Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | ISO/IEC 14496-14:2003. Information technology -- Coding of audio-visual objects -- Part 14: MP4 File Format (formal name) MPEG-4 file format, version 2 (common name) |
| Description | The second MPEG-4 file format developed by the Motion Picture Experts Group (MPEG). The format's object-based design defines a set of tools that present binary coded representation of individual audiovisual objects, text, graphics, and synthetic objects. (See Notes below.) This format is intended to serve web and other online applications; mobile devices, i.e., cell phones and PDAs; and broadcasting and other professional applications. See also Notes below. |
| Production phase | Generally a final-state (end-user delivery) format, may also serve as middle-state format. |
| Relationship to other formats | |
| Subtype of | ISO_BMFF, ISO Base Media File Format |
| Has subtype | MP4_FF_2_V, MPEG-4 File Format, V.2, with Visual Encoding (All Profiles) |
| Has subtype | MP4_FF_2_AVC, MPEG-4 File Format, V.2, with AVC, No Profile Indicated |
| Has subtype | MP4_FF_2_AVC_BP, MPEG-4 File Format, V.2, with AVC, Baseline Profile |
| Has subtype | MP4_FF_2_AVC_MP, MPEG-4 File Format, V.2, with AVC, Main Profile |
| Has subtype | MP4_FF_2_AVC_EP, MPEG-4 File Format, V.2, with AVC, Extended Profile |
| Has subtype | MP4_FF_2_AVC_HP, MPEG-4 File Format, V.2, with AVC, High Profile |
| Has subtype | MP4_FF_2_AVC_H10P, MPEG-4 File Format, V.2, with AVC, High 10 Profile |
| Has subtype | MP4_FF_2_AVC_H422P, MPEG-4 File Format, V.2, with AVC, High 4:2:2 Profile |
| Has subtype | MP4_FF_2_AVC_H444P, MPEG-4 File Format, V.2, with AVC, High 4:4:4 Profile |
| Has subtype | MP4_FF_2_AAC, MPEG-4 File Format, V.2, with Advanced Audio Coding |
| Has subtype | For other object types, not described at this time |
| Has earlier version | MP4_FF_1, MPEG-4 File Format, Version 1 |
| LC experience or existing holdings | Emerging project in the Office of Strategic Initiatives, the Motion Picture, Broadcasting, and Recorded Sound Division, and the Area Studies directorate pertaining to foreign broadcasts from SCOLA includes the capture and management of MP4_FF_2 files with what is believed to be Part 2 video coding. |
| LC preference |
| Disclosure | Open standard. Developed by ISO technical program JTC 1/SC 29 (WG11), aka the Motion Picture Experts Group (MPEG). See http://www.iso.org/iso/en/stdsdevelopment/techprog/workprog/ TechnicalProgrammeSCDetailPage.TechnicalProgrammeSCDetail?COMMID=148. |
| Documentation | ISO/IEC 14496-14:2003. Information technology -- Coding of audio-visual objects -- Part 14: MP4 File Format. The total documentation package for ISO/IEC 14496 is extensive; 17 parts have been published from 1998 to 2004, with more to come. See complete list of documents in Format specifications below. |
| Adoption | Appears to be more widely adopted than MP4_FF_1. Overall, the adoption of MPEG-4 has been slowed by licensing terms that require some content disseminators to pay fees according to the number of endusers or the extent of content delivered. As adoption advances, it may not extend to all profiles, levels, or parts of the standard. |
| Licensing and patent claims | MPEG-4 Visual, Systems, and Advanced Video Coding licensing is managed by MPEG LA LLC (http://www.mpegla.com/). These licenses cover the manufacture and sale of devices or software and, for some content disseminators, levy fees according to number of endusers or the extent of content delivered. The arrangements are updated periodically; for example, in January 2005, MPEG LA announced that the patent portfolio had been expanded to cover the FRExt (Fidelity Range Extensions) associated with MPEG-4_AVC and ITU H.264 MPEG-4 Audio licensing is managed by Via Licensing Corporation (http://www.vialicensing.com/), an independent subsidiary of Dolby Laboratories. MPEG-4 Audio licensing appears to be limited to the manufacture of devices or software. |
| Transparency | Depends upon included encodings, but all MPEG-4 encodings depend upon algorithms and tools to read and require sophistication to build tools. |
