Content deleted Content added
No edit summary |
No edit summary |
||
Line 37:
The first digital video coding standard was [[H.120]], developed by the [[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]],<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 journal
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 }}</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>
| |||