Format
M4A Audio
Summary
- Name
- M4A Audio
- Identifiers
-
- PUID: fmt/2094
- MIME: audio/mp4
- Format type
- Audio
- Description
- M4A is an audio format based on the MPEG-4 Part 14 file format (ISO/IEC 14496-14), using the lossy AAC (Advanced Audio Coding) codec for audio encoding. It shares the same underlying container structure as MPEG-4 video files, and shares the .m4a file extension with ALAC (Apple Lossless Audio Codec) files, from which it is distinguished by its use of lossy rather than lossless compression. The format was introduced by Apple and is commonly associated with the iTunes ecosystem.
- File extensions
-
m4a,m4b - Source
- Preservica / Preservica
Relationships
- Has lower priority than
- Has priority over
Internal signatures
M4A Audio
- Note
- BOF, offset 4: 'ftyp' specifying 'M4A ' as the major brand. Note that not all AAC audio files using the .m4a extension will carry this signature. Files produced by non-Apple toolchains may use a generic major brand such as 'mp42' or 'isom' despite containing equivalent audio content. For now any such files will continue to identify as fmt/199 MPEG-4 Media.
Byte sequences
- Min Frag Length
- Absolute from BOF
- Offset
- 4
- Max offset
- 0
- Byte Sequence
667479704D344120- Endianness
- None
Changelog
-
Added in V123
- Release date
- 9 June 2026
M4A Audio: Signature researched and samples provided by Preservica, Archives New Zealand and Brigham Young University.
M4A Audio: Full entry added. Submitted by Preservica, Archives New Zealand and Brigham Young University.