Video coding format: Difference between revisions

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{{Short description|Content formatFormat for digital video content}}

{{Use mdy dates|date=January 2024}}

A '''video coding format'''{{efn|The term ''video coding'' includes [[Advanced Video Coding]], [[High Efficiency Video Coding]], and [[Video Coding Experts Group]].<ref>{{cite web|url=http://654lab.webstarts.com/uploads/csvt_overview.pdf|title=Overview of the H.264 / AVC Video Coding Standard|publisher=IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY|date=July 2003|author1=Thomas Wiegand | author1-link=Thomas Wiegand |author2=Gary J. Sullivan |author3=Gisle Bjontegaard |author4=Ajay Luthra |name-list-style=amp }}</ref>}} (or sometimes '''video compression format''') is aan [[Contentencoded format|content representation format]] of [[digital video]] content, such as in a data file or [[Bitstream format|bitstream]]. It typically uses a standardized [[video compression]] algorithm, most commonly based on [[discrete cosine transform]] (DCT) coding and [[motion compensation]]. A specific software,computer [[firmwaresoftware]], or [[computer hardware|hardware]] implementationcomponent capablethat of compressioncompresses or decompression indecompresses a specific video coding format is called a [[video codec]].

Some video coding formats are documented by a detailed [[technical specification]] document known as a '''video coding specification'''. Some such specifications are written and approved by [[standardization organization]]s as [[technical standard]]s, and are thus known as a '''video coding standard'''. There are [[de facto standard|''de facto'' standards]] and formal standards.

Video content encoded using a particular video coding format is normally bundled with an audio stream (encoded using an [[audio coding format]]) inside a [[container format (digital)#Multimedia container formats|multimedia container format]] such as [[Audio Video Interleave|AVI]], [[MP4 file format|MP4]], [[Flash Video|FLV]], [[RealMedia]], or [[Matroska]]. As such, the user normally does not have a [[H.264/MPEG-4 AVC|H.264]] file, but instead has a [[video file format|video file]], which is an MP4 container of H.264-encoded video, normally alongside [[Advanced Audio Coding|AAC]]-encoded audio. Multimedia container formats can contain one of several different video coding formats; for example, the MP4 container format can contain video coding formats such as [[MPEG-2 Part 2]] or H.264. Another example is the initial specification for the file type [[WebM]], which specifies the container format (Matroska), but also exactly which video ([[VP8]]) and audio ([[Vorbis]]) compression format is inside the Matroska container, even though Matroska is capable of containing [[VP9]] video, and [[Opus (audio format)|Opus]] audio support was later added to the [[WebM]] specification.

==Distinction between ''format'' and ''codec''==

A ''format'' is the layout plan for data produced or consumed by a ''codec''.

Although video coding formats such as H.264 are sometimes referred to as ''codecs'', there is a clear conceptual difference between a specification and its implementations. Video coding formats are described in specifications, and software, [[firmware]], or hardware to encode/decode data in a given video coding format from/to uncompressed video are implementations of those specifications. As an analogy, the video coding format [[H.264]] (specification) is to the [[codec]] [[OpenH264]] (specific implementation) what the [[C (programming language)|C Programming Language]] (specification) is to the compiler [[GNU Compiler Collection|GCC]] (specific implementation). Note that for each specification (e.g., [[H.264]]), there can be many codecs implementing that specification (e.g., [[x264]], OpenH264, [[H.264/MPEG-4 AVC products and implementations]]).

This distinction is not consistently reflected terminologically in the literature. The H.264 specification calls [[H.261]], [[H.262]], [[H.263]], and [[H.264]] ''video coding standards'' and does not contain the word ''codec''.<ref name="h264" /> The [[Alliance for Open Media]] clearly distinguishes between the [[AV1]] video coding format and the accompanying codec they are developing, but calls the video coding format itself a ''[[video codec]] specification''.<ref>{{cite web|url=http://aomedia.org/|publisher=Alliance for Open Media|title=Front Page|access-date=May 23, 2016}}</ref> The [[VP9]] specification calls the video coding format VP9 itself a ''codec''.<ref>{{cite web|url=https://storage.googleapis.com/downloads.webmproject.org/docs/vp9/vp9-bitstream-specification-v0.6-20160331-draft.pdf|title=VP9 Bitstream & Decoding Process Specification|author1=Adrian Grange |author2=Peter de Rivaz |author3=Jonathan Hunt |name-list-style=amp }}</ref>

As an example of conflation, Chromium's<ref>{{cite web|url=https://www.chromium.org/audio-video|title=Audio/Video|publisher=The Chromium Projects

|access-date=May 23, 2016}}</ref> and Mozilla's<ref>{{cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats|title=Media formats supported by the HTML audio and video elements|publisher=Mozilla|access-date=May 23, 2016}}</ref> pages listing their video formatformats support both call video coding formats, such as H.264 ''codecs''. As another example, in Cisco's announcement of a free-as-in-beer video codec, the press release refers to the H.264 video coding format as a ''codec'' ("choice of a common video codec"), but calls Cisco's implementation of a H.264 encoder/decoder a ''codec'' shortly thereafter ("open-source our H.264 codec").<ref>{{cite web|url=https://blogs.cisco.com/collaboration/open-source-h-264-removes-barriers-webrtc|title=Open-Sourced H.264 Removes Barriers to WebRTC|publisher=Cisco|access-date=May 23, 2016|date=October 30, 2013|author=Rowan Trollope|archive-date=May 14, 2019|archive-url=https://web.archive.org/web/20190514053018/https://blogs.cisco.com/collaboration/open-source-h-264-removes-barriers-webrtc|url-status=dead}}</ref>

A video coding format does not dictate all [[algorithm]]s used by a [[codec]] implementing the format. For example, a large part of how video compression typically works is by finding [[Video compression picture types|similarities between video frames]] (block-matching), and then achieving compression by copying previously-coded similar subimages (such as [[macroblock]]s) and adding small differences when necessary. Finding optimal combinations of such predictors and differences is an [[NP-hard]] problem,<ref>{{cite web|url=http://shodhganga.inflibnet.ac.in/bitstream/10603/8175/8/08_chapter%203.pdf|title=Chapter 3 : Modified A* Prune Algorithm for finding K-MCSP in video compression|publisher=Shodhganga.inflibnet.ac.in|access-date=January 6, 2015}}</ref> meaning that it is practically impossible to find an optimal solution. Though the video coding format must support such compression across frames in the bitstream format, by not needlessly mandating specific algorithms for finding such block-matches and other encoding steps, the codecs implementing the video coding specification have some freedom to optimize and innovate in their choice of algorithms. For example, section 0.5 of the H.264 specification says that encoding algorithms are not part of the specification.<ref name="h264">{{cite web|url=http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-H.264-200305-S!!PDF-E&type=items|title=SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS : Infrastructure of audiovisual services – Coding of moving video : Advanced video coding for generic audiovisual services|publisher=Itu.int|access-date=January 6, 2015}}</ref> Free choice of algorithm also allows different [[Analysis of algorithms|space–time complexity]] trade-offs for the same video coding format, so a live feed can use a fast but space-inefficient algorithm, and a one-time [[DVD]] encoding for later mass production can trade long encoding-time for space-efficient encoding.

==History==

The concept of [[analog video]] compression dates back to 1929, when R.D. Kell in [[United Kingdom|Britain]] proposed the concept of transmitting only the portions of the scene that changed from frame-to-frame. The concept of [[digital video]] compression dates back to 1952, when [[Bell Labs]] researchers B.M. Oliver and [[Chris Harrison (American football)|C.W. Harrison]] proposed the use of [[differential pulse-code modulation]] (DPCM) in video coding. In 1959, the concept of [[inter-frame]] [[motion compensation]] was proposed by [[NHK]] researchers Y. Taki, M. Hatori and S. Tanaka, who proposed predictive inter-frame video coding in the [[temporal dimension]].<ref name="ITU">{{cite web |title=History of Video Compression |url=https://www.itu.int/wftp3/av-arch/jvt-site/2002_07_Klagenfurt/JVT-D068.doc |website=[[ITU-T]] |publisher=Joint Video Team (JVT) of ISO/IEC MPEG & ITU-T VCEG (ISO/IEC JTC1/SC29/WG11 and ITU-T SG16 Q.6) |date=July 2002 |pages=11, 24–9, 33, 40–1, 53–6 |access-date=November 3, 2019}}</ref> In 1967, [[University of London]] researchers A.H. Robinson and C. Cherry proposed [[run-length encoding]] (RLE), a [[lossless compression]] scheme, to reduce the transmission bandwidth of [[analog television]] signals.<ref name="robinson">{{cite journal |author1-last=Robinson |author1-first=A. H. |author2-last=Cherry |author2-first=C. |title=Results of a prototype television bandwidth compression scheme |journal=[[Proceedings of the IEEE]] |publisher=[[IEEE]] |volume=55 |number=3 |date=1967 |pages=356–364 |doi=10.1109/PROC.1967.5493}}</ref>

