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{{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
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.
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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]] block compression [[transform coding]] technique that was first proposed by [[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 }}</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 }}</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 }}</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"/>
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[[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]],<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 book |doi=10.1016/B978-0-444-81844-7.50072-3 |chapter=An HDTV Coding Scheme using Adaptive-Dimension DCT |title=Signal Processing of HDTV |date=1994 |last1=Shishikui |first1=Yoshiaki |last2=Nakanishi |first2=Hiroshi |last3=Imaizumi |first3=Hiroyuki |pages=611–618 |isbn=978-0-444-81844-7 |chapter-url={{GBurl|j9XSBQAAQBAJ|p=611}} }}</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 |bibcode=2006ITCSV..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 [[HTML 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]], [[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==
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| 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]], [[SVCD]], [[SDTV]]
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| 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
|- style="text-align:center;"
| [[MPEG-4 Part 2]] (MPEG-4 Visual)
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| 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]], [[HDTV]] ([[DVB]], [[ATSC]]), [[video streaming]] ([[YouTube]], [[Netflix]], [[Vimeo]]), [[iTunes Store]], [[iPod Video]], [[Apple TV]], videoconferencing, [[Flash Player]], [[Silverlight]], [[VOD]]
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| [[SMPTE]]
| [[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
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| ISO, IEC, ITU-T
| MPEG, VCEG
| Samsung, [[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%
|[[UHD Blu-ray]], DVB, [[ATSC 3.0]], [[Ultra-high-definition television|UHD]] streaming, [[HEIF]], [[macOS High Sierra]], [[iOS 11]]
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==Lossless, lossy, and uncompressed==
Consumer video is generally compressed using [[lossy]] [[video codec]]s, since that results in significantly smaller files than [[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]] 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
==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.
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==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
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"/>
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