Video Codecs, What are they?


Have you ever asked yourself why sometimes aren't you able to watch some video files on your computer? this may be due to the lack of a video codec on your computer.

What is a Video Codec?

A codec is software that is used to compress or decompress a digital media file, such as a song or video. Windows Media Player and other programs use codecs to play and create digital media files.

A codec can consist of two components: an encoder and a decoder. The encoder performs the compression (encoding) function and the decoder performs the decompression (decoding) function. Some codecs include both of these components and some codecs only include one of them.

The goal of all codec designers is to maintain audio and video quality while compressing the binary data further.

Most codecs are LOSSY, in order to get a reasonably small file size. There are LOSSLESS codecs as well, but for most purposes the almost imperceptible increase in quality is not worth the considerable increase in data size. The main exception is if the data will undergo more processing in the future, in which case the repeated lossy encoding would damage the eventual quality too much.

Examples of Lossy file formats: AAC (Advanced Audio Coding), MP3, Vorbis (filename extension .OGG), lossy Windows Media Audio (filename extension .WMA)... Example of Lossless file formats: Apple Lossless (filename extension .m4a), FLAC, Monkey's Audio (filename extension .APE), Shorten, TTA, lossless Windows Media Audio (filename extension .WMA), WavPack.

Why can't i play some videos or music files on my computer?
This might happen if your computer at home doesn't have the required codecs installed.

How do i find a codec?
If you know the name of the codec or its ID (known as a FourCC identifier for video codecs or a WaveFormat identifier for audio codecs), try searching the Internet. You can often go to a codec manufacturer's website to download the most recent version of a codec.

Are codecs and file formats the same?
No, although it can be confusing because they sometimes have the same name. You can think of a file format as a type of container. Inside the container is data that has been compressed by using a particular codec. For example, a file format such asWindows Media Audio contains data that is compressed by using the Windows Media Audio codec. However, a file format such as Audio Video Interleaved (AVI) can contain data that is compressed by any of a number of different codecs, including the MPEG-2, DivX, or XviD codecs. AVI files can also contain data that is not compressed by any codec. Consequently, you might be able to play some AVI files and not others, depending on which codecs were used to compress the file and which codecs you have installed on your computer. For the same reason, you also might be able to play the audio portion of an AVI file, but not the video portion.

Some popular codecs

Below are listed - by name and purpose - some of the most popular audio/speech and video codecs.


- AAC: music with digital rights (DRM)

- music (VoiceAge)

- AIFