H.263
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H.263 is a
video compression standard A video coding format (or sometimes video compression format) is a content representation format for storage or transmission of digital video content (such as in a data file or bitstream). It typically uses a standardized video compression algori ...
originally designed as a low-bit-rate compressed format for
videotelephony Videotelephony, also known as videoconferencing and video teleconferencing, is the two-way or multipoint reception and transmission of audio and video signals by people in different locations for real time communication.McGraw-Hill Concise Ency ...
. It was standardized by the
ITU-T The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Commu ...
Video Coding Experts Group The Video Coding Experts Group or Visual Coding Experts Group (VCEG, also known as Question 6) is a working group of the ITU Telecommunication Standardization Sector (ITU-T) concerned with standards for compression coding of video, images, audio, ...
(VCEG) in a project ending in 1995/1996. It is a member of the
H.26x The Video Coding Experts Group or Visual Coding Experts Group (VCEG, also known as Question 6) is a working group of the ITU Telecommunication Standardization Sector (ITU-T) concerned with standards for compression coding of video, images, audio, ...
family of video coding standards in the domain of the ITU-T. Like the previous H.26x standards, H.263 is a block-based hybrid video coding scheme using 16×16
macroblock The macroblock is a processing unit in image and video compression formats based on linear block transforms, typically the discrete cosine transform (DCT). A macroblock typically consists of 16×16 samples, and is further subdivided into transform ...
s of
YCbCr YCbCr, Y′CbCr, or Y Pb/Cb Pr/Cr, also written as YCBCR or Y′CBCR, is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and CB and CR are the blue-diffe ...
color sample arrays, motion-compensated prediction, an 8×8 discrete cosine transform for prediction differences, zig-zag scanning of transform coefficients,
scalar quantization Quantization, in mathematics and digital signal processing, is the process of mapping input values from a large set (often a continuous set) to output values in a (countable) smaller set, often with a finite number of elements. Rounding and t ...
, run-length transform coefficient symbols, and variable-length coding (basically like
Huffman coding In computer science and information theory, a Huffman code is a particular type of optimal prefix code that is commonly used for lossless data compression. The process of finding or using such a code proceeds by means of Huffman coding, an algori ...
but with structured coding tables). The first (1995) version of H.263 included some optional features including overlapped block motion compensation and variable block-size motion compensation, and the spec was later extended to add various additional enhanced features in 1998 and 2000. Smaller additions were also made in 1997 and 2001, and a unified edition was produced in 2005.