The earliest digital video coding algorithms were either for [[uncompressed video]] or used [[lossless compression]], both methods inefficient and impractical for digital video coding.<ref name="Ghanbari">{{cite book |last1=Ghanbari |first1=Mohammed |title=Standard Codecs: Image Compression to Advanced Video Coding |date=2003 |publisher=[[Institution of Engineering and Technology]] |isbn=9780852967102 |pages=1–2 |url=https://books.google.com/books?id=7XuU8T3ooOAC&pg=PA1}}</ref><ref name="Lea">{{cite book |last1=Lea |first1=William |title=Video on demand: Research Paper 94/68 |date=1994 |publisher=[[House of Commons Library]] |url=https://researchbriefings.parliament.uk/ResearchBriefing/Summary/RP94-68 |access-date=September 20, 2019}}</ref> Digital video was introduced in the 1970s,<ref name="Ghanbari"/> initially using uncompressed [[pulse-code modulation]] (PCM), requiring high [[bitrate]]s around 45{{ndash}}200 [[Mbit/s]] for [[standard-definition]] (SD) video,<ref name="Ghanbari"/><ref name="Lea"/> which was up to 2,000 times greater than the [[telecommunication]] [[Bandwidth (computing)|bandwidth]] (up to 100{{nbsp}}[[kilobits per second|kbit/s]]) available until the 1990s.<ref name="Lea"/> Similarly, uncompressed [[high-definition video|high-definition]] (HD) [[1080p]] video requires bitrates exceeding 1{{nbsp}}[[Gbit/s]], significantly greater than the bandwidth available in the 2000s.<ref>{{cite book |last1=Lee |first1=Jack |title=Scalable Continuous Media Streaming Systems: Architecture, Design, Analysis and Implementation |date=2005 |publisher=[[John Wiley & Sons]] |isbn=9780470857649 |page=25 |url=https://books.google.com/books?id=7fuvu52cyNEC&pg=PA25}}</ref>

===Motion-compensated DCT===

Practical [[video compression]] emerged with the development of [[motion compensation|motion-compensated]] [[Discrete cosine transform|DCT]] (MC DCT) coding,<ref name="Lea"/><ref name="Ghanbari"/> also called block motion compensation (BMC)<ref name="ITU"/> or DCT motion compensation. This is a hybrid coding algorithm,<ref name="ITU"/> which combines two key [[data compression]] techniques: [[discrete cosine transform]] (DCT) coding<ref name="Lea"/><ref name="Ghanbari"/> in the [[spatial dimension]], and predictive [[motion compensation]] in the [[temporal dimension]].<ref name="ITU"/>

DCT coding is a [[lossy compression|lossy]] block compression [[transform coding]] technique that was first proposed by [[N.Nasir Ahmed (engineer)|Nasir Ahmed]], who initially intended it for [[image compression]], while he was working at [[Kansas State University]] in 1972. It was then developed into a practical image compression algorithm by Ahmed with T. Natarajan and [[K. R. Rao]] at the [[University of Texas]] in 1973, and was published in 1974.<ref name="Ahmed">{{cite journal |last=Ahmed |first=Nasir |author-link=N. Ahmed |title=How I Came Up With the Discrete Cosine Transform |journal=[[Digital Signal Processing (journal)|Digital Signal Processing]] |date=January 1991 |volume=1 |issue=1 |pages=4–5 |doi=10.1016/1051-2004(91)90086-Z |bibcode=1991DSP.....1....4A |url=https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform|url-access=subscription }}</ref><ref name="pubDCT">{{Citation |first1=Nasir |last1=Ahmed |author1-link=N. Ahmed |first2=T. |last2=Natarajan |first3=K. R. |last3=Rao |title=Discrete Cosine Transform |journal=IEEE Transactions on Computers |date=January 1974 |volume=C-23 |issue=1 |pages=90–93 |doi=10.1109/T-C.1974.223784|s2cid=149806273 }}</ref><ref name="pubRaoYip">{{Citation |last1=Rao |first1=K. R. |author-link1=K. R. Rao |last2=Yip |first2=P. |title=Discrete Cosine Transform: Algorithms, Advantages, Applications |publisher=Academic Press |___location=Boston |year=1990 |isbn=978-0-12-580203-1}}</ref>

