924 MPEG-4 Media File Audio, Video Container format that can contain any of a number of audio and video codecs. It may also contain subtitle data or file metadata. This family of container can be used with several different file extensions. Text 1 Digital Preservation Department / The National Archives 27 Oct 2009 08/2023 (v.113) - Priority added over fmt/1616 (BibTeX Database File). Internally researched; 04/2024 (v.118): Description added as part of PRONOM Research Week 2023. Submitted by The Church of Jesus Christ of Latter-day Saints; v.123- New extension added of .m4b. Submitted by Archives New Zealand. 9 Jun 2026 application/mp4 MIME fmt/199 PUID video/mp4 MIME mp4 File extension m4v File extension m4a File extension f4v File extension f4a File extension m4b File extension File extension 278 MP4 Media File Represents the following character sequence: {4}ftyp{0-64}(mp42|mp41|isom|iso2)*moov 1 Absolute from BOF 4 Little-endian 66747970{0-64}(6D703432|6D703431|69736F6D|69736F32)*6D6F6F76 Has lower priority than 1103 3GPP Audio/Video File Has lower priority than 1388 Apple Lossless Audio Codec Has lower priority than 2422 Canon Raw Has priority over 658 Quicktime Has priority over 2443 BibTeX Database File