History and background

The H.263 standard was first designed to be utilized in
H.324 H.324 is an ITU-T recommendation for voice, video and data transmission over regular analog phone lines. It uses a regular 33,600 bit/s modem for transmission, the H.263 codec for video encoding and G.723.1 for audio. H.324 standard is formally ...
based systems (
PSTN The public switched telephone network (PSTN) provides infrastructure and services for public telecommunication. The PSTN is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local teleph ...
and other circuit-switched network
videoconferencing Videotelephony, also known as videoconferencing and video teleconferencing, is the two-way or multipoint reception and transmission of audio signal, audio and video signals by people in different locations for Real-time, real time communication. ...
and
videotelephony Videotelephony, also known as videoconferencing and video teleconferencing, is the two-way or multipoint reception and transmission of audio and video signals by people in different locations for real time communication.McGraw-Hill Concise Ency ...
), but it also found use in
H.323 H.323 is a recommendation from the ITU Telecommunication Standardization Sector (ITU-T) that defines the protocols to provide audio-visual communication sessions on any packet network. The H.323 standard addresses call signaling and control, m ...
( RTP/IP-based videoconferencing),
H.320 H.320 or Narrow-band visual telephone systems and terminal equipment is an ''umbrella Recommendation'' by the ITU-T for running Multimedia (Audio/Video/Data) over ISDN based networks. The main protocols in this suite are H.221, H.230, H.242, au ...
(
ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Wo ...
-based videoconferencing, where it became the most widely used video compression standard),
RTSP The Real Time Streaming Protocol (RTSP) is an application-level network protocol designed for multiplexing and packetizing multimedia transport streams (such as interactive media, video and audio) over a suitable transport protocol. RTSP i ...
(
streaming media Streaming media is multimedia that is delivered and consumed in a continuous manner from a source, with little or no intermediate storage in network elements. ''Streaming'' refers to the delivery method of content, rather than the content it ...
) and SIP (IP-based videoconferencing) solutions. H.263 is a required video coding format in
ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...
3GPP technical specifications for
IP Multimedia Subsystem The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is a standardised architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-styl ...
(IMS),
Multimedia Messaging Service Multimedia Messaging Service (MMS) is a standard way to send messages that include multimedia content to and from a mobile phone over a cellular network. Users and providers may refer to such a message as a PXT, a picture message, or a multimedia ...
(MMS) and Transparent end-to-end Packet-switched Streaming Service (PSS). In 3GPP specifications, H.263 video is usually used in 3GP container format. H.263 also found many applications on the internet: much
Flash Video Flash Video is a container file format used to deliver digital video content (e.g., TV shows, movies, etc.) over the Internet using Adobe Flash Player version 6 and newer. Flash Video content may also be embedded within SWF files. There ar ...
content (as used on sites such as
YouTube YouTube is a global online video platform, online video sharing and social media, social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by ...
,
Google Video Google Video was a free video hosting service launched by the multinational technology company Google on January 25, 2005. Similar to YouTube, this platform allowed video clips to be hosted on Google servers and embedded on to other websites ...
, and MySpace) used to be encoded in
Sorenson Spark Sorenson Media was an American software company specializing in video encoding technology. Established in December 1995 as Sorenson Vision, the company developed technology which was licensed and ultimately acquired from Utah State University. T ...
format (an incomplete implementation of H.263). The original version of the
RealVideo RealVideo, or also spelled as Real Video, is a suite of proprietary video compression formats developed by RealNetworks – the specific format changes with the version. It was first released in 1997 and was at version 10. RealVideo is supported ...
codec was based on H.263 until the release of RealVideo 8. H.263 was developed as an evolutionary improvement based on experience from
H.261 H.261 is an ITU-T video compression standard, first ratified in November 1988. It is the first member of the H.26x family of video coding standards in the domain of the ITU-T Study Group 16 Video Coding Experts Group (VCEG, then Specialists Gro ...
and
H.262 H.262 or MPEG-2 Part 2 (formally known as ITU-T Recommendation H.262 and ISO/IEC 13818-2, also known as MPEG-2 Video) is a video coding format standardised and jointly maintained by ITU-T Study Group 16 Video Coding Experts Group (VCEG) and Inte ...
(aka
MPEG-2 Video H.262 or MPEG-2 Part 2 (formally known as ITU-T Recommendation H.262 and ISO/IEC 13818-2, also known as MPEG-2 Video) is a video coding format standardised and jointly maintained by ITU-T Study Group 16 Video Coding Experts Group (VCEG) and ISO/ ...
), the previous ITU-T standards for video compression, and the
MPEG-1 MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to about 1.5 Mbit/s (26:1 and 6:1 compression ratios respectively) without excessive quality loss, making ...
standard developed in ISO/IEC. The first version of H.263 was completed in 1995 and provided a suitable replacement for
H.261 H.261 is an ITU-T video compression standard, first ratified in November 1988. It is the first member of the H.26x family of video coding standards in the domain of the ITU-T Study Group 16 Video Coding Experts Group (VCEG, then Specialists Gro ...
at all bit rates. It was further enhanced in projects known as H.263v2 (also known as H.263+ or H.263 1998) and H.263v3 (also known as H.263++ or H.263 2000). It was also used as the basis for the development of
MPEG-4 Part 2 MPEG-4 Part 2, MPEG-4 Visual (formally ISO/IEC 14496-2) is a video compression format developed by the Moving Picture Experts Group (MPEG). It belongs to the MPEG-4 ISO/IEC standards. It uses block-wise motion compensation and a discrete cosine tr ...
. MPEG-4 Part 2 is H.263 compatible in the sense that basic "baseline" H.263 bitstreams are correctly decoded by an MPEG-4 Video decoder. The next enhanced format developed by ITU-T
VCEG The Video Coding Experts Group or Visual Coding Experts Group (VCEG, also known as Question 6) is a working group of the ITU Telecommunication Standardization Sector (ITU-T) concerned with standards for compression coding of video, images, audio, ...
(in partnership with
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 ...
) after H.263 was the
H.264 Advanced Video Coding (AVC), also referred to as H.264 or MPEG-4 Part 10, is a video compression standard based on block-oriented, motion-compensated coding. It is by far the most commonly used format for the recording, compression, and distr ...
standard, also known as AVC and
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 tec ...
part 10. As H.264 provides a significant improvement in capability beyond H.263, the H.263 standard is now considered a legacy design that is only used for compatibility with older products. Newer videoconferencing products now include H.264 as well as, or instead of, H.263 and
H.261 H.261 is an ITU-T video compression standard, first ratified in November 1988. It is the first member of the H.26x family of video coding standards in the domain of the ITU-T Study Group 16 Video Coding Experts Group (VCEG, then Specialists Gro ...
capabilities. Even newer standard formats,
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 compari ...
and VVC, have also been developed by VCEG and MPEG, and have begun to replace H.264 in some applications.


