Newsgroups: alt.binaries.sounds.d,alt.sex.sounds
Subject: Format of the IFF header (Amiga sounds)
Message-ID: <2509@tardis.Tymnet.COM>
From: jms@tardis.Tymnet.COM (Joe Smith)
Date: 23 Oct 91 23:54:38 GMT
Followup-To: alt.binaries.sounds.d
Organization: BT North America (Tymnet)
The first 12 bytes of an IFF file are used to distinguish between an Amiga picture (FORM-ILBM), an Amiga sound sample (FORM-8SVX), or other file conforming to the IFF specification. The middle 4 bytes is the count of bytes that follow the "FORM" and byte count longwords. (Numbers are stored in M68000 form, high order byte first.)
FutureSound audio file, 15000 samples at 10.000KHz, file is 15048 bytes long.
| 0000: | 464F524D F O R M | 00003AC0 15040 | 38535658 8 S V X | 56484452 V H D R | FORM..:.8SVXVHDR |
| 0010: | 00000014 20 | 00003A98 15000 | 00000000 0 | 00000000 0 | ......:......... |
| 0020: | 27100100 10000 1 0 | 00010000 1.0 | 424F4459 B O D Y | 00003A98 15000 | '.......BODY..:. |
0000000..03 = "FORM", identifies this as an IFF format file. FORM+00..03 (ULONG) = number of bytes that follow. (Unsigned long int.) FORM+03..07 = "8SVX", identifies this as an 8-bit sampled voice.
????+00..03 = "VHDR", Voice8Header, describes the parameters for the BODY. VHDR+00..03 (ULONG) = number of bytes to follow. VHDR+04..07 (ULONG) = samples in the high octave 1-shot part. VHDR+08..0B (ULONG) = samples in the high octave repeat part. VHDR+0C..0F (ULONG) = samples per cycle in high octave (if repeating), else 0. VHDR+10..11 (UWORD) = samples per second. (Unsigned 16-bit quantity.) VHDR+12 (UBYTE) = number of octaves of waveforms in sample. VHDR+13 (UBYTE) = data compression (0=none, 1=Fibonacci-delta encoding). VHDR+14..17 (FIXED) = volume. (The number 65536 means 1.0 or full volume.)
????+00..03 = "BODY", identifies the start of the audio data. BODY+00..03 (ULONG) = number of bytes to follow. BODY+04..NNNNN = Data, signed bytes, from -128 to +127.
0030: 04030201 02030303 04050605 05060605 0040: 06080806 07060505 04020202 01FF0000 0050: 00000000 FF00FFFF FFFEFDFD FDFEFFFF 0060: FDFDFF00 00FFFFFF 00000000 00FFFF00 0070: 00000000 00FF0000 00FFFEFF 00000000 0080: 00010000 000101FF FF0000FE FEFFFFFE 0090: FDFDFEFD FDFFFFFC FDFEFDFD FEFFFEFE 00A0: FFFEFEFE FEFEFEFF FFFFFEFF 00FFFF01
This small section of the audio sample shows the number ranging from -5 (0xFD) to +8 (0x08). Warning: Do not assume that the BODY starts 48 bytes into the file. In addition to "VHDR", chunks labeled "NAME", "AUTH", "ANNO", or "(c) " may be present, and may be in any order. You will have to check the byte count in each chunk to determine how many bytes to skip.
[ Index | Previous paragraph | Next Paragraph ]