are in the range 0 through
127. Middle C is 60.
The detune field determines how much the instrument should alter the pitch of
the sound when it is played back. Units are in cents (1/100 of a semitone)
and range from -50 to +50. Negative numbers mean that the pitch of the sound
should be lowered, while positive numbers mean that it should be raised.
The lowNote and highNote fields specify the suggested range on a keyboard for
playback of the sound data. The sound data should be played if the instrument
is requested to play a note between the low and high, inclusive. The base
note does not have to be within this range. Units for lowNote and highNote
are MIDI note values.
The lowVelocity and highVelocity fields specify the suggested range of
velocities for playback of the sound data. The sound data should be played
if the note-on velocity is between low and high velocity, inclusive. Units
are MIDI velocity values, 1 (lowest velocity) through 127 (highest velocity).
The gain is the amount by which to change the gain of the sound when it is
played. Units are decibels. For example, 0db means no change, 6db means
double the value of each sample point, while -6db means halve the value of
each sample point.
The sustainLoop field specifies a loop that is to be played when an instrument
is sustaining a sound.
The releaseLoop field specifies a loop that is to be played when an instrument
is in the release phase of playing back a sound. The release phase usually
occurs after a key on an instrument is released.
The Instrument Chunk is optional. No more than one Instrument Chunk can
appear in a FORM AIFF.
ASIF Note: The Apple IIGS Sampled Instrument Format also defines a
chunk with ID of "INST," which is not the same as the Audio
IFF Instrument Chunk. A good way to tell the two chunks
apart in generic IFF-style readers is by the ckSize fields.
The Audio IFF Instrument Chunk's ckSize field is always 20,
whereas the Apple IIGS Sampled Instrument Format Instrument
Chunk's ckSize field, for structural reasons, can never be
20.
The MIDI Data Chunk
The MIDI Data Chunk can be used to store MIDI data. Please refer to Musical
Instrument Digital Interface Specification 1.0, available from the
International MIDI Association, for more details on MIDI.
The primary purpose of this chunk is to store MIDI System Exclusive messages,
although other types of MIDI data can be stored in the block as well. As more
instruments come to market, they will likely have parameters that have not
been included in the Audio IFF specification. The MIDI System Exclusive
messages for these instruments may contain many parameters that are not
included in the Instrument Chunk. For example, a new sampling instrument may
have more than the two loops defined in the Instrument Chunk. These loops
will likely be represented in the MIDI System Exclusive message for the new
machine. This MIDI System Exclusive message can be stored in the MIDI Data
Chunk.
#define MIDIDataID 'MIDI' /* ckID for MIDI Data Chunk */
typedef struct {
ID ckID;
long ckSize;
unsigned char MIDIdata[];
} MIDIDataChunk;
The ckID is always 'MIDI'. ckSize of the data portion of the chunk, in bytes.
It does not include the 8 bytes used by ckID and ckSize.
The MIDIData field contains a stream of MIDI data.
The MIDI Data Chunk is optional. Any number of MIDI Data Chunks may exist in
a FORM AIFF. If MIDI System Exclusive messages for several instruments are to
be stored in a FORM AIFF, it is better to use one MIDI Data Chunk per
instrument than one big MIDI Data Chunk for all of the instruments.
The Audio Recording Chunk
The Audio Recording Chunk contains information pertinent to audio recording
devices.
#define AudioRecordingID 'AESD' /* ckID for Audio Recording */
/* Chunk. */
typedef struct {
ID ckID
long ckSize;
unsigned char AESChannelStatusData[24];
} AudioRecordingChunk;
The ckID is always 'AESD'. The ckSize is the size of the data portion of the
chunk, in bytes For the Audio Recording Chunk, ckSize is always 24.
The 24 bytes of AESCChannelStatusData are specified in the "AES Recommended
Practice for Digital Audio Engineering - Serial Transmission Format for Linearly
Represented Digital Audio Data", transmission of digital audio between audio
devices. This information is duplicated in the Audio Recording Chunk for
convenience. Of general interest would be bits 2, 3, and 4 of byte 0, which
describe recording emphasis.
The Audio Recording Chunk is optional. No more than one Audio Recording Chunk
may appear in a FORM AIFF.
The Application Specific Chunk
The Application Specific Chunk can be used for any purposes whatsoever by
developers and application authors. For example, an application that edits
sounds might want to use this chunk to store editor state parameters such as
magnification levels, last cursor position, etc.
#define ApplicationSpecificID 'APPL' /* ckID for Application */
/* Specific Chunk. */
typedef struct {
ID ckID;
long ckSize;
OSType applicationSignature;
char data[];
} ApplicationSpecificChunk;
The ckID is always 'APPL'. The ckSize is the size of the data portion of the
chunk, in bytes. It does not include the 8 bytes used by ckID and ckSize.
The applicationSignature identifies a particular application. For Macintosh
applications, this will be the application's four character signature.
The OSType field is used by applications which run on platforms from Apple
Computer, Inc. For the Apple II, the OStype field should be set to 'pdos'.
For the Macintosh, this field should be set to the four character signature
as registered with Apple Technical Support.
The data field is the data specific to the application.
The Application Specific Chunk is optional. Any number of Application
Specific Chunks may exist in a single FORM AIFF.
The Comments Chunk
The Comments Chunk is used to store comments in the FORM AIFF. "EA IFF 85"
has an Annotation Chunk (used in ASIF) that can be used for comments, but the
Comments Chunk has two features not found in the "EA IFF 85" chunk. They are
a time-stamp for the comment and a link to a marker.
Comment
A comment consists of a time stamp, marker id, and a text count followed by
text.
typedef struct {
unsigned long timeStamp;
MarkerID marker;
unsigned short count;
char text;
} Comment;
The timeStamp indicates when the comment was created. On the Amiga, units
are the number of seconds since January 1, 1978. On the Macintosh, units are
the number of seconds since January 1, 1904.
A comment can be linked to a marker. This allows applications to store long
descriptions of markers as a comment. If the comment is referring to a marker,
then the marker field is the ID of that marker. Otherwise, marker is zero,
indicating that this comment is not linked to a marker.
The count is the length of the text that makes up the comment. This is a 16-bit
quantity, allowing much longer comments than would be available with a pstring.
The text field contains the comment itself.
The Comments Chunk is optional. No more than one Comments Chunk may appear in
a single FORM AIFF.
Comments Chunk Format
#define CommentID 'COMT' /* ckID for Comments Chunk */
typedef struct {
ID ckID;
long ckSize;
unsigned short numComments;
Comment comments[];
}CommentsChunk;
The ckID is always 'COMT'. The ckSize is the size of the data portion of
the chunk, in bytes. It does not include the 8 bytes used by ckID and ckSize.
The numComments field contains the number of comments in the Comments Chunk.
This is followed by the comments themselves. Comments are always even
numbers of bytes in length, so there is no padding between comments in
the Comments Chunk.
The Comments Chunk is optional. No more than one Comments Chunk may appear
in a single FORM AIFF.
The Text Chunks, Name, Author, Copyright, Annotation
These four chunks are included in the definition of every "EA IFF 85" file.
All are text chunks; their data portion consists solely of text. Each of
these chunks is optional.
#define NameID 'NAME' /* ckID for Name Chunk */
#define NameID 'AUTH' /* ckID for Author Chunk */
#define NameID '(c) ' /* ckID for Copyright Chunk */
#define NameID 'ANNO' /* ckID for Annotation Chunk */
typedef struct {
ID ckID;
long ckSize;
char text[];
}TextChunk;
The ckID is either 'NAME', 'AUTH', '(c) ', or 'ANNO' depending on whether the
chunk is a Name Chunk, Author Chunk, Copyright Chunk, or Annotation Chunk,
respectively. For the Copyright Chunk, the 'c' is lowercase and there is a
space (0x20) after the close parenthesis.
The ckSize is the size of the data portion of the chunk, in this case the text.
The text field contains pure ASCII characters. it is not a pstring or a C
string. The number of characters in text is determined by ckSize. The
contents of text depend on the chunk, as described below:
Name Chunk. The text contains the name of the sampled sound. The Name Chunk
is optional. No more than one Name Chunk may exist within a FORM AIFF.
Author Chunk. The text contains one or more author names. An author in this
case is the creator of a sampled sound. The Author Chunk is optional. No
more than one Author Chunk may exist within a FORM AIFF.
Copyright Chunk. The Copyright Chunk contains a copyright notice for the
sound. The text field contains a date followed by the name of the copyright
owner. The chunk ID '(c) ' serves as the copyright character. For example,
a Copyright Chunk containing the text "1991 Commodore-Amiga, Inc." means
"(c) 1991 Commodore-Amiga, Inc." The Copyright Chunk is optional. No more
than one Copyright Chunk may exist within a FORM AIFF.
Annotation Chunk. The text contains a comment. Use of this chunk is
discouraged within a FORM AIFF. The more powerful Comments Chunk should be
used instead. The Annotation Chunk is optional. Many Annotation Chunks may
exist within a FORM AIFF.
Chunk Precedence
Several of the local chunks for FORM AIFF may contain duplicate information.
For example, the Instrument Chunk defines loop points and MIDI System
Exclusive data in the MIDI Data Chunk may also define loop points. What
happens if these loop points are different? How is an application supposed to
loop the sound? Such conflicts are resolved by defining a precedence for
chunks. This precedence is illustrated in Figure 10.
Common Chunk Highest Precedence
|
Sound Data Chunk
|
Marker Chunk
|
Instrument Chunk
|
Comment Chunk
|
Name Chunk
|
Author Chunk
|
Copyright Chunk
|
Annotation Chunk
|
Audio Recording Chunk
|
MIDI Data Chunk
|
Application Specific Chunk Lowest Precedence
Figure 10: Chunk Precedence
The Common Chunk has the highest precedence, while the Application Specific
Chunk has the lowest. Information in the Common Chunk always takes precedence
over conflicting information in any other chunk. The Application Specific
Chunk always loses in conflicts with other chunks. By looking at the chunk
hierarchy, for example, one sees that the loop points in the Instrument Chunk
take precedence over conflicting loop points found in the MIDI Data Chunk.
It is the responsibility of applications that write data into the lower
precedence chunks to make sure that the higher precedence chunks are updated
accordingly.
Figure 11 illustrates an example of a FORM AIFF. An Audio IFF file is simple
a file containing a single FORM AIFF. The FORM AIFF is stored in the data
fork of Macintosh file systems that can handle resource forks.
_____________________________________________________________________
| FORM AIFF |
| _____________ |
| ckID |_ 'FORM' ____| |
| ckSize |_ 176516 ____| |
| _____________ formType |_ 'AIFF' ____| __________________________ |
| | Common ckID |_ 'COMM' ____| | |
| | Chunk ckSize |_ 18 ________| | |
| | numChannels |_ 2 ___|_____ | |
| | numSampleFrames |_ 88200 _____| | |
| | sampleSize |_ 16 __|_______________________________ | |
| |___________ sampleRate |_ 44100.00 ____________________________| | |
| | Marker ckID |_ 'MARK' _____| | |
| | Chunk ckSize |_ 34 _________| | |
| | numMarkers |_ 2 ___| | |
| | id |_ 1 ___|_______ | |
| | position |_ 44100 ___ ___|___ ___ ___ ___ ___ ___ | |
| | markerName | 8 |'b'|'e'|'g'|' '|'l'|'o'|'o'|'p'| 0 | | |
| | id |_ 2 ___|_______ | |
| | position |_ 88200 _______|___ ___ ___ ___ ___ ___ | |
| |___________ markerName | 8 |'e'|'n'|'d'|' '|'l'|'o'|'o'|'p'| 0 | | |
| | Instrument ckID |_ 'INST' ______| | |
| | Chunk ckSize |_ 20 __________| | |
| | baseNote | 60| | |
| | detune | -3| | |
| | lowNote | 57| | |
| | highNote | 63| | |
| | lowVelocity | 1 | | |
| | highVelocity |127|__ | |
| | gain |_ 6 __| | |
| | sustainLoop.playMode |_ 1 __| | |
| | sustainLoop.beginLoop |_ 1 __| | |
| | sustainLoop.endLoop |_ 2 __| | |
| | releaseLoop.playMode |_ 0 __| | |
| | releaseLoop.beginLoop |_ - __| | |
| |__ releaseLoop.endLoop |_ - __|__________________________________| |
| | Sound ckID |_ 'SSND' ______| | |
| | Data ckSize |_ 176408 ______| | |
| | Chunk offset |_ 0 ___________| | |
| | blockSize |_ 0 ___________| _______ _______ | |
| | soundData |_ch 1 _|_ch 2 _| . . . |_ch 1 _|_ch 2 _| | |
| | first sample frame 88200th sample frame | |
| |_________________________________________________________________| |
|_____________________________________________________________________|
Figure 11: Sample FORM AIFF
Further Reference
_____________________________________________________________________________
o "Inside Macintosh", Volume II, Apple Computer, Inc.
o "Apple Numerics Manual", Second Edition, Apple Computer, Inc.
o "File Type Note: File Type $D8, Auxiliary Type $0002, Apple IIGS
Sampled Instrument Format", Apple Computer, Inc.
o "Audio Interchange File Format v1.3", APDA
o "AES Recommended Practice for Digital Audio Engineering--Serial
Transmission Format for Linearly Represented Digital Audio Data",
Audio Engineering Society, 60 East 42nd Street, New York, NY 10165
o "MIDI: Musical Instrument Digital Interface, Specification 1.0", the
International MIDI Association.
o "`EA IFF 85' Standard for Interchange Format Files", Electronic Arts
o "`8SVX' IFF 8-bit Sampled Voice", Electronic Arts
Animated bitmap
Animated bitmap form (Framer, Deluxe Video)
TITLE: Form ANBM (animated bitmap form used by Framer, Deluxe Video)
(note from the author)
The format was designed for simplicity at a time when the IFF
standard was very new and strange to us all. It was not designed
to be a general purpose animation format. It was intended to be
a private format for use by DVideo, with the hope that a more
powerful format would emerge as the Amiga became more popular.
I hope you will publish this format so that other formats will
not inadvertantly conflict with it.
PURPOSE: To define simple animated bitmaps for use in DeluxeVideo.
In Deluxe Video objects appear and move in the foreground
with a picture in the background. Objects are "small" bitmaps
usually saved as brushes from DeluxePaint and pictures are large
full screen bitmaps saved as files from DeluxePaint.
Two new chunk headers are defined: ANBM and FSQN.
An animated bitmap (ANBM) is a series of bitmaps of the same
size and depth. Each bitmap in the series is called a frame and
is labeled by a character, 'a b c ...' in the order they
appear in the file.
The frame sequence chunk (FSQN) specifies the playback
sequence of the individual bitmaps to achieve animation.
FSQN_CYCLE and FSQN_TOFRO specify two algorithmic sequences. If
neither of these bits is set, an arbitrary sequence can be used
instead.
ANBM - identifies this file as an animated bitmap
.FSQN - playback sequence information
.LIST ILBM - LIST allows following ILBMs to share properties
..PROP ILBM - properties follow
...BMHD - bitmap header defines common size and depth
...CMAP - colormap defines common colors
..FORM ILBM - first frame follows
..BODY - the first frame
. - FORM ILBM and BODY for each remaining frame
.
.
Chunk Description:
The ANBM chunk identifes this file as an animated bitmap
Chunk Spec:
#define ANBM MakeID('A','N','B','M')
Disk record:
none
Chunk Description:
The FSQN chunk specifies the frame playback sequence
Chunk Spec:
#define FSQN MakeID('F','S','Q','N')
/* Flags */
#define FSQN_CYCLE 0x0001 /* Ignore sequence, cycle a,b,..y,z,a,b,.. */
#define FSQN_TOFRO 0x0002 /* Ignore sequence, cycle a,b,..y,z,y,..a,b, */
/* Disk record */
typedef struct {
WORD numframes; /* Number of frames in the sequence */
LONG dt; /* Nominal time between frames in jiffies */
WORDBITS flags; /* Bits modify behavior of the animation */
UBYTE sequence[80]; /* string of 'a'..'z' specifying sequence */
} FrameSeqn;
Supporting Software:
DeluxeVideo by Mike Posehn and Tom Case for Electronic Arts
Thanks,
Mike Posehn
ANIM brush
Dpaint Anim Brush IFF Format
From a description by the author of DPaint,
Dan Silva
Electronic Arts
The "Anim Brushes" of DPaint III are saved on disk in the IFF "ANIM"
format. Basically, an ANIM Form consists of an initial ILBM
which is the first frame of the animation, and any number of
subsequent "ILBM"S (which aren't really ILBM's) each of which
contains an ANHD animation header chunk and a DLTA chunk
comprised of the encoded difference between a frame and a previous one.
To use ANIM terminology (for a description of the ANIM format,
see the IFF Anim Spec, by Gary Bonham). Anim Brushes use a "type
5" encoding, which is a vertical, byte-oriented delta encoding
(based on Jim Kent's RIFF). The deltas have an interleave of 1,
meaning deltas are computed between adjacent frames, rather than
between frames 2 apart, which is the usual ANIM custom for the
purpose of fast hardware page-flipping. Also, the deltas use
Exclusive Or to allow reversable play.
However, to my knowledge, all the existing Anim players in the Amiga
world will only play type 5 "Anim"s which have an interleave of 0 (i.e. 2)
and which use a Store operation rather than Exclusive Or, so no existing
programs will read Anim Brushes anyway. The job of modifying existing
Anim readers to read Anim Brushes should be simplified, however.
Here is an outline of the structure of the IFF Form output by
DPaint III as an "Anim Brush". The IFF Reader should of course be
flexible enough to tolerate variation in what chunks actually
appear in the initial ILBM.
FORM ANIM
. FORM ILBM first frame
. . BMHD
. . CMAP
. . DPPS
. . GRAB
. . CRNG
. . CRNG
. . CRNG
. . CRNG
. . CRNG
. . CRNG
. . DPAN my own little chunk.
. . CAMG
. . BODY
. FORM ILBM frame 2
. . ANHD animation header chunk
. . DLTA delta mode data
. FORM ILBM frame 3
. . ANHD animation header chunk
. . DLTA delta mode data
. FORM ILBM frame 4
. . ANHD animation header chunk
. . DLTA delta mode data
...
. FORM ILBM frame N
. . ANHD animation header chunk
. . DLTA delta mode data
--- Here is the format of the DPAN chunk:
typedef struct {
UWORD version; /* current version=4 */
UWORD nframes; /* number of frames in the animation.*/
ULONG flags; /* Not used */
} DPAnimChunk;
The version number was necessary during development. At present
all I look at is "nframes".
--- Here is the ANHD chunk format:
typedef struct {
UBYTE operation; /* =0 set directly
=1 XOR ILBM mode,
=2 Long Delta mode,
=3 Short Delta mode
=4 Generalize short/long Delta mode,
=5 Byte Vertical Delta (riff)
=74 (Eric Grahams compression mode)
*/
UBYTE mask; /* XOR ILBM only: plane mask where data is*/
UWORD w,h;
WORD x,y;
ULONG abstime;
ULONG reltime;
UBYTE interleave; /* 0 defaults to 2 */
UBYTE pad0; /* not used */
ULONG bits; /* meaning of bits:
bit# =0 =1
0 short data long data
1 store XOR
2 separate info one info for
for each plane for all planes
3 not RLC RLC (run length encoded)
4 horizontal vertical
5 short info offsets long info offsets
-------------------------*/
UBYTE pad[16];
} AnimHdr;
for Anim Brushes, I set:
animHdr.operation = 5; /* RIFF encoding */
animHdr.interleave = 1;
animHdr.w = curAnimBr.bmob.pict.box.w;
animHdr.h = curAnimBr.bmob.pict.box.h;
animHdr.reltime = 1;
animHdr.abstime = 0;
animHdr.bits = 4; /* indicating XOR */
-- everything else is set to 0.
NOTE: the "bits" field was actually intended ( by the original
creator of the ANIM format, Gary Bonham of SPARTA, Inc.) for use
with only with compression method 4. I am using bit 2 of the bits
field to indicate the Exclusive OR operation in the context of
method 5, which seems like a reasonable generalization.
For an Anim Brush with 10 frames, there will be an initial frame
followed by 10 Delta's (i.e ILBMS containing ANHD and DLTA
chunks). Applying the first Delta to the initial frame generates
the second frame, applying the second Delta to the second frame
generates the third frame, etc. Applying the last Delta thus
brings back the first frame.
The DLTA chunk begins with 16 LONG plane offets, of which DPaint
only uses the first 6 (at most). These plane offsets are either
the offset (in bytes ) from the beginning of the DLTA chunk to
the data for the corresponding plane, or Zero, if there was no
change in that plane. Thus the first plane offset is either 0 or
64.
(The following description of the method is based on Gary Bonham's
rewording of Jim Kent's RIFF documentation.)
Compression/decompression is performed on a plane-by-plane
basis.
Each byte-column of the bitplane is compressed separately. A
320x200 bitplane would have 40 columns of 200 bytes each. In
general, the bitplanes are always an even number of bytes wide,
so for instance a 17x20 bitplane would have 4 columns of 20
bytes each.
Each column starts with an op-count followed by a number of
ops. If the op-count is zero, that's ok, it just means there's
no change in this column from the last frame. The ops are of
three kinds, and followed by a varying amount of data depending
on which kind:
1. SKIP - this is a byte with the hi bit clear that says
how many rows to move the "dest" pointer forward, ie to
skip. It is non-zero.
2. DUMP - this is a byte with the hi bit set. The hi bit is
masked off and the remainder is a count of the number of
bytes of data to XOR directly. It is followed by the
bytes to copy.
3. RUN - this is a 0 byte followed by a count byte, followed
by a byte value to repeat "count" times, XOR'ing it into
the destination.
Bear in mind that the data is compressed vertically rather than
horizontally, so to get to the next byte in the destination you
add the number of bytes per row instead of one.
The Format of DLTA chunks is as described in section 2.2.2
of the Anim Spec. The encoding for type 5 is described in section
2.2.3 of the Anim Spec.
Cel animation
A N I M
An IFF Format For CEL Animations
Revision date: 4 May 1988
prepared by:
SPARTA Inc.
23041 de la Carlota
Laguna Hills, Calif 92653
(714) 768-8161
contact: Gary Bonham
also by:
Aegis Development Co.
2115 Pico Blvd.
Santa Monica, Calif 90405
213) 392-9972
1.0 Introduction
The ANIM IFF format was developed at Sparta originally for the
production of animated video sequences on the Amiga computer. The
intent was to be able to store, and play back, sequences of frames
and to minimize both the storage space on disk (through compression)
and playback time (through efficient de-compression algorithms).
It was desired to maintain maximum compatibility with existing
IFF formats and to be able to display the initial frame as a normal
still IFF picture.
Several compression schemes have been introduced in the ANIM format.
Most of these are strictly of historical interest as the only one
currently being placed in new code is the vertical run length
encoded byte encoding developed by Jim Kent.
1.1 ANIM Format Overview
The general philosophy of ANIMs is to present the initial frame
as a normal, run-length-encoded, IFF picture. Subsequent
frames are then described by listing only their differences
from a previous frame. Normally, the "previous" frame is two
frames back as that is the frame remaining in the hidden
screen buffer when double-buffering is used. To better
understand this, suppose one has two screens, called A and B,
and the ability to instantly switch the display from one to
the other. The normal playback mode is to load the initial
frame into A and duplicate it into B. Then frame A is displayed
on the screen. Then the differences for frame 2 are used to
alter screen B and it is displayed. Then the differences for
frame 3 are used to alter screen A and it is displayed, and so
on. Note that frame 2 is stored as differences from frame 1,
but all other frames are stored as differences from two frames
back.
