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|Full name||ISO/IEC 14496-10:2003. Information technology -- Coding of audio-visual objects -- Part 10: Advanced Video Coding (formal name); MPEG-4, Advanced Video Coding (common name)|
Compression encoding for video identical to ITU-T (International Telecommunications Union-Telecommunication Standardization Sector) recommendation H.264. MPEG-4_V based on H.263 is a sibling that appears to be less widely adopted. In order to distinguish the two, technical writers sometimes call this encoding H.264 video and the other MPEG-4 video. An overview of AVC encoding is provided in Notes below.
This page is used in this Web site to represent encodings with no profile indicated. The established profiles for MPEG-4_AVC are listed (and linked) as subtypes below. They are defined in terms of bitstream characteristics and relate to the conformance of players. The Baseline, Main, and Extended profiles were specified in Annex A of the 2003 edition of the standard. The four High profiles are part of what is called FRExt (Fidelity Range Extensions) which exist in draft form in 2005; an amendment to the ISO specification expected in the foreseeable future. All profiles can be wrapped in MP4_FF_2. There is another coding variant: MPEG-4_AVC_EXT, a specialized subset of AVC that appears not to be a "profile," although it requires the use of its own wrapper: MP4_FF_AVCE. Comments welcome.
|Production phase||Generally a final-state (end-user delivery) format, although the FRExt additions will serve middle-state postproduction and archiving uses.|
|Relationship to other formats|
|Used by||MP4_FF_2_AVC, MPEG-4 File Format, Version 2, with Advanced Video Coding (No Profile Indicated)|
|Used by||QTV_MP4_AVC, QuickTime Video, MPEG-4 Advanced Video Coding|
|Used by||Matroska_AVC, Matroska File Format with MPEG-4, Advanced Video Coding (Part 10) (H.264)|
|Used by||Other file wrappers, not documented here|
|Has subtype||MPEG-4_AVC_BP, MPEG-4 Advanced Video Coding, Baseline Profile|
|Has subtype||MPEG-4_AVC_MP, MPEG-4 Advanced Video Coding, Main Profile|
|Has subtype||MPEG-4_AVC_EP, MPEG-4 Advanced Video Coding, Extended Profile|
|Has subtype||MPEG-4_AVC_HP, MPEG-4 Advanced Video Coding, High Profile|
|Has subtype||MPEG-4_AVC_H10P, MPEG-4 Advanced Video Coding, High 10 Profile|
|Has subtype||MPEG-4_AVC_H422P, MPEG-4 Advanced Video Coding, High 4:2:2 Profile|
|Has subtype||MPEG-4_AVC_H444P, MPEG-4 Advanced Video Coding, High 4:4:4 Profile|
|Has subtype||MPEG-4_AVC_EXT, MPEG-4, Advanced Video Coding, Non-FRExt Extensions|
|LC experience or existing holdings|
|Disclosure||Open standard. Developed by ISO technical program JTC 1/SC 29 (WG11), aka the Motion Picture Experts Group (MPEG). See http://wg11.sc29.org/|
|Documentation||ISO/IEC 14496-10:2003. Information technology -- Coding of audio-visual objects -- Part 10: Advanced Video Coding.|
|Adoption||The underlying encoding, sometimes under the name of ITU-T H.264, is being adopted in various sectors. In 2004, for example, a key group of Japanese broadcasters adopted the format for transmission to mobile telephones and other devices, and the format received provisional approval for use in DVD systems, where it will coexist with MPEG-2 and Microsoft's VC-9 video codec (see WMV9_PRO). In 2005, the ability of MPEG-4_AVC to support high definition contributed to further adoptions by direct broadcast satellite (DBS) services in the United States (DirecTV) and in Europe. The FRExt high-end profiles are being introduced in 2005; adoption not determined.
The specifications for the video-capable iPod introduced by Apple in late 2005 state that device will play H.264 video in the Baseline Profile, i.e., MPEG-4_AVC_BP. This was reinforced in early 2006, as Google began to offer downloadable videos, including files for the iPod that have the .mp4 extension and an encoding variously listed as "H.264" or "avc1" (MPEG-4_AVC_BP).