Versions

Since the original ratification of H.263 in March 1996 (approving a document that was produced in November 1995), there have been two subsequent additions which improved on the original standard by additional optional extensions (for example, the H.263v2 project added a
deblocking filter A deblocking filter is a video filter applied to decoded compressed video to improve visual quality and prediction performance by smoothing the sharp edges which can form between macroblocks when block coding techniques are used. The filter aims ...
in its Annex J).


Version 1 and Annex I

The original version of H.263 specified the following annexes: * Annex A – Inverse transform accuracy specification * Annex B – Hypothetical Reference Decoder * Annex C – Considerations for Multipoint * Annex D – Unrestricted Motion Vector mode * Annex E – Syntax-based Arithmetic Coding mode * Annex F – Advanced Prediction mode * Annex G – PB-frames mode * Annex H – Forward Error Correction for coded video signal The first version of H.263 supported a limited set of picture sizes: * 128×96 (a.k.a. Sub-QCIF) * 176×144 (a.k.a. QCIF) * 352×288 (a.k.a.
CIF Cif is a French brand of household cleaning products owned by the Anglo-Dutch company Unilever, known as Jif in Australia, New Zealand, Japan, Middle East and the Nordic countries. Cif was launched in France in 1965 and was marketed in competit ...
) * 704×576 (a.k.a. 4CIF) * 1408×1152 (a.k.a. 16CIF) In March 1997, an informative Appendix I describing Error Tracking – an encoding technique for providing improved robustness to data losses and errors, was approved to provide information for the aid of implementers having an interest in such techniques.


H.263v2 (H.263+)

H.263v2 (also known as ''H.263+'', or as ''the 1998 version of H.263'') is the informal name of the second edition of the ITU-T H.263 international video coding standard. It retained the entire technical content of the original version of the standard, but enhanced H.263 capabilities by adding several annexes which can substantially improve encoding efficiency and provide other capabilities (such as enhanced robustness against data loss in the transmission channel). The H.263+ project was ratified by the ITU in February 1998. It added the following Annexes: * Annex I – Advanced INTRA Coding mode * Annex J – Deblocking Filter mode * Annex K – Slice Structured mode * Annex L – Supplemental Enhancement Information Specification * Annex M – Improved PB-frames mode * Annex N – Reference Picture Selection mode * Annex O – Temporal, SNR, and Spatial Scalability mode * Annex P – Reference picture resampling * Annex Q – Reduced-Resolution Update mode (see implementors' guide correction as noted below) * Annex R – Independent Segment Decoding mode * Annex S – Alternative INTER VLC mode * Annex T – Modified Quantization mode H.263v2 also added support for flexible customized picture formats and custom picture clock frequencies. As noted above, the only picture formats previously supported in H.263 had been Sub-QCIF, QCIF,
CIF Cif is a French brand of household cleaning products owned by the Anglo-Dutch company Unilever, known as Jif in Australia, New Zealand, Japan, Middle East and the Nordic countries. Cif was launched in France in 1965 and was marketed in competit ...
, 4CIF, and 16CIF, and the only picture clock frequency had been 30000/1001 (approximately 29.97) clock ticks per second. H.263v2 specified a set of recommended modes in an informative appendix (Appendix II, since deprecated):


