Video compression refers to reducing the quantity of data used to represent video images. Compressed video can effectively reduce the bandwidth required to transmit digital video. A video codec is a device or software that enables video compression and or decompression for digital video.
The video compression usually employs lossy data compression. It operates on the premise that much of the data present before compression is not necessary for achieving good perceptual quality.
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.
There are many different technologies and standards by different standard organizations and companies for video compression available. In the following table, the main ones are listed.
| CODEC Name | Standard by | Compression Type | Notes |
| H.261 | ITU-T | Used primarily in older videoconferencing and video telephony products. | |
| H.263 | ITU-T | Used primarily for videoconferencing, video telephony, and internet video. | |
| H.264 | ITU-T version of MPEG-4 Part 10 | Also known as MPEG-4 Part 10, or AVC (for Advanced Video Coding). | |
| MPEG-1 Part 2 | MPEG | Used for Video CDs, and also sometimes for online video | |
| MPEG-2 Part 2 | MPEG | Used on DVD, SVCD, and in most digital video broadcasting and cable distribution systems. | |
| MPEG-4 Part 2 | MPEG | Used for internet, broadcast, and on storage media. | |
| MPEG-4 Part 10 | MPEG | Also known as H.264 or AVC, it is used for internet, broadcast, and on storage media. | |
| Cinepak | SuperMac Technologies | Lossy compression | A very early codec used by Apple's QuickTime. |
| DivX | Based on MPEG-4 Part 2 | Used for internet, broadcast, and on storage media. | |
| Huffyuv | Ben Rudiak-Gould | Lossless compression | Free codec under GPL. |
| RealVideo | RealNetworks | Lossy compression | Supported on Windows, Mac, Linux, Unix, and several mobile phones. |
| SheerVideo | BitJazz Inc | Lossless compression | A family of ultrafast lossless QuickTime and AVI codecs. |
| Sorenson | Sorenson Media | Lossy compression | also known as Sorenson Video Codec, Sorenson Video Quantizer or SVQ, It is used in Apple's QuickTime and in Macromedia Flash. |
| Theora | Based on VP 3 By Xiph.Org Foundation | Lossy compression | Used for internet, broadcast, and on storage media. |
| VP6 | On2 Technologies | Used for broadcasting in the field. | |
| WMV Windows Media Video | Microsoft | It can do anything from low resolution video for dial up internet users to HDTV. | |
| X264 | Based on H.264; GPL | A GPL-licensed implementation of H.264 encoding standard. |
Related Terms: H.261, H.263, H.264, MPEG-1, MPEG-2, MPEG-4, Cinepak, DivX, Huffyuv, SheerVideo, Sorenson, Theora, VP 6, WMV, X264