The other key development was motion-compensated hybrid coding.<ref name="ITU"/> In 1974, Ali Habibi at the [[University of Southern California]] introduced hybrid coding,<ref name="Habibi">{{cite journal |last1=Habibi |first1=Ali |title=Hybrid Coding of Pictorial Data |journal=IEEE Transactions on Communications |date=1974 |volume=22 |issue=5 |pages=614–624 |doi=10.1109/TCOM.1974.1092258}}</ref><ref>{{cite journal |last1=Chen |first1=Z. |last2=He |first2=T. |last3=Jin |first3=X. |last4=Wu |first4=F. |title=Learning for Video Compression |journal=IEEE Transactions on Circuits and Systems for Video Technology |date=2019 |volume=30 |issue=2 |pages=566–576 |doi=10.1109/TCSVT.2019.2892608 |arxiv=1804.09869 |s2cid=13743007 }}</ref><ref>{{cite book |last1=Pratt |first1=William K. |title=Advances in Electronics and Electron Physics: Supplement |date=1984 |publisher=[[Academic Press]] |isbn=9780120145720 |page=158 |url=https://books.google.com/books?id=OX00AAAAIAAJ |quote=A significant advance in image coding methodology occurred with the introduction of the concept of hybrid transform/DPCM coding (Habibi, 1974).}}</ref> which combines predictive coding with transform coding.<ref name="ITU"/><ref>{{cite book |last1=Ohm |first1=Jens-Rainer |title=Multimedia Signal Coding and Transmission |date=2015 |publisher=Springer |isbn=9783662466919 |pages=364 |url=https://books.google.com/books?id=e7xnBwAAQBAJ&pg=PA364}}</ref> He examined several transform coding techniques, including the DCT, [[Hadamard transform]], [[Fourier transform]], slant transform, and [[Karhunen-Loeve transform]].<ref name="Habibi"/> However, his algorithm was initially limited to [[intra-frame]] coding in the spatial dimension. In 1975, John A. Roese and Guner S. Robinson extended Habibi's hybrid coding algorithm to the temporal dimension, using transform coding in the spatial dimension and predictive coding in the temporal dimension, developing [[inter-frame]] motion-compensated hybrid coding.<ref name="ITU"/><ref name="Roese">{{cite journal |last1=Roese |first1=John A. |last2=Robinson |first2=Guner S. |editor-first1=Andrew G. |editor-last1=Tescher |title=Combined Spatial And Temporal Coding Of Digital Image Sequences |journal=Efficient Transmission of Pictorial Information |date=October 30, 1975 |volume=0066 |pages=172–181 |doi=10.1117/12.965361 |publisher=International Society for Optics and Photonics |bibcode=1975SPIE...66..172R |s2cid=62725808 }}</ref> For the spatial transform coding, they experimented with different transforms, including the DCT and the [[fast Fourier transform]] (FFT), developing inter-frame hybrid coders for them, and found that the DCT is the most efficient due to its reduced complexity, capable of compressing image data down to 0.25-[[bit]] per [[pixel]] for a [[videotelephone]] scene with image quality comparable to a typical intra-frame coder requiring 2-bit per pixel.<ref>{{cite book |last1=Huang |first1=T. S. |title=Image Sequence Analysis |date=1981 |publisher=[[Springer Science & Business Media]] |isbn=9783642870378 |page=29 |url=https://books.google.com/books?id=bAirCAAAQBAJ&pg=PA29}}</ref><ref name="Roese"/>

The DCT was applied to video encoding by Wen-Hsiung Chen,<ref name="Stankovic">{{cite journal |last1=Stanković |first1=Radomir S. |last2=Astola |first2=Jaakko T. |title=Reminiscences of the Early Work in DCT: Interview with K.R. Rao |journal=Reprints from the Early Days of Information Sciences |date=2012 |volume=60 |url=http://ticsp.cs.tut.fi/reports/ticsp-report-60-reprint-rao-corrected.pdf |access-date=October 13, 2019}}</ref> who developed a fast DCT algorithm with C.H. Smith and S.C. Fralick in 1977,<ref>{{cite journal |last1=Chen |first1=Wen-Hsiung |last2=Smith |first2=C. H. |last3=Fralick |first3=S. C. |title=A Fast Computational Algorithm for the Discrete Cosine Transform |journal=[[IEEE Transactions on Communications]] |date=September 1977 |volume=25 |issue=9 |pages=1004–1009 |doi=10.1109/TCOM.1977.1093941}}</ref><ref name="t81">{{cite web |title=T.81 – Digital compression and coding of continuous-tone still images – Requirements and guidelines |url=https://www.w3.org/Graphics/JPEG/itu-t81.pdf |publisher=[[CCITT]] |date=September 1992 |access-date=July 12, 2019}}</ref> and founded [[Compression Labs, Inc.|Compression Labs]] to commercialize DCT technology.<ref name="Stankovic"/> In 1979, [[Anil K. Jain (electrical engineer, born 1946)|Anil K. Jain]] and Jaswant R. Jain further developed motion-compensated DCT video compression.<ref>{{cite book |last1=Cianci |first1=Philip J. |title=High Definition Television: The Creation, Development and Implementation of HDTV Technology |date=2014 |publisher=McFarland |isbn=9780786487974 |page=63 |url=https://books.google.com/books?id=0mbsfr38GTgC&pg=PA63}}</ref><ref name="ITU"/> This led to Chen developing a practical video compression algorithm, called motion-compensated DCT or adaptive scene coding, in 1981.<ref name="ITU"/> Motion-compensated DCT later became the standard coding technique for video compression from the late 1980s onwards.<ref name="Ghanbari"/><ref name="Li">{{cite book |last1=Li |first1=Jian Ping |title=Proceedings of the International Computer Conference 2006 on Wavelet Active Media Technology and Information Processing: Chongqing, China, 29-31 August 2006 |date=2006 |publisher=[[World Scientific]] |isbn=9789812709998 |page=847 |url=https://books.google.com/books?id=FZiK3zXdK7sC&pg=PA847}}</ref>