ANIM is an IFF FORM and its basic format is as follows (this
assumes the reader has a basic understanding of IFF format
files):
FORM ANIM
. FORM ILBM first frame
. . BMHD normal type IFF data
. . ANHD optional animation header
chunk for timing of 1st frame.
. . CMAP
. . BODY
. FORM ILBM frame 2
. . ANHD animation header chunk
. . DLTA delta mode data
. FORM ILBM frame 3
. . ANHD
. . DLTA
...
The initial FORM ILBM can contain all the normal ILBM chunks,
such as CRNG, etc. The BODY will normally be a standard
run-length-encoded data chunk (but may be any other legal
compression mode as indicated by the BMHD). If desired, an ANHD
chunk can appear here to provide timing data for the first
frame. If it is here, the operation field should be =0.
The subsequent FORMs ILBM contain an ANHD, instead of a BMHD,
which duplicates some of BMHD and has additional parameters
pertaining to the animation frame. The DLTA chunk contains
the data for the delta compression modes. If
the older XOR compression mode is used, then a BODY chunk
will be here. In addition, other chunks may be placed in each
of these as deemed necessary (and as code is placed in player
programs to utilize them). A good example would be CMAP chunks
to alter the color palette. A basic assumption in ANIMs is
that the size of the bitmap, and the display mode (e.g. HAM)
will not change through the animation. Take care when playing
an ANIM that if a CMAP occurs with a frame, then the change must
be applied to both buffers.
Note that the DLTA chunks are not interleaved bitmap representations,
thus the use of the ILBM form is inappropriate for these frames.
However, this inconsistency was not noted until there were a number
of commercial products either released or close to release which
generated/played this format. Therefore, this is probably an
inconsistency which will have to stay with us.
1.2 Recording ANIMs
To record an ANIM will require three bitmaps - one for
creation of the next frame, and two more for a "history" of the
previous two frames for performing the compression calculations
(e.g. the delta mode calculations).
There are five frame-to-frame compression methods currently
defined. The first three are mainly for historical interest.
The product Aegis VideoScape 3D utilizes the third method in
version 1.0, but switched to method 5 on 2.0. This is
the only instance known of a commercial product generating
ANIMs of any of the first three methods. The fourth method
is a general short or long word compression scheme which has
several options including whether the compression is horizontal
or vertical, and whether or not it is XOR format. This offers
a choice to the user for the optimization of file size and/or
playback speed. The fifth method is the byte vertical run length
encoding as designed by Jim Kent. Do not confuse
this with Jim's RIFF file format which is different than ANIM.
Here we utilized his compression/decompression routines within the
ANIM file structure.
The following paragraphs give a general outline of each of the
methods of compression currently included in this spec.
1.2.1 XOR mode
This mode is the original and is included here for historical
interest. In general, the delta modes are far superior.
The creation of XOR mode is quite simple. One simply
performs an exclusive-or (XOR) between all corresponding
bytes of the new frame and two frames back. This results
in a new bitmap with 0 bits wherever the two frames were
identical, and 1 bits where they are different. Then this
new bitmap is saved using run-length-encoding. A major
obstacle of this mode is in the time consumed in performing
the XOR upon reconstructing the image.
1.2.2 Long Delta mode
This mode stores the actual new frame long-words which are
different, along with the offset in the bitmap. The
exact format is shown and discussed in section 2 below.
Each plane is handled separately, with no data being saved
if no changes take place in a given plane. Strings of
2 or more long-words in a row which change can be run
together so offsets do not have to be saved for each one.
Constructing this data chunk usually consists of having
a buffer to hold the data, and calculating the data as
one compares the new frame, long-word by long-word, with
two frames back.
1.2.3 Short Delta mode
This mode is identical to the Long Delta mode except that
short-words are saved instead of long-words. In most
instances, this mode results in a smaller DLTA chunk.
The Long Delta mode is mainly of interest in improving
the playback speed when used on a 32-bit 68020 Turbo Amiga.
1.2.4 General Delta mode
The above two delta compression modes were hastily put together.
This mode was an attempt to provide a well-thought-out delta
compression scheme. Options provide for both short and long
word compression, either vertical or horizontal compression,
XOR mode (which permits reverse playback), etc. About the time
this was being finalized, the fifth mode, below, was developed
by Jim Kent. In practice the short-vertical-run-length-encoded
deltas in this mode play back faster than the fifth mode (which
is in essence a byte-vertical-run-length-encoded delta mode) but
does not compress as well - especially for very noisy data such
as digitized images. In most cases, playback speed not being
terrifically slower, the better compression (sometimes 2x) is
preferable due to limited storage media in most machines.
Details on this method are contained in section 2.2.2 below.
1.2.5 Byte Vertical Compression
This method does not offer the many options that method 4 offers,
but is very successful at producing decent compression even for
very noisy data such as digitized images. The method was devised
by Jim Kent and is utilized in his RIFF file format which is
different than the ANIM format. The description of this method
in this document is taken from Jim's writings. Further, he has
released both compression and decompression code to public domain.
Details on this method are contained in section 2.2.3 below.
1.3 Playing ANIMs
Playback of ANIMs will usually require two buffers, as mentioned
above, and double-buffering between them. The frame data from
the ANIM file is used to modify the hidden frame to the next
frame to be shown. When using the XOR mode, the usual run-
length-decoding routine can be easily modified to do the
exclusive-or operation required. Note that runs of zero bytes,
which will be very common, can be ignored, as an exclusive or
of any byte value to a byte of zero will not alter the original
byte value.
The general procedure, for all compression techniques, is to first
decode the initial ILBM picture into the hidden buffer and double-
buffer it into view. Then this picture is copied to the other (now
hidden) buffer. At this point each frame is displayed with the
same procedure. The next frame is formed in the hidden buffer by
applying the DLTA data (or the XOR data from the BODY chunk in the
case of the first XOR method) and the new frame is double-buffered
into view. This process continues to the end of the file.
A master colormap should be kept for the entire ANIM which would
be initially set from the CMAP chunk in the initial ILBM. This
colormap should be used for each frame. If a CMAP chunk appears
in one of the frames, then this master colormap is updated and the
new colormap applies to all frames until the occurrance of another
CMAP chunk.
Looping ANIMs may be constructed by simply making the last two frames
identical to the first two. Since the first two frames are special
cases (the first being a normal ILBM and the second being a delta from
the first) one can continually loop the anim by repeating from frame
three. In this case the delta for creating frame three will modify
the next to the last frame which is in the hidden buffer (which is
identical to the first frame), and the delta for creating frame four
will modify the last frame which is identical to the second frame.
Multi-File ANIMs are also supported so long as the first two frames
of a subsequent file are identical to the last two frames of the
preceeding file. Upon reading subsequent files, the ILBMs for the
first two frames are simply ignored, and the remaining frames are
simply appended to the preceeding frames. This permits splitting
ANIMs across multiple floppies and also permits playing each section
independently and/or editing it independent of the rest of the ANIM.
Timing of ANIM playback is easily achieved using the vertical blank
interrupt of the Amiga. There is an example of setting up such
a timer in the ROM Kernel Manual. Be sure to remember the timer
value when a frame is flipped up, so the next frame can be flipped
up relative to that time. This will make the playback independent
of how long it takes to decompress a frame (so long as there is enough
time between frames to accomplish this decompression).
2.0 Chunk Formats
2.1 ANHD Chunk
The ANHD chunk consists of the following data structure:
UBYTE operation The compression method:
=0 set directly (normal ILBM BODY),
=1 XOR ILBM mode,
=2 Long Delta mode,
=3 Short Delta mode,
=4 Generalized short/long Delta mode,
=5 Byte Vertical Delta mode
=6 Stereo op 5 (third party)
=74 (ascii 'J') reserved for Eric Graham's
compression technique (details to be
released later).
UBYTE mask (XOR mode only - plane mask where each
bit is set =1 if there is data and =0
if not.)
UWORD w,h (XOR mode only - width and height of the
area represented by the BODY to eliminate
unnecessary un-changed data)
WORD x,y (XOR mode only - position of rectangular
area representd by the BODY)
ULONG abstime (currently unused - timing for a frame
relative to the time the first frame
was displayed - in jiffies (1/60 sec))
ULONG reltime (timing for frame relative to time
previous frame was displayed - in
jiffies (1/60 sec))
UBYTE interleave (unused so far - indicates how may frames
back this data is to modify. =0 defaults
to indicate two frames back (for double
buffering). =n indicates n frames back.
The main intent here is to allow values
of =1 for special applications where
frame data would modify the immediately
previous frame)
UBYTE pad0 Pad byte, not used at present.
ULONG bits 32 option bits used by options=4 and 5.
At present only 6 are identified, but the
rest are set =0 so they can be used to
implement future ideas. These are defined
for option 4 only at this point. It is
recommended that all bits be set =0 for
option 5 and that any bit settings
used in the future (such as for XOR mode)
be compatible with the option 4
bit settings. Player code should check
undefined bits in options 4 and 5 to assure
they are zero.
The six bits for current use are:
bit # set =0 set =1
===============================================
0 short data long data
1 set XOR
2 separate info one info list
for each plane for all planes
3 not RLC RLC (run length coded)
4 horizontal vertical
5 short info offsets long info offsets
UBYTE pad[16] This is a pad for future use for future
compression modes.
2.2 DLTA Chunk
This chunk is the basic data chunk used to hold delta compression
data. The format of the data will be dependent upon the exact
compression format selected. At present there are two basic
formats for the overall structure of this chunk.
2.2.1 Format for methods 2 & 3
This chunk is a basic data chunk used to hold the delta
compression data. The minimum size of this chunk is 32 bytes
as the first 8 long-words are byte pointers into the chunk for
the data for each of up to 8 bitplanes. The pointer for the
plane data starting immediately following these 8 pointers will
have a value of 32 as the data starts in the 33-rd byte of the
chunk (index value of 32 due to zero-base indexing).
The data for a given plane consists of groups of data words. In
Long Delta mode, these groups consist of both short and long
words - short words for offsets and numbers, and long words for
the actual data. In Short Delta mode, the groups are identical
except data words are also shorts so all data is short words.
Each group consists of a starting word which is an offset. If
the offset is positive then it indicates the increment in long
or short words (whichever is appropriate) through the bitplane.
In other words, if you were reconstructing the plane, you would
start a pointer (to shorts or longs depending on the mode) to
point to the first word of the bitplane. Then the offset would
be added to it and the following data word would be placed at
that position. Then the next offset would be added to the
pointer and the following data word would be placed at that
position. And so on... The data terminates with an offset
equal to 0xFFFF.
A second interpretation is given if the offset is negative. In
that case, the absolute value is the offset+2. Then the
following short-word indicates the number of data words that
follow. Following that is the indicated number of contiguous
data words (longs or shorts depending on mode) which are to
be placed in contiguous locations of the bitplane.
If there are no changed words in a given plane, then the pointer
in the first 32 bytes of the chunk is =0.
2.2.2 Format for method 4
The DLTA chunk is modified slightly to have 16 long pointers at
the start. The first 8 are as before - pointers to the start of
the data for each of the bitplanes (up to a theoretical max of 8
planes). The next 8 are pointers to the start of the offset/numbers
data list. If there is only one list of offset/numbers for all
planes, then the pointer to that list is repeated in all positions
so the playback code need not even be aware of it. In fact, one
could get fancy and have some bitplanes share lists while others
have different lists, or no lists (the problems in these schemes
lie in the generation, not in the playback).
The best way to show the use of this format is in a sample playback
routine.
SetDLTAshort(bm,deltaword)
struct BitMap *bm;
WORD *deltaword;
{
int i;
LONG *deltadata;
WORD *ptr,*planeptr;
register int s,size,nw;
register WORD *data,*dest;
deltadata = (LONG *)deltaword;
nw = bm->BytesPerRow >>1;
for (i=0;i<bm->Depth;i++) {
planeptr = (WORD *)(bm->Planes[i]);
data = deltaword + deltadata[i];
ptr = deltaword + deltadata[i+8];
while (*ptr != 0xFFFF) {
dest = planeptr + *ptr++;
size = *ptr++;
if (size < 0) {
for (s=size;s<0;s++) {
*dest = *data;
dest += nw;
}
data++;
}
else {
for (s=0;s<size;s++) {
*dest = *data++;
dest += nw;
}
}
}
}
return(0);
}
The above routine is for short word vertical compression with
run length compression. The most efficient way to support
the various options is to replicate this routine and make
alterations for, say, long word or XOR. The variable nw
indicates the number of words to skip to go down the vertical
column. This one routine could easily handle horizontal
compression by simply setting nw=1. For ultimate playback
speed, the core, at least, of this routine should be coded in
assembly language.
2.2.2 Format for method 5
In this method the same 16 pointers are used as in option 4.
The first 8 are pointers to the data for up to 8 planes.
The second set of 8 are not used but were retained for several
reasons. First to be somewhat compatible with code for option
4 (although this has not proven to be of any benefit) and
second, to allow extending the format for more bitplanes (code
has been written for up to 12 planes).
Compression/decompression is performed on a plane-by-plane basis.
For each plane, compression can be handled by the skip.c code
(provided Public Domain by Jim Kent) and decompression can be
handled by unvscomp.asm (also provided Public Domain by Jim Kent).
Compression/decompression is performed on a plane-by-plane basis.
The following description of the method is taken directly from
Jim Kent's code with minor re-wording. Please refer to Jim's
code (skip.c and unvscomp.asm) for more details:
Each column of the bitplane is compressed separately.
A 320x200 bitplane would have 40 columns of 200 bytes each.
Each column starts with an op-count followed by a number
of ops. If the op-count is zero, that's ok, it just means
there's no change in this column from the last frame.
The ops are of three classes, and followed by a varying
amount of data depending on which class:
1. Skip ops - this is a byte with the hi bit clear that
says how many rows to move the "dest" pointer forward,
ie to skip. It is non-zero.
2. Uniq ops - this is a byte with the hi bit set. The hi
bit is masked down and the remainder is a count of the
number of bytes of data to copy literally. It's of
course followed by the data to copy.
3. Same ops - this is a 0 byte followed by a count byte,
followed by a byte value to repeat count times.
Do bear in mind that the data is compressed vertically rather
than horizontally, so to get to the next byte in the destination
we add the number of bytes per row instead of one!
2-D Object standard format
Description by Ross Cunniff and John Orr
A standard IFF FORM to describe 2D drawings has been sorely needed for
a long time. Several commercial drawing packages have been available
for some time but none has established its file format as the Amiga
standard. The absence of a 2D drawing standard hinders the
development of applications that use 2D drawings as it forces each
application to understand several private standards instead of a
single one. Without a standard, data exchange for both the developer
and the user is difficult, if not impossible.
The DR2D FORM fills this void. This FORM was developed by Taliesin,
Inc. for use as the native file format for their two-dimensional
structured drawing package, ProVector. Saxon Industries and Soft
Logik Publishing Corporation are planning to support this new FORM in
the near future.
Many of the values stored in the DR2D FORM are stored as IEEE single
precision floating point numbers. These numbers consist of 32 bits,
arranged as follows:
_______________________________________________________________________
| s e e e e e e e | e m m m m m m m | m m m m m m m m | m m m m m m m m |
-----------------------------------------------------------------------
31 24 23 16 15 8 7 0
where:
s is the sign of the number where 1 is negative and 0 is
positive.
e is the 8 bit exponent in excess 127 form. This number
is the power of two to which the mantissa is raised
(Excess 127 form means that 127 is added to the
exponent before packing it into the IEEE number.)
m is the 23 bit mantissa. It ranges from 1.0000000 to
1.999999..., where the leading base-ten one is
assumed.
An IEEE single precision with the value of 0.0000000 has all its bits
cleared.
The DR2D Chunks
FORM (0x464F524D) /* All drawings are a FORM */
struct FORMstruct {
ULONG ID; /* DR2D */
ULONG Size;
};
DR2D (0x44523244) /* ID of 2D drawing */
The DR2D chunks are broken up into three groups: the global drawing
attribute chunks, the object attribute chunks, and the object chunks.
The global drawing attribute chunks describe elements of a 2D drawing
that are common to many objects in the drawing. Document preferences,
palette information, and custom fill patterns are typical
document-wide settings defined in global drawing attribute chunks.
The object attribute chunks are used to set certain properties of the
object chunk(s) that follows the object attribute chunk. The current
fill pattern, dash pattern, and line color are all set using an object
attribute chunk. Object chunks describe the actual DR2D drawing.
Polygons, text, and bitmaps are found in these chunks.
The Global Drawing Attribute Chunks
The following chunks describe global attributes of a DR2D document.
DRHD (0x44524844) /* Drawing header */
The DRHD chunk contains the upper left and lower right extremes of the
document in (X, Y) coordinates. This chunk is required and should
only appear once in a document in the outermost layer of the DR2D file
(DR2Ds can be nested).
struct DRHDstruct {
ULONG ID;
ULONG Size; /* Always 16 */
IEEE XLeft, YTop,
XRight, YBot;
};
The point (XLeft,YTop) is the upper left corner of the project and the
point (XRight,YBot) is its lower right corner. These coordinates not
only supply the size and position of the document in a coordinate
system, they also supply the project's orientation. If XLeft <
XRight, the X-axis increases toward the right. If YTop < YBot, the
Y-axis increases toward the bottom. Other combinations are possible;
for example in Cartesian coordinates, XLeft would be less than XRight
but YTop would be greater than YBot.
PPRF (0x50505249) /* Page preferences */
The PPRF chunk contains preference settings for ProVector. Although
this chunk is not required, its use is encouraged because it contains
some important environment information.
struct PPRFstruct {
ULONG ID;
ULONG Size;
char Prefs[Size];
};
DR2D stores preferences as a concatenation of several null-terminated
strings, in the Prefs[] array. The strings can appear in any order.
The currently supported strings are:
Units=<unit-type>
Portrait=<boolean>
PageType=<page-type>
GridSize=<number>
where:
<unit-type> is either Inch, Cm, or Pica
<boolean> is either True or False
<page-type> is either Standard, Legal, B4, B5, A3,
A4, A5, or Custom
<number> is a floating-point number
The DR2D FORM does not require this chunk to explicitly state all the
possible preferences. In the absence of any particular preference
string, a DR2D reader should fall back on the default value. The
defaults are:
Units=Inch
Portrait=True
PageType=Standard
GridSize=1.0
CMAP (0x434D4150) /* Color map (Same as ILBM CMAP) */
This chunk is identical to the ILBM CMAP chunk as described in the IFF
ILBM documentation.
struct CMAPstruct {
ULONG ID;
ULONG Size;
UBYTE ColorMap[Size];
};
ColorMap is an array of 24-bit RGB color values. The 24-bit value is
spread across three bytes, the first of which contains the red
intensity, the next contains the green intensity, and the third
contains the blue intensity. Because DR2D stores its colors with
24-bit accuracy, DR2D readers must not make the mistake that some ILBM
readers do in assuming the CMAP chunk colors correspond directly to
Amiga color registers.
FONS (0x464F4E53) /* Font chunk (Same as FTXT FONS chunk) */
The FONS chunk contains information about a font used in the DR2D
FORM. ProVector does not include support for Amiga fonts. Instead,
ProVector uses fonts defined in the OFNT FORM which is documented
later in this article.
struct FONSstruct {
ULONG ID;
ULONG Size;
UBYTE FontID; /* ID the font is referenced by */
UBYTE Pad1; /* Always 0 */
UBYTE Proportional; /* Is it proportional? */
UBYTE Serif; /* does it have serifs? */
CHAR Name[Size-4]; /* The name of the font */
};
The UBYTE FontID field is the number DR2D assigns to this font.
References to this font by other DR2D chunks are made using this
number.
The Proportional and Serif fields indicate properties of this font.
Specifically, Proportional indicates if this font is proportional, and
Serif indicates if this font has serifs. These two options were
created to allow for font substitution in case the specified font is
not available. They are set according to these values:
0 The DR2D writer didn't know if this font is
proportional/has serifs.
1 No, this font is not proportional/does not have
serifs.
2 Yes, this font is proportional/does have serifs.
The last field, Name[], is a NULL terminated string containing the
name of the font.
DASH (0x44415348) /* Line dash pattern for edges */
This chunk describes the on-off dash pattern associated with a line.
struct DASHstruct {
ULONG ID;
ULONG Size;
USHORT DashID; /* ID of the dash pattern */
USHORT NumDashes; /* Should always be even */
IEEE Dashes[NumDashes]; /* On-off pattern */
};
DashID is the number assigned to this specific dash pattern.
References to this dash pattern by other DR2D chunks are made using
this number.
The Dashes[] array contains the actual dash pattern. The first number
in the array (element 0) is the length of the ``on'' portion of the
pattern. The second number (element 1) specifies the ``off'' portion
of the pattern. If there are more entries in the Dashes array, the
pattern will continue. Even-index elements specify the length of an
``on'' span, while odd-index elements specify the length of an ``off''
span. There must be an even number of entries. These lengths are not
in the same units as specified in the PPRF chunk, but are multiples of
the line width, so a line of width 2.5 and a dash pattern of 1.0, 2.0
would have an ``on'' span of length 1.0 x 2.5 = 2.5 followed by an
``off'' span of length 2.0 x 2.5 = 5. The following figure shows
several dash pattern examples. Notice that for lines longer than the
dash pattern, the pattern repeats.
[figure 1 - dash patterns]
By convention, DashID 0 is reserved to mean `No line pattern at all',
i.e. the edges are invisible. This DASH pattern should not be defined
by a DR2D DASH chunk. Again by convention, a NumDashes of 0 means
that the line is solid.
AROW (0x41524F57) /* An arrow-head pattern */
The AROW chunk describes an arrowhead pattern. DR2D open polygons
(OPLY) can have arrowheads attached to their endpoints. See the
description of the OPLY chunk later in this article for more
information on the OPLY chunk.
#define ARROW_FIRST 0x01 /* Draw an arrow on the OPLY's first point */
#define ARROW_LAST 0x02 /* Draw an arrow on the OPLY's last point */
struct AROWstruct {
ULONG ID;
ULONG Size;
UBYTE Flags; /* Flags, from ARROW_*, above */
UBYTE Pad0; /* Should always 0 */
USHORT ArrowID; /* Name of the arrow head */
USHORT NumPoints;
IEEE ArrowPoints[NumPoints*2];
};
The Flags field specifies which end(s) of an OPLY to place an
arrowhead based on the #defines above. ArrowID is the number by which
an OPLY will reference this arrowhead pattern.
The coordinates in the array ArrowPoints[] define the arrowhead's
shape. These points form a closed polygon. See the section on the
OPLY/CPLY object chunks for a descriptionof how DR2D defines shapes.
The arrowhead is drawn in the same coordinate system relative to the
endpoint of the OPLY the arrowhead is attached to. The arrowhead's
origin (0,0) coincides with the OPLY's endpoint. DR2D assumes that
the arrowhead represented in the AROW chunk is pointing to the right
so the proper rotation can be applied to the arrowhead. The arrow is
filled according to the current fill pattern set in the ATTR object
attribute chunk.
FILL (0x46494C4C) /* Object-oriented fill pattern */
The FILL chunk defines a fill pattern. This chunk is only valid
inside nested DR2D FORMs. The GRUP object chunk section of this
article contans an example of the FILL chunk.
struct FILLstruct {
ULONG ID;
ULONG Size;
USHORT FillID; /* ID of the fill */
};
FillID is the number by which the ATTR object attribute chunk
references fill patterns. The FILL chunk must be the first chunk
inside a nested DR2D FORM. A FILL is followed by one DR2D object plus
any of the object attribute chunks (ATTR, BBOX) associated with the
object.
