.AIFC File Format

Audio Interchange File Format with compression (AIFF-C)

Introduction

AIFF-C is the 1991 extension of Apple’s AIFF for compressed audio. The file’s form type is AIFC, and the common chunk gains a compression type and name. Despite the name, many AIFF-C files hold plain PCM: the compression type NONE means big-endian PCM, and sowt, which Apple added for Mac OS X, means little-endian PCM. Others carry floats, µ-law, A-law or a real codec such as IMA ADPCM.

Files use the extensions .aifc, .aiff and .aif. The extension does not decide the format; the form type does.

Structure

An AIFF-C file is one IFF FORM chunk with the form type AIFC, holding chunks in any order; see Chunks. Three chunks are required: the format version chunk FVER, the common chunk COMM, and the sound data chunk SSND, unless there are no sample frames. Compression types name the codec. Optional metadata chunks carry markers, comments and instrument settings.

  1. 0FORM chunk ID, length, form type AIFC12 bytes
    1. 12FVER format version12 bytes
    2. 24COMM channels, frames, sample size, rate, compression type and namevaries
    3. …SSND offset, block size, then the audiovaries
    4. …MARK, COMT, INST and other optional chunksvaries
An AIFF-C file.

Telling it apart

Bytes 0 to 3 are FORM and bytes 8 to 11 are AIFC. A file with AIFF at offset 8 is plain AIFF. The Mac’s own file-type code can differ from the form type, so the bytes are the reliable test.

Variants

Links

Software

  • QuickTime Player – Apple’s built-in media player, which plays AIFF-C (macOS)
  • Audacity – free audio editor that opens AIFF-C (Windows, macOS, Linux)
  • VLC media player – free player for almost any audio or video file (Windows, macOS, Linux, mobile)
  • FFmpeg – command-line tool that reads and writes AIFF-C with many of the compression types (Windows, macOS, Linux)

Developers

  • libsndfile – library that reads and writes AIFF-C (C)
  • libavformat – FFmpeg’s container library, which demuxes AIFF-C (C)

Reference