.MP4 File Format – Brands

Reading a brand

A brand is four bytes, compared byte for byte, so case matters: M4A  and m4a  are different codes. Codes shorter than four characters are padded with spaces (0x20); in the table a trailing space is shown as a gap after the code, so qt   is the bytes 71 74 20 20.

The brands met most often in video files are isom, iso2 to iso9 (the edition of ISO/IEC 14496-12 whose features the file uses), mp41 and mp42 (MP4 version 1 and 2), avc1, M4V  and M4A  (iTunes), qt   (a QuickTime movie), 3gp4 to 3gp9 (3GP), and dash and the cmf* brands for streaming segments. A typical camera or phone MP4 starts:

00 00 00 20 66 74 79 70  69 73 6F 6D 00 00 02 00   ... ftypisom....
69 73 6F 6D 69 73 6F 32  61 76 63 31 6D 70 34 31   isomiso2avc1mp41

That is a 32-byte ftyp with major brand isom, minor version 0x200, and compatible brands isom, iso2, avc1 and mp41.

Registered brands

The Specification column names the registering body or standard as the registry does: ISO is ISO/IEC 14496-12 itself, HEIF is ISO/IEC 23008-12, NALu Video is ISO/IEC 14496-15, OMAF is ISO/IEC 23090-2, CMAF is ISO/IEC 23000-19, DASH is ISO/IEC 23009-1, and 3GPP is TS 26.244.