[Figure 2 - fill patterns]
DR2D makes a ``tile'' out of the fill pattern, giving it a virtual
bounding box based on the extreme X and Y values of the FILL's object
(Fig. A). The bounding box shown in Fig. A surrounding the pattern
(the two ellipses) is invisible to the user. In concept, this
rectangle is pasted on the page left to right, top to bottom like
floor tiles (Fig. B). Again, the bounding boxes are not visible. The
only portion of this tiled pattern that is visible is the part that
overlaps the object (Fig. C) being filled. The object's path is
called a clipping path, as it ``clips'' its shape from the tiled
pattern (Fig. D). Note that the fill is only masked on top of
underlying objects, so any ``holes'' in the pattern will act as a
window, leaving visible underlying objects.
LAYR (0x4C415952) /* Define a layer */
A DR2D project is broken up into one or more layers. Each DR2D object
is in one of these layers. Layers provide several useful features.
Any particular layer can be ``turned off'', so that the objects in the
layer are not displayed. This eliminates the unnecessary display of
objects not currently needed on the screen. Also, the user can lock a
layer to protect the layer's objects from accidental changes.
struct LAYRstruct {
ULONG ID;
ULONG Size;
USHORT LayerID; /* ID of the layer */
char LayerName[16]; /* Null terminated and padded */
UBYTE Flags; /* Flags, from LF_*, below */
UBYTE Pad0; /* Always 0 */
};
LayerID is the number assigned to this layer. As the field's name
indicates, LayerName[] is the NULL terminated name of the layer.
Flags is a bit field who's bits are set according to the #defines
below:
#define LF_ACTIVE 0x01 /* Active for editing */
#define LF_DISPLAYED 0x02 /* Displayed on the screen */
If the LF_ACTIVE bit is set, this layer is unlocked. A set
LF_DISPLAYED bit indicates that this layer is currently visible on the
screen. A cleared LF_DISPLAYED bit implies that LF_ACTIVE is not set.
The reason for this is to keep the user from accidentally editing
layers that are invisible.
The Object Attribute Chunks
ATTR (0x41545452) /* Object attributes */
The ATTR chunk sets various attributes for the objects that follow it.
The attributes stay in effect until the next ATTR changes the
attributes, or the enclosing FORM ends, whichever comes first.
/* Various fill types */
#define FT_NONE 0 /* No fill */
#define FT_COLOR 1 /* Fill with color from palette */
#define FT_OBJECTS 2 /* Fill with tiled objects */
struct ATTRstruct {
ULONG ID;
ULONG Size;
UBYTE FillType; /* One of FT_*, above */
UBYTE JoinType; /* One of JT_*, below */
UBYTE DashPattern; /* ID of edge dash pattern */
UBYTE ArrowHead; /* ID of arrowhead to use */
USHORT FillValue; /* Color or object with which to fill */
USHORT EdgeValue; /* Edge color index */
USHORT WhichLayer; /* ID of layer it's in */
IEEE EdgeThick; /* Line width */
};
FillType specifies what kind of fill to use on this ATTR chunk's
objects. A value of FT_NONE means that this ATTR chunk's objects are
not filled. FT_COLOR indicates that the objects should be filled in
with a color. That color's ID (from the CMAP chunk) is stored in the
FillValue field. If FillType is equal to FT_OBJECTS, FillValue
contains the ID of a fill pattern defined in a FILL chunk.
JoinType determines which style of line join to use when connecting
the edges of line segments. The field contains one of these four
values:
/* Join types */
#define JT_NONE 0 /* Don't do line joins */
#define JT_MITER 1 /* Mitered join */
#define JT_BEVEL 2 /* Beveled join */
#define JT_ROUND 3 /* Round join */
DashPattern and ArrowHead contain the ID of the dash pattern and arrow
head for this ATTR's objects. A DashPattern of zero means that there
is no dash pattern so lines will be invisible. If ArrowHead is 0,
OPLYs have no arrow head. EdgeValue is the color of the line
segments. WhichLayer contains the ID of the layer this ATTR's objects
are in. EdgeThick is the width of this ATTR's line segments.
BBOX (0x42424F48) /* Bounding box of next object in FORM */
The BBOX chunk supplies the dimensions and position of a bounding box
surrounding the DR2D object that follows this chunk in the FORM. A
BBOX chunk can apply to a FILL or AROW as well as a DR2D object. The
BBOX chunk appears just before its DR2D object, FILL, or AROW chunk.
struct BBOXstruct {
ULONG ID;
ULONG Size;
IEEE XMin, YMin, /* Bounding box of obj. */
XMax, YMax; /* including line width */
};
In a Cartesian coordinate system, the point (XMin, YMin) is the
coordinate of the lower left hand corner of the bounding box and
(XMax, YMax) is the upper right. These coordinates take into
consideration the width of the lines making up the bounding box.
XTRN (0x5854524E) /* Externally controlled object */
The XTRN chunk was created primarily to allow ProVector to link DR2D
objects to ARexx functions.
struct XTRNstruct {
ULONG ID;
ULONG Size;
short ApplCallBacks; /* From #defines, below */
short ApplNameLength;
char ApplName[ApplNameLength]; /* Name of ARexx func to call */
};
ApplName[] contains the name of the ARexx script ProVector calls when
the user manipulates the object in some way. The ApplCallBacks field
specifies the particular action that triggers calling the ARexx script
according to the #defines listed below.
/* Flags for ARexx script callbacks */
#define X_CLONE 0x0001 /* The object has been cloned */
#define X_MOVE 0x0002 /* The object has been moved */
#define X_ROTATE 0x0004 /* The object has been rotated */
#define X_RESIZE 0x0008 /* The object has been resized */
#define X_CHANGE 0x0010 /* An attribute (see ATTR) of the
object has changed */
#define X_DELETE 0x0020 /* The object has been deleted */
#define X_CUT 0x0040 /* The object has been deleted, but
stored in the clipboard */
#define X_COPY 0x0080 /* The object has been copied to the
clipboard */
#define X_UNGROUP 0x0100 /* The object has been ungrouped */
For example, given the XTRN object:
FORM xxxx DR2D {
XTRN xxxx { X_RESIZE | X_MOVE, 10, "Dimension" }
ATTR xxxx { 0, 0, 1, 0, 0, 0, 0.0 }
FORM xxxx DR2D {
GRUP xxxx { 2 }
STXT xxxx { 0, 0.5, 1.0, 6.0, 5.0, 0.0, 4, "3.0" }
OPLY xxxx { 2, { 5.5, 5.5, 8.5, 5.5 } }
}
}
ProVector would call the ARexx script named Dimension if the user
resized or moved this object. What exactly ProVector sends depends
upon what the user does to the object. The following list shows what
string(s) ProVector sends according to which flag(s) are set. The
parameters are described below.
X_CLONE ``appl CLONE objID dx dy''
X_MOVE ``appl MOVE objID dx dy''
X_ROTATE ``appl ROTATE objID cx cy angle''
X_RESIZE ``appl RESIZE objID cx cy sx sy''
X_CHANGE ``appl CHANGE objID et ev ft fv ew jt fn''
X_DELETE ``appl DELETE objID''
X_CUT ``appl CUT objID''
X_COPY ``appl COPY objID''
X_UNGROUP ``appl UNGROUP objID''
where:
appl is the name of the ARexx script
CLONE, MOVE, ROTATE, RESIZE, etc. are literal strings
objID is the object ID that ProVector assigns to this object
(dx, dy) is the position offset of the CLONE or MOVE
(cx, cy) is the point around which the object is rotated or resized
angle is the angle (in degrees) the object is rotated
sx and sy are the scaling factors in the horizontal and
vertical directions, respectively.
et is the edge type (the dash pattern index)
ev is the edge value (the edge color index)
ft is the fill type
fv is the fill index
ew is the edge weight
jt is the join type
fn is the font name
The X_CHANGE message reflects changes to the attributes found in the
ATTR chunk.
If the user resized the XTRN object shown above by factor of 2,
ProVector would call the ARexx script Dimension like this:
Dimension RESIZE 1985427 7.0 4.75 2.0 2.0
The Object Chunks
The following chunks define the objects available in the DR2D FORM.
VBM (0x56424D20) /* Virtual BitMap */
The VBM chunk contains the position, dimensions, and file name of an
ILBM image.
struct VBMstruct {
IEEE XPos, YPos, /* Virtual coords */
XSize, YSize, /* Virtual size */
Rotation; /* in degrees */
USHORT PathLen; /* Length of dir path */
char Path[PathLen]; /* Null-terminated path of file */
};
The coordinate (XPos, YPos) is the position of the upper left hand
corner of the bitmap and the XSize and YSize fields supply the x and y
dimensions to which the image should be scaled. Rotation tells how
many degrees to rotate the ILBM around its upper left hand corner.
ProVector does not currently support rotation of bitmaps and will
ignore this value. Path contains the name of the ILBM file and may
also contain a partial or full path to the file. DR2D readers should
not assume the path is correct. The full path to an ILBM on one
system may not match the path to the same ILBM on another system. If
a DR2D reader cannot locate an ILBM file based on the full path name
or the file name itself (looking in the current directory), it should
ask the user where to find the image.
CPLY (0x43504C59) /* Closed polygon */
OPLY (0x4F504C59) /* Open polygon */
Polygons are the basic components of almost all 2D objects in the DR2D
FORM. Lines, squares, circles, and arcs are all examples of DR2D
polygons. There are two types of DR2D polygons, the open polygon
(OPLY) and the closed polygon (CPLY). The difference between a closed
and open polygon is that the computer adds a line segment connecting
the endpoints of a closed polygon so that it is a continuous path. An
open polygon's endpoints do not have to meet, like the endpoints of a
line segment.
struct POLYstruct {
ULONG ID;
ULONG Size;
USHORT NumPoints;
IEEE PolyPoints[2*NumPoints];
};
The NumPoints field contains the number of points in the polygon and
the PolyPoints array contains the (X, Y) coordinates of the points of
the non-curved parts of polygons. The even index elements are X
coordinates and the odd index elements are Y coordinates.
[Figure 3 - Bezier curves]
DR2D uses Bezier cubic sections, or cubic splines, to describe curves
in polygons. A set of four coordinates (P1 through P4) defines the
shape of a cubic spline. The first coordinate (P1) is the point where
the curve begins. The line from the first to the second coordinate
(P1 to P2) is tangent to the curve at the first point. The line from
P3 to P4 is tangent to the cubic section, where it ends at P4.
The coordinates describing the cubic section are stored in the
PolyPoints[] array with the coordinates of the normal points. DR2D
inserts an indicator point before a set of cubic section points to
differentiate a normal point from the points that describe a curve.
An indicator point has an X value of 0xFFFFFFFF. The indicator
point's Y value is a bit field. If this bit field's low-order bit is
set, the points that follow the indicator point make up a cubic
section.
The second lowest order bit in the indicator point's bit field is the
MOVETO flag. If this bit is set, the point (or set of cubic section
points) starts a new polygon, or subpolygon. This subpolygon will
appear to be completely separate from other polygons but there is an
important connection between a polygon and its subpolygon.
Subpolygons make it possible to create holes in polygons. An example
of a polygon with a hole is the letter ``O''. The ``O'' is a filled
circular polygon with a smaller circular polygon within it. The
reason the inner polygon isn't covered up when the outer polygon is
filled is that DR2D fills are done using the even-odd rule.
The even-odd rule determines if a point is ``inside'' a polygon by
drawing a ray outward from that point and counting the number of path
segments the ray crosses. If the number is even, the point is outside
the object and shouldn't be filled. Conversely, an odd number of
crossings means the point is inside and should be filled. DR2D only
applies the even-odd rule to a polygon and its subpolygons, so no
other objects are considered in the calculations.
Taliesin, Inc. supplied the following algorithm to illustrate the
format of DR2D polygons. OPLYs, CPLYs, AROWs, and ProVector's outline
fonts all use the same format:
typedef union {
IEEE num;
LONG bits;
} Coord;
#define INDICATOR 0xFFFFFFFF
#define IND_SPLINE 0x00000001
#define IND_MOVETO 0x00000002
/* A common pitfall in attempts to support DR2D has
been to fail to recognize the case when an
INDICATOR point indicates the following
coordinate to be the first point of BOTH a
Bezier cubic and a sub-polygon, ie. the
value of the flag = (IND_CURVE | IND_MOVETO) */
Coord Temp0, Temp1;
int FirstPoint, i, Increment;
/* Initialize the path */
NewPath();
FirstPoint = 1;
/* Draw the path */
i = 0;
while( i < NumPoints ) {
Temp0.num = PolyPoints[2*i]; Temp1.num = PolyPoints[2*i + 1];
if( Temp0.bits == INDICATOR ) {
/* Increment past the indicator */
Increment = 1;
if( Temp1.bits & IND_MOVETO ) {
/* Close and fill, if appropriate */
if( ID == CPLY ) {
FillPath();
}
else {
StrokePath();
}
/* Set up the new path */
NewPath();
FirstPoint = 1;
}
if( Temp1.bits & IND_CURVE ) {
/* The next 4 points are Bezier cubic control points */
if( FirstPoint )
MoveTo( PolyPoints[2*i + 2], PolyPoints[2*i + 3] );
else
LineTo( PolyPoints[2*i + 2], PolyPoints[2*i + 3] );
CurveTo( PolyPoints[2*i + 4], PolyPoints[2*i + 5],
PolyPoints[2*i + 6], PolyPoints[2*i + 7],
PolyPoints[2*i + 8], PolyPoints[2*i + 9] );
FirstPoint = 0;
/* Increment past the control points */
Increment += 4;
}
}
else {
if( FirstPoint )
MoveTo( PolyPoints[2*i], PolyPoints[2*i + 1] );
else
LineTo( PolyPoints[2*i], PolyPoints[2*i + 1] );
FirstPoint = 0;
/* Increment past the last endpoint */
Increment = 1;
}
/* Add the increment */
i += Increment;
}
/* Close the last path */
if( ID == CPLY ) {
FillPath();
}
else {
StrokePath();
}
GRUP (0x47525550) /* Group */
The GRUP chunk combines several DR2D objects into one. This chunk is
only valid inside nested DR2D FORMs, and must be the first chunk in
the FORM.
struct GROUPstruct {
ULONG ID;
ULONG Size;
USHORT NumObjs;
};
The NumObjs field contains the number of objects contained in this
group. Note that the layer of the GRUP FORM overrides the layer of
objects within the GRUP. The following example illustrates the layout
of the GRUP (and FILL) chunk.
FORM { DR2D /* Top-level drawing... */
DRHD { ... } /* Confirmed by presence of DRHD chunk */
CMAP { ... } /* Various other things... */
FONS { ... }
FORM { DR2D /* A nested form... */
FILL { 1 } /* Ah! The fill-pattern table */
CPLY { ... } /* with only 1 object */
}
FORM { DR2D /* Yet another nested form */
GRUP { ..., 3 } /* Ah! A group of 3 objects */
TEXT { ... }
CPLY { ... }
OPLY { ... }
}
FORM { DR2D /* Still another nested form */
GRUP { ..., 2 } /* A GRUP with 2 objects */
OPLY { ... }
TEXT { ... }
}
}
STXT (0x53545854) /* Simple text */
The STXT chunk contains a text string along with some information on
how and where to render the text.
struct STXTstruct {
ULONG ID;
ULONG Size;
UBYTE Pad0; /* Always 0 (for future expansion) */
UBYTE WhichFont; /* Which font to use */
IEEE CharW, CharH, /* W/H of an individual char */
BaseX, BaseY, /* Start of baseline */
Rotation; /* Angle of text (in degrees) */
USHORT NumChars;
char TextChars[NumChars];
};
The text string is in the character array, TextChars[]. The ID of the
font used to render the text is WhichFont. The font's ID is set in a
FONS chunk. The starting point of the baseline of the text is (BaseX,
BaseY). This is the point around which the text is rotated. If the
Rotation field is zero (degrees), the text's baseline will originate
at (BaseX, BaseY) and move to the right. CharW and CharH are used to
scale the text after rotation. CharW is the average character width
and CharH is the average character height. The CharW/H fields are
comparable to an X and Y font size.
TPTH (0x54505448) /* A text string along a path */
This chunk defines a path (polygon) and supplies a string to render
along the edge of the path.
struct TPTHstruct {
ULONG ID;
ULONG Size;
UBYTE Justification; /* see defines, below */
UBYTE WhichFont; /* Which font to use */
IEEE CharW, CharH; /* W/H of an individual char */
USHORT NumChars; /* Number of chars in the string */
USHORT NumPoints; /* Number of points in the path */
char TextChars[NumChars];/* PAD TO EVEN #! */
IEEE Path[2*NumPoints]; /* The path on which the text lies */
};
WhichFont contains the ID of the font used to render the text.
Justification controls how the text is justified on the line.
Justification can be one of the following values:
#define J_LEFT 0x00 /* Left justified */
#define J_RIGHT 0x01 /* Right justified */
#define J_CENTER 0x02 /* Center text */
#define J_SPREAD 0x03 /* Spread text across path */
CharW and CharH are the average width and height of the font
characters and are akin to X and Y font sizes, respectively. A
negative FontH implies that the font is upsidedown. Note that CharW
must not be negative. NumChars is the number of characters in the
TextChars[] string, the string containing the text to be rendered.
NumPoints is the number of points in the Path[] array. Path[] is the
path along which the text is rendered. The path itself is not
rendered. The points of Path[] are in the same format as the points
of a DR2D polygon.
A Simple DR2D Example
Here is a (symbolic) DR2D FORM:
FORM { DR2D
DRHD 16 { 0.0, 0.0, 10.0, 8.0 }
CMAP 6 { 0,0,0, 255,255,255 }
FONS 9 { 1, 0, 1, 0, "Roman" } 0
DASH 12 { 1, 2, {1.0, 1.0} }
ATTR 14 { 0, 0, 1, 0, 0, 0, 0, 0.0 }
BBOX 16 { 2.0, 2.0, 8.0, 6.0 }
FORM { DR2D
GRUP 2 { 2 }
BBOX 16 { 3.0, 4.0, 7.0, 5.0 }
STXT 36 { 0,1, 0.5, 1.0, 3.0, 5.0, 0.0, 12, "Hello, World" }
BBOX 16 { 2.0, 2.0, 8.0, 6.0 }
OPLY 42 { 5, {2.0,2.0, 8.0,2.0, 8.0,6.0, 2.0,6.0, 2.0,2.0 }
}
}
[Figure 4 - Simple DR2D drawing]
The OFNT FORM
OFNT (0x4F464E54) /* ID of outline font file */
ProVector's outline fonts are stored in an IFF FORM called OFNT. This
IFF is a separate file from a DR2D. DR2D's FONS chunk refers only to
fonts defined in the OFNT form.
OFHD (0x4F464844) /* ID of OutlineFontHeaDer */
This chunk contains some basic information on the font.
struct OFHDstruct {
char FontName[32]; /* Font name, null padded */
short FontAttrs; /* See FA_*, below */
IEEE FontTop, /* Typical height above baseline */
FontBot, /* Typical descent below baseline */
FontWidth; /* Typical width, i.e. of the letter O */
};
#define FA_BOLD 0x0001
#define FA_OBLIQUE 0x0002
#define FA_SERIF 0x0004
The FontName field is a NULL terminated string containing the name of
this font. FontAttrs is a bit field with flags for several font
attributes. The flags, as defined above, are bold, oblique, and
serif. The unused higher order bits are reserved for later use. The
other fields describe the average dimensions of the characters in this
font. FontTop is the average height above the baseline, FontBot is
the average descent below the baseline, and FontWidth is the average
character width.
KERN (0x4B45524C) /* Kerning pair */
The KERN chunk describes a kerning pair. A kerning pair sets the
distance between a specific pair of characters.
struct KERNstruct {
short Ch1, Ch2; /* The pair to kern (allows for 16 bits...) */
IEEE XDisplace, /* Amount to displace -left +right */
YDisplace; /* Amount to displace -down +up */
};
The Ch1 and Ch2 fields contain the pair of characters to kern. These
characters are typically stored as ASCII codes. Notice that OFNT
stores the characters as a 16-bit value. Normally, characters are
stored as 8-bit values. The wary programmer will be sure to cast
assigns properly to avoid problems with assigning an 8-bit value to a
16-bit variable. The remaining fields, XDisplace and YDisplace,
supply the baseline shift from Ch1 to Ch2.
CHDF (0x43484446) /* Character definition */
This chunk defines the shape of ProVector's outline fonts.
struct CHDFstruct {
short Ch; /* The character we're defining (ASCII) */
short NumPoints; /* The number of points in the definition */
IEEE XWidth, /* Position for next char on baseline - X */
YWidth; /* Position for next char on baseline - Y */
/* IEEE Points[2*NumPoints]*/ /* The actual points */
};
#define INDICATOR 0xFFFFFFFF /* If X == INDICATOR, Y is an action */
#define IND_SPLINE 0x00000001 /* Next 4 pts are spline control pts */
#define IND_MOVETO 0x00000002 /* Start new subpoly */
#define IND_STROKE 0x00000004 /* Stroke previous path */
#define IND_FILL 0x00000008 /* Fill previous path */
Ch is the value (normally ASCII) of the character outline this chunk
defines. Like Ch1 and Ch2 in the KERN chunk, Ch is stored as a 16-bit
value. (XWidth,YWidth) is the offset to the baseline for the
following character. OFNT outlines are defined using the same method
used to define DR2D's polygons (see the description of OPLY/CPLY for
details).
Because the OFNT FORM does not have an ATTR chunk, it needed an
alternative to make fills and strokes possible. There are two extra
bits used in font indicator points not found in polygon indicator
points, the IND_STROKE and IND_FILL bits (see defines above). These
two defines describe how to render the current path when rendering
fonts.
The current path remains invisible until the path is either filled
and/or stroked. When the IND_FILL bit is set, the currently defined
path is filled in with the current fill pattern (as specified in the
current ATTR chunk). A set IND_STROKE bit indicates that the
currently defined path itself should be rendered. The current ATTR's
chunk dictates the width of the line, as well as several other
attributes of the line. These two bits apply only to the OFNT FORM
and should not be used in describing DR2D polygons.
