A video codec is a software that enables video compression and or decompression for digital video. The compression usually employs lossy data compression. Historically, video was stored as an analog signal on magnetic tape. Around the time when the compact disc entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form, and a variety of such technologies began to emerge.
Audio and video call for customized methods of compression. Engineers and mathematicians have tried a number of solutions for tackling this problem. There is a complex balance between the video quality, the quantity of the data needed to represent it, also known as the bit rate, the complexity of the encoding and decoding algorithms, robustness to data losses and errors, ease of editing, random access, the state of the art of compression algorithm design, end-to-end delay, and a number of other factors. A common problem when an end user wants to watch a video stream encoded with a specific codec is that if the exact codec is not present and properly installed on the user's machine, the video won't play (or won't play optimally).
- MPEG-1 Part 2: Used for Video CDs, and also sometimes for online video.
- MPEG-2 Part 2 (a common-text standard with H.262): Used on DVD, SVCD, and in most digital video broadcasting and cable distribution systems.
- H.263: Used primarily for videoconferencing, videotelephony, and internet video.
- MPEG-4 Part 2: An MPEG standard that can be used for internet, broadcast, and on storage media.
- MPEG-4 Part 10 (a technically aligned standard with the ITU-T's H.264 and often also referred to as AVC). This emerging new standard is the current state of the art of ITU-T and MPEG standardized compression technology, and is rapidly gaining adoption into a wide variety of applications.
- DivX, Xvid, FFmpeg MPEG-4 and 3ivx: Different implementations of MPEG-4 Part 2.
- VP6: A proprietary video codec developed by On2 Technologies.
- Sorenson 3: A codec that is popularly used by Apple's QuickTime, basically the ancestor of H.264. Many of the QuickTime movie trailers found on the web use this codec.
- Theora: Theora is targeted at competing with MPEG-4 video and similar lower-bitrate video compression schemes.
- WMV (Windows Media Video): Microsoft's family of video codec designs including WMV 7, WMV 8, and WMV 9. It can do anything from low resolution video for dial up internet users to HDTV.
- RealVideo: A popular codec technology a few years ago, now fading in importance for a variety of reasons.
- Cinepak: A very early codec used by Apple's QuickTime.
- X264: A GPL-licensed implementation of H.264 encoding standard.
- Huffyuv: Huffyuv (or HuffYUV) is a very fast, lossless Win32 video codec written by Ben Rudiak-Gould and published under the terms of the GPL as free software, meant to replace uncompressed YCbCr as a video capture format. See Lagarith as a more up-to-date codec.
- Lagarith: A more up-to-date fork of Huffyyuv is available as Lagarith.
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