Audio File Format Specifications
File Description: AIFF, AIFF-C sound file
File Extension: Commonly .aif,
sometimes .aiff or
File Byte Order: Big-endian, although some (little used) formats contain
little-endian sound data
Prof. Peter Kabal, MMSP Lab, ECE, McGill University: Last update:
AIFF / AIFF-C Specifications
The AIFF and the later AIFF-C specifications came from Apple Computer. This
format is used on SGI machines. The latest data formats from Apple Computer are
supported by the QuickTime player from Apple.
The AIFF and AIFF-C file formats use IFF chunks, each chunk consisting of a
chunk identifier, chunk length and chunk data.
- An implementation for reading and writing AIFF and AIFF-C files is
available as part of the
Audio File Library Project.
AIFF files support only PCM data. They can specify any bit depth within a
container which has a size which is rounded up to a multiple of 8 bits. Thus
they can specify, for instance, 18 bits in a 24-bit container. The data in the
container is left justified and zero padded. Data can be read as if it were the
full precision of the container. The chunk information and the data (in most
cases) is in big-endian byte order.
AIFF-C files can specify a compression type in the
COMM chunk. The compression type is "NONE"
for PCM data. The compression type is accompanied by a printable name. The
following is a table of common compression types.
||IEEE 32-bit float
||IEEE 64-bit float
||8-bit ITU-T G.711 A-law
||8-bit ITU-T G.711 µ-law
||"CCITT G.711 u-law"
||8-bit ITU-T G.711 µ-law (64 kb/s)
||"CCITT G.711 A-law"
||8-bit ITU-T G.711 A-law (64 kb/s)
||IEEE 32-bit float
||SoundHack & Csound
Differences Between AIFF and AIFF-C Files
- The identifier changes from "AIFF"
- The FVER chunk appears only in
- AIFF-C files adds the compression type fields to the
- More information on compression codes recognized by Apple Computer are in
the header files AIFF.h and
in the QuickTime developer kit:
QuickTime Windows SDK.
- Information on SGI's compression codes is found in the header files
- Other compression types appear in
aiff c information.
- Many of the compression schemes listed in the above sources are now
considered obsolete. Of the codes for sample-by-sample coding, the following
are still relevant: "NONE", "ulaw",
and "fl64". Some systems also
recognize the uppercase versions of these names.
- Float values in the Apple Computer schemes are normalized by default to a
full-scale value of one.
- Apple maps Microsoft ACM formats into a compression code of the form "ms??"
where the second two characters are the Microsoft Audio Compression Manager
(ACM) code. For instance, Microsoft ADPCM, with ACM value of 1, is
mapped to the code "ms\x00\x01".
- Apple Computer's QuickTime player recognize only the Apple
compression types. Although "ALAW" and
"ULAW" contain identical sound samples
to the "alaw" and "ulaw"
formats and were in use long before Apple introduced the new codes,
QuickTime does not recognize them.
- The AIFF/AIFF-C specifications allow for the local chunks to occur in any
order. However, most commonly the sound data itself (SSND
chunk) occurs at the end of the file.
- The sampling frequency in the COMM
chunk is stored as an 80-bit IEEE float value.