Fantavision movie format
FORM FANT
/*********************************************************************/
/* **
** - FantForm.h **
** **
** This is the IFF movie format for Amiga Fantavision. **
** **
** (c) Copyright 1988 Broderbund Software **
** **
** - FORMAT FROZED May 5, 1988 - **
** **
** Implemented by Steve Hales **
** **
** Overvue - **
** This is a description of the format used for Amiga **
** Fantavision. It assumes you have intimate knowledge of how **
** IFF-FORMs are constructed, layed out, and read. This file **
** can be used as a header file. This is fairly complete, but **
** I'm sure there are a few things missing. **
** **
** I can be reached in the following ways: **
** UseNet: Steve_A_Hales@cup.portal.com OR **
** sun!cup.portal.com!Steve_A_Hales **
** **
** US Mail: 882 Hagemann Drive **
** Livermore, CA, 94550-2420 **
** **
** Phone: (415) 449-5297 **
** **
** NOTE: I cannot, by contract, give out any code to load or **
** play Fantavision movies. If that is want you want **
** then you will need to contact Broderbund Software **
** directly. Their number is (415) 492-3200. **
** **
** Enjoy! Aloha. **
** */
/*********************************************************************/
/* Misc Fantavision structures
*/
typedef struct Rect
{
int left, top, right, bottom;
};
typedef struct Point
{
int h, v;
};
/* Frame opcodes */
#define opNEXT 0 /* go on to next frame */
#define opREPEAT 1 /* repeat sequence starting from frame Parm rep1 times */
#define opGOTO 2 /* goto frame Parm */
/* Frame modes */
#define fNORMAL 0x0000 /* redraw every frame */
#define fTRACE 0x0001 /* draw into both paged screens */
#define fLIGHTNING 0x0020 /* don't erase background */
/* Fantavision FORM defines
*/
#define ID_FANT 'FANT' /* FORM type */
#define ID_FHDR 'FHDR' /* Movie Header */
#define ID_FRAM 'FRAM' /* Format info for a Frame */
#define ID_POLY 'POLY' /* Format info for a Polygon */
#define ID_CSTR 'CSTR' /* \0 terminated string */
/* Polygon modes */
#define pTYPEMASK 0x00FF /* type mask to get just type of poly */
#define pSELECT 0x8000 /* is object selected? */
#define pOUTLINE 0x4000 /* outlined polygon using DotModeSide to
** determine when to not connect a line.
** ex. 0 draws on all sides, 1 will draw on
** everyother side, 2 will leave every second
** side blank, 3 will every third side
** blank, etc. */
#define pBACKDROP 0x2000 /* polygon will be dropped into the background
** during animation. */
#define pMSKBITMAP 0x1000 /* bitmap has a mask */
/* Polygon types */
#define pDELETE 0x7000 /* object is a filler (its deleted from display) */
#define pFILLED 0 /* filled polygon */
#define pLINE 1 /* not-connected line polygon */
#define pLINED 2 /* connected line polygon */
#define pTEXTBLOCK 3 /* text block to draw */
#define pCIRCLEDOT 4 /* draw circle dots at vertex's using
** dotSize at size. */
#define pRECTDOT 5 /* draw square dots at vertex's using
** dotSize at size. */
#define pBITMAPDOT 6 /* draw dots using a bitmap at vertex's using
** BitMap. */
#define pBITMAP 7 /* draw just bitmap image */
/* These are used for the pTEXTBLOCK polygon type
*/
/* Text justification
*/
#define tLEFT 0
#define tCENTER 1
#define tRIGHT 2
/* Text style
*/
#define tNORMAL (int)(FS_NORMAL)
#define tBOLD (int)(FSF_BOLD)
#define tITALIC (int)(FSF_ITALIC)
#define tUNDERLINE (int)(FSF_UNDERLINED)
#define tEXTENDED (int)(FSF_EXTENDED)
/* Fantavision movie header -
**
** This header defines how much RAM is needed, how many frames, and sounds
** in the movie.
*/
typedef struct FantHeader
{
int PointsPerObj; /* number of vertexs per object */
int ObjsPerFrame; /* number of objects per frame */
int ScreenDepth; /* 0 to 6, for number of bit planes */
int ScreenWidth; /* in pixels */
int ScreenHeight; /* in pixels */
int BackColor; /* background color palette number */
long SizeOfMovie; /* RAM Size of movie, expanded */
int pad[30]; /* padding for expanding */
int NumberOfFrames;
int NumberOfSounds;
int NumberOfBitMaps;
int Background; /* non-zero if first bitmap is a background */
int SpeedOfMovie; /* 100 is normal speed, 50 is half speed, etc */
int pad[3]; /* expansion */
};
/* Fantavision frame info -
**
** Each frame has this structure defined.
*/
typedef struct FrameFormat
{
int OpCode; /* Frame opcode */
long Parm; /* contains frame number for opNEXT, opREPEAT */
char Rep1, Rep2; /* Rep1 is repeat counter, Rep2 is not used */
int TweenRate; /* number of tweens per frame */
int ChannelIndex[2]; /* -3 stop sound is this channel
** -2 modify current sound
** -1 no sound for this channel
** (all others) is an index into the sound
** list. Which sound to use.
*/
int NumberOfPolys; /* number of polygons in this frame */
int ColorPalette[32]; /* xRGB - format 4 bits per register */
int Pan, Tilt; /* 0 is centered, (+-) amounts are in pixels */
int Modes; /* Frame modes */
int pad; /* expansion */
};
/* Fantavision polygon info -
**
** Each polygon has this structure defined.
*/
typedef struct PolyFormat
{
int NumberOfPoints; /* how many vertexs for this polygon */
int Type; /* polygon type */
int Color; /* palette color number (see note 1) */
Rect Bounds; /* enclosing rectangle of polygon */
int Depth; /* polygon view depth (see note 2) */
char DotModeSize; /* in pixels, not larger than 40 */
char DotModeSide; /* determines outlining features */
int OutlineColor; /* palette color number for outline */
int BitMapIndex; /* if not -1, then bitmap index into bitmap list */
int BMRealWidth; /* in pixels */
int BMRealHeight;
int TextLength; /* length of text for pTEXTBLOCK */
int TextJust;
char TextSize; /* size in pixels */
char TextStyle;
long pad; /* expansion */
Point p[]; /* array of points defining vertexs */
};
/* Fantavision high-level IFF format.
**
FORM FANT
FHDR
- background -
FORM ILBM if Background is non-zero
BMHD
BODY
- bitmap list -
NOTE: If a bitmap has a mask, it will be compute during load time.
FORM ILBM times NumberOfBitMaps
BMHD
BODY
- sound list -
{ FORM 8SVX times NumberOfSounds
VHDR
BODY
SEFX } Default parameters for sound
- frame list -
{ FRAM times NumberOfFrames
SEFX if sound for channel 1.
SEFX if sound for channel 2.
POLY times NumberOfPolys
{ CSTR Text of poly if PolyType = pTEXTBLOCK
CSTR } } Name of font
*/
/******- NOTES -**********************************************************/
/*
** 1 - The color palette is a number from 0 to 1120. The first 32 numbers
** are normal RGB colors, but the rest index into a pre-defined
** set of patterns.
**
** 2 - The view depth of each polygon determines the display order. The
** higher the number the closer the polygon is to the viewer. During
** editing, each polygon is assigned numbers in multiplies of 100,
** but to function, any number can work.
*/
Flow
TITLE: HEAD (FORM used by Flow - New Horizons Software, Inc.)
IFF FORM / CHUNK DESCRIPTION
============================
Form/Chunk ID: FORM HEAD, Chunks NEST, TEXT, FSCC
Date Submitted: 03/87
Submitted by: James Bayless - New Horizons Software, Inc.
FORM
====
FORM ID: HEAD
FORM Description:
FORM HEAD is the file storage format of the Flow idea processor
by New Horizons Software, Inc. Currently only the TEXT and NEST
chunks are used. There are plans to incorporate FSCC and some
additional chunks for headers and footers.
CHUNKS
======
CHUNK ID: NEST
This chunk consists of only of a word (two byte) value that gives
the new current nesting level of the outline. The initial nesting level
(outermost level) is zero. It is necessary to include a NEST chunk only
when the nesting level changes. Valid changes to the nesting level are
either to decrease the current value by any amount (with a minimum of 0)
or to increase it by one (and not more than one).
CHUNK ID: TEXT
This chunk is the actual text of a heading. Each heading has a TEXT
chunk (even if empty). The text is not NULL terminated - the chunk
size gives the length of the heading text.
CHUNK ID: FSCC
This chunk gives the Font/Style/Color changes in the heading from the
most recent TEXT chunk. It should occur immediately after the TEXT chunk
it modifies. The format is identical to the FSCC chunk for the IFF
form type 'WORD' (for compatibility), except that only the 'Location'
and 'Style' values are used (i.e., there can be currently only be style
changes in an outline heading). The structure definition is:
typedef struct {
UWORD Location; /* Char location of change */
UBYTE FontNum; /* Ignored */
UBYTE Style; /* Amiga style bits */
UBYTE MiscStyle; /* Ignored */
UBYTE Color; /* Ignored */
UWORD pad; /* Ignored */
} FSCChange;
The actual chunk consists of an array of these structures, one entry
for each Style change in the heading text.
Color Lookup Table
TITLE: CLUT IFF chunk proposal
"CLUT" IFF 8-Bit Color Look Up Table
Date: July 2, 1989
From: Justin V. McCormick
Status: Public Proposal
Supporting Software: FG 2.0 by Justin V. McCormick for PP&S
Introduction:
This memo describes the IFF supplement for the new chunk "CLUT".
Description:
A CLUT (Color Look Up Table) is a special purpose data module
containing table with 256 8-bit entries. Entries in this table
can be used directly as a translation for one 8-bit value to
another.
Purpose:
To store 8-bit data look up tables in a simple format for
later retrieval. These tables are used to translate or bias
8-bit intensity, contrast, saturation, hue, color registers, or
other similar data in a reproducable manner.
Specifications:
/* Here is the IFF chunk ID macro for a CLUT chunk */
#define ID_CLUT MakeID('C','L','U','T')
/*
* Defines for different flavors of 8-bit CLUTs.
*/
#define CLUT_MONO 0L /* A Monochrome, contrast or intensity LUT */
#define CLUT_RED 1L /* A LUT for reds */
#define CLUT_GREEN 2L /* A LUT for greens */
#define CLUT_BLUE 3L /* A LUT for blues */
#define CLUT_HUE 4L /* A LUT for hues */
#define CLUT_SAT 5L /* A LUT for saturations */
#define CLUT_UNUSED6 6L /* How about a Signed Data flag */
#define CLUT_UNUSED7 7L /* Or an Assumed Negative flag */
/* All types > 7 are reserved until formally claimed */
#define CLUT_RESERVED_BITS 0xfffffff8L
/* The struct for Color Look-Up-Tables of all types */
typedef struct
{
ULONG type; /* See above type defines */
ULONG res0; /* RESERVED FOR FUTURE EXPANSION */
UBYTE lut[256]; /* The 256 byte look up table */
} ColorLUT;
CLUT Example:
Normally, the CLUT chunk will appear after the BMHD of an FORM
ILBM before the BODY chunk, in the same "section" as CMAPs are
normally found. However, a FORM may contain only CLUTs with no
other supporting information.
As a general guideline, it is desirable to group all CLUTs
together in a form without other chunk types between them.
If you were using CLUTs to store RGB intensity corrections, you
would write three CLUTs in a row, R, G, then B.
Here is a box diagram for a 320x200x8 image stored as an IFF ILBM
with a single CLUT chunk for intensity mapping:
+-----------------------------------+
|'FORM' 64284 | FORM 64284 ILBM
+-----------------------------------+
|'ILBM' |
+-----------------------------------+
| +-------------------------------+ |
| | 'BMHD' 20 | | .BMHD 20
| | 320, 200, 0, 0, 8, 0, 0, ... | |
| | ------------------------------+ |
| | 'CLUT' 264 | | .CLUT 264
| | 0, 0, 0; 32, 0, 0; 64,0,0; .. | |
| +-------------------------------+ |
| +-------------------------------+ |
| |'BODY' 64000 | | .BODY 64000
| |0, 0, 0, ... | |
| +-------------------------------+ |
+-----------------------------------+
Design Notes:
-------------
I have deliberately kept this chunk simple (KISS) to
facilitate implementation. In particular, no provision is made
for expansion to 16-bit or 32-bit tables. My reasoning is that
a 16-bit table can have 64K entries, and thus would benefit from
data compression. My suggestion would be to propose another
chunk or FORM type better suited for large tables rather than
small ones like CLUT.
NewTek Dynamic HAM color
Newtek Dynamic Ham color chunks Newtek for Digiview IV (dynamic Ham) ILBM.DYCP - dynamic color palette 3 longwords (file setup stuff) ILBM.CTBL - array of words, one for each color (0rgb)
Dots per inch
ILBM DPI chunk
==============
Registered by:
Spencer Shanson
16 Genesta Rd
Plumstead
London SE18 3ES
ENGLAND
1-16-90
ILBM.DPI Dots Per Inch to allow output of an image at the
same resolution it was scanned at
typedef struct {
UWORD dpi_x;
UWORD dpi_y;
} DPIHeader ;
For example, an image scanned at horizontal resolution of
240dpi and vertical resolution of 300dpi would be saved as:
44504920 00000004 00F0 012C
D P I size dpi_x dpi_y
DPaint perspective
Form/Chunk ID: Chunk DPPV (DPaint II ILBM perspective chunk)
Date Submitted: 12/86
Submitted by: Dan Silva
Chunk Description:
The DPPV chunk describes the perspective state in a DPaintII ILBM.
Chunk Spec:
/* The chunk identifier DPPV */
#define ID_DPPV MakeID('D','P','P','V')
typedef LONG LongFrac;
typedef struct ( LongFrac x,y,z; ) LFPoint;
typedef LongFrac APoint[3];
typedef union {
LFPoint l;
APoint a;
} UPoint;
/* values taken by variable rotType */
#define ROT_EULER 0
#define ROT_INCR 1
/* Disk record describing Perspective state */
typedef struct {
WORD rotType; /* rotation type */
WORD iA, iB, iC; /* rotation angles (in degrees) */
LongFrac Depth; /* perspective depth */
WORD uCenter, vCenter; /* coords of center perspective,
* relative to backing bitmap,
* in Virtual coords
*/
WORD fixCoord; /* which coordinate is fixed */
WORD angleStep; /* large angle stepping amount */
UPoint grid; /* gridding spacing in X,Y,Z */
UPoint gridReset; /* where the grid goes on Reset */
UPoint gridBrCenter; /* Brush center when grid was last on,
* as reference point
*/
UPoint permBrCenter; /* Brush center the last time the mouse
* button was clicked, a rotation performed,
* or motion along "fixed" axis
*/
LongFrac rot[3][3]; /* rotation matrix */
} PerspState;
SUPPORTING SOFTWARE
===================
DPaint II by Dan Silva for Electronic Arts
DPaint IV enhanced color cycling
Submitted by Lee Taran
Purpose:
Enhanced Color Cycling Capabilities
-------------------------------------
* DPaintIV supports a new color cycling model which does NOT
require that color cycles contain a contiguous range of color
registers.
For example:
If your range looks like: [1][3][8][2]
then at each cycle tick
temp = [2],
[2] = [8],
[8] = [3],
[3] = [1],
[1] = temp
* You can now cycle a single register thru a series of rgb values.
For example:
If your range looks like: [1] [orange] [blue] [purple]
then at each cycle tick color register 1 will take on the
next color in the cycle.
ie: t=0: [1] = curpal[1]
t=1: [1] = purple
t=2: [1] = blue
t=3: [1] = orange
t=4: goto t=0
* You can combine rgb cycling with traditional color cycling.
For example:
Your range can look like:
[1] [orange] [blue] [2] [green] [yellow]
t=0: [1] = curpal[1], [2] = curpal[2]
t=1: [1] = yellow, [2] = blue
t=2: [1] = green, [2] = orange
t=3: [1] = curpal[2], [2] = curpal[1]
t=4: [1] = blue, [2] = yellow
t=5: [1] = orange, [2] = green
t=6: goto t=0
Note:
* DPaint will save out an old style range CRNG if the range fits
the CRNG model otherwise it will save out a DRNG chunk.
* no thought has been given (yet) to interlocking cycles
/* ---------------------------------------------------------------------
IFF Information: DPaintIV DRNG chunk
DRNG ::= "DRNG" # { DRange DColor* DIndex* }
a <cell> is where the color or register appears within the range
The RNG_ACTIVE flags is set when the range is cyclable. A range
should only have the RNG_ACTIVE if it:
1> contains at least one color register
2> has a defined rate
3> has more than one color and/or color register
If the above conditions are met then RNG_ACTIVE is a user/program
preference. If the bit is NOT set the program should NOT cycle the
range.
The RNG_DP_RESERVED flags should always be 0!!!
--------------------------------------------------------------------- */
typedef struct {
UBYTE min; /* min cell value */
UBYTE max; /* max cell value */
SHORT rate; /* color cycling rate, 16384 = 60 steps/second */
SHORT flags; /* 1=RNG_ACTIVE,4=RNG_DP_RESERVED */
UBYTE ntrue; /* number of DColor structs to follow */
UBYTE nregs; /* number of DIndex structs to follow */
} DRange;
typedef struct { UBYTE cell; UBYTE r,g,b; } DColor; /* true color cell */
typedef struct { UBYTE cell; UBYTE index; } DIndex; /* color register cell */
Encapsulated PostScript
Pixelations Kevin Saltzman 617-277-5414 Chunk to hold encapsulated postscript Used by PixelScript in their clip art. Holds a postscript representation of the ILBM's graphic image. EPSF length ; Bounding box WORD lowerleftx; WORD lowerlefty; WORD upperrightx; WORD upperrighty; CHAR [] ; ascii postscript file
Numerical data storage
Numerical data storage (MathVision - Seven Seas)
MTRX FORM, for matrix data storage 19-July-1990
Submitted by: Doug Houck
Seven Seas Software
(address, etc)
INTRODUCTION:
Numerical data, as it comes from the real world, is an ill-mannered beast.
Often much is assumed about the data, such as the number of dimensions,
formatting, compression, limits, and sizes. As such, data is not portable.
The MTRX FORM will both store the data, and completely describe its
format, such that programs no longer need to guess the parameters of
a data file. There needs to be but one program to read ascii files and
output MTRX IFF files.
A matrix, by our definition, is composed of three types of things.
Firstly, the atomic data, such as an integer, or floating point number.
Secondly, arrays, which are simply lists of things which are all the same.
Thirdly, structures, which are lists of things which are different.
Both arrays and structures may be composed of things besides atomic data -
they may contain other structures and arrays as well. This concept
of nesting structures may be repeated to any desired depth.
For example, a list of data pairs could be encoded as an array of structures,
where each structure contains two numbers. A two-dimensional array is
simply an array of arrays.
Since space conservation is often desirable, there is provision for
representing each number with fewer bits, and compressing the bits together.
CHUNKS
The MTRX FORM is composed of the definition of the structure, followed
by the BODY which contains the data which is defined. Usually, there
is only one set of data, but a smarter IFF read could use the definition
as a PROPerty, with identically formatted data sets (BODYs) in a LIST.
FORM MTRX
definition (ARRY | STRU | DTYP)
BODY
ARRY: The array chunk defines a counted list of similar items.
The first (required) chunk in an ARRY is ELEM, which gives the number
of elements in the array. Optionally, there may be limits given, (LOWR
and UPPR), which could be used in scaling during sampling of the data.
Lastly is the definition of an element of the array, which may be a
nested definition like everything else.
ARRY ::= "ARRY" #{ ELEM [LOWR] [UPPR] [PACK] ARRY|STRU|DTYP }
STRU: The structure chunk defines a counted list of dissimilar things.
The first (required) chunk in a STRU is FLDS, which gives the number
of fields in the structure. Lastly are definitions of each field
in the structure. Again, each field may have a nested definition like
everything else.
STRU ::= "STRU" #{ FLDS ([PACK] ARRY|STRU|DTYP)* }
VALU: The value contains a datatype, and then a constant of that type.
The datatype contains the size of the constant, so this chunk has variable
size. VALU is used in the ARRY chunk to give the scaling limits of the array.
BODY: This is the actual data we went to so much effort to describe.
It is stored in "row-first" format, that is, items at the bottom of the
nested description are stored next to each other. In most cases, it
should be sufficient to simply block-read the whole chunk from disk,
unless the reader needs to adjust byte-ordering or store in a more
time-efficient format in memory. Data is assumed to be byte-aligned.
PACK: The PACK chunk is necessary when the bit length of the data is
not a multiple of 8, that is, not byte-aligned, and the user wishes
to conserve space by packing data items together. PACK is simply a
number - the number of items to bit-pack before aligning on a byte.
A PACK is in effect for the remainder of its nested scope, or until
overridden by a new specification. A STRU or ARRY is assumed to have
a PACK of 1 by default - it is not affected by PACKs in definitions above.
A PACK of 0 means to byte-align before processing the next definition.
The PACK specifier should be normalized. For example, when packing a large
array of 3-bit numbers, PACK should be 8 since 3*8 = 24. In this case 8 is
the smallest PACK number which aligns on a byte naturally.
DTYP: The DataType is the most interesting chunk, as it attempts to define
every conceivable type of numeric data with 32 bits. The 32 bits are broken
down into three fields, 1) the size in bits, 2) the Class, and 3) SubClass.
The Class makes the most major distinction, separating integers from floating
point numbers from Binary Coded Decimal and etc. Within each class is a
SubClass, which gives the specific encoding used. Finally, the Size tells
what how much room the data occupies. The basic division of datatypes is
given in the tree structure below.
Class SubClass Size Final Specific Type
===== ======== ==== ===================
|
Binary Unsigned - 0 ------------ 8 UByte
| 16 UWord
| 32 ULong
|
Binary Signed --- 0 ------------ 8 Byte
| 16 Word
| 32 ULong
|
Real ------------Ieee38 -------- 32 Ieee Single Precision
| |
| Ieee308 ------- 64 Double Precision
| | 32 Truncated Double Precision
| |
| FFP ----------- 32 Motorola Fast Floating Point
|
Text ----------- Text0 --------- ?? Null-terminated text
| |
| CText --------- ?? Number of characters in first byte
| |
| FText --------- ?? Fixed length, space padded
|
BCD ------------ Nibble -------- ??
|
Character ----- ??
A design goal was to create a classification system which other people
can easily plug into. Many data types are simply size variations on
existing data types. For example, a 4-bit integer can be specified by
giving the size as four bits in the Signed Binary class. Be aware that
not all MTRX readers may support your new type, but there will not be
any type clashes or ambiguities by following these rules. If you have
a truly unique Class or SubClass, you will need to register it with
Commodore to prevent clashes.
A second design goal was to create a format which is easily decoded
by software. By aligning fields on bytes, you have the option of redefining
the datatype as a structure, so as to avoid shifting when accessing the
fields. Since the numbers are sequentially assigned, they are suitable
as array indicies, and may be optimized in a C switch statement.
A third design goal was allowing for naive and sophisticated readers.
In checking for a certain datatype, a naive reader can simply compare
the whole datatype with a small set of known types, which assumes that
each different Size defines a unique datatype. Sophisticated readers
will consider the Class, SubClass and Size separately, so as to support
arbitrary size integers, and truncated Floating Point numbers, for example.
*
* MTRX ::= "FORM" #{ "MTRX" ARRY|STRU|DTYP BODY } Matrix
* ARRY ::= "ARRY" #{ ELEM [LOWR] [UPPR] [PACK] ARRY|STRU|DTYP } Array
* STRU ::= "STRU" #{ FLDS ([PACK] ARRY|STRU|DTYP)* } Structure
* ELEM ::= "ELEM" #{ elements } Array elements
* LOWR ::= "LOWR" { VALU } Minimum limit
* UPPR ::= "UPPR" { VALU } Maximum limit
* VALU ::= #{ dtyp value } Value (in union)
* dtyp ::= { size, subclass, class } Data Type (scalar)
* DTYP ::= "DTYP" #{ dtyp }
* FLDS ::= "FLDS" #{ number of fields } Number of Fields
* PACK ::= "PACK" #{ units packed b4 byte alignment } Packing
* BODY ::= "BODY" #{ inner-first binary dump } Data
*
* [] means optional
* # means the size of the unit following
* * means one or more of
*
Program traceback
Program traceback (SAS Institute)
FORM PGTB
Proposal:
New IFF chunk type, to be named PGTB, meaning ProGram TraceBack.