===Video coding standards===

The first digital video coding standard was [[H.120]], developed by the [[ITU-T|CCITT]] (now ITU-T) in 1984.<ref name="history">{{cite web |title=The History of Video File Formats Infographic |url=http://www.real.com/resources/digital-video-file-formats/ |website=[[RealNetworks]] |access-date=August 5, 2019 |date=April 22, 2012}}</ref> H.120 was not usable in practice, as its performance was too poor.<ref name="history" /> H.120 used motion-compensated DPCM coding,<ref name="ITU"/> a lossless compression algorithm that was inefficient for video coding.<ref name="Ghanbari"/> During the late 1980s, a number of companies began experimenting with [[discrete cosine transform]] (DCT) coding, a much more efficient form of compression for video coding. The CCITT received 14 proposals for DCT-based video compression formats, in contrast to a single proposal based on [[vector quantization]] (VQ) compression. The [[H.261]] standard was developed based on motion-compensated DCT compression.<ref name="Ghanbari"/><ref name="Li"/> H.261 was the first practical video coding standard,<ref name="history" /> and uses [[patents]] licensed from a number of companies, including [[Hitachi]], [[PictureTel]], [[Nippon Telegraph and Telephone|NTT]], [[BT Group|BT]], and [[Toshiba]], among others.<ref name="h261-patents"/> Since H.261, motion-compensated DCT compression has been adopted by all the major video coding standards (including the [[H.26x]] and [[MPEG]] formats) that followed.<ref name="Ghanbari"/><ref name="Li"/>

[[MPEG-1]], developed by the [[Moving Picture Experts Group]] (MPEG), followed in 1991, and it was designed to compress [[VHS]]-quality video.<ref name="history"/> It was succeeded in 1994 by [[MPEG-2]]/[[H.262/MPEG-2 Part 2|H.262]],<ref name="history"/> which was developed with patents licensed from a number of companies, primarily [[Sony]], [[Technicolor SA|Thomson]] and [[Mitsubishi Electric]].<ref name="mp2-patents"/> MPEG-2 became the standard video format for [[DVD]] and [[SD digital television]].<ref name="history"/> Its motion-compensated DCT algorithm was able to achieve a [[compression ratio]] of up to 100:1, enabling the development of [[digital media]] technologies such as [[video on demand]] (VOD)<ref name="Lea"/> and [[high-definition television]] (HDTV).<ref name="Shishikui">{{cite journalbook |last1doi=Shishikui10.1016/B978-0-444-81844-7.50072-3 |first1=Yoshiaki |last2=Nakanishi |first2=Hiroshi |last3=Imaizumi |first3=Hiroyuki |titlechapter=An HDTV Coding Scheme using Adaptive-Dimension DCT |journaltitle=Signal Processing of HDTV: Proceedings|date=1994 of|last1=Shishikui the|first1=Yoshiaki International|last2=Nakanishi Workshop|first2=Hiroshi on HDTV '93, Ottawa, Canada|last3=Imaizumi |datefirst3=October 26–28, 1993Hiroyuki |pages=611–618 |doiisbn=10.1016/B978978-0-444-81844-7.50072-3 |chapter-url=https://books.google.com/books?id={{GBurl|j9XSBQAAQBAJ&pg=PA611 |publisherp=[[Elsevier]]611}} |isbn=9781483298511}}</ref> In 1999, it was followed by [[MPEG-4 Visual|MPEG-4]]/[[H.263]], which was a major leap forward for video compression technology.<ref name="history"/> It uses patents licensed from a number of companies, primarily Mitsubishi, [[Hitachi]] and [[Panasonic]].<ref name="mp4-patents"/>

The most widely used video coding format {{as of|2019|lc=y}} is [[H.264/MPEG-4 AVC]].<ref name="Bitmovin">{{cite web |url=https://cdn2.hubspot.net/hubfs/3411032/Bitmovin%20Magazine/Video%20Developer%20Report%202019/bitmovin-video-developer-report-2019.pdf |title=Video Developer Report 2019 |website=[[Bitmovin]] |year=2019 |access-date=November 5, 2019}}</ref> It was developed in 2003, and uses patents licensed from a number of organizations, primarily Panasonic, [[Godo kaisha|Godo Kaisha IP Bridge]] and [[LG Electronics]].<ref name="avc-patents"/> In contrast to the standard DCT used by its predecessors, AVC uses the [[Discrete cosine transform|integer DCT]].<ref name="Stankovic"/><ref name="Wang">{{cite journal |last1=Wang |first1=Hanli |last2=Kwong |first2=S. |last3=Kok |first3=C. |title=Efficient prediction algorithm of integer DCT coefficients for H.264/AVC optimization |journal=IEEE Transactions on Circuits and Systems for Video Technology |date=2006 |volume=16 |issue=4 |pages=547–552 |doi=10.1109/TCSVT.2006.871390 |s2cidbibcode=20609372006ITCSV..16..547W }}</ref> H.264 is one of the video encoding standards for [[Blu-ray Disc]]s; all Blu-ray Disc players must be able to decode H.264. It is also widely used by streaming internet sources, such as videos from [[YouTube]], [[Netflix]], [[Vimeo]], and the [[iTunes Store]], web software such as the [[Adobe Flash Player]] and [[Microsoft Silverlight]], and also various [[HDTV]] broadcasts over terrestrial ([[ATSC standards]], [[ISDB-T]], [[DVB-T]] or [[DVB-T2]]), cable ([[DVB-C]]), and satellite ([[DVB-S2]]).<ref>{{Cite web|title=Digital Video Broadcasting (DVB); Specification for the use of video and audio coding in DVB services delivered directly over IP|url=https://www.etsi.org/deliver/etsi_ts/102000_102099/102005/01.01.01_60/ts_102005v010101p.pdf}}</ref>

