ISO base media file format

The ISO base media file format is directly based on Apple's QuickTime container format. It was developed by MPEG (in ISO/IEC JTC 1/SC 29, originally Working Group 11 MPEG, currently Working Group 3 MPEG Systems). The first MP4 file format specification was created on the basis of the QuickTime format specification published in 2001. The MP4 file format known as "version 1" was published in 2001 as ISO/IEC 14496-1:2001, as revision of the MPEG-4 Part 1: Systems. In 2003, the first version of the MP4 file format was revised and replaced by MPEG-4 Part 14: MP4 file format (ISO/IEC 14496-14:2003), commonly known as MPEG-4 file format "version 2". The MP4 file format was generalized into the ISO base media file format (ISO/IEC 14496-12:2004 or ISO/IEC 15444-12:2004), which defines a general structure for time-based media files. It is used as the basis for other file formats in the family such as MP4, 3GP, and Motion JPEG 2000). == Extensions ==

video compression. The High Efficiency Image File Format (HEIF) is an image container format using the ISO base media file format as the basis. While HEIF can be used with any image compression format, it specifically includes support for HEVC intra-coded images and HEVC-coded image sequences, taking advantage of inter-picture prediction. Some of the above-mentioned MPEG standard extensions are used by other formats based on ISO base media file format (e.g., 3GP). The 3GPP file format (.3gp) specification also defined extensions to support H.263 video, AMR-NB, AMR-WB, AMR-WB+ audio, and 3GPP Timed Text in files based on the ISO base media file format. The 3GPP2 file format (.3g2) defined extensions for usage of EVRC, SMV, or 13K (QCELP) voice compression formats. The MPEG-21 File Format (.m21, .mp21) defined the storage of an MPEG-21 Digital Item in the ISO base media file format, with some or all of its ancillary data (such as movies, images, or other non-XML data) within the same file. The OMA DRM Content Format (.dcf) specification from Open Mobile Alliance defined the content format for DRM protected encrypted media objects and associated metadata. There are also other extensions, such as ISMA ISMACryp specification for encrypted/protected audio and video, G.719 audio compression specification, AC3 and E-AC-3 audio compression, DTS audio compression, Dirac video compression, VC-1 video compression specification and others, which are named on the MP4 Registration authority's website. There are some extensions of the ISO base media file format that were not registered by the MP4 Registration authority. Adobe Systems introduced the F4V file format for Flash Video in 2007 and said it is based on the ISO base media file format. The F4V file format was not registered by the MP4 registration authority, but the F4V technical specification is publicly available. This format can contain H.264 video compression and MP3 or AAC audio compression. In addition, the F4V file format can contain data corresponding to the ActionScript Message Format and still frame of video data using image formats GIF, JPEG and PNG. Microsoft Corporation announced a file format based on the ISO base media file format in 2009 called ISMV (Smooth Streaming format), also known as Protected Interoperable File Format (PIFF). As announced, this format can, for example, contain VC-1, WMA, H.264, and AAC compression formats. Microsoft published a Protected Interoperable File Format (PIFF) specification in 2010. It defined another usage of multiple encryption and DRM systems in a single file container. The PIFF brand was registered by the MP4 registration authority in 2010. Some extensions used by this format (e.g., for WMA support) were not registered. Usage of the WMA compression format in the ISO base media file format was not publicly documented. == Technical details ==

The ISO base media file format includes timing, structure, and media information for timed sequences of media data, such as audio-visual presentations. The file structure is object-oriented. A file can be decomposed into basic objects very simply, and the structure of the objects is implied from their type. Files conforming to the ISO base media file format are formed as a series of objects, called "boxes". All data is contained in boxes, and there is no other data within the file. This includes any initial signature required by the specific file format. The "box" is an object-oriented building block defined by a unique type identifier and length. It was called an "atom" in some specifications (e.g., the first definition of the MP4 file format). A brand might indicate the type of encoding used, how the data of each encoding is stored, constraints and extensions that are applied to the file, the compatibility, or the intended usage of the file. Brands are printable four-character codes. A file type box contains two kinds of brands. One is "major_brand", which identifies the specification of the best use for the file. It is followed by "minor_version", an informative 4-byte integer for the minor version of the major brand. The second kind of brand is "compatible_brands", which identifies multiple specifications to which the file complies. All files shall contain a file type box, but for compatibility reasons with an earlier version of the specification, files may be conformant to ISO/IEC base media file format and not contain a file type box. In that case, they should be read as if they contained an ftyp with a major and compatible brand "mp41" (MP4 v1 – ISO 14496-1, Chapter 13). == References ==