H.263v3 (H.263++) and Annex X

The definition of H.263v3 (also known as H.263++ or as the 2000 version of H.263) added three annexes. These annexes and an additional annex that specified profiles (approved the following year) were originally published as separate documents from the main body of the standard itself. The additional annexes specified are: * Annex U – Enhanced reference picture selection mode * Annex V – Data-partitioned slice mode * Annex W – Additional supplemental enhancement information specification * Annex X (originally specified in 2001) – Profiles and levels definition The prior informative Appendix II (recommended optional enhancement) was obsoleted by the creation of the normative Annex X. In June 2001, another informative appendix (Appendix III, Examples for H.263 encoder/decoder implementations) was approved. It describes techniques for encoding and for error/loss concealment by decoders. In January 2005, a unified H.263 specification document was produced (with the exception of Appendix III, which remains as a separately-published document). In August 2005, an implementors' guide was approved to correct a small error in the seldom-used Annex Q reduced-resolution update mode.


Patent rights and open-source implementation

H.263 was developed under the "
reasonable and non-discriminatory Reasonable and non-discriminatory (RAND) terms, also known as fair, reasonable, and non-discriminatory (FRAND) terms, denote a voluntary licensing commitment that standards organizations often request from the owner of an intellectual property r ...
" patent licensing policy of ITU-T, although in practice, the licensing for patent rights on the standard did not become the subject of substantial litigation. Due to the age of the standard, most or all relevant patents would currently be expired at least for patents that would apply to the early versions of the standard. Open-source implementations include the
LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
-licensed
libavcodec libavcodec is a free and open-source library of codecs for encoding and decoding video and audio data. libavcodec is an integral part of many open-source multimedia applications and frameworks. The popular MPV, xine and VLC media players use ...
library (part of the
FFmpeg FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of vid ...
project) which is used by programs such as
ffdshow ffdshow is an open-source unmaintained codec library that is mainly used for decoding of video in the MPEG-4 ASP (e.g. encoded with DivX or Xvid) and H.264/MPEG-4 AVC video formats, but it supports numerous other video and audio formats as we ...
,
VLC media player VLC media player (previously the VideoLAN Client and commonly known as simply VLC) is a free and open-source, portable, cross-platform media player software and streaming media server developed by the VideoLAN project. VLC is available for desk ...
and
MPlayer MPlayer is a free and open-source media player software application. It is available for Linux, OS X and Microsoft Windows. Versions for OS/2, Syllable, AmigaOS, MorphOS and AROS Research Operating System are also available. A port for DOS usi ...
.


See also

* H.262/MPEG-2 Part 2 *
MPEG-4 Part 2 MPEG-4 Part 2, MPEG-4 Visual (formally ISO/IEC 14496-2) is a video compression format developed by the Moving Picture Experts Group (MPEG). It belongs to the MPEG-4 ISO/IEC standards. It uses block-wise motion compensation and a discrete cosine tr ...
(MPEG-4 Visual)


References


External links

*
The ITU-T specification for H.263
*

- Group that reviews codec packetizations for RTP ** - RTP Payload Format for ITU-T Rec. H.263 Video ** - RTP Payload Format for the 1998 Version of ITU-T Rec. H.263 Video (H.263+) (Obsolete, upgraded spec in RFC 4629) ** - RTP Payload Format for H.263 Video Streams (Historic)
H.263 - MultimediaWiki



H.263 implementation in vic (source code available)
{{Authority control H.26x ITU-T H Series Recommendations ITU-T recommendations Open standards covered by patents Video codecs Videotelephony