It is worth noting that adoptions of AVC/H.264 are generally in closed systems like satellite television or mobile phone delivery. In contrast, digital terrestrial broadcasting to homes in the United States and several other nations is governed by the ATSC (Advanced Television Systems Committee). The ATSC specifications require the use of MPEG-2 compression.
|Licensing and patents||See MP4_FF_2.|
|Transparency||Depends upon algorithms and tools to read; will require sophistication to build tools.|
|Self-documentation||Pertains to the file format; see MP4_FF_2.|
|Technical protection considerations||Pertains to the file format; see MP4_FF_2.|
|Normal rendering||Good support.|
|Clarity (high image resolution)||For all profiles, MPEG-4_AVC (MPEG-4 Advanced Video Coding, part 10) is more efficient than the MPEG-4_V (MPEG-4 Visual Coding, part 2), i.e., MPEG-4_AVC provides better quality at the same data rate, or equal quality at a lower data rate.
Clarity is excellent for the profiles covered by the Fidelity Range Extensions (FRExt), which extend to lossless or near lossless levels, and support 4:4:4 chroma and bit depths as high as 12. See MPEG-4_AVC_HP, MPEG-4_AVC_H10P, MPEG-4_AVC_H422P, and MPEG-4_AVC_H444P.
Clarity in other profiles ranges from moderate to very good, given that chroma subsampling is limited to 4:2:0, and that these profiles will generally be implemented with significant amounts of lossy compression.See MPEG-4_AVC_BP, MPEG-4_AVC_MP, and MPEG-4_AVC_EP.
The outcome in all cases will depend on the extent of compression and the encoder used. All profiles support both progressive and interlaced video, at resolutions from sub-QCIF to HDTV.
[See Notes below for more detail on resolution terms.]
|Functionality beyond normal rendering||Not investigated at this time.|
|Normal rendering||Not relevant; see MP4_FF_2.|
|Fidelity (high audio resolution)||Not relevant; see MP4_FF_2.|
|Multiple channels||Not relevant; see MP4_FF_2.|
|Functionality beyond normal rendering||Not relevant; see MP4_FF_2.|
|Filename extension||See note.||
|Internet Media Type||See related format.||
|Magic numbers||See related format.||
|File type brand (ISO Base Media File Format)||See note.||Indicated in file wrapper and relates to "brands" defined in ISO_BMFF. Wrapping MPEG-4_V bitstreams in MP4_FF_1 would occasion the use of mp41; in MP4_FF_2, use mp42. See Part 15 of the standard, pp. 2-9, 13.|
|Indicator for profile, level, version, etc.||See note.||Codes for profile_idc are provided in Annex A of Part 10 of the standard, pp. 204-05. As of the 2003 version (amendments may be coming in 2005-06), this covers the Baseline, Main, and Extended Profiles.|
From the specification: "The coded representation specified in the syntax is designed to enable a high compression capability for a desired image quality. The algorithm is not lossless, as the exact source sample values are typically not preserved through the encoding and decoding processes. A number of techniques may be used to achieve highly efficient compression. Encoding algorithms (not specified in this Recommendation | International Standard) may select between inter and intra coding for block-shaped regions of each picture. Inter coding uses motion vectors for block-based inter prediction to exploit temporal statistical dependencies between different pictures. Intra coding uses various spatial prediction modes to exploit spatial statistical dependencies in the source signal for a single picture. Motion vectors and intra prediction modes may be specified for a variety of block sizes in the picture. The prediction residual is then further compressed using a transform to remove spatial correlation inside the transform block before it is quantised, producing an irreversible process that typically discards less important visual information while forming a close approximation to the source samples. Finally, the motion vectors or intra prediction modes are combined with the quantised transform coefficient information and encoded using either variable length codes or arithmetic coding." (p. ix) The specification also includes a number of additional elements.
The FRExt (Fidelity Range Extensions) as drafted in 2005 feature higher quality profiles, including one that is sometimes described as "lossless," which may mean that the second sentence in the preceding is no longer accurate. The four FRExt profiles are described on the following pages:
Terms used for spatial resolution: QCIF stands for Quarter Common Intermediate Format (176 pixels by 144 lines), CIF is Common Intermediate Format (352 pixels by 288 lines), while HDTV is High Definition Television (various, including 1920 pixels by 1080 lines).
See also MP4_FF_2.