The ISO base media file format (ISOBMFF) is a
container file format that defines a general structure for files that contain time-based
multimedia
Multimedia is a form of communication that uses a combination of different content forms, such as Text (literary theory), writing, Sound, audio, images, animations, or video, into a single presentation. T ...
data such as video and audio.
It is standardized in
ISO
The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries.
Me ...
/
IEC 14496-12, a.k.a.
MPEG-4
MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related ...
Part 12, and was formerly also published as ISO/IEC 15444-12, a.k.a.
JPEG 2000
JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding their ...
Part 12.
It is designed as a flexible, extensible format that facilitates interchange, management, editing and presentation of the media. The presentation may be local, or via a network or other stream delivery mechanism. The file format is designed to be independent of any particular network protocol while enabling support for them in general.
[
The format has become very widely used for media file storage and as the basis for various other media ]file format
A file format is a Computer standard, standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary format, pr ...
s (e.g. the MP4 and 3GP container formats), and its widespread use was recognized by a Technology & Engineering Emmy Award
The Technology and Engineering Emmy Awards, or Technology and Engineering Emmys, are one of two sets of Emmy Awards that are presented for outstanding achievement in engineering development in the television industry. The Technology and Engineer ...
presented on 4 November 2021 by the National Academy of Television Arts and Sciences
The National Academy of Television Arts and Sciences (NATAS), also known as the National Television Academy until 2007, is an American professional service organization founded in 1955 for "the advancement of the arts and sciences of televisio ...
.
History
The ISO base media file format is directly based on Apple
An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...
's QuickTime container format. It was developed by MPEG
The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by International Organization for Standardization, ISO and International Electrotechnical Commission, IEC that sets standards for media coding, includ ...
(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).[
Historically, the text was also published as ISO/IEC 15444-12 (JPEG 2000 Part 12), although the JPEG 2000 version of the standard was withdrawn in January 2017 since it was redundant with the MPEG-4 publication.][
]
Extensions
The ISO base media file format is designed as an extensible file format. A list of all registered extensions for the ISO base media file format is published on the official registration authority website, www.mp4ra.org.[ The registration authority for code-points (identifier values) in "MP4 Family" files is Apple Inc., and it is named in Annex D (informative) in MPEG-4 Part 12.][ Codec designers should register the codes they invent, but the registration is not mandatory] and some of the invented and used code-points are not registered. When someone is creating a new specification derived from the ISO base media file format, all the existing specifications should be used both as examples and a source of definitions and technology. If an existing specification already covers how a particular media type is stored in the file format (e.g., MPEG-4 audio or video in MP4), that definition should be used and a new one should not be invented.[
]MPEG
The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by International Organization for Standardization, ISO and International Electrotechnical Commission, IEC that sets standards for media coding, includ ...
has standardized a number of specifications extending the ISO base media file format: The MP4 file format (ISO/IEC 14496-14) defined some extensions over the ISO base media file format to support MPEG-4
MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related ...
visual/audio codecs and various MPEG-4 Systems features such as object descriptors and scene descriptions. The MPEG-4 Part 3 (MPEG-4 Audio) standard also defined storage of some audio compression formats. Storage of MPEG-1/2 Audio ( MP3, MP2, MP1) in the ISO base media file format was defined in ISO/IEC 14496-3:2001/Amd 3:2005. The Advanced Video Coding (AVC) file format (ISO/IEC 14496-15) defined support for H.264/MPEG-4 AVC 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
High Efficiency Video Coding (HEVC), also known as H.265 and MPEG-H Part 2, is a video compression standard designed as part of the MPEG-H project as a successor to the widely used Advanced Video Coding (AVC, H.264, or MPEG-4 Part 10). In co ...
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 ]JPEG 2000
JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding their ...
specification (ISO/IEC 15444-3) defined usage of Motion JPEG 2000 video compression and uncompressed audio ( PCM) in the ISO base media file format (.mj2). The "DVB File Format" (.dvb) defined by the DVB Project allowed storage of DVB services in the ISO base media file format. It allows the storage of audio, video, and other content in any of three main ways: encapsulated in a MPEG transport stream, stored as a reception hint track; encapsulated in an RTP stream, stored as a reception hint track or stored directly as media tracks. The MPEG-21
The MPEG-21 standard, from the Moving Picture Experts Group, aims at defining an open framework for multimedia applications. MPEG-21 is ratified in the standards ISO/IEC 21000 - Multimedia framework (MPEG-21).
MPEG-21 is based on two essential con ...
File Format (.m21, .mp21) defined the storage of an MPEG-21 Digital Item Digital Item is the basic unit of transaction in the MPEG-21 framework. It is a structured digital object, including a standard representation, identification and metadata.
A Digital Item may be a combination of resources like videos, audio tracks ...
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
The Graphics Interchange Format (GIF; or , ) is a Raster graphics, bitmap Image file formats, image format that was developed by a team at the online services provider CompuServe led by American computer scientist Steve Wilhite and released ...
, 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 presentation (motion sequence) may be contained in several files. All timing and framing (position and size) information must be in the ISO base media file, and the ancillary files may essentially use any format.][
]
File type box
In order to identify the specifications to which a file based on the ISO base media file format complies, "brands" are used as identifiers in the file format. These are set in a box named file type box ("ftyp"), which must be placed in the beginning of the file. It is somewhat analogous to the so-called fourcc code, used for a similar purpose for media embedded in AVI container 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).[ Some in-use brands (ftyps) are not registered and can be found on some webpages.][
A multimedia file structured upon ISO/IEC base media file format may be compatible with more than one concrete specification, and it is therefore not always possible to speak of a single "type" or "brand" for the file. In this regard, the utility of the Multipurpose Internet Mail Extension type and file name extension is somewhat reduced. In spite of that, when a derived specification is written, a new file extension will be used, a new MIME type, and a new Macintosh file type.][
]
Streaming
The ISO/IEC base media file format supports streaming
Streaming media refers to multimedia delivered through a network for playback using a media player. Media is transferred in a ''stream'' of packets from a server to a client and is rendered in real-time; this contrasts with file downl ...
of media data over a network as well as local playback. A file that supports streaming includes information about the data units to stream (how to serve the elementary stream data in the file over streaming protocols). This information is placed in additional tracks of the file called "hint" tracks. Separate "hint" tracks for different protocols may be included within the same file. The media will play over all such protocols without making any additional copies or versions of the media data. Existing media can be easily made streamable for other specific protocols by the addition of appropriate hint tracks. The media data itself need not be reformatted in any way. The streams sent by the servers under the direction of the hint tracks, need to contain no trace of file-specific information. When the presentation is played back locally (not streamed), the hint tracks may be ignored. Hint tracks may be created by an authoring tool or may be added to an existing file (presentation) by a hinting tool.[ In media authored for progressive download, the moov box, which contains the index of frames, should precede the movie data mdat box.][.]
References
External links
* – The Codecs Parameter for "Bucket" Media Types
*
*
*
*
*
{{MPEG
Digital container formats
ISO/IEC standards
MPEG-4 Part 12