AIFC (AIFF-C Compressed Audio)
Apple's 1991 extension to AIFF that adds a codec field so any compression algorithm can ride inside the same chunk-based container.
| Full name | AIFF-C Compressed Audio |
| Extension | .aifc |
| MIME type | audio/x-aiff |
| Developer | Apple Computer, Inc. |
| Released | 1991 (specification dated August 26, 1991) |
| Type | Compressed/uncompressed audio container |
| Base format | AIFF 1.3 (itself derived from EA's IFF) |
| Supported codecs | NONE (PCM), sowt (little-endian PCM), IMA4 (ADPCM 4:1), MACE 3:1, MACE 6:1, µ-law, A-law, fl32, fl64 |
What is a AIFC file?
AIFC is Apple's compressed extension of the Audio Interchange File Format, published in August 1991. It adds a four-character codec field to the AIFF Common chunk, letting the file carry audio compressed with any registered algorithm rather than only raw PCM. The file type identifier changes from AIFF to AIFC, which is how players tell the two formats apart.
AIFC is a chunk-based audio container. Every file opens with a FORM chunk that wraps all the inner chunks, and the type field in that FORM chunk reads AIFC instead of AIFF. The Common chunk (COMM) is extended with two extra fields: a four-character codec code and a human-readable codec name string. The audio data itself lives in the Sound Sample Data chunk (SSND), encoded according to whatever codec the COMM chunk specifies. Because the codec code is just a FourCC identifier, any compression scheme can be added without changing the container format.
History
Apple released AIFF 1.3 on January 4, 1989, as an uncompressed audio container for the Macintosh. Two years later, on August 26, 1991, Apple published the AIFF-C specification to give QuickTime and other Mac software a standard way to store compressed audio. Early codecs bundled with the spec included MACE (Macintosh Audio Compression/Expansion), which shipped at 3:1 and 6:1 ratios, and IMA4, a 4:1 ADPCM variant. Over time, newer formats like AAC, ALAC, and FLAC displaced AIFC's compressed variants, though the AIFC container itself remains common in professional audio software.
How it works
An AIFC file is a nested set of IFF chunks, each with a four-byte chunk ID, a four-byte big-endian length, and the chunk payload. The outermost FORM chunk acts as the envelope; its type field is the literal bytes AIFC. Inside, the mandatory COMM chunk describes the audio: number of channels, total sample frames, bit depth, and sample rate stored as an 80-bit IEEE 754 extended-precision float. The COMM chunk in AIFC also carries the codec FourCC and a Pascal-style codec name string. The SSND chunk holds the actual audio samples, preceded by an offset and a block-size field for alignment. Optional chunks such as MARK (markers) and INST (instrument loops) may also appear.
What it is used for
- Storing Mac-era audio compressed with Apple MACE or IMA4 codecs from legacy QuickTime projects
- Archiving original recording sessions in software that defaults to AIFC with the NONE codec (equivalent to uncompressed AIFF but with the AIFC wrapper)
- Reading and converting game audio assets from 1990s Mac and IRIX titles that shipped audio data in IMA4-compressed AIFC files
- Professional audio software workflows on macOS where Final Cut Pro, Logic Pro, or Pro Tools generate AIFC sidecar files alongside video exports
How to open it
macOS opens AIFC files natively in QuickTime Player and iTunes/Music. On Windows and Linux, VLC, Audacity, and FFmpeg handle AIFC files for most codec variants, though very old MACE-compressed files may need a dedicated Mac-compatible player.
Pros and cons
Strengths
- Same chunk structure as AIFF, so existing AIFF-aware software can parse the container with minimal changes
- Codec is declared explicitly in the file header, removing ambiguity about how the audio data is encoded
- Supports uncompressed PCM through the NONE and sowt codec codes, making AIFC a drop-in AIFF replacement when no compression is needed
- Widely supported on macOS at the OS level, requiring no additional codecs for common variants
Trade-offs
- Compressed variants (MACE, older ADPCM) are largely obsolete and unsupported in modern players outside macOS
- Big-endian byte order by default adds a conversion step on little-endian hardware unless the sowt codec is used
- Practically replaced by ALAC for lossless and AAC for lossy on Apple platforms, leaving AIFC in a legacy position
- The 80-bit extended-precision sample rate field is unusual and causes compatibility problems in some third-party parsers
Convert AIFC files
Free, in your browser, no signup. Start at the AIFC converter, or jump straight to a popular conversion below.
Curious how fast and how small? See our measured conversion benchmarks.
AIFC FAQ
What is the difference between AIFF and AIFC?
AIFF stores only uncompressed PCM audio. AIFC extends the AIFF Common chunk with a codec field, so it can store either compressed or uncompressed audio. The FORM chunk type changes from AIFF to AIFC to signal the difference. In practice, many tools treat AIFF and AIFC as the same format because AIFC with the NONE codec is functionally identical to AIFF.
Can I play an AIFC file on Windows?
Yes, with the right software. VLC and Audacity both support AIFC on Windows for common codecs like IMA4 and uncompressed PCM. Older MACE-compressed AIFC files are harder to decode outside macOS because MACE decoders are rare on Windows.
Is AIFC lossless?
It depends on the codec stored inside the file. AIFC with the NONE or sowt codec is fully lossless (raw PCM). AIFC with IMA4, MACE, µ-law, or A-law is lossy. The file extension alone does not tell you which codec is used; you need a tool that reads the COMM chunk to find out.
What should I convert AIFC to for modern use?
For lossless audio, convert to FLAC or WAV, both of which have broad cross-platform support. For lossy audio where file size matters, AAC or MP3 are the standard choices. If you are staying in the Apple ecosystem and want lossless, ALAC inside an M4A container is the modern equivalent.