A main problem for many video coding formats has been [[patent]]s, making it expensive to use or potentially risking a patent lawsuit due to [[submarine patent]]s. The motivation behind many recently designed video coding formats such as [[Theora]], [[VP8]], and [[VP9]] have been to create a ([[Free software|libre]]) video coding standard covered only by royalty-free patents.<ref>{{Cite web|url=https://blogs.cisco.com/collaboration/world-meet-thor-a-project-to-hammer-out-a-royalty-free-video-codec|title = World, Meet Thor – a Project to Hammer Out a Royalty Free Video Codec|date = August 11, 2015}}</ref> Patent status has also been a major point of contention for the choice of which video formats the mainstream [[web browser]]s will support inside the [[HTML5HTML video]] tag.

The current-generation video coding format is [[HEVC]] (H.265), introduced in 2013. AVC uses the integer DCT with 4x4 and 8x8 block sizes, and HEVC uses integer DCT and [[Discrete sine transform|DST]] transforms with varied block sizes between 4x4 and 32x32.<ref name="apple">{{cite web |last1=Thomson |first1=Gavin |last2=Shah |first2=Athar |title=Introducing HEIF and HEVC |url=https://devstreaming-cdn.apple.com/videos/wwdc/2017/503i6plfvfi7o3222/503/503_introducing_heif_and_hevc.pdf |publisher=[[Apple Inc.]] |year=2017 |access-date=August 5, 2019}}</ref> HEVC is heavily patented, mostly by [[Samsung Electronics]], [[General Electric|GE]], [[Nippon Telegraph and Telephone|NTT]], and [[JVCKenwood]].<ref name="hevc-patents"/> It is challenged by the [[AV1]] format, intended for free license. {{As of|2019}}, AVC is by far the most commonly used format for the recording, compression, and distribution of video content, used by 91% of video developers, followed by HEVC, which is used by 43% of developers.<ref name="Bitmovin"/>

==List of video coding standards==

Line 59:

! Popular implementations

|- style="text-align:center;"

| [[Differential pulse-code modulation|DPCM]]

| [[H.120]]

| 1984 ||[[ITU-T|CCITT]]

| [[Video Coding Experts Group|VCEG]]

| {{n/a}}

| {{n/a}}

Line 79:

| [[Joint Photographic Experts Group|JPEG]]

| [[Joint Photographic Experts Group|JPEG]]

| [[International Organization for Standardization|ISO]] / [[Open source|Open Source does NOT mean free!]] <ref>{{cite web |last1=ISO |title=Home |url=https://www.iso.org/home.html |website=International Standards Organization |publisher=ISO |access-date=August 3, 2022}}</ref>

| {{n/a}}

| [[QuickTime]]

|- style="text-align:center;"

| [[MPEG-1 Part 2]]

| 1993||[[International Organization for Standardization|ISO]], [[International Electrotechnical Commission|IEC]]

| [[MPEG]]

| [[Fujitsu]], [[IBM]], [[Matsushita Electric|Matsushita]], [[MPEG-1#Patent holders|etc.]]<ref>{{cite web |title=ISO Standards and Patents |url=https://www.iso.org/iso-standards-and-patents.html |website=ISO |access-date=July 10, 2019}}</ref>

Line 93:

| 1995|| ISO, IEC, [[ITU-T]]

| MPEG, VCEG

| [[Sony]], [[Technicolor SA|Thomson]], [[Mitsubishi Electric|Mitsubishi]], [[H.262/MPEG-2 Part 2#Patent holders|etc.]]<ref name="mp2-patents">{{cite web |title=MPEG-2 Patent List |url=https://www.mpegla.com/wp-content/uploads/m2-att1.pdf |website=[[MPEG LA]] |access-date=July 7, 2019 |archive-date=May 29, 2019 |archive-url=https://web.archive.org/web/20190529164140/https://www.mpegla.com/wp-content/uploads/m2-att1.pdf |url-status=dead }}</ref>

| 29%

| [[DVD|DVD Video]], [[Blu-ray]], [[DVB]], [[ATSC standards|ATSC]], [[Super Video CD|SVCD]], [[Standard-definition television|SDTV]]

|- style="text-align:center;"

| [[DV (video format)|DV]]

| 1995

| IEC

| [[IEC]]

| [[International Electrotechnical Commission|IEC]]

| Sony, [[Panasonic]]

| {{unk}}

Line 108:

| 1996|| ITU-T

| VCEG

| Mitsubishi, [[Hitachi]], Panasonic, [[MPEG-4 Part 2#Patent holders|etc.]]<ref name="mp4-patents">{{cite web |title=MPEG-4 Visual - Patent List |url=https://www.mpegla.com/wp-content/uploads/m4v-att1.pdf |website=[[MPEG LA]] |access-date=July 6, 2019 |archive-date=July 6, 2019 |archive-url=https://web.archive.org/web/20190706184814/https://www.mpegla.com/wp-content/uploads/m4v-att1.pdf |url-status=dead }}</ref>