| Self-documentation | The inclusion of metadata of various types is a key element in MPEG-4. As indicated in the notes below, object and scene descriptions are required in order for MPEG-4 content to be presented. Semantic description is carried by Object Content Information (OCI) descriptors and streams; the standard also permits the inclusion of MPEG-7 data, a separately standardized structure for metadata to support discovery and other purposes. |
| External dependencies | Playback of surround sound requires multiple loudspeakers. |
| Technical protection considerations | MPEG-4 offers a standardized Intellectual Property Management and Protection (IPMP) interface consisting of IPMP-Descriptors (IPMP-Ds) and IPMP-Elementary Streams (IPMP-ES) that allow the design and use of domain-specific IPMP systems. |
| Video elements | |
| Normal rendering for video | Good support. The format supports timescales that manage the playout of time-based media streams and hint tracks employed in streaming applications. |
| Clarity (support for high image resolution) | Depends upon encoding; see MPEG-4_V and MPEG-4_AVC. |
| Functionality beyond normal video rendering | MPEG-4 program streams may be multiplexed in MPEG-2 transport streams. Random access and other features are discussed in the specification. |
| Sound elements | |
| Fidelity (support for high audio resolution) | Moderate to very good, given that this is a format for compression. Outcome will depend on the type and extent of compression, and the encoder used. Some of the current appeal of MPEG-4 has to do with its implementation and extension of AAC_MP2 (Advanced Audio Coding) into AAC_MP4, an audio compression encoding initially developed in the context of MPEG-2 and considered to be superior to MP3 (MPEG-2 layer 3 audio) at a given bit rate. The MPEG-4 standard also provides support for other "natural" sound encodings, e.g., parametric coding (HILN or Harmonic and Individual Lines plus Noise) and CELP (Code Excited Linear Prediction) and other encodings for speech. The standard also supports the synthesis of audio, and for what is called Synthetic-Natural Hybrid Coding (SNHC). The presentation of these elements depends upon the use of AudioBIFs (Audio BInary Format for Scenes). In 2005, the MPEG committee announced two additional audio capabilities: Audio Lossless coding (ALS; lossless compression of multi-channel sound using time-domain prediction and entrogy coding) and Scalable to Lossless coding (SLS; a scalable enhancement layer is added to a lossy bitstream that extends the representation to lossless but which can be truncated at delivery time). The compilers of this document do not know the degree to which any of these various elements may be implemented in practice. |
| Support for multiple sound channels | The AAC_MP4 audio structure provides a capability of up to 48 main audio channels, 16 LFE (Low Frequency Encoding or Effects) channels, 16 overdub/multilingual channels, and 16 data streams. SNHC [and other note-based or synthetic?] sound can be spatially presented using extensions of the concepts initially implemented in Virtual Reality Modeling Language (VRML). |
| Functionality beyond normal rendering for sound | Not fully investigated at this time. Recent published or announced additions to the standard include Part 16, the Animation Extension Framework; Part 17 for "timed text," e.g., subtitles or karaoke; Part 18 for font compression and streaming; and Part 22 for Open Fonts based on the OpenType specification. |
| Tag type | Value | Note |
| Filename Extension | mp4, m4a | Paraphrased from www.m4a.com: MP4 can be used for MPEG 4 video files, combined video and audio files, or just plain MPEG 4 audio. M4A files contain only MPEG 4 Audio. Apple started using M4A to identify files unprotected by digital rights management; protected QTA_AAC files carry the M4P extension. Apple felt that MP4 was too general (video, video/audio, or audio) and might confuse some media players. Until recently, encoder and player software like Nero and Compaact used .mp4 for audio files while WinAmp 5.02, Apple iTunes, and others used .m4a. Today, most audio software developers allow you to choose the file extension you prefer. |
| Internet Media Type | video/mp4 | The typical MIME type and the first one listed in http://www.ietf.org/internet-drafts/draft-lim-mpeg4-mime-03.txt (October 2004) from the IETF (Internet Engineering Task Force). See Useful references for IETF RFCs that pertain to MPEG-4. The compiler of this document welcomes comments on the use of MIME types for various types of MPEG-4. |
