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Give more detail on why H.264 explains so well, plus link to the x264 project -- some readers may want to try generating H.264 videos themselves! |
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The intents of H.264/AVC project were to create a standard that would lead to fast implementations, using low bitrates. That is: implementations that would demand little from the decoder hardware and from the network bandwidth.
H.264/AVC contains several innovative, useful new features that allow it to compress video much more effectively than older codecs. CABAC (Context-Adaptive Binary Arithmetic Coding) is a clever technique that can be used in H.264 to losslessly compress syntax elements in the video stream. It also implements an in-loop deblocking filter which can prevent the ringing and blocking artifacts that are common to other [[DCT]]-based image compression techniques. In previous video standards, [[motion compensation]] is handled by allowing blocks in a frame to refer only to the frame before it. H.264/AVC allows the possibility of predicting new frames from other frames that are arbitrarily far in the past. This usually allows modest improvements in bitrate and quality in most scenes. But (for example) in rapidly flashing scenes, it allows a massive reduction in bitrate. These ideas, along with many other new ideas, help H.264 to perform significantly better than MPEG-4 ASP can. H.264 can usually perform radically better than [[MPEG-2]] at a fraction of the bitrate.
In addition, the JVT is nearing completion of the development of some extensions to the original standard that are known as the Fidelity Range Extensions. These extensions will support higher-fidelity video coding by supporting increased sample accuracy (including 10-bit and 12-bit coding) and higher-resolution color information (including sampling structures known as [[YUV 4:2:2]] and [[YUV 4:4:4]]). Several other features are also included in the Fidelity Range Extensions project. The drafting work on the Fidelity Range Extensions should be completed in the Summer of 2004.
H.264 is already widely used for videoconferencing, including its support in products of the two main companies in that market (Polycom and Tandberg). It has also been preliminarily adopted as a mandatory part of the future DVD specification known as HD-DVD, now under development by the DVD Forum. A number of broadcasters in Japan and Korea have announced future support for the codec, and it is under consideration for other broadcast use -- for example, it is under consideration in the United States' Advanced Television Systems Committee ([[ATSC]]) and in Europe's Digital Video Broadcast ([[DVB]]) standards bodies. In the wireless world, it is under consideration for adoption by the 3rd-Generation Partnership Project (3GPP).
Like many [[ISO]] video standards, H.264/AVC has a reference implementation that can be freely downloaded. Its main concern is to give examples of H.264/AVC features, instead of being a useful application per se.
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*[ftp://ftp ftp.imtc-files.org/jvt-experts] FTP site for reference implementation history as well as expert meetings
*[http://www.mpegla.com/news/n_03-11-17_avc.html MPEG LA Announces Terms of Joint H.264/MPEG-4 AVC Patent License]
*[http://www.videolan.org/x264.html A fast [[GPL]] H.264 encoder library with support for most H.264 features]
[[Category:Video codecs]]
[[Category:ITU-T recommendations]]
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