| {{unk}}

| Videoconferencing, videotelephony, [[H.320]], [[ISDN]],<ref>{{cite news |last1=Davis |first1=Andrew |title=The H.320 Recommendation Overview |url=https://www.eetimes.com/document.asp?doc_id=1275886 |access-date=November 7, 2019 |work=[[EE Times]] |date=June 13, 1997}}</ref><ref>{{cite book |doi=10.1109/WESCAN.1997.627108 |chapter=H.263 based facial image compression for low bitrate communications |title=IEEE WESCANEX 97: communicationsCommunications, power,Power and computingComputing. :Conference conference proceedingsProceedings |date=May 22–23, 1997 |publisherlast1=[[InstituteLi ofDing Electrical|last2=Takaya and Electronics Engineers]]|first2=K. |___locationpages=University of Manitoba, Winnipeg, Manitoba, Canada30–34 |isbn=97807803414700-7803-4147-3 |quote-page=30 |url=https://books.google.com/books?id=8vhEAQAAIAAJ |quote=H.263 is similar to, but more complex than H.261. It is currently the most widely used international video compression standard for video telephony on ISDN (Integrated Services Digital Network) telephone lines. }}</ref> [[mobile video]] ([[3GP]]), [[MPEG-4 Visual]]

|- style="text-align:center;"

| [[MPEG-4 Part 2]] (MPEG-4 Visual)

Line 129:

| 2003|| ISO, IEC, ITU-T

| MPEG, VCEG

| Panasonic, [[Godo kaisha|Godo Kaisha IP Bridge]], [[LG Electronics|LG]], [[H.264/MPEG-4 AVC#Patent holders|etc.]]<ref name="avc-patents">{{cite web |title=AVC/H.264 {{ndash}} Patent List |url=https://www.mpegla.com/wp-content/uploads/avc-att1.pdf |website=MPEG LA |access-date=July 6, 2019 |archive-date=January 25, 2023 |archive-url=https://web.archive.org/web/20230125102953/https://www.mpegla.com/wp-content/uploads/avc-att1.pdf |url-status=dead }}</ref>

| 91%

| [[Blu-ray]], [[HD DVD]], [[High-definition television|HDTV]] ([[DVB]], [[ATSC standards|ATSC]]), [[video streaming]] ([[YouTube]], [[Netflix]], [[Vimeo]]), [[iTunes Store]], [[iPod Video]], [[Apple TV]], videoconferencing, [[Flash Player]], [[Microsoft Silverlight|Silverlight]], [[Video on demand|VOD]]

|- style="text-align:center;"

| [[Theora]]

| 2004

| [[Xiph.Org Foundation|Xiph]]

| [[Xiph.Org Foundation|Xiph]]

| {{n/a}}

| {{unk}}

Line 143:

| [[VC-1]]

| 2006

| [[SMPTE]]

| [[Society of Motion Picture and Television Engineers|SMPTE]]

| [[SMPTE]]

| [[Society of Motion Picture and Television Engineers|SMPTE]]

| [[Microsoft]], Panasonic, LG, [[Samsung Electronics|Samsung]], [[VC-1#Patent holders|etc.]]<ref>{{cite web |title=VC-1 Patent List |url=https://www.mpegla.com/wp-content/uploads/vc-1-att1.pdf |website=[[MPEG LA]] |access-date=July 11, 2019 |archive-date=July 6, 2019 |archive-url=https://web.archive.org/web/20190706203225/https://www.mpegla.com/wp-content/uploads/hevc-att1.pdf |url-status=dead }}</ref>

| {{unk}}

| Blu-ray, Internet video

Line 161:

| ISO, IEC, ITU-T

| MPEG, VCEG

| Samsung, [[General Electric|GE]], [[Nippon Telegraph and Telephone|NTT]], [[JVCKenwood]], [[High Efficiency Video Coding#Patent holders|etc.]]<ref name="hevc-patents">{{cite web |title=HEVC Patent List |url=https://www.mpegla.com/wp-content/uploads/hevc-att1.pdf |website=[[MPEG LA]] |access-date=July 6, 2019 |archive-date=April 10, 2021 |archive-url=https://web.archive.org/web/20210410171930/https://www.mpegla.com/wp-content/uploads/hevc-att1.pdf |url-status=dead }}</ref><ref name="hevcadvance">{{cite web|url=https://www.hevcadvance.com/licensors/|title=HEVC Advance Patent List|website=[[HEVC Advance]]|access-date=July 6, 2019|archive-date=August 24, 2020|archive-url=https://web.archive.org/web/20200824174620/https://www.hevcadvance.com/licensors/|url-status=dead}}</ref>

| 43%

|[[Ultra HD Blu-ray|UHD Blu-ray]], DVB, [[ATSC 3.0]], [[Ultra-high-definition television|UHD]] streaming, [[High Efficiency Image File Format|HEIF]], [[macOS High Sierra]], [[iOS 11]]

|- style="text-align:center;"

| [[AV1]]

| 2018

| [[Alliance for Open Media|AOMedia]]

| [[Alliance for Open Media|AOMedia]]

| {{n/a}}

| 7%

| [[HTML5HTML video]]

|- style="text-align:center;"

| [[Versatile Video Coding]] (VVC / H.266)