| Internet Media Type | audio/mp4 | MP4 file with audio but without visual presentation, from http://www.ietf.org/internet-drafts/draft-lim-mpeg4-mime-03.txt (October 2004). |
| Internet Media Type | application/mp4 | MP4 file with MPEG-4 system stream and neither visual nor audio presentation, from http://www.ietf.org/internet-drafts/draft-lim-mpeg4-mime-03.txt (October 2004). |
| Internet Media Type |
application/mpeg4-iod application/mpeg4-iod-xmt | IOD (Initial Object Descriptor) in binary format and (with appended xmt) in textual format, from http://www.ietf.org/internet-drafts/draft-lim-mpeg4-mime-03.txt (October 2004). |
| Internet Media Type |
video/mp4v-es video/mpeg4-generic |
Additional MIME types referred to in various documents. RFC 3016 reports that MIME types may have indicators for data rate or profile-level appended to them. |
| Magic numbers | None | |
| File type brand | mp42 | ISO_BMFF includes a file type box that contains major and minor brands (identifiers); this brand is specified in Part 14, Section 4 (ISO/IEC 14496-14:2003. Information technology -- Coding of audio-visual objects -- Part 14: MP4 File Format, p. 6). |
| General | The four file formats associated with the ISO/IEC 14496 family of specifications are: • MP4_FF_1, "version 1" from Part 1 (2001) • MP4_FF_2, "version 2," this document, from Part 14 • MP4_FF_AVCE, for Advanced Video Coding extensions, from Part 15 • MP4_XMT, "textual format" from Part 11 Version 2 is very similar to its predecessor MP4_FF_1 as both owe a debt to the QuickTime file format that preceded them. This lineage is shared with the supertype for MP4_FF_2, ISO_BMFF, defined in Parts 12 of both the MPEG-4 and JPEG 2000 standards. Note that "object-oriented building blocks" are called boxes in this file format and its parent, ISO_BMFF; in contrast, they are called atoms in the predecessor MP4_FF_1 and QuickTime. The object-based design of MPEG-4 is characterized as follows in Fernando Pereira and Touradj Ebrahimi's The MPEG-4 Book (Upper Saddle River, NJ: IMSC Press, 2002): "MPEG-4 is an ISO/IES standard developed by MPEG for communicating interactive audiovisual scenes. The standard defines a set of tools that provide binary coded representation of individual audiovisual objects, text, graphics, and synthetic objects. The interactive behaviors of these objects and the way they are composed in space and time to form an MPEG-4 scene are dependent on the scene description, which is coded in a binary format known as binary format for scenes (BIFS) . . . . The audiovisual streams are defined as elementary streams (ESs) and managed according to the object descriptor (OD) framework . . . . In addition, the OD framework defines additional streams for object content information (OCI), MPEG-J [Java APIs], and intellectual property management and protection (IPMP)." (p. 188) BIFS owes a debt to the Virtual Reality Modeling Language (VRML), even as it extends VRML's capabilities and employs binary encoding. Timing of elements in MPEG-4 is managed by a Synchronization Layer (SL). The delivery of MPEG-4 content is supported by the Delivery Multimedia Framework or DMIF and its application interface. MPEG-J is described in Part 1 of the standard (ISO/IEC 14496-1:2004). This API for the interoperation of MPEG-4 media players with Java code is contrasted with a conventional parametric system. "By combining MPEG-4 media and safe executable code, content creators may embed complex control and data processing mechanisms with their media data to intelligently manage the operation of the audio-visual session. The parametric MPEG-4 System forms the Presentation Engine while the MPEG-J subsystem controlling the Presentation Engine forms the Application Engine. The Java application is delivered as a separate elementary stream to the MPEG-4 terminal. There it will be directed to the MPEG-J run time environment, from where the MPEG-J program will have access to the various components and required data of the MPEG-4 player to control it." (p. xii) |
| History |
URLs
Print
Part 14 applies to this file format. For reference, however, the following list enumerates all of the MPEG-4 standards documents listed at the ISO web site (http://www.iso.ch/ISO/en/) as of November 24, 2004, including Part 14.