Format:
'PGTB' - chunk identifier
length - longword for length of chunk
'FAIL' - subfield giving environment at time of crash
length - longword length of subfield
NameLen - length of program name in longwords (BSTR)
Name - program name packed in longwords
Environment - copy of AttnFlags field from ExecBase,
gives type of processor, and existence of
math chip
VBlankFreq - copy of VBlankFrequency field from ExecBase
PowerSupFreq - copy of PowerSupplyFrequency field from ExecBase
above fields may be used to determine whether
machine was PAL or NTSC
Starter - non-zero = CLI, zero = WorkBench
GURUNum - exception number of crash
SegCount - number of segments for program
SegList - copy of seglist for program
(Includes all seglist pointers, paired with
sizes of the segments)
'REGS' - register dump subfield
length - length of subfield in longwords
GURUAddr - PC at time of crash
Flags - copy of Condition Code Register
DDump - dump of data registers
ADump - dump of address registers
'VERS' - revision of program which created this file
length - length of subfield in longwords
version - main version of writing program
revision - minor revision level of writing program
TBNameLen - length of name of writing program
TBName - name of writing program packed in longwords (BSTR)
'STAK' - stack dump subfield
length - length of subfield in longwords
(type) - tells type of stack subfield, which can be any of
the following:
-----------------------------------------------------------
Info - value 0
StackTop - address of top of stack
StackPtr - stack pointer at time of crash
StackLen - number of longwords on stack
-----------------------------------------------------------
Whole stack - value 1
only used if total stack to be dumped is 8k
or less in size
Stack - dump of stack from current to top
-----------------------------------------------------------
Top 4k - value 2
if stack used larger than 8k, this part
is a dump of the top 4k
Stack - dump of stack from top - 4k to top
-----------------------------------------------------------
Bottom 4k - value 3
if stack used larger than 8k, this part
is a dump of the bottom 4k
Stack - dump of stack from current to current + 4k
In other words, we will dump a maximum of 8k of stack data. This
does NOT mean the stack must be less than 8k in size to dump the
entire stack, just that the amount of stack USED be less than 8k.
'UDAT' - Optional User DATa chunk. If the user assigns
a function pointer to the label "_ONGURU", the
catcher will call this routine prior to closing
the SnapShot file, passing one parameter on the
stack - an AmigaDOS file pointer to the SnapShot
file. Spec for the _ONGURU routine:
void <function name>(fp)
long fp;
In other words, your routine must be of type 'void'
and must take one parameter, an AmigaDOS file
handle (which AmigaDOS wants to see as a LONG).
length - length of the UserDATa chunk, calculated after the
user routine terminates.
DPaint IV perspective move
/* -----------------------------------------------------------------------
IFF Information:
PRSP ::= "FORM" # {"PSRP" MOVE }
MOVE ::= "MOVE" # { MoveState }
* ---------------------------------------------------------------------- */
typedef struct {
BYTE reserved; /* initialize to 0 */
BYTE moveDir; /* 0 = from point 1 = to point */
BYTE recordDir; /* 0 = FORWARD, 1 = STILL, 2 = BACKWARD */
BYTE rotationType; /* 0 = SCREEN_RELATIVE, 1 = BRUSH_RELATIVE */
BYTE translationType; /* 0 = SCREEN_RELATIVE, 1 = BRUSH_RELATIVE */
BYTE cyclic; /* 0 = NO, 1 = YES */
SHORT distance[3]; /* x,y,z distance displacement */
SHORT angle[3]; /* x,y,z rotation angles */
SHORT nframes; /* number of frames to move */
SHORT easeout; /* number of frames to ease out */
SHORT easein; /* number of frames to ease in */
} MoveState;
RGB image
FORM RGBN and FORM RGB8
-----------------------
RGBN and RGB8 files are used in Impulse's Turbo Silver and Imagine.
They are almost identical to FORM ILBM's except for the BODY chunk
and slight differences in the BMHD chunk.
A CAMG chunk IS REQUIRED.
The BMHD chunk specfies the number of bitplanes as 13 for type RGBN
and 25 for type RGB8, and the compression type as 4.
The FORM RGBN uses 12 bit RGB values, and the FORM RGB8 uses
24 bit RGB values.
The BODY chunk contains RGB values, a "genlock" bit, and repeat
counts. In Silver, when "genlock" bit is set, a "zero color" is
written into the bitplanes for genlock video to show through.
In Diamond and Light24 (Impulse 12 & 24 bit paint programs),
the genlock bit is ignored if the file is loaded as a picture
(and the RGB color is used instead), and if the file is loaded
as a brush the genlock bit marks pixels that are not part of
the brush.
For both RGBN and RGB8 body chunks, each RGB value always has a
repeat count. The values are written in different formats depending
on the magnitude of the repeat count.
For the RGBN BODY chunk:
For each RGB value, a WORD (16-bits) is written: with the
12 RGB bits in the MSB (most significant bit) positions;
the "genlock" bit next; and then a 3 bit repeat count.
If the repeat count is greater than 7, the 3-bit count is
zero, and a BYTE repeat count follows. If the repeat count
is greater than 255, the BYTE count is zero, and a WORD
repeat count follows. Repeat counts greater than 65536 are
not supported.
For the RGB8 body chunk:
For each RGB value, a LONG-word (32 bits) is written:
with the 24 RGB bits in the MSB positions; the "genlock"
bit next, and then a 7 bit repeat count.
In a previous version of this document, there appeared the
following line:
"If the repeat count is greater than 127, the same rules apply
as in the RGBN BODY."
But Impulse has never written more than a 7 bit repeat count,
and when Imagine and Light24 were written, they didn't support
reading anything but 7 bit counts.
Sample BODY code:
if(!count) {
if (Rgb8) {
fread (&w, 4, 1, RGBFile);
lock = w & 0x00000080;
rgb = w >> 8;
count = w & 0x0000007f;
} else {
w = (UWORD) getw (RGBFile);
lock = w & 8;
rgb = w >> 4;
count = w & 7;
}
if (!count)
if (!(count = (UBYTE) getc (RGBFile)))
count = (UWORD) getw (RGBFile);
}
The pixels are scanned from left to right across horizontal
lines, processing from top to bottom. The (12 or 24 bit) RGB
values are stored with the red bits as the MSB's, the green
bits next, and the blue bits as the LSB's.
Special note: As of this writing (Sep 88), Silver does NOT
support anything but black for color zero.
Sampled sound
IFF FORM "SAMP" Sampled Sound
Date: Dec 3,1989
From: Jim Fiore and Jeff Glatt, dissidents
The form "SAMP" is a file format used to store sampled sound data in some
ways like the current standard, "8SVX". Unlike "8SVX", this new format is not
restricted to 8 bit sample data. There can be more than one waveform per
octave, and the lengths of different waveforms do not have to be factors of
2. In fact, the lengths (waveform size) and playback mapping (which musical
notes each waveform will "play") are independently determined for each wave-
form. Furthermore, this format takes into account the MIDI sample dump stan-
dard (the defacto standard for musical sample storage), while also incorpo-
rating the ability to store Amiga specific info (for example, the sample data
that might be sent to an audio channel which is modulating another channel).
Although this form can be used to store "sound effects" (typically oneShot
sounds played at a set pitch), it is primarily intended to correct the many
deficiencies of the "8SVX" form in regards to musical sampling. Because the
emphasis is on musical sampling, this format relies on the MIDI (Musical
Instrument Digital Interface) method of describing "sound events" as does
virtually all currently manufactured, musical samplers. In addition, it at-
tempts to incorporate features found on many professional music samplers, in
anticipation that future Amiga models will implement 16 bit sampling, and
thus be able to achieve this level of performance. Because this format is
more complex than "8SVX", programming examples to demonstrate the use of this
format have been included in both C and assembly. Also, a library of func-
tions to read and write SAMP files is available, with example applications.
SEMANTICS: When MIDI literature talks about a sample, usually it means a
collection of many sample points that make up what we call a "wave".
=====SIMILARITIES AND DIFFERENCES FROM THE "8SVX" FORM=======
Like "8SVX", this new format uses headers to separate the various sections
of the sound file into chunks. Some of the chunks are exactly the same since
there wasn't a need to improve them. The chunks that remain unchanged are as
follows:
"(c) "
"AUTH"
"ANNO"
Since these properties are all described in the original "8SVX" document,
please refer to that for a description of these chunks and their uses. Like
the "8SVX" form, none of these chunks are required to be in a sound file.
If they do appear, they must be padded out to an even number of bytes.
Furthermore, two "8SVX" chunks no longer exist as they have been incorpo-
rated into the "BODY" chunk. They are:
"ATAK"
"RLSE"
Since each wave can be completely different than the other waves in the
sound file (one wave might be middle C on a piano, and another might be a
snare drum hit), it is necessary for each wave to have its own envelope de-
scription, and name.
The major changes from the "8SVX" format are in the "MHDR", "NAME", and
"BODY" chunks.
=================THE "SAMP" HEADER================
At the very beginning of a sound file is the "SAMP" header. This is used to
determine if the disk file is indeed a SAMP sound file. It's attributes are
as follows:
#define ID_SAMP MakeID('S','A','M','P')
In assembly, this looks like:
CNOP 0,2 ;word-align
SAMP dc.b 'SAMP'
sizeOfChunks dc.l [sizes of all subsequent chunks summed]
=================THE "MHDR" CHUNK=================
The required "MHDR" chunk immediately follows the "SAMP" header and consists
of the following components:
#define ID_MHDR MakeID('M','H','D','R')
/* MHDR size is dependant on the size of the imbedded PlayMap. */
typedef struct{
UBYTE NumOfWaves, /* The number of waves in this file */
Format, /* # of ORIGINAL significant bits from 8-28 */
Flags, /* Various bits indicate various functions */
PlayMode, /* determines play MODE of the PlayMap */
NumOfChans,
Pad,
PlayMap[128*4], /* a map of which wave numbers to use for
each of 128 possible Midi Notes. Default to 4 */
} MHDRChunk;
The PlayMap is an array of bytes representing wave numbers. There can be a
total of 255 waves in a "SAMP" file. They are numbered from 1 to 255. A wave
number of 0 is reserved to indicate "NO WAVE". The Midi Spec 1.0 designates
that there are 128 possible note numbers (pitches), 0 to 127. The size of an
MHDR's PlayMap is determined by (NumOfChans * 128). For example, if NumOfChans
= 4, then an MHDR's PlayMap is 512 bytes. There are 4 bytes in the PlayMap
for EACH of the 128 Midi Note numbers. For example, the first 4 bytes
in PlayMap pertain to Midi Note #0. Of those 4 bytes, the first byte is the
wave number to play back on Amiga audio channel 0. The second byte is the
wave number to play back on Amiga audio channel 1, etc. In this way, a single
Midi Note Number could simultaneously trigger a sound event on each of the 4
Amiga audio channels. If NumOfChans is 1, then the PlayMap is 128 bytes and
each midi note has only 1 byte in the PlayMap. The first byte pertains to midi
note #0, the second pertains to midi note #1, etc. In this case, a player
program might elect to simply play back the PlayMap wave number on any
available amiga audio channel. If NumOfChans = 0, then there is no imbedded
PlayMap in the MHDR, no midi note assignments for the waves, and an application
should play back waves on any channel at their default sampleRates.
In effect, the purpose of the PlayMap array is to determine which (if any)
waves are to be played back for each of the 128 possible Midi Note Numbers.
Usually, the MHDR's NumOfChans will be set to 4 since the Amiga has 4 audio
channels. For the rest of this document, the NumOfChans is assumed to be 4.
As mentioned, there can be a total of 255 waves in a "SAMP" file, numbered
from 1 to 255. A PlayMap wave number of 0 is reserved to indicate that NO WAVE
number should be played back. Consider the following example:
The first 4 bytes of PlayMap are 1,3,0,200.
If a sample playing program receives (from the serial port or another task
perhaps) Midi Note Number 0, the following should occur:
1) The sampler plays back wave 1 on Amiga audio channel
number 0 (because the first PlayMap byte is 1).
2) The sampler plays back wave 3 on Amiga audio channel
number 1 (because the second PlayMap byte is 3).
3) The sampler does not effect Amiga audio channel 2 in
any way (because the third PlayMap byte is a 0).
4) The sampler plays back wave 200 on Amiga audio channel
number 4 (because the fourth PlayMap byte is 200).
(This assumes INDEPENDANT CHANNEL play MODE to be discussed later in this
document.)
All four of the PlayMap bytes could even be the same wave number. This would
cause that wave to be output of all 4 Amiga channels simultaneously.
NumOfWaves is simply the number of waves in the sound file.
Format is the number of significant bits in every sample of a wave.
For example, if Format = 8, then this means that the sample data is an
8 bit format, and that every sample of the wave can be expressed by a single
BYTE. (A 16 bit sample would need a WORD for every sample point).
Each bit of the Flags byte, when set, means the following:
Bit #0 - File continued on another disc. This might occur if the SAMP file
was too large to fit on 1 floppy. The accepted practice (as incor-
porated by Yamaha's TX sampler and Casio's FZ-1 for example) is to
dump as much as possible onto one disc and set a flag to indicate
that more is on another disc's file. The name of the files must
be the related. The continuation file should have its own SAMP header
MHDR, and BODY chunks. This file could even have its continuation
bit set, etc. Never chop a sample wave in half. Always close the
file on 1 disc after the last wave which can be completely saved.
Resume with the next wave within the BODY of the continuation file.
Also, the NumOfWaves in each file's BODY should be the number saved
on that disc (not the total number in all combined disk files).
See the end of this document for filename conventions.
In C, here is how the PlayMap is used when receiving a midi note-on event:
MapOffset = (UBYTE) MidiNoteNumber * numOfChans;
/* MidiNoteNumber is the received note number (i.e. the second byte of a
midi note-on event. numOfChans is from the SAMP MHDR. */
chan0waveNum = (UBYTE) playMap[MapOffset];
chan1waveNum = (UBYTE) playMap[MapOffset+1];
chan2waveNum = (UBYTE) playMap[MapOffset+2];
chan3waveNum = (UBYTE) playMap[MapOffset+3];
if (chan0waveNum != 0)
{ /* get the pointer to wave #1's data, determine the values
that need to be passed to the audio device, and play this
wave on Amiga audio channel #0 (if INDEPENDANT PlayMode) */
}
/* do the same with the other 3 channel's wave numbers */
In assembly, the "MHDR" structure looks like this:
CNOP 0,2
MHDR dc.b 'MHDR'
sizeOfMHDR dc.l [this is 6 + (NumOfChans * 128) ]
NumOfWaves dc.b [a byte count of the # of waves in the file]
Format dc.b [a byte count of the # of significant bits in a sample point]
Flags dc.b [bit mask]
PlayMode dc.b [play MODE discussed later]
NumOfChans dc.b [# of bytes per midi note for PlayMap]
PlayMap ds.b [128 x NumOfChans bytes of initialized values]
and a received MidiNoteNumber is interpreted as follows:
moveq #0,d0
move.b MidiNoteNumber,d0 ;this is the received midi note #
bmi.s Illegal_Number ;exit, as this is an illegal midi note #
moveq #0,d1
move.b NumOfChans,d1
mulu.w d1,d0 ;MidiNoteNumber x NumOfChans
lea PlayMap,a0
adda.l d0,a0
move.b (a0)+,chan0waveNum
move.b (a0)+,chan1waveNum
move.b (a0)+,chan2waveNum
move.b (a0),chan3waveNum
tst.b chan0waveNum
beq.s Chan1
;Now get the address of this wave number's sample data, determine the
;values that need to be passed to the audio device, and output the wave's
;data on Amiga chan 0 (assuming INDEPENDANT PlayMode).
Chan1 tst.b chan1waveNum
beq.s Chan2
;do the same for the other wave numbers, etc.
=====================THE "NAME" CHUNK=========================
#define ID_NAME MakeID('N','A','M','E')
If a NAME chunk is included in the file, then EVERY wave must have a name.
Each name is NULL-terminated. The first name is for the first wave, and it
is immediately followed by the second wave's name, etc. It is legal for a
wave's name to be simply a NULL byte. For example, if a file contained 4
waves and a name chunk, the chunk might look like this:
CNOP 0,2
Name dc.b 'NAME'
sizeOfName dc.l 30
dc.b 'Snare Drum',0 ;wave 1
dc.b 'Piano 1',0 ;wave 2
dc.b 'Piano A4',0 ;wave 3
dc.b 0 ;wave 4
dc.b 0
NAME chunks should ALWAYS be padded out to an even number of bytes. (Hence
the extra NULL byte in this example). The chunk's size should ALWAYS be even
consequently. DO NOT USE the typical IFF method of padding a chunk out to an
even number of bytes, but allowing an odd number size in the header.
==============THE "BODY" CHUNK===============
The "BODY" chunk is CONSIDERABLY different than the "8SVX" form. Like all
chunks it has an ID.
#define ID_BODY MakeID('B','O','D','Y')
Every wave has an 80 byte waveHeader, followed by its data. The waveHeader
structure is as follows:
typedef struct {
ULONG WaveSize; /* total # of BYTES in the wave (MUST be even) */
UWORD MidiSampNum; /* ONLY USED for Midi Dumps */
UBYTE LoopType, /* ONLY USED for Midi Dumps */
InsType; /* Used for searching for a certain instrument */
ULONG Period, /* in nanoseconds at original pitch */
Rate, /* # of samples per second at original pitch */
LoopStart, /* an offset in BYTES (from the beginning of the
of the wave) where the looping portion of the
wave begins. Set to WaveSize if no loop. */
LoopEnd; /* an offset in BYTES (from the beginning of the
of the wave) where the looping portion of the
wave ends. Set to WaveSize if no loop. */
UBYTE RootNote, /* the Midi Note # that plays back original pitch */
VelStart; /* 0 = NO velocity effect, 128 =
negative direction, 64 = positive
direction (it must be one of these 3) */
UWORD VelTable[16]; /* contains 16 successive offset values
in BYTES from the beginning of the wave */
/* The ATAK and RLSE segments contain an EGPoint[] piece-wise
linear envelope just like 8SVX. The structure of an EGPoint[]
is the same as 8SVX. See that document for details. */
ULONG ATAKsize, /* # of BYTES in subsequent ATAK envelope.
If 0, then no ATAK data for this wave. */
RLSEsize, /* # of BYTES in subsequent RLSE envelope
If 0, then no RLSE envelope follows */
/* The FATK and FRLS segments contain an EGPoint[] piece-wise
linear envelope for filtering purposes. This is included in
the hope that future Amiga audio will incorporate a VCF
(Voltage Controlled Filter). Until then, if you are doing any
non-realtime digital filtering, you could store info here. */
sizeOfFATK, /* # of BYTES in FATK segment */
sizeOfFRLS, /* # of BYTES in FRLS segment */
USERsize; /* # of BYTES in the following data
segment (not including USERtype).
If zero, then no user data */
UWORD USERtype; /* See explanation below. If USERsize
= 0, then ignore this. */
/* End of the waveHeader. */
/* The data for any ATAK, RLSE, FATK, FRLS, USER, and the actual wave
data for wave #1 follows in this order:
Now list each EGPoint[] (if any) for the VCA's (Voltage Controlled Amp)
attack portion.
Now list each EGPoint[] for the VCA's (Voltage Controlled Amp)
release portion.
List EGPoints[] (if any) for FATK.
List EGPoints[] if any for FRLS */
Now include the user data here if there is any. Just pad it out
to an even number of bytes and have USERsize reflect that.
Finally, here is the actual sample data for the wave. The size (in BYTES)
of this data is WaveSize. It MUST be padded out to an even number of bytes. */
} WaveFormInfo;
/* END OF WAVE #1 */
/* The waveHeader and data for the next wave would now follow. It is
the same form as the first wave */
In assembly, the BODY chunk looks like this:
CNOP 0,2
BodyHEADER dc.b 'BODY'
sizeOfBody dc.l [total bytes in the BODY chunk not counting 8 byte header]
; Now for the first wave
WaveSize dc.l ;[total # of BYTES in this wave (MUST be even)]
MidiSampNum dc.w ;[from Midi Sample Dump] ; ONLY USED for Midi Dumps
LoopType dc.b ;[0 or 1] ; ONLY USED for Midi Dumps
InsType dc.b 0
Period dc.l ;[period in nanoseconds at original pitch]
Rate dc.l ;[# of samples per second at original pitch]
LoopStart dc.l ;[an offset in BYTES (from the beginning of the
; of the wave) to where the looping
; portion of the wave begins.]
LoopEnd dc.l ;[an offset in BYTES (from the beginning of the
; of the wave) to where the looping
; portion of the wave ends]
RootNote dc.b ;[the Midi Note # that plays back original pitch]
VelStart dc.b ;[0, 64, or 128]
VelTable dc.w ;[first velocity offset]
dc.w ;[second velocity offset]...etc
ds.w 14 ;...for a TOTAL of 16 velocity offsets
ATAKsize dc.l ;# of BYTES in subsequent ATAK envelope.
;If 0, then no ATAK data for this wave.
RLSEsize dc.l ;# of BYTES in subsequent RLSE envelope
;If 0, then no RLSE data
FATKsize dc.l ;# of BYTES in FATK segment
FRLSsize dc.l ;# of BYTES in FRLS segment
USERsize dc.l ;# of BYTES in the following User data
;segment (not including USERtype).
;If zero, then no user data
USERtype dc.w ; See explanation below. If USERsize
; = 0, then ignore this.
;Now include the EGpoints[] (data) for the ATAK if any
;Now the EGpoints for the RLSE
;Now the EGpoints for the FATK
;Now the EGpoints for the FLSR
;Now include the user data here if there is any. Just pad
;it out to an even number of bytes.
;After the userdata (if any) is the actual sample data for
;the wave. The size (in BYTES) of this segment is WaveSize.
;It MUST be padded out to an even number of bytes.
; END OF WAVE #1
=============STRUCTURE OF AN INDIVIDUAL SAMPLE POINT=============
Even though the next generation of computers will probably have 16 bit
audio, and 8 bit sampling will quickly disappear, this spec has sizes expressed
in BYTES. (ie LoopStart, WaveSize, etc.) This is because each successive
address in RAM is a byte to the 68000, and so calculating address offsets
will be much easier with all sizes in BYTES. The Midi sample dump, on the
other hand, has sizes expressed in WORDS. What this means is that if you
have a 16 bit wave, for example, the WaveSize is the total number of BYTES,
not WORDS, in the wave.
Also, there is no facility for storing a compression type. This is because
sample data should be stored in linear format (as per the MIDI spec). Currently,
all music samplers, regardless of their internal method of playing sample data
must transmit and expect to receive sample dumps in a linear format. It is
up to each device to translate the linear format into its own compression
scheme. For example, if you are using an 8 bit compression scheme that yields
a 14 bit linear range, you should convert each sample data BYTE to a decom-
pressed linear WORD when you save a sound file. Set the MHDR's Format
to 14. It is up to the application to do its own compression upon loading
a file. The midi spec was set up this way because musical samplers need to
pass sample data between each other, and computers (via a midi interface).
Since there are almost as many data compression schemes on the market as
there are musical products, it was decided that all samplers should expect
data received over midi to be in LINEAR format. It seems logical to store it
this way on disc as well. Therefore, any software program "need not know" how
to decompress another software program's SAMP file. When 16 bit sampling is
eventually implemented there won't be much need for compression on playback
anyway. The continuation Flag solves the problem of disc storage as well.
Since the 68000 can only perform math on BYTES, WORDS, or LONGS, it has
been decided that a sample point should be converted to one of these sizes
when saved in SAMP as follows:
ORIGINAL significant bits SAMP sample point size
8 BYTE
9 to 16 WORD
17 to 28 LONG
Furthermore, the significant bits should be left-justified since it is
easier to perform math on the samples.
So, for example, an 8 bit sample point (like 8SVX) would be saved as a
BYTE with all 8 bits being significant. The MHDR's Format = 8. No
conversion is necessary.
A 12 bit sample point should be stored as a WORD with the significant bits
being numbers 4 to 15. (i.e shift the 12-bit WORD 4 places to the left). Bits
0, 1, 2 and 3 may be zero (unless some 16-bit math was performed and you wish to
save these results). The MHDR's Format = 12. In this way, the sample
may be loaded and manipulated as a 16-bit wave, but when transmitted via
midi, it can be converted back to 12 bits (rounded and shifted right by 4).
A 16 bit sample point would be saved as a WORD with all 16 bits being
significant. The MHDR's Format = 16. No conversion is necessary.
============== The waveHeader explained ==============
The WaveSize is, as stated, the number of BYTES in the wave's sample table.