Line 183:

==Lossless, lossy, and uncompressed==

Consumer video is generally compressed using [[lossy compression|lossy]] [[video codec]]s, since that results in significantly smaller files than [[lossless compression|lossless]] compression. Some video coding formats are designed explicitly for either lossy or lossless compression, and some video coding formats such as [[Dirac (video compression format)|Dirac]] and [[H.264/MPEG-4 AVC|H.264]] support both.<ref>{{Cite journal|title=RFC 8761 - Video Codec Requirements and Evaluation Methodology|url=https://datatracker.ietf.org/doc/html/rfc8761|access-date=February 10, 2022|website=datatracker.ietf.org|date=April 2020 |language=en |last1=Filippov |first1=Alexey |last2=Norkin |first2=Aney |last3=Alvarez |first3=José Roberto }}</ref>

[[Uncompressed video]] formats, such as ''Clean HDMI'', is a form of lossless video used in some circumstances, such as when sending video to a display over aan [[HDMI]] connection. Some high-end cameras can also capture video directly in this format.{{Example needed|s|date=December 2024}}

==Intra-frame==

Interframe compression complicates editing of an encoded video sequence.<ref name="Bhojani">{{cite web|last=Bhojani|first=D.R.|title=4.1 Video Compression|url=http://shodh.inflibnet.ac.in/bitstream/123456789/821/5/05_hypothesis.pdf|work=Hypothesis|access-date=March 6, 2013|archive-date=May 10, 2013|archive-url=https://web.archive.org/web/20130510133020/http://shodh.inflibnet.ac.in/bitstream/123456789/821/5/05_hypothesis.pdf|url-status=dead}}</ref>

One subclass of relatively simple video coding formats are the [[intra-frame]] video formats, such as [[DV (video format)|DV]], in which each frame of the video stream is compressed independently without referring to other frames in the stream, and no attempt is made to take advantage of correlations between successive pictures over time for better compression. One example is [[Motion JPEG]], which is simply a sequence of individually [[JPEG]]-compressed images. This approach is quick and simple, at the expense of the encoded video being much larger than a video coding format supporting [[Inter frame]] coding.

Because interframe compression copies data from one frame to another, if the original frame is simply cut out (or lost in transmission), the following frames cannot be reconstructed properly. Making '[[Cut (transition)|cuts']] in intraframe-compressed video while [[video editing]] is almost as easy as editing uncompressed video: one finds the beginning and ending of each frame, and simply copies bit-for-bit each frame that one wants to keep, and discards the frames one does not want. Another difference between intraframe and interframe compression is that, with intraframe systems, each frame uses a similar amount of data. In most interframe systems, certain frames (such as "[[Video compression picture types|I frames-frame]]"s in [[MPEG-2]]) are not allowed to copy data from other frames, so they require much more data than other frames nearby.<ref name="Jaiswal">{{cite book|last=Jaiswal|first=R.C.|title=Audio-Video Engineering|year=2009|publisher=Nirali Prakashan|___location=Pune, Maharashtra|isbn=9788190639675|page=3.55}}</ref>

It is possible to build a computer-based video editor that spots problems caused when I frames are edited out while other frames need them. This has allowed newer formats like [[HDV]] to be used for editing. However, this process demands a lot more computing power than editing intraframe compressed video with the same picture quality. But, this compression is not very effective to use for any audio format.<ref>{{Cite web|title=WebCodecs|url=https://www.w3.org/TR/webcodecs/Overview.html|access-date=February 10, 2022|website=www.w3.org}}</ref>

==Profiles and levels==

A video coding format can define optional restrictions to encoded video, called [[profile (engineering)|profile]]s and levels. It is possible to have a decoder whichthat only supports decoding a subset of profiles and levels of a given video format, for example, to make the decoder program/hardware smaller, simpler, or faster.<ref>{{Cite web|title=Video Rendering - an overview {{!}} ScienceDirect Topics|url=https://www.sciencedirect.com/topics/computer-science/video-renderingfact|access-date=FebruaryJanuary 10, 2022|website=www.sciencedirect.com2025}}</ref>

A ''profile'' restricts which encoding techniques are allowed. For example, the H.264 format includes the profiles ''baseline'', ''main'' and ''high'' (and others). While [[Video compression picture types|P-slices]] (which can be predicted based on preceding slices) are supported in all profiles, [[Video compression picture types|B-slices]] (which can be predicted based on both preceding and following slices) are supported in the ''main'' and ''high'' profiles but not in ''baseline''.<ref name="adobe"/>