• ISO/IEC 14496-1:2001 Information technology -- Coding of audio-visual objects -- Part 1: Systems
• ISO/IEC 14496-1:2004 Information technology -- Coding of audio-visual objects -- Part 1: Systems
• ISO/IEC 14496-1:2001/Amd 1:2001 Extended BIFS
• ISO/IEC 14496-1:2001/Amd 4:2003 SL extensions and AFX streams
• ISO/IEC 14496-1:2001/Amd 8:2004 New ObjectTypeIndiciation code points
• ISO/IEC 14496-2:2004 Information technology -- Coding of audio-visual objects -- Part 2: Visual
• ISO/IEC 14496-2:2004/Cor 1:2004
• ISO/IEC 14496-2:2004/Amd 1:2004 Error resilient simple scalable profile
• ISO/IEC 14496-3:2001 Information technology -- Coding of audio-visual objects -- Part 3: Audio
• ISO/IEC 14496-3:2001/Cor 1:2002
• ISO/IEC 14496-3:2001/Amd 1:2003 Bandwidth extension
• ISO/IEC 14496-3:2001/Amd 1:2003/Cor 1:2004
• ISO/IEC 14496-3:2001/Cor 2:2004M
• ISO/IEC 14496-3:2001/Amd 2:2004 Parametric coding for high-quality audio
• ISO/IEC 14496-4:2000 Information technology -- Coding of audio-visual objects -- Part 4: Conformance testing
• ISO/IEC 14496-4:2000/Cor 1:2002
• ISO/IEC 14496-5:2001 Information technology -- Coding of audio-visual objects -- Part 5: Reference software
• ISO/IEC 14496-5:2001/Amd 1:2002 Reference software for MPEG-4
• ISO/IEC 14496-5:2001/Amd 2:2003 MPEG-4 reference software extensions for XMT and media nodes
• ISO/IEC 14496-5:2001/Amd 3:2003 Visual new level and tools
• ISO/IEC 14496-5:2001/Amd 4:2004 IPMPX reference software extensions
• ISO/IEC 14496-5:2001/Amd 5:2004 Reference software extensions for error resilient simple scalable profile
• ISO/IEC 14496-6:2000 Information technology -- Coding of audio-visual objects -- Part 6: Delivery Multimedia Integration Framework (DMIF)
• ISO/IEC TR 14496-7:2002 Information technology -- Coding of audio-visual objects -- Part 7: Optimized reference software for coding of audio-visual objects
• ISO/IEC 14496-8:2004 Information technology -- Coding of audio-visual objects -- Part 8: Carriage of ISO/IEC 14496 contents over IP networks
• ISO/IEC TR 14496-9:2004 Information technology -- Coding of audio-visual objects -- Part 9: Reference hardware description
• ISO/IEC 14496-10:2003 Information technology -- Coding of audio-visual objects -- Part 10: Advanced Video Coding
• ISO/IEC 14496-12:2004 Information technology -- Coding of audio-visual objects -- Part 12: ISO base media file format
• ISO/IEC 14496-13:2004 Information technology -- Coding of audio-visual objects -- Part 13: Intellectual Property Management and Protection (IPMP) extensions
• ISO/IEC 14496-14:2003 Information technology -- Coding of audio-visual objects -- Part 14: MP4 file format
• ISO/IEC 14496-15:2004 Information technology -- Coding of audio-visual objects -- Part 15: Advanced Video Coding (AVC) file format
• ISO/IEC 14496-16:2004 Information technology -- Coding of audio-visual objects -- Part 16: Animation Framework eXtension (AFX)
• ISO/IEC 14496-18:2004 Information technology -- Coding of audio-visual objects -- Part 18: Font compression and streaming
• ISO/IEC 14496-19:2004 Information technology - Coding of audio-visual objects -- Part 19: Synthesized texture stream
URLs
• http://www.chiariglione.org/mpeg/ from the founder
• MPEG-4 Industry Forum (http://www.m4if.org/)
• MIME Type Registration for MPEG-4 by Y Lim (net&tv) and D. Singer (Apple Computer), October 2004 draft document, (http://www.ietf.org/internet-drafts/draft-lim-mpeg4-mime-03.txt)
• RFC 3640: RTP Payload Format for Transport of MPEG-4 Elementary Streams (http://www.rfc-editor.org/rfc/rfc3640.txt) from the IETF (Internet Engineering Task Force, http://www.ietf.org/)
• RFC 3016: RTP Payload Format for MPEG-4 Audio/Visual Streams (http://www.rfc-archive.org/getrfc?rfc=3016) from the IETF (Internet Engineering Task Force, http://www.ietf.org/)
• MPEG-4 Systems Elementary Stream Management (ESM) (http://www.chiariglione.org/mpeg/faq/mp4-sys/sys-faq-esm.htm)
• MPEG-J FAQ (http://www.chiariglione.org/mpeg/faq/mp4-sys/sys-faq-mpegj.htm)
• http://www.apple.com/mpeg4/
• MPEG-4 on the Diffuse Web Site from Web Archive Wayback collection (http://web.archive.org/web/20030218051108/http://www.diffuse.org/video.html#MPEG-4)
• Site for users of the AAC audio format (http://www.m4a.com/)
Print
• Pereira, Fernando and Touradj Ebrahimi. The MPEG-4 Book. Upper Saddle River, NJ: IMSC Press, 2002.
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