If your sample data consisted of the following 8 bit samples:
BYTE 100,-90,80,-60,30,35,40,-30,-35,-40,00,12,12,10
then WaveSize = 14. (PAD THE DATA OUT TO AN EVEN NUMBER OF BYTES!)
The MidiSampNum is ONLY used to hold the sample number received from a MIDI
Sample Dump. It has no bearing on where the wave should be placed in a SAMP
file. Also, the wave numbers in the PlayMap are between 1 to 255, with 1 being
the number of the first wave in the file. Remember that a wave number of 0 is
reserved to mean "no wave to play back". Likewise, the LoopType is only used
to hold info from a MIDI sample dump.
The InsType is explained at the end of this document. Often it will be set
to 0.
The RootNote is the Midi Note number that will play the wave back at it's
original, recorded pitch. For example, consider the following excerpt of a
PlayMap:
PlayMap {2,0,0,4 /* Midi Note #0 channel assignment */
4,100,1,0 /* Midi Note #1 " " */
1,4,0,0 /* Midi Note #2 " " */
60,2,1,1...} /* Midi Note #3 " " */
Notice that Midi Notes 0, 1, and 2 are all set to play wave number 4 (on
Amiga channels 3, 0, and 1 respectively). If we set wave 4's RootNote = 1,
then receiving Midi Note number 1 would play back wave 4 (on Amiga channel 0)
at it's original pitch. If we receive a Midi Note number 0, then wave 4 would
be played back on channel 3) a half step lower than it's original pitch. If we
receive Midi Note number 2, then wave 4 would be played (on channel 1) a half
step higher than it's original pitch. If we receive Midi Note number 3, then
wave 4 would not be played at all because it isn't specified in the PlayMap
bytes for Midi Note number 3.
The Rate is the number of samples per second of the original pitch.
For example, if Rate = 20000, then to play the wave at it's original
pitch, the sampling period would be:
(1/20000)/.279365 = .000178977
#define AUDIO_HARDWARE_FUDGE .279365
where .279365 is the Amiga Fudge Factor (a hardware limitation). Since the
amiga needs to see the period in terms of microseconds, move the decimal place
to the right 6 places and our sampling period = 179 (rounded to an integer).
In order to play the wave at higher or lower pitches, one would need to
"transpose" this period value. By specifying a higher period value, the Amiga
will play back the samples slower, and a lower pitch will be achieved. By
specifying a lower period value, the amiga will play back the sample faster,
and a higher pitch will be achieved. By specifying this exact period, the wave
will be played back exactly "as it was recorded (sampled)". ("This period is
JUST RIGHT!", exclaimed GoldiLocks.) Later, a method of transposing pitch will
be shown using a "look up" table of periods. This should prove to be the
fastest way to transpose pitch, though there is nothing in the SAMP format
that compels you to do it this way.
The LoopStart is a BYTE offset from the beginning of the wave to where
the looping portion of the wave begins. For example, if SampleData points to
the start of the wave, then SampleData + LoopStart is the start address
of the looping portion. In 8SVX, the looping portion was referred to as
repeatHiSamples. The data from the start of the wave up to the start of the
looping portion is the oneShot portion of the wave. LoopEnd is a BYTE
offset from the beginning of the wave to where the looping portion ends. This
might be the very end of the wave in memory, or perhaps there might be still
more data after this point. You can choose to ignore this "trailing" data and
play back the two other portions of the wave just like an 8SVX file (except
that there are no other interpolated octaves of this wave).
VelTable contains 16 BYTE offsets from the beginning of the wave. Each
successive value should be greater (or equal to) the preceding value. If
VelStart = POSITIVE (64), then for each 8 increments in Midi Velocity
above 0, you move UP in the table, add this offset to the wave's beginning
address (start of oneShot), and start playback at that address. Here is a
table relating received midi note-on velocity vs. start playback address for
POSITIVE VelStart. SamplePtr points to the beginning of the sample.
If midi velocity = 0, then don't play a sample, this is a note off
If midi velocity = 1 to 7, then start play at SamplePtr + VelTable[0]
If midi velocity = 8 to 15, then start at SamplePtr + VelTable[1]
If midi velocity = 16 to 23, then start at SamplePtr + VelTable[2]
If midi velocity = 24 to 31, then start at SamplePtr + VelTable[3]
If midi velocity = 32 to 39, then start at SamplePtr + VelTable[4]
If midi velocity = 40 to 47, then start at SamplePtr + VelTable[5]
If midi velocity = 48 to 55, then start at SamplePtr + VelTable[6]
If midi velocity = 56 to 63, then start at SamplePtr + VelTable[7]
If midi velocity = 64 to 71, then start at SamplePtr + VelTable[8]
If midi velocity = 72 to 79, then start at SamplePtr + VelTable[9]
If midi velocity = 80 to 87, then start at SamplePtr + VelTable[10]
If midi velocity = 88 to 95, then start at SamplePtr + VelTable[11]
If midi velocity = 96 to 103, then start at SamplePtr + VelTable[12]
If midi velocity = 104 to 111, then start at SamplePtr + VelTable[13]
If midi velocity = 112 to 119, then start at SamplePtr + VelTable[14]
If midi velocity = 120 to 127, then start at SamplePtr + VelTable[15]
We don't want to specify a scale factor and use integer division to find the
sample start. This would not only be slow, but also, it could never be certain
that the resulting sample would be a zero crossing if the start point is calcu-
lated "on the fly". The reason for having a table is so that the offsets can be
be initially set on zero crossings via an editor. This way, no audio "clicks"
guaranteed. This table should provide enough resolution.
If VelStart = NEGATIVE (128), then for each 8 increments in midi
velocity, you start from the END of VelTable, and work backwards. Here
is a table for NEGATIVE velocity start.
If midi velocity = 0, then don't play a sample, this is a note off
If midi velocity = 1 to 7, then start play at SamplePtr + VelTable[15]
If midi velocity = 8 to 15, then start at SamplePtr + VelTable[14]
If midi velocity = 16 to 23, then start at SamplePtr + VelTable[13]
If midi velocity = 24 to 31, then start at SamplePtr + VelTable[12]
If midi velocity = 32 to 39, then start at SamplePtr + VelTable[11]
If midi velocity = 40 to 47, then start at SamplePtr + VelTable[10]
If midi velocity = 48 to 55, then start at SamplePtr + VelTable[9]
If midi velocity = 56 to 63, then start at SamplePtr + VelTable[8]
If midi velocity = 64 to 71, then start at SamplePtr + VelTable[7]
If midi velocity = 72 to 81, then start at SamplePtr + VelTable[6]
If midi velocity = 80 to 87, then start at SamplePtr + VelTable[5]
If midi velocity = 88 to 95, then start at SamplePtr + VelTable[4]
If midi velocity = 96 to 103, then start at SamplePtr + VelTable[3]
If midi velocity = 104 to 111, then start at SamplePtr + VelTable[2]
If midi velocity = 112 to 119, then start at SamplePtr + VelTable[1]
If midi velocity = 120 to 127, then start at SamplePtr + VelTable[0]
In essence, increasing midi velocity starts playback "farther into" the wave
for POSITIVE VelStart. Increasing midi velocity "brings the start point
back" toward the beginning of the wave for NEGATIVE VelStart.
If VelStart is set to NONE (0), then the wave's playback start should
not be affected by the table of offsets.
What is the use of this feature? As an example, when a snare drum is hit with
a soft volume, its initial attack is less pronounced than when it is struck
hard. You might record a snare being hit hard. By setting VelStart to a
NEGATIVE value and setting up the offsets in the Table, a lower midi velocity
will "skip" the beginning samples and thereby tend to soften the initial
attack. In this way, one wave yields a true representation of its instrument
throughout its volume range. Furthermore, stringed and plucked instruments
(violins, guitars, pianos, etc) exhibit different attacks at different
volumes. VelStart makes these kinds of waves more realistic via a software
implementation. Also, an application program can allow the user to enable/
disable this feature. See the section "Making the Velocity Table" for info on
how to best choose the 16 table values.
=========MIDI VELOCITY vs. AMIGA CHANNEL VOLUME============
The legal range for Midi Velocity bytes is 0 to 127. (A midi velocity of 0
should ALWAYS be interpreted as a note off).
The legal range for Amiga channel volume is 0 to 64. Since this is half of
the midi range, a received midi velocity should be divided by 2 and add 1
(but only AFTER checking for a received midi velocity of 0).
An example of how to implement a received midi velocity in C:
If ( ReceivedVelocity != 0 && ReceivedVelocity < 128 )
{ /* the velocity byte of a midi message */
If (velStart != 0)
{
tableEntry = ReceivedVelocity / 8;
If (velStart == 64)
{ /* Is it POSITIVE */
startOfWave = SamplePtr + velTable[tableEntry];
/* ^where to find the sample start point */
}
If (velStart == 128)
{ /* Is it NEGATIVE */
startOfWave = SamplePtr + velTable[15 - tableEntry];
}
volume = (receivedVelocity/2 + 1; /* playback volume */
/* Now playback the wave */
}
}
In assembly,
lea SampleData,a0 ;the start addr of the sample data
moveq #0,d0
move.b ReceivedVelocity,d0 ;the velocity byte of a midi message
beq A_NoteOff ;If zero, branch to a routine to
;process a note-off message.
bmi Illegal_Vol ;exit if received velocity > 127
;---Check for velocity start feature ON, and direction
move.b VelStart,d1
beq.s Volume ;skip the velocity offset routine if 0
bmi.s NegativeVel ;is it NEGATIVE? (128)
;---Positive velocity offset
move.l d0,d1 ;duplicate velocity
lsr.b #3,d1 ;divide by 8
add.b d1,d1 ;x 2 because we need to fetch a word
lea VelTable,a1 ;start at table's HEAD
adda.l d1,a1 ;go forward
move.w (a1),d1 ;get the velocity offet
adda.l d1,a0 ;where to start actual playback
bra.s Volume
NegativeVel:
;---Negative velocity offset
move.l d0,d1 ;duplicate velocity
lsr.b #3,d1 ;divide by 8
add.b d1,d1 ;x 2 because we need to fetch a word
lea VelTable+30,a1 ;start at table's END
suba.l d1,a1 ;go backwards
move.w (a1),d1 ;get the velocity offset
adda.l d1,a0 ;where to start actual playback
;---Convert Midi velocity to an Amiga volume
Volume lsr.b #1,d0 ;divide by 2
addq.b #1,d0 ;an equivalent Amiga volume
;---Now a0 and d0 are the address of sample start, and volume
================= AN EGpoint (envelope generator) ================
A single EGpoint is a 6 byte structure as follows:
EGpoint1: dc.w ;[the duration in milliseconds]
dc.l ;[the volume factor - fixed point, 16 bits to the left of the
;decimal point and 16 to the right.]
The volume factor is a fixed point where 1.0 ($00010000) represents the
MAXIMUM volume possible. (i.e. No volume factor should exceed this value.)
The last EGpoint in the ATAK is always the sustain point. Each EG's volume
is determined from 0.0, not as a difference from the previous EG's volume.
I hope that this clears up the ambiguity in the original 8SVX document.
So, to recreate an amplifier envelope like this:
/\
/ \____
/ \
/ \
| | | | |
1 2 3 4
Stages 1, 2, and 3 would be in the ATAK data, like so:
;Stage 1
dc.w 100 ;take 100ms
dc.l $00004000 ;go to this volume
dc.w 100
dc.l $00008000
dc.w 100
dc.l $0000C000
dc.w 100
dc.l $00010000 ;the "peak" of our attack is full volume
;Stage 2
dc.w 100
dc.l $0000C000 ;back off to this level
dc.l 100
dc.l $00008000 ;this is where we hold (SUSTAIN) until the note is turned
;off. (We are now holding at stage 3)
Now the RLSE data would specify stage 4 as follows:
dc.w 100
dc.l $00004000
dc.w 100
dc.l $00000000 ;the volume is 0
===============ADDITIONAL USER DATA SECTION=================
There is a provision for storing user data for each wave. This is where an
application can store Amiga hardware info, or other, application specific info.
The waveHeader's USERtype tells what kind of data is stored. The current
types are:
#define SPECIFIC 0
#define VOLMOD 1
#define PERMOD 2
#define LOOPING 3
SPECIFIC (0) - application specific data. It should be stored
in a format that some application can immediately
recognize. (i.e. a "format within" the SAMP format)
If the USERtype is SPECIFIC, and an application
doesn't find some sort of header that it can re-
cognize, it should conclude that this data was
put there by "someone else", and ignore the data.
VOLMOD (1) - This data is for volume modulation of an Amiga
channel as described by the ADKCON register. This
data will be sent to the modulator channel of the
channel set to play the wave.
PERMOD (2) - This data is for period modulation of an Amiga
channel as described by the ADKCON register. This
data will be sent to the modulator channel of the
channel set to play the wave.
LOOPING (3) - This contains more looping points for the sample.
There are some samplers that allow more than just
one loop (Casio products primarily). Additional
looping info can be stored in this format:
UWORD numOfLoops; /* number of loop points to follow */
ULONG StartLoop1, /* BYTE offset from the beginning of
the sample to the start of loop1 */
EndLoop1, /* BYTE offset from the beginning of
the sample to the end of loop1 */
StartLoop2, /* ...etc */
=========Converting Midi Sample Dump to SAMP=========
SEMANTICS: When MIDI literature talks about a sample, usually it means a
collection of many sample points that make up what we call "a wave".
Therefore, a Midi Sample Dump sends all the sample data that makes up ONE
wave. A SAMP file is designed to hold up to 255 of these waves (midi dumps).
The Midi Sample Dump specifies playback rate only in terms of a sample
PERIOD in nanoseconds. SAMP also expresses playback in terms of samples per
second (frequency). The Amiga needs to see its period rounded to the nearest
microsecond. If you take the sample period field of a Midi sample Dump (the
8th, 9th, and 10th bytes of the Dump Header LSB first) which we will call
MidiSamplePer, and the Rate of a SAMP file, here is the relationship:
Rate = (1/MidiSamplePer) x 10E9
Also the number of samples (wave's length) in a Midi Sample Dump (the 11th,
12th, and 13th bytes of the Dump header) is expressed in WORDS. SAMP's
WaveSize is expressed in the number of BYTES. (For the incredibly stupid),
the relationship is:
WaveSize = MidiSampleLength x 2
A Midi sample dump's LoopStart point and LoopEnd point are also in WORDS as
versus the SAMP equivalents expressed in BYTES.
A Midi sample dump's sample number can be 0 to 65535. A SAMP file can hold
up to 255 waves, and their numbers in the playmap must be 1 to 255. (A single,
Midi Sample Dump only sends info on one wave.) When recieving a Midi Sample
Dump, just store the sample number (5th and 6th bytes of the Dump Header LSB
first) in SAMP's MidiSampNum field. Then forget about this number until you
need to send the wave back to the Midi instrument from whence it came.
A Midi Dump's loop type can be forward, or forward/backward. Amiga hardware
supports forward only. You should store the Midi Dump's LoopType byte here,
but ignore it otherwise until/unless Amiga hardware supports "reading audio
data" in various ways. If so, then the looptype is as follows:
forward = 0, backward/forward = 1
A Midi Dump's sample format byte is the same as SAMP's.
===================== INTERPRETING THE PLAYMODE ==========================
PlayMode specifies how the bytes in the PlayMap are to be interpreted.
Remember that a PlayMap byte of 0 means "No Wave to Play".
#define INDEPENDANT 0
#define MULTI 1
#define STEREO 2
#define PAN 3
PlayMode types:
INDEPENDANT (0) - The wave #s for a midi note are to be output on
Amiga audio channels 0, 1, 2, and 3 respectively.
If the NumOfChans is < 4, then only use that many channels.
MULTI (1) - The first wave # (first of the PlayMap bytes) for a
midi note is to be output on any free channel. The other
wave numbers are ignored. If all four channels are in
play, the application can decide whether to "steal" a
channel.
STEREO (2) - The first wave # (first of the PlayMap bytes) is to be
output of the Left stereo jack (channel 1 or 3) and if
there is a second wave number (the second of the PlayMap
bytes), it is to be output the Right jack (channel 2 or 4).
The other wave numbers are ignored.
PAN (3) - This is just like STEREO except that the volume of wave 1
should start at its initial volume (midi velocity) and
fade to 0. At the same rate, wave 2 should start at 0
volume and rise to wave #1's initial level. The net
effect is that the waves "cross" from Left to Right in
the stereo field. This is most effective when the wave
numbers are the same. (ie the same wave) The application
program should set the rate. Also, the application can
reverse the stereo direction (ie Right to Left fade).
The most important wave # to be played back by a midi note should be the
first of the PlayMap bytes. If the NumOfChans > 1, the second PlayMap byte
should be a defined wave number as well (even if it is deliberately set to the
same value as the first byte). This insures that all 4 PlayModes will have some
effect on a given SAMP file. Also, an application should allow the user to
change the PlayMode at will. The PlayMode stored in the SAMP file is only a
default or initial set-up condition.
=================== MAKING A TRANSPOSE TABLE =====================
In order to allow a wave to playback over a range of musical notes, (+/-
semitones), its playback rate must be raised or lowered by a set amount.
From one semitone to the next, this set amount is by a factor of the 12th
root of 2 (assuming a western, equal-tempered scale). Here is a table that
shows what factor would need to be multiplied by the sampling rate in order
to transpose the wave's pitch.
Pitch in relation to the Root Multiply Rate by this amount
------------------------------- ------------------------------
DOWN 6 semitones 0.5
DOWN 5 1/2 semitones 0.529731547
DOWN 5 semitones 0.561231024
DOWN 4 1/2 semitones 0.594603557
DOWN 4 semitones 0.629960525
DOWN 3 1/2 semitones 0.667419927
DOWN 3 semitones 0.707106781
DOWN 2 1/2 semitones 0.749153538
DOWN 2 semitones 0.793700526
DOWN 1 1/2 semitones 0.840896415
DOWN 1 semitones 0.890898718
DOWN 1/2 semitone 0.943874312
ORIGINAL_PITCH 1.0 /* rootnote's pitch */
UP 1/2 semitone 1.059463094
UP 1 semitones 1.122562048
UP 1 1/2 semitones 1.189207115
UP 2 semitones 1.259921050
UP 2 1/2 semitones 1.334839854
UP 3 semitones 1.414213562
UP 3 1/2 semitones 1.498307077
UP 4 semitones 1.587401052
UP 4 1/2 semitones 1.681792830
UP 5 semitones 1.781797436
UP 5 1/2 semitones 1.887748625
UP 6 semitones 2
For example, if the wave's Rate is 18000 hz, and you wish to play
the wave UP 1 semitone, then the playback rate is:
18000 x 1.122562048 = 20206.11686 hz
The sampling period for the Amiga is therefore:
(1/20206.11686)/.279365 = .000177151
and to send it to the Audio Device, it is rounded and expressed in micro-
seconds: 177
Obviously, this involves floating point math which can be time consuming
and impractical for outputing sound in real-time. A better method is to con-
struct a transpose table that contains the actual periods already calculated
for every semitone. The drawback of this method is that you need a table for
EVERY DIFFERENT Rate in the SAMP file. If all the Rates in the
file happened to be the same, then only one table would be needed. Let's
assume that this is the case, and that the Rate = 18000 hz. Here is a
table containing enough entries to transpose the waves +/- 6 semitones.
Pitch in relation to the Root The Amiga Period (assuming rate = 18000 hz)
------------------------------- ------------------------------
Transposition_table[TRANS_TABLE_SIZE]={
/* DOWN 6 semitones */ 398,
/* DOWN 5 1/2 semitones */ 375,
/* DOWN 5 semitones */ 354,
/* DOWN 4 1/2 semitones */ 334,
/* DOWN 4 semitones */ 316,
/* DOWN 3 1/2 semitones */ 298,
/* DOWN 3 semitones */ 281,
/* DOWN 2 1/2 semitones */ 265,
/* DOWN 2 semitones */ 251,
/* DOWN 1 1/2 semitones */ 236,
/* DOWN 1 semitones */ 223,
/* DOWN 1/2 semitone */ 211,
/* ORIGINAL_PITCH */ 199, /* rootnote's pitch */
/* UP 1/2 semitone */ 187,
/* UP 1 semitones */ 177,
/* UP 1 1/2 semitones */ 167,
/* UP 2 semitones */ 157,
/* UP 2 1/2 semitones */ 148,
/* UP 3 semitones */ 141,
/* UP 3 1/2 semitones */ 133,
/* Since the minimum Amiga period = 127 the following
are actually out of range. */
/* UP 4 semitones */ 125,
/* UP 4 1/2 semitones */ 118,
/* UP 5 semitones */ 112,
/* UP 5 1/2 semitones */ 105,
/* UP 6 semitones */ 99 };
Let's assume that (according to the PlayMap) midi note #40 is set to play
wave number 3. Upon examining wave 3's structure, we discover that the
Rate = 18000, and the RootNote = 38. Here is how the Amiga sampling
period is calulated using the above 18000hz "transpose chart" in C:
/* MidiNoteNumber is the received midi note's number (here 40) */
#define ORIGINAL_PITCH TRANS_TABLE_SIZE/2 + 1
/* TRANS_TABLE_SIZE is the number of entries in the transposition table
(dynamic, ie this can change with the application) */
transposeAmount = (LONG) (MidiNoteNumber - rootNote); /* make it a SIGNED LONG */
amigaPeriod = Transposition_table[ORIGINAL_PITCH + transposeAmount];
In assembly, the 18000hz transpose chart and above example would be:
Table dc.w 398
dc.w 375
dc.w 354
dc.w 334
dc.w 316
dc.w 298
dc.w 281
dc.w 265
dc.w 251
dc.w 236
dc.w 223
dc.w 211
ORIGINAL_PITCH dc.w 199 ; rootnote's pitch
dc.w 187
dc.w 177
dc.w 167
dc.w 157
dc.w 148
dc.w 141
dc.w 133
; Since the minimum Amiga period = 127, the following
; are actually out of range.
dc.w 125
dc.w 118
dc.w 112
dc.w 105
dc.w 99
lea ORIGINAL_PITCH,a0
move.b MidiNoteNumber,d0 ;the received note number
sub.b RootNote,d0 ;subtract the wave's root note
ext.w d0
ext.l d0 ;make it a signed LONG
add.l d0,d0 ;x 2 in order to fetch a WORD
adda.l d0,a0
move.w (a0),d0 ;the Amiga Period (WORD)
Note that these examples don't check to see if the transpose amount is
beyond the number of entries in the transpose table. Nor do they check if
the periods in the table are out of range of the Amiga hardware.
===================== MAKING THE VELOCITY TABLE ======================
The 16 entries in the velocity table should be within the oneShot portion of
the sample (ie not in the looping portion). THe first offset, VelTable[0]
should be set to zero (in order to play back from the beginning of the data).
The subsequent values should be increasing numbers. If you are using a graphic
editor, try choosing offsets that will keep you within the initial attack
portion of the wave. In practice, these values will be relatively close
together within the wave. Always set the offsets so that when they are added
to the sample start point, the resulting address points to a sample value of
zero (a zero crossing point). This will eliminate pops and clicks at the
beginning of the playback.
In addition, the start of the wave should be on a sample with a value of
zero. The last sample of the oneShot portion and the first sample of the
looping portion should be approximately equal, (or zero points). The same is
true of the first and last samples of the looping portion. Finally, try to
keep the slopes of the end of the oneShot, the beginning of the looping, and
the end of the looping section, approximately equal. All this will eliminate
noise on the audio output and provide "seamless" looping.
