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|Full name||ISO/IEC 14496-12. Information technology -- Coding of audio-visual objects -- Part 12: ISO Base Media File Format (formal name). ISO base media file format (common name)|
The ISO Base Media File Format, referred to in this description as ISO_BMFF, is an international standard, developed and maintained under the auspices of ISO/IEC JTC1 SC29. To paraphrase from the Introduction in the specification, ISO_BMFF is a base format for media file formats, designed primarily to contain time-based audio-visual information in a flexible, extensible format that facilitates interchange, management, editing, and presentation of the media. This presentation may be 'local' to the system containing the presentation or may be via a network or other stream delivery mechanism. The file structure is object-oriented; a file can be decomposed into constituent objects very simply, and the structure of the objects inferred directly from their type. The file format is designed to be independent of any particular network protocol while enabling efficient support for them in general.
Annex A of the 5th edition of the specification (2015) is an informative Overview and Introduction for the format. Annex B provides Guidelines on deriving from this specification.
The summary of the physical organization of an ISO BMFF file below draws on Annex A and on An Overview of the ISO Base Media File Format, a presentation from 2018.
By structuring the box-based ISO BMFF files in different ways, the same base specification can be used for files for many use cases: capture; exchange and download, including incremental download and play; local playback; editing and composition; streaming from streaming servers; and capturing streams to files.
|Production phase||Generally used for middle- and final-state archiving or end-user delivery.|
|Relationship to other formats|
|Has subtype||MJP2_FF, Motion JPEG 2000 File Format|
|Has subtype||MP4_FF_2, MPEG-4 File Format, version 2|
|Has subtype||MP4_FF_AVCE, MPEG-4 File Format for AVC (Extensions; Part 15)|
|Has subtype||JP2_FF, JPEG 2000 Part 1 (Core) jp2 File Format|
|Has subtype||JPX_FF, JPEG 2000 Part 2 (Extensions) jpf File Format|
|Has subtype||JPM_FF, JPEG 2000 Part 1 (Compound) jpm File Format|
|Has subtype||HEIF, High Efficiency Image File Format. Some internal structures required for HEIF were added into the ISO_BMFF specification in a 2018 amendment. See ISO/IEC 14496-12:2015/Amd 2:2018.|
|Has subtype||A number of other audiovisual file formats not described on this website are based on the ISO_BMFF structure. See Adoption below.|
|Affinity to||QuickTime, QuickTime File Format. ISO_BMFF is largely based on the Classic Version of the QuickTime File Format Specification.|
|LC experience or existing holdings||For JPEG 2000 still image implementations, see JP2_FF. For moving image implementations, see MP4_FF_2.|
|LC preference||For JPEG 2000 still image implementations, see JP2_FF. For moving image implementations, no relevant preferences established.|
|Disclosure||International standard, fully disclosed. Developed jointly by the Motion Pictures Expert Group (MPEG) and the Joint Photographic Experts Group (JPEG), two working groups within the ISO/IEC committee structure formally known as ISO/IEC JTC 1/SC 29. The Introduction to the specification, through the 5th edition (2015), stated that it was intended that the ISO Base Media File Format would be jointly maintained by WG1 (JPEG 2000) and WG11 (MPEG). After re-organization of SC 29 in 2020, maintenance of the standard will be by a new WG3 (MPEG Systems).|
Published as part of both MPEG-4 and JPEG 2000 as technically identical ISO standards:
In October 2020, https://www.iso.org/standard/74428.html indicates that a 6th edition of the standard is "approved and "under publication."
As stated in clause C.2.1 of the specification, "A number of existing file formats use the ISO Base Media File Format, not least the MPEG-4 MP4 File Format (ISO/IEC 14496-14), and the Motion JPEG 2000 MJ2 File Format (ISO/IEC 15444-3). MP4RA is the Official Registration Authority for the ISOBMFF family of standards. For a list that includes the most important file formats based on ISO_BMFF, see Boxes/atoms format from fileformats.archiveteam.org.