======================== THE INSTRUMENT TYPE ==========================
Many SMUS players search for certain instruments by name. Not only is this
slow (comparing strings), but if the exact name can't be found, then it is
very difficult and time-consuming to search for a suitable replacement. For
this reason, many SMUS players resort to "default" instruments even if these
are nothing like the desired instruments. The InsType byte in each
waveHeader is meant to be a numeric code which will tell an SMUS player
exactly what the instrument is. In this way, the SMUS player can search for
the correct "type" of instrument if it can't find the desired name. The type
byte is divided into 2 nibbles (4 bits for you C programmers) with the low
4 bits representing the instrument "family" as follows:
1 = STRING, 2 = WOODWIND, 3 = KEYBOARD, 4 = GUITAR, 5 = VOICE, 6 = DRUM1,
7 = DRUM2, 8 = PERCUSSION1, 9 = BRASS1, A = BRASS2, B = CYMBAL, C = EFFECT1,
D = EFFECT2, E = SYNTH, F is undefined at this time
Now, the high nibble describes the particular type within that family.
For the STRING family, the high nibble is as follows:
1 = VIOLIN BOW, 2 = VIOLIN PLUCK, 3 = VIOLIN GLISSANDO, 4 = VIOLIN TREMULO,
5 = VIOLA BOW, 6 = VIOLA PLUCK, 7 = VIOLA GLIS, 8 = VIOLA TREM, 9 = CELLO
BOW, A = CELLO PLUCK, B = CELLO GLIS, C = CELLO TREM, D = BASS BOW, E =
BASS PLUCK (jazz bass), F = BASS TREM
For the BRASS1 family, the high nibble is as follows:
1 = BARITONE SAX, 2 = BARI GROWL, 3 = TENOR SAX, 4 = TENOR GROWL, 5 = ALTO
SAX, 6 = ALTO GROWL, 7 = SOPRANO SAX, 8 = SOPRANO GROWL, 9 = TRUMPET, A =
MUTED TRUMPET, B = TRUMPET DROP, C = TROMBONE, D = TROMBONE SLIDE, E =
TROMBONE MUTE
For the BRASS2 family, the high nibble is as follows:
1 = FRENCH HORN, 2 = TUBA, 3 = FLUGAL HORN, 4 = ENGLISH HORN
For the WOODWIND family, the high nibble is as follows:
1 = CLARINET, 2 = FLUTE, 3 = PAN FLUTE, 4 = OBOE, 5 = PICCOLO, 6 = RECORDER,
7 = BASSOON, 8 = BASS CLARINET, 9 = HARMONICA
For the KEYBOARD family, the high nibble is as follows:
1 = GRAND PIANO, 2 = ELEC. PIANO, 3 = HONKYTONK PIANO, 4 = TOY PIANO, 5 =
HARPSICHORD, 6 = CLAVINET, 7 = PIPE ORGAN, 8 = HAMMOND B-3, 9 = FARFISA
ORGAN, A = HARP
For the DRUM1 family, the high nibble is as follows:
1 = KICK, 2 = SNARE, 3 = TOM, 4 = TIMBALES, 5 = CONGA HIT, 6 = CONGA SLAP,
7 = BRUSH SNARE, 8 = ELEC SNARE, 9 = ELEC KICK, A = ELEC TOM, B = RIMSHOT,
C = CROSS STICK, D = BONGO, E = STEEL DRUM, F = DOUBLE TOM
For the DRUM2 family, the high nibble is as follows:
1 = TIMPANI, 2 = TIMPANI ROLL, 3 = LOG DRUM
For the PERCUSSION1 family, the high nibble is as follows:
1 = BLOCK, 2 = COWBELL, 3 = TRIANGLE, 4 = TAMBOURINE, 5 = WHISTLE, 6 =
MARACAS, 7 = BELL, 8 = VIBES, 9 = MARIMBA, A = XYLOPHONE, B = TUBULAR BELLS,
C = GLOCKENSPEIL
For the CYMBAL family, the high nibble is as follows:
1 = CLOSED HIHAT, 2 = OPEN HIHAT, 3 = STEP HIHAT, 4 = RIDE, 5 = BELL CYMBAL,
6 = CRASH, 7 = CHOKE CRASH, 8 = GONG, 9 = BELL TREE, A = CYMBAL ROLL
For the GUITAR family, the high nibble is as follows:
1 = ELECTRIC, 2 = MUTED ELECTRIC, 3 = DISTORTED, 4 = ACOUSTIC, 5 = 12-STRING,
6 = NYLON STRING, 7 = POWER CHORD, 8 = HARMONICS, 9 = CHORD STRUM, A = BANJO,
B = ELEC. BASS, C = SLAPPED BASS, D = POPPED BASS, E = SITAR, F = MANDOLIN
(Note that an acoustic picked bass is found in the STRINGS - Bass Pluck)
For the VOICE family, the high nibble is as follows:
1 = MALE AHH, 2 = FEMALE AHH, 3 = MALE OOO, 4 = FEMALE OOO, 5 = FEMALE
BREATHY, 6 = LAUGH, 7 = WHISTLE
For the EFFECTS1 family, the high nibble is as follows:
1 = EXPLOSION, 2 = GUNSHOT, 3 = CREAKING DOOR OPEN, 4 = DOOR SLAM, 5 = DOOR
CLOSE, 6 = SPACEGUN, 7 = JET ENGINE, 8 = PROPELLER, 9 = HELOCOPTER, A =
BROKEN GLASS, B = THUNDER, C = RAIN, D = BIRDS, E = JUNGLE NOISES, F =
FOOTSTEP
For the EFFECTS2 family, the high nibble is as follows:
1 = MACHINE GUN, 2 = TELEPHONE, 3 = DOG BARK, 4 = DOG GROWL, 5 = BOAT
WHISTLE, 6 = OCEAN, 7 = WIND, 8 = CROWD BOOS, 9 = APPLAUSE, A = ROARING
CROWDS, B = SCREAM, C = SWORD CLASH, D = AVALANCE, E = BOUNCING BALL,
F = BALL AGAINST BAT OR CLUB
For the SYNTH family, the high nibble is as follows:
1 = STRINGS, 2 = SQUARE, 3 = SAWTOOTH, 4 = TRIANGLE, 5 = SINE, 6 = NOISE
So, for example if a wave's type byte was 0x26, this would be a SNARE DRUM.
If a wave's type byte is 0, then this means "UNKNOWN" instrument.
===================== THE ORDER OF THE CHUNKS =========================
The SAMP header obviously must be first in the file, followed by the MHDR
chunk. After this, the ANNO, (c), AUTH and NAME chunks may follow in any
order, though none of these need appear in the file at all. The BODY chunk
must be last.
================= FILENAME CONVENTIONS =================
For when it becomes necessary to split a SAMP file between floppies using
the Continuation feature, the filenames should be related. The method is the
following:
The "root" file has the name that the user chose to save under. Subsequent
files have an ascii number appended to the name to indicate what sublevel the
file is in. In this way, a program can reload the files in the proper order.
For example, if a user saved a file called "Gurgle", the first continuation
file should be named "Gurgle1", etc.
============ WHY DOES ANYONE NEED SUCH A COMPLICATED FILE? ==============
(or "What's wrong with 8SVX anyway?")
In a nutshell, 8SVX is not adequate for professional music sampling. First
of all, it is nearly impossible to use multi-sampling (utilizing several,
different samples of any instrument throughout its musical range). This very
reason alone makes it impossible to realistically reproduce a musical in-
strument, as none in existance (aside from an electronic organ) uses inter-
polations of a single wave to create its musical note range.
Also, stretching a sample out over an entire octave range does grotesque
(and VERY unmusical) things to such elements as the overtone structure,
wind/percussive noises, the instrument's amplitude envelope, etc. The 8SVX
format is designed to stretch the playback in exactly this manner.
8SVX ignores MIDI which is the de facto standard of musical data transmission.
8SVX does not allow storing data for features that are commonplace to pro-
fessional music samplers. Such features are: velocity sample start, separate
filter and envelopes for each sample, separate sampling rates, and various
playback modes like stereo sampling and panning.
SAMP attempts to remedy all of these problems with a format that can be
used by a program that simulates these professional features in software. The
format was inspired by the capabilities of the following musical products:
EMU's EMAX, EMULATOR
SEQUENTIAL CIRCUIT's PROPHET 2000, STUDIO 440
ENSONIQ's MIRAGE
CASIO's FZ-1
OBERHEIM's DPX
YAMAHA TX series
So why does the Amiga need the SAMP format? Because professional musician's
are buying computers. With the firm establishment of MIDI, musician's are
buying and using a variety of sequencers, patch editors, and scoring programs.
It is now common knowledge amoung professional musicians that the Amiga
lags far behind IBM clones, Macintosh, and Atari ST computers in both music
software and hardware support. Both Commodore and the current crop of short-
sighted 3rd party Amiga developers are pigeon-holing the Amiga as "a video
computer". It is important for music software to exploit whatever capabili-
ties the Amiga offers before the paint and animation programs, genlocks,
frame-grabbers, and video breadboxes are the only applications selling
for the Amiga. Hopefully, this format, with the SAMP disk I/O library will
make it possible for Amiga software to attain the level of professionalism
that the other machines now boast, and the Amiga lacks.
3-D rendering data
FORM TDDD is used by Impulse's Turbo Silver 3.0 for 3D rendering
data. TDDD stands for "3D data description". The files contain
object and (optionally) observer data.
Turbo Silver's successor, "Imagine", uses an upgraded FORM TDDD
when it reads/writes object data.
Currently, in "standard IFF" terms, a FORM TDDD has only two chunk
types: an INFO chunk describing observer data; and an OBJ chunk
describing an object heirarchy. The INFO chunk appears only in
Turbo Silver's "cell" files, and the OBJ chunk appears in both
"cell" files and "object" files.
The FORM has an (optional) INFO chunk followed by some number of
OBJ chunks. (Note: OBJ is followed by a space -- ckID = "OBJ ")
The INFO and OBJ chunks, in turn, are made up of smaller chunks with
the standard IFF structure: <ID> <data-size> <data>.
The INFO "sub-chunks" are relatively straightforward to interpret.
The OBJ "sub-chunks" support object heirarchies, and are slightly
more difficult to interpret. Currently, there are 3 types of OBJ
sub-chunks: an EXTR chunk, describing an "external" object in a
seperate file; a DESC chunk, describing one node of a heirarchy;
and a TOBJ chunk marking the end of a heirarchy chain. For each
DESC chunk, there must be a corresponding TOBJ chunk. And an
EXTR chunk is equivalent to a DESC/TOBJ pair.
In Turbo Silver and Imagine, the structure of the object heirarchy
is as follows. There is a head object, and its (sexist) brothers.
Each brother may have child objects. The children may have
grandchildren, and so on. The brother nodes are kept in a doubly
linked list, and each node has a (possibly NULL) pointer to a
doubly linked "child" list. The children point to the "grandchildren"
lists, and so on. (In addition, each node has a "back" pointer to
its parent).
Each of the "head" brothers is written in a seperate OBJ chunk,
along with all its descendants. The descendant heirarchy is
supported as follows:
for each node of a doubly linked list,
1) A DESC chunk is written, describing its object.
2) If it has children, steps 1) to 3) are performed
for each child.
3) A TOBJ chunk is written, marking the end of the children.
For "external" objects, steps 1) to 3) are not performed, but
an EXTR chunk is written instead. (This means that an external
object cannot have children unless they are stored in the same
"external" file).
The TOBJ sub-chunks have zero size -- and no data. The DESC
and EXTR sub-chunks are made up of "sub-sub-chunks", again,
with the standard IFF structure: <ID> <data-size> <data>.
( "External" objects were used by Turbo Silver to allow a its
"cell" data files to refer to an "object" data file that is
"external" to the cell file. Imagine abandons the idea of
individual cell files, and deals only in TDDD "object" files.
Currently, Imagine does not support EXTR chunks in TDD files.)
Reader software WILL FOLLOW the standard IFF procedure of
skipping over any un-recognized chunks -- and "sub-chunks"
or "sub-sub-chunks". The <data-size> field indicates how many
bytes to skip. In addition it WILL OBSERVE the IFF rule that
an odd <data-size> may appear, in which case the corredponding
<data> field will be padded at the end with one extra byte to
give it an even size.
Now, on with the details.
First, there are several numerical fields appearing in the data,
describing object positions, rotation angles, scaling factors, etc.
They are stored as "32-bit fractional" numbers, such that the true
number is the 32-bit number divided by 65536. So as an example,
the number 3.14159 is stored as (hexadecimal) $0003243F. This
allows the data to be independant of any particular floating point
format. And it (actually) is the internal format used in the
"integer" version of Turbo Silver. Numbers stored in this format
are called as "FRACT"s below.
Second, there are several color (or RGB) fields in the data.
They are always stored as three UBYTEs representing the red,
green and blue components of the color. Red is always first,
followed by green, and then blue. For some of the data chunks,
Turbo Silver reads the color field into the 24 LSB's of a
LONGword. In such cases, the 3 RGB bytes are preceded by a
zero byte in the file.
The following "typedef"s are used below:
typedef LONG FRACT; /* 4 bytes */
typedef UBYTE COLOR[3]; /* 3 bytes */
typedef struct vectors {
FRACT X; /* 4 bytes */
FRACT Y; /* 4 bytes */
FRACT Z; /* 4 bytes */
} VECTOR; /* 12 bytes total */
typedef struct matrices {
VECTOR I; /* 12 bytes */
VECTOR J; /* 12 bytes */
VECTOR K; /* 12 bytes */
} MATRIX; /* 36 bytes total */
typedef struct _tform {
VECTOR r; /* 12 bytes - position */
VECTOR a; /* 12 bytes - x axis */
VECTOR b; /* 12 bytes - y axis */
VECTOR c; /* 12 bytes - z axis */
VECTOR s; /* 12 bytes - size */
} TFORM; /* 60 bytes total */
The following structure is used in generating animated cells
from a single cell. It can be attached to an object or to the
camera. It is also used for Turbo Silver's "extrude along a
path" feature. (It is ignored & forgotten by Imagine)
typedef struct story {
UBYTE Path[18]; /* 18 bytes */
VECTOR Translate; /* 12 bytes */
VECTOR Rotate; /* 12 bytes */
VECTOR Scale; /* 12 bytes */
UWORD info; /* 2 bytes */
} STORY; /* 56 bytes total */
The Path[] name refers to a named object in the cell data.
The path object should be a sequence of points connected
with edges. The object moves from the first point of the
first edge, to the last point of the last edge. The edge
ordering is important. The path is interpolated so that
the object always moves an equal distance in each frame of
the animation. If there is no path the Path[] field should
be set to zeros.
The Translate vector is not currently used.
The Rotate "vector" specifies rotation angles about the
X, Y, and Z axes.
The Scale vector specfies X,Y, and Z scale factors.
The "info" word is a bunch of bit flags:
ABS_TRA 0x0001 - translate in world coorinates (not used)
ABS_ROT 0x0002 - rotation in world coorinates
ABS_SCL 0x0004 - scaling in world coorinates
LOC_TRA 0x0010 - translate in local coorinates (not used)
LOC_ROT 0x0020 - rotation in local coorinates
LOC_SCL 0x0040 - scaling in local coorinates
X_ALIGN 0x0100 - (not used)
Y_ALIGN 0x0200 - align Y axis to path's direction
Z_ALIGN 0x0400 - (not used)
FOLLOW_ME 0x1000 - children follow parent on path
DESC sub-sub-chunks
-------------------
NAME - size 18
BYTE Name[18]; ; a name for the object.
Used for camera tracking, specifying story paths, etc.
SHAP - size 4
WORD Shape; ; number indicating object type
WORD Lamp; ; number indicating lamp type
Lamp numbers are composed of several bit fields:
Bits 0-1:
0 - not a lamp
1 - like sunlight
2 - like a lamp - intensity falls off with distance.
3 - unused/reserved
Bits 2:
0 - non-shadow-casting light
4 - shadow-casting light
Bits 3-4:
0 - Spherical light source
8 - Cylindrical light source.
16 - Conical light source.
24 - unused/reserved
Shape numbers are:
0 - Sphere
1 - Stencil ; not supported by Imagine
2 - Axis ; custom objects with points/triangles
3 - Facets ; illegal - for internal use only
4 - Surface ; not supported by Imagine
5 - Ground
Spheres have thier radius set by the X size parameter.
Stencils and surfaces are plane-parallelograms, with one
point at the object's position vector; one side lying along
the object's X axis with a length set by the X size; and
another side starting from the position vector and going
"Y size" units in the Y direction and "Z size" units in
the X direction. A ground object is an infinte plane
perpendicular to the world Z axis. Its Z coordinate sets
its height, and the X and Y coordinates are only relevant
to the position of the "hot point" used in selecting the
object in the editor. Custom objects have points, edges
and triangles associated with them. The size fields are
relevant only for drawing the object axes in the editor.
Shape number 3 is used internally for triangles of custom
objects, and should never appear in a data file.
POSI - size 12
VECTOR Position; ; the object's position.
Legal coordinates are in the range -32768 to 32767 and 65535/65536.
Currently, the ray-tracer only sees objects in the -1024 to 1024
range. Light sources, and the camera may be placed outside that
range, however.
AXIS - size 36
VECTOR XAxis;
VECTOR YAxis;
VECTOR ZAxis;
These are direction vectors for the object coordinate system.
They must be "orthogonal unit vectors" - i.e. the sum of the
squares of the vevtor components must equal one (or close to it),
and the vectors must be perpendicular.
SIZE - size 12
VECTOR Size;
See SHAP chunk above. The sizes are used in a variety of ways
depending on the object shape. For custom objects, they are
the lengths of the coordinate axes drawn in the editor. If the
object has its "Quickdraw" flag set, the axes lengths are also
used to set the size of a rectangular solid that is drawn rather
than drawing all the points and edges.
PNTS - size 2 + 12 * point count
UWORD PCount; ; point count
VECTOR Points[]; ; points
This chunk has all the points for custom objects. The are
refered to by thier position in the array.
EDGE - size 4 + 4 * edge cout
UWORD ECount; ; edge count
UWORD Edges[][2]; ; edges
This chunk contins the edge list for custom objects.
The Edges[][2] array is pairs of point numbers that
are connected by the edges. Edges are refered to by thier
position in the Edges[] array.
FACE - size 2 + 6 * face count
UWORD TCount; ; face count
UWORD Connects[][3]; ; faces
This chunk contains the triangle (face) list for custom objects.
The Connects[][3] array is triples of edge numbers that are
connected by triangles.
PTHD - size 2 + 6 * axis count - Imagine only
UWORD ACount; ; axis count
TFORM PData[][3]; ; axis data
This chunk contains the axis data for Imagine "path" objects.
The PData array contains a TFORM structure for each point along
the path. The "Y size" item for the last point on the path tells
whether the path is closed or not. Zero means closed, non-zero
means open. Otherwise the Y size field is the distance along
the path to the next path point/axis.
COLR - size 4
REFL - size 4
TRAN - size 4
SPC1 - size 4 - Imagine only
BYTE pad; ; pad byte - must be zero
COLOR col; ; RGB color
These are the main object RGB color, and reflection, transmission
and specularity coefficients.
CLST - size 2 + 3 * count
RLST - size 2 + 3 * count
TLST - size 2 + 3 * count
UWORD count; ; count of colors
COLOR colors[]; ; colors
These are the color, reflection and transmission coefficients
for each face in custom objects. The count should match the
face count in the FACE chunk. The ordering corresponds to the
face order.
TPAR - size 64 - not written by Imagine - see TXT1 below
FRACT Params[16]; ; texture parameters
This is the list of parameters for texture modules when
texture mapping is used.
TXT1 - variable size - Imagine only
This chunk contains texture data when texture mapping is used.
UWORD Flags; ; texture flags:
; 1 - TXTR_CHILDREN - apply to child objs
TFORM TForm; ; local coordinates of texture axes.
FRACT Params[16]; ; texture parameters
UBYTE PFlags[16]; ; parameter flags (currently unused)
UBYTE Length; ; length of texture file name
UBYTE Name[Length]; ; texture file name (not NULL terminated)
UBYTE pad; ; (if necessary to make an even length)
BRS1 - variable size - Imagine only (version 1.0)
BRS2 - variable size - Imagine only (version 1.1)
UWORD Flags; ; brush type:
; 0 - Color
; 1 - Reflection
; 2 - Filter
; 3 - Altitude
UWORD WFlags; ; brush wrapping flags:
; 1 WRAP_X - wrap type
; 2 WRAP_Z - wrap type
; 4 WRAP_CHILDREN - apply to children
; 8 WRAP_REPEAT - repeating brush
; 16 WRAP_FLIP - flip with repeats
TFORM TForm; ; local coordinates of brush axes.
(UWORD FullScale;) ; full scale value
(UWORD MaxSeq;) ; highest number for sequenced brushes
UBYTE Length; ; length of brush file name
UBYTE Name[Length]; ; brush file name (not NULL terminated)
UBYTE pad; ; (if necessary to make an even length)
The FullScale and MaxSeq items are in BRS2 chunks only.
SURF - size 5 - not written by Imagine
BYTE SProps[5]; ; object properties
This chunk contains object (surface) properties used
by Turbo Silver.
SProps[0] - PRP_SURFACE ; surface type
; 0 - normal
; 4 - genlock
; 5 - IFF brush
SProps[1] - PRP_BRUSH ; brush number (if IFF mapped)
SProps[2] - PRP_WRAP ; IFF brush wrapping type
; 0 - no wrapping
; 1 - wrap X
; 2 - wrap Z
; 3 - wrap X and Z
SProps[3] - PRP_STENCIL ; stencil number for stencil objects
SProps[4] - PRP_TEXTURE ; texture number if texture mapped
MTTR - size 2 - not written by Imagine - see PRP1 chunk.
UBYTE Type; ; refraction type (0-4)
UBYTE Index; ; custom index of refraction
This chunk contains refraction data for transparent or
glossy objects. If the refraction type is 4, the object
has a "custom" refractive index stored in the Index field.
The Index field is 100 * (true index of refraction - 1.00)
-- so it must be in the range of 1.00 to 3.55. The
refraction types is 0-3 specify 0) Air - 1.00, 1) Water - 1.33,
2) Glass - 1.67 or 3) Crystal 2.00.
SPEC - size 2 - not written by Imagine - see SPC1 above.
UBYTE Specularity; ; range of 0-255
UBYTE Hardness; ; specular exponent (0-31)
This chunk contains specular information. The Specularity
field is the amount of specular reflection -- 0 is none,
255 is fully specular. The "specular exponent" controls
the "tightness" of the specular spots. A value of zero
gives broad specular spots and a value of 31 gives smaller
spots.
PRP0 - size 6 - not written by Imagine
UBYTE Props[6]; ; more object properties
This chunk contains object properties that programs other
than Turbo Silver might support.
Props[0] - PRP_BLEND ; blending factor (0-255)
Props[1] - PRP_SMOOTH ; roughness factor
Props[2] - PRP_SHADE ; shading on/off flag
Props[3] - PRP_PHONG ; phong shading on/off flag
Props[4] - PRP_GLOSSY ; glossy on/off flag
Props[5] - PRP_QUICK ; Quickdraw on/off flag
The blending factor controls the amount of dithering used
on the object - 255 is fully dithered.
The roughness factor controls how rough the object should
appear - 0 is smooth, 255 is max roughness.
The shading flag is interpreted differently depending on
whether the object is a light source or not. For light
sources, it sets the light to cast shadows or not. For
normal objects, if the flag is set, the object is always
considered as fully lit - i.e. it's color is read directly
from the object (or IFF brush), and is not affected by light
sources.
The phong shading is on by default - a non-zero value turns
it off.
The glossy flag sets the object to be glossy or not. If
the object is glossy, the "transmit" colors and the index
of refraction control the amount of "sheen". The glossy
feature is meant to simulate something like a wax coating
on the object with the specified index of refraction. The
trasmission coefficients control how much light from the
object makes it through the wax coating.
The Quickdraw flag, if set, tells the editor not to draw
all the points and edges for the object, but to draw a
rectanglular solid centered at the object position, and
with sizes detemined by the axis lengths.
PRP1 - size 8 - Imagine only
UBYTE IProps[8]; ; more object properties
This chunk contains object properties that programs other
than Imagine might support.
IProps[0] - IPRP_DITHER ; blending factor (0-255)
IProps[1] - IPRP_HARD ; hardness factor (0-255)
IProps[2] - IPRP_ROUGH ; roughness factor (0-255)
IProps[3] - IPRP_SHINY ; shinyness factor (0-255)
IProps[4] - IPRP_INDEX ; index of refraction
IProps[5] - IPRP_QUICK ; flag - Quickdraw on/off
IProps[6] - IPRP_PHONG ; flag - Phong shading on/off
IProps[7] - IPRP_GENLOCK ; flag - Genlock on/off
The blending factor controls the amount of dithering used
on the object - 255 is fully dithered.
The hardness factor controls how tight the specular spot
should be - 0 is a big soft spot, 255 is a tight hot spot
The roughness factor controls how rough the object should
appear - 0 is smooth, 255 is max roughness.
The shiny factor in interaction with the object's filter
values controls how shiny the object appears. Setting it
to anything but zero forces the object to be non-transparent
since then the filter values are used in the shiny (reflection)
calculations. A value of 255 means maximum shinyness.
INTS - size 4 - not written by Imagine
FRACT Intensity; ; light intensity
This is the intensity field for light source objects.
an intensity of 255 for a sun-like light fully lights
object surfaces which are perpendicular to the direction
to the light source. For lamp-like light sources, the
necessary intensity will depend on the distance to the light.
INT1 - size 12 - Imagine only
VECTOR Intensity; ; light intensity
This is like INTS above, but has seperate R, G & B intensities.
STRY - size 56 - not written by Imagine
STORY story; ; a story structure for the object.
The story structure is described above.
ANID - size 64 - Imagine only
LONG Cellno; ; cell number
TFORM TForm; ; object position/axes/size in that cell.
For Imagine's "Cycle" objects, within EACH DESC chunk in the
file - that is, for each object of the group, there will be
a series of ANID chunks. The cell number sequences of each
part of the must agree with the sequence for the head object,
and the first cell number must be zero.
FORD - size 56 + 12 * PC - Imagine only
WORD NumC; ; number of cross section points
WORD NumF; ; number of slices
WORD Flags; ; orientation flag
WORD pad; ; reserved
MATRIX TForm; ; object rotation/scaling transformation
VECTOR Shift; ; object translation
VECTOR Points[PC]; ; "Forms" editor points
For Imagine's "Forms" objects, the "PNTS" chunk above is not
written out, but this structure is written instead. The point
count is PC = NumC + 4 * NumF. The object's real points are
then calculated from these using a proprietary algorithm.
The tranformation parameters above allow the axes of the
real object be moved around relative to the "Forms" points.
DESC notes
----------
Again, most of these fields are optional, and defaults are supplied.
However, if there is a FACE chunk, there must also be a CLST chunk,
an RLST chunk and a TLST chunk -- all with matching "count" fields.
The SHAP chunk is not optional.
Defaults are: Colors set to (240,240,240); reflection and
transmission coefficients set to zero; illegal shape; no story or
special surface types; position at (0,0,0); axes aligned to the
world axes; size fields all 32.0; intensity at 300; no name;
no points/edges or faces; texture parameters set to zero; refraction
type 0 with index 1.00; specular, hardness and roughness set to zero;
blending at 255; glossy off; phong shading on; not a light source;
not brightly lit;
In Imagine, defaults are the same, but with colors (255,255,255).
INFO sub-chunks
---------------
BRSH - size 82
WORD Number; ; Brush number (between 0 and 7)
CHAR Filename[80]; ; IFF ILBM filename
There may be more than one of these.
STNC - size 82
Same format as BRSH chunk.
TXTR - size 82
Same format as BRSH chunk. The Filename field is the name of
a code module that can be loaded with LoadSeg().
OBSV - size 28
VECTOR Camera; ; Camera position
VECTOR Rotate; ; Camera rotation angles
FRACT Focal; ; Camera focal length
This tells where the camera is, how it is aimed, and its
focal length. The rotation angles are in degrees, and specify
rotations around the X, Y, and Z axes. The camera looks down
its own Y axis, with the top of the picture in the direction of
the Z axis. If the rotation angles are all zero, its axes
are aligned with the world coordinate axes. The rotations are
performed in the order ZXY about the camera axes. A positive
angle rotates Y toward Z, Z toward X, and X toward Y for
rotations about the X, Y, and Z axes respectively. To
understand the focal length, imagine a 320 x 200 pixel
rectangle perpendicular to, and centered on the camera's
Y axis. Any objects in the infinite rectangular cone defined
by the camera position and the 4 corners of the rectangle will
appear in the picture.
OTRK - size 18
BYTE Trackname[18];
This chunk specifies the name of an object that the camera
is "tracked" to. If the name is NULL, the camera doesn't
track. Otherwise, if the object is moved inside Turbo Silver,
the camera will follow it.
OSTR - size 56
STORY CStory; ; a STORY structure for the camera
The story structure is defined above.
FADE - size 12
FRACT FadeAt; ; distance to start fade
FRACT FadeBy; ; distance of total fade
BYTE pad; ; pad byte - must be zero
COLOR FadeTo; ; RGB color to fade to
SKYC - size 8
BYTE pad; ; pad byte - must be zero
COLOR Horizon; ; horizon color
BYTE pad; ; pad byte - must be zero
COLOR Zenith; ; zenith color
AMBI - size 4
BYTE pad; ; pad byte - must be zero
COLOR Ambient; ; abmient light color
GLB0 - size 8
BYTE Props[8]; ; an array of 8 "global properties" used
; by Turbo Silver.
Props[0] - GLB_EDGING ; edge level (globals requester)
Props[1] - GLB_PERTURB ; perturbance (globals requester)
Props[2] - GLB_SKY_BLEND ; sky blending factor (0-255)
Props[3] - GLB_LENS ; lens type (see below)
Props[4] - GLB_FADE ; flag - Sharp/Fuzzy focus (globals)
Props[5] - GLB_SIZE ; "apparant size" (see below)
Props[6] - GLB_RESOLVE ; resolve depth (globals requester)
Props[7] - GLB_EXTRA ; flag - genlock sky on/off
The edging and perturbance values control the heuristics in
ray tracing. The sky blending factor is zero for no blending,
and 255 for full blending. The lens type is a number from 0
4, corresponding to the boxes in the "camera" requester, and
correspond to 0) Manual, 1) Wide angle, 2) Normal, 3) Telephoto,
and 4) Custom. It is used in setting the camera's focal length
if the camera is tracked to an object. The Sharp/Fuzzy flag
turns the "fade" feature on and off - non-zero means on.
The "apparant size" parameter is 100 times the "custom size"
parameter in the camera requester. And is used to set the
focal length for a custom lens. The "resolve depth" controls
the number of rays the ray tracer will shoot for a single pixel.
Each reflective/refractive ray increments the depth counter, and
the count is never allowed to reach the "resolve depth". If both
a reflective and a refractive ray are traced, each ray gets its
own version of the count - so theoretically, a resolve depth of
4 could allow much more than 4 rays to be traced. The "genlock
sky" flag controls whether the sky will be colored, or set to
the genlock color (color 0 - black) in the final picture.
All of the INFO sub-chunks are optional, as is the INFO chunk.
Default values are supplied if the chunks are not present. The
defaults are: no brushes, stencils, or textures defined; no story
for the camera; horizon and zenith and ambient light colors set
to black; fade color set to (80,80,80); un-rotated, un-tracked
camera at (-100, -100, 100); and global properties array set to
[30, 0, 0, 0, 0, 100, 8, 0].
EXTR sub-sub-chunks
-------------------
MTRX - size 60
VECTOR Translate; ; translation vector
VECTOR Scale; ; X,Y and Z scaling factors
MATRIX Rotate; ; rotation matrix
The translation vector is i world coordinates.
The scaling factors are with respect to local axes.
The rotation matrix is with respect to the world axes,
and it should be a "unit matrix".
The rotation is such that a rotated axis's X,Y, and Z
components are the dot products of the MATRIX's I,J,
and K vectors with the un-rotated axis vector.
LOAD - size 80
BYTE Filename[80]; ; the name of the external file
This chunk contains the name of an external object file.
The external file should be a FORM TDDD file. It may contain
an any number of objects possibly grouped into heirarchy(ies).
Both of these chunks are required.
ProWrite document format
IFF FORM / CHUNK DESCRIPTION
============================
Form/Chunk IDs:
FORM WORD
Chunks FONT,COLR,DOC,HEAD,FOOT,PCTS,PARA,TABS,PAGE,TEXT,FSCC,PINF
Date Submitted: 03/87
Submitted by: James Bayless - New Horizons Software, Inc.
FORM
====
FORM ID: WORD
FORM Purpose: Document storage (supports color, fonts, pictures)
FORM Description:
This include file describes FORM WORD and its Chunks
/*
* IFF Form WORD structures and defines
* Copyright (c) 1987 New Horizons Software, Inc.
*
* Permission is hereby granted to use this file in any and all
* applications. Modifying the structures or defines included
* in this file is not permitted without written consent of
* New Horizons Software, Inc.
*/
#include ":IFF/ILBM.h" /* Makes use of ILBM defines */
#define ID_WORD MakeID('W','O','R','D') /* Form type */
#define ID_FONT MakeID('F','O','N','T') /* Chunks */
#define ID_COLR MakeID('C','O','L','R')
#define ID_DOC MakeID('D','O','C',' ')
#define ID_HEAD MakeID('H','E','A','D')
#define ID_FOOT MakeID('F','O','O','T')
#define ID_PCTS MakeID('P','C','T','S')
#define ID_PARA MakeID('P','A','R','A')
#define ID_TABS MakeID('T','A','B','S')
#define ID_PAGE MakeID('P','A','G','E')
#define ID_TEXT MakeID('T','E','X','T')
#define ID_FSCC MakeID('F','S','C','C')
#define ID_PINF MakeID('P','I','N','F')
/*
* Special text characters for page number, date, and time
* Note: ProWrite currently supports only PAGENUM_CHAR, and only in
* headers and footers
*/
#define PAGENUM_CHAR 0x80
#define DATE_CHAR 0x81
#define TIME_CHAR 0x82
/*
* Chunk structures follow
*/
/*
* FONT - Font name/number table
* There are one of these for each font/size combination
* These chunks should appear at the top of the file (before document data)
*/
typedef struct {
UBYTE Num; /* 0 .. 255 */
UWORD Size;
/* UBYTE Name[]; */ /* NULL terminated, without ".font" */
} FontID;
/*
* COLR - Color translation table
* Translates from color numbers used in file to ISO color numbers
* Should be at top of file (before document data)
* Note: Currently ProWrite only checks these values to be its current map,
* it does no translation as it does for FONT chunks
*/
typedef struct {
UBYTE ISOColors[8];
} ISOColors;
/*
* DOC - Begin document section
* All text and paragraph formatting following this chunk and up to a
* HEAD, FOOT, or PICT chunk belong to the document section
*/
#define PAGESTYLE_1 0 /* 1, 2, 3 */
#define PAGESTYLE_I 1 /* I, II, III */
#define PAGESTYLE_i 2 /* i, ii, iii */
#define PAGESTYLE_A 3 /* A, B, C */
#define PAGESTYLE_a 4 /* a, b, c */
typedef struct {
UWORD StartPage; /* Starting page number */
UBYTE PageNumStyle; /* From defines above */
UBYTE pad1;
LONG pad2;
} DocHdr;
/*
* HEAD/FOOT - Begin header/footer section
* All text and paragraph formatting following this chunk and up to a
* DOC, HEAD, FOOT, or PICT chunk belong to this header/footer
* Note: This format supports multiple headers and footers, but currently
* ProWrite only allows a single header and footer per document
*/
#define PAGES_NONE 0
#define PAGES_LEFT 1
#define PAGES_RIGHT 2
#define PAGES_BOTH 3
typedef struct {
UBYTE PageType; /* From defines above */
UBYTE FirstPage; /* 0 = Not on first page */
LONG pad;
} HeadHdr;
/*
* PCTS - Begin picture section
* Note: ProWrite currently requires NPlanes to be three (3)
*/
typedef struct {
UBYTE NPlanes; /* Number of planes used in picture bitmaps */
UBYTE pad;
} PictHdr;
/*
* PARA - New paragraph format
* This chunk should be inserted first when a new section is started (DOC,
* HEAD, or FOOT), and again whenever the paragraph format changes
*/
#define SPACE_SINGLE 0
#define SPACE_DOUBLE 0x10
#define JUSTIFY_LEFT 0
#define JUSTIFY_CENTER 1
#define JUSTIFY_RIGHT 2
#define JUSTIFY_FULL 3
#define MISCSTYLE_NONE 0
#define MISCSTYLE_SUPER 1 /* Superscript */
#define MISCSTYLE_SUB 2 /* Subscript */
typedef struct {
UWORD LeftIndent; /* In decipoints (720 dpi) */
UWORD LeftMargin;
UWORD RightMargin;
UBYTE Spacing; /* From defines above */
UBYTE Justify; /* From defines above */
UBYTE FontNum; /* FontNum, Style, etc. for first char in para*/
UBYTE Style; /* Standard Amiga style bits */
UBYTE MiscStyle; /* From defines above */
UBYTE Color; /* Internal number, use COLR to translate */
LONG pad;
} ParaFormat;
/*
* TABS - New tab stop types/locations
* Use an array of values in each chunk
* Like the PARA chunk, this should be inserted whenever the tab settings
* for a paragraph change
* Note: ProWrite currently does not support TAB_CENTER
*/
#define TAB_LEFT 0
#define TAB_CENTER 1
#define TAB_RIGHT 2
#define TAB_DECIMAL 3
typedef struct {
UWORD Position; /* In decipoints */
UBYTE Type;
UBYTE pad;
} TabStop;
/*
* PAGE - Page break
* Just a marker -- this chunk has no data
*/
/*
* TEXT - Paragraph text (one block per paragraph)
* Block is actual text, no need for separate structure
* If the paragraph is empty, this is an empty chunk -- there MUST be
* a TEXT block for every paragraph
* Note: The only ctrl characters ProWrite can currently handle in TEXT
* chunks are Tab and PAGENUM_CHAR, ie no Return's, etc.
*/
/*
* FSCC - Font/Style/Color changes in previous TEXT block
* Use an array of values in each chunk
* Only include this chunk if the previous TEXT block did not have
* the same Font/Style/Color for all its characters
*/
typedef struct {
UWORD Location; /* Character location in TEXT chunk of change */
UBYTE FontNum;
UBYTE Style;
UBYTE MiscStyle;
UBYTE Color;
UWORD pad;
} FSCChange;
/*
* PINF - Picture info
* This chunk must only be in a PCTS section
* Must be followed by ILBM BODY chunk
* Pictures are treated independently of the document text (like a
* page-layout system), this chunk includes information about what
* page and location on the page the picture is at
* Note: ProWrite currently only supports mskTransparentColor and
* mskHasMask masking
*/
typedef struct {
UWORD Width, Height; /* In pixels */
UWORD Page; /* Which page picture is on (0..max) */
UWORD XPos, YPos; /* Location on page in decipoints */
Masking Masking; /* Like ILBM format */
Compression Compression; /* Like ILBM format */
UBYTE TransparentColor; /* Like ILBM format */
UBYTE pad;
} PictInfo;
/* end */
Additional documents
Intro to IFF Amiga ILBM Files and Amiga Viewmodes
The IFF (Interchange File Format) for graphic images on the Amiga is called FORM ILBM (InterLeaved BitMap). It follows a standard parsable IFF format.
Sample hex dump of beginning of an ILBM
Important note! You can NOT ever depend on any particular ILBM chunk being at any particular offset into the file! IFF files are composed, in their simplest form, of chunks within a FORM. Each chunk starts starts with a 4-letter chunkID, followed by a 32-bit length of the rest of the chunk. You PARSE IFF files, skipping past unneeded or unknown chunks by seeking their length (+1 if odd length) to the next 4-letter chunkID.
0000: 464F524D 00016418 494C424D 424D4844 FORM..d.ILBMBMHD 0010: 00000014 01400190 00000000 06000100 .....@.......... 0020: 00000A0B 01400190 43414D47 00000004 .....@..CAMG.... 0030: 00000804 434D4150 00000030 001100EE ....CMAP...0.... 0040: EEEE0000 22000055 33333355 55550033 .... ..P000PPP.0 0050: 99885544 77777711 66EE2266 EE6688DD ..P@ppp.`. `.`.. 0060: AAAAAAAA 99EECCCC CCDDAAEE 424F4459 ............BODY 0070: 000163AC F8000F80 148A5544 2ABDEFFF ..c.......UD*... etc.
Interpretation:
'F O R M' length 'I L B M''B M H D'<-start of BitMapHeader chunk
0000: 464F524D 00016418 494C424D 424D4844 FORM..d.ILBMBMHD
length WideHigh XorgYorg PlMkCoPd <- Planes Mask Compression Pad
0010: 00000014 01400190 00000000 06000100 .....@..........
start of C-AMiGa
TranAspt PagwPagh 'C A M G' length <- View modes chunk
0020: 00000A0B 01400190 43414D47 00000004 .....@..CAMG....
Viewmode 'C M A P' length R g b R <- Viewmode 800=HAM | 4=LACE
0030: 00000804 434D4150 00000030 001100EE ....CMAP...0....
g b R g b R g b R g b R g b R g <- Rgb's are for reg0 thru regN
0040: EEEE0000 22000055 33333355 55550033 .... ..P000PPP.0
b R g b R g b R g b R g b R g b
0050: 99885544 77777711 66EE2266 EE6688DD ..P@ppp.`. `.`..
R g b R g b R g b R g b 'B O D Y'
0060: AAAAAAAA 99EECCCC CCDDAAEE 424F4459 ............BODY
Compacted
length start of body data <- (Compression=1 above)
0070: 000163AC F8000F80 148A5544 2ABDEFFF ..c.......UD*...
0080: FFBFF800 0F7FF7FC FF04F85A 77AD5DFE ...........Zw.]. etc.
Notes on CAMG Viewmodes: HIRES=0x8000 LACE=0x4 HAM=0x800 HALFBRITE=0x80
Interpreting ILBMs
ILBM is a fairly simple IFF FORM. All you really need to deal with to extract the image are the following chunks:
(Note - Also watch for AUTH Author chunks and (c) Copyright chunks
and preserve any copyright information if you rewrite the ILBM)
BMHD - info about the size, depth, compaction method
(See interpreted hex dump above)
CAMG - optional Amiga viewmodes chunk
Most HAM and HALFBRITE ILBMs should have this chunk. If no
CAMG chunk is present, and image is 6 planes deep, assume
HAM and you'll probably be right. Some Amiga viewmodes
flags are HIRES=0x8000, LACE=0x4, HAM=0x800, HALFBRITE=0x80.
Note that new Amiga 2.0 ILBMs may have more complex 32-bit
numbers (modeid) stored in the CAMG. However, the bits
described above should get you a compatible old viewmode.
CMAP - RGB values for color registers 0 to n
(each component left justified in a byte)
If a deep ILBM (like 12 or 24 planes), there should be no CMAP
and instead the BODY planes are interpreted as the bits of RGB
in the order R0...Rn G0...Gn B0...Bn
BODY - The pixel data, stored in an interleaved fashion as follows:
(each line individually compacted if BMHD Compression = 1)
plane 0 scan line 0
plane 1 scan line 0
plane 2 scan line 0
...
plane n scan line 0
plane 0 scan line 1
plane 1 scan line 1
etc.
Body Compression
The BODY contains pixel data for the image. Width, Height, and depth (Planes) is specified in the BMHD.
If the BMHD Compression byte is 0, then the scan line data is not compressed. If Compression=1, then each scan line is individually compressed as follows:
More than 2 bytes the same stored as BYTE code value n from -1 to -127 followed by byte to be repeated (-n) + 1 times. Varied bytes stored as BYTE code n from 0 to 127 followed by n+1 bytes of data.
The byte code -128 is a NOP.
Interpreting the Scan Line Data
If the ILBM is not HAM or HALFBRITE, then after parsing and uncompacting if necessary, you will have N planes of pixel data. Color register used for each pixel is specified by looking at each pixel thru the planes. I.e., if you have 5 planes, and the bit for a particular pixel is set in planes 0 and 3:
PLANE 4 3 2 1 0 PIXEL 0 1 0 0 1
then that pixel uses color register binary 01001 = 9
The RGB value for each color register is stored in the CMAP chunk of the ILBM, starting with register 0, with each register’s RGB value stored as one byte of R, one byte G, and one byte of B, with each component scaled to 8-bits. (ie. 4-bit Amiga R, G, and B components are each stored in the high nibble of a byte. The low nibble may also contain valid data if the color was stored with 8-bit-per-gun color resolution).
BUT - if the picture is HAM or HALFBRITE, it is interpreted differently.
Hopefully, if the picture is HAM or HALFBRITE, the package that saved it properly saved a CAMG chunk (look at a hex dump of your file with ACSII interpretation - you will see the chunks - they all start with a 4-ASCII- character chunk ID). If the picture is 6 planes deep and has no CAMG chunk, it is probably HAM. If you see a CAMG chunk, the "CAMG" is followed by the 32-bit chunk length, and then the 32-bit Amiga Viewmode flags.
HAM pics with a 16-bit CAMG will have the 0x800 bit set in CAMG ViewModes. HALBRITE pics will have the 0x80 bit set.
To transport a HAM or HALFBRITE picture to another machine, you must understand how HAM and HALFBRITE work on the Amiga.
How Amiga HAM mode works
Amiga HAM (Hold and Modify) mode lets the Amiga display all 4096 RGB values. In HAM mode, the bits in the two last planes describe an R G or B modification to the color of the previous pixel on the line to create the color of the current pixel. So a 6-plane HAM picture has 4 planes for specifying absolute color pixels giving up to 16 absolute colors which would be specified in the ILBM CMAP chunk. The bits in the last two planes are color modification bits which cause the Amiga, in HAM mode, to take the RGB value of the previous pixel (Hold and), substitute the 4 bits in planes 0-3 for the previous color’s R G or B component (Modify) and display the result for the current pixel. If the first pixel of a scan line is a modification pixel, it modifies the RGB value of the border color (register 0). The color modification bits in the last two planes (planes 4 and 5) are interpreted as follows:
00 - no modification. Use planes 0-3 as normal color register index 10 - hold previous, replacing Blue component with bits from planes 0-3 01 - hold previous, replacing Red component with bits from planes 0-3 11 - hold previous. replacing Green component with bits from planes 0-3
How Amiga HALFBRITE mode works
This one is simpler. In HALFBRITE mode, the Amiga interprets the bit in the last plane as HALFBRITE modification. The bits in the other planes are treated as normal color register numbers (RGB values for each color register is specified in the CMAP chunk). If the bit in the last plane is set (1), then that pixel is displayed at half brightness. This can provide up to 64 absolute colors.
Other Notes
Amiga ILBMs images must be a even number of bytes wide. Smaller images (such as brushes) are padded to an even byte width.
ILBMs created with Electronic Arts IBM and Amiga “DPaintII” packages are compatible (though you may have to use a ’.lbm’ filename extension on an IBM). The ILBM graphic files may be transferred between the machines (or between the Amiga and IBM sides your Amiga if you have a CBM Bridgeboard card installed) and loaded into either package.