JPEG 2000 still image implementations using JP2_FF are being widely adopted. The breadth of adoption of implementations of JPX_FF and JPM_FF is unknown to the compilers of this document. For moving image implementations, there is some adoption of MP4_FF_2; the breadth of adoption of other moving image implementations is unknown to the compilers of this document. At this writing (September 2020), Motion JPEG 2000 encoding, which would use MJP2_FF, does not appear to be widely adopted. Professional broadcasters appear to favor standards from SMPTE, e.g., Material Exchange Format (MXF) and Interoperable Master Format (IMF). Comments welcome.
Open source libraries for parsing files in this format can be found at: https://github.com/MPEGGroup/isobmff (Official repository of the ISO Base Media File Format Reference Software); https://github.com/DigiDNA/ISOBMFF; and ISOBMFF (from Imazing).
|Licensing and patents||The original specification identified Apple and Matsushita Electric Industrial Co. as holders of relevant patents, adding that "the holders of these patent rights have assured the ISO and IEC that they are willing to negotiate licenses under reasonable and non-discriminatory terms." The specification also cautions that "some of the elements . . . may be the subject of patent rights other than those identified."|
|Transparency||ISO_BMFF itself is transparent as a wrapper. Transparency of subtypes is determined by the encoding of the wrapped content. See subtypes listed above.|
|Self-documentation||The structure includes boxes and headers that contain the technical metadata needed to manage the media streams. Other boxes may contain descriptive ("bibliographic") metadata; for example, see MJP2_FF. Comments welcome.|
|External dependencies||The format allows for media data (e.g., tracks and segments of audio and video) to be stored outside the primary file and referred to by URL. This capability is important for streaming applications. See DataReferenceBox in subclause 8.7.2. in ISO_BMFF specification.|
|Technical protection considerations||None. Files may employ an optional IPR (Intellectual Property Rights) box that indicates whether an item is protected and provides an identifier; see JP2_FF. Another possible approach is using the ISO Common Encryption standard defined in ISO/IEC 23001-7:2016 Information technology — MPEG systems technologies — Part 7: Common encryption in ISO base media file format files.|
|Normal rendering.||Many relevant aspects depend on subtype. The format supports timescales that manage the playout of time-based media streams and hint tracks employed in streaming applications.|
|Filename extension||See note.||Depends upon subtype.|
|Internet Media Type||See note.||Depends upon subtype.|
|Magic numbers||See note.||Depends upon subtype.|
|File type brand (ISO Base Media File Format)||isom
||ISO_BMFF includes a file type box that contains major and minor brands (identifiers). Regarding isom, the specification states that this would typically be used as the minor or secondary brand. For examples of major brands in ISO_BMFF files, see subtypes listed above; a file type brand has also been established for the related MP4_FF_1 format.|
In the summer of 2020, ISO/IEC JTC1/SC29 reorganized its work groups. WG11, formerly equivalent to the MPEG working group, was broken into a number of more specific working groups. The WG responsible for ISO_BMFF going forward is ISO/IEC JTC1/SC29/WG3 for MPEG Systems. For background, see Future of SC 29 with JPEG and MPEG, MPEG home page as of July 6, 2020, and further Useful References below.
An Overview of the ISO Base Media File Format, a 2018 Powerpoint presentation from ISO/IEC JTC1/SC29/WG11, provides a useful history for the file format.
As indicated above, ISO_BMFF is derived from Apple's QuickTime. The Apple connection was celebrated in an item in MacWeek, February 16, 1998: "QuickTime received a ringing endorsement last week when a consortium of high-tech companies announced that the International Organization for Standardization, better known as ISO, had adopted QuickTime's file format as a centerpiece of MPEG-4, the forthcoming multimedia standard." See ISO ratifies QuickTime as keystone of MPEG-4 by John Poultney (link now via Internet Archive).
In 2004, the specification for ISO_BMFF was published simultaneously as ISO/IEC 14496-12 (as part of MPEG-4) and as ISO/IEC 15444-12 (as part of JPEG 2000). In 2017, ISO/IEC 15444-12 was withdrawn, and replaced with a reference to ISO/IEC 14496-12 for "up-to-date content." See https://www.iso.org/standard/68963.html.
The 2018 presentation An Overview of the ISO Base Media File Format discusses areas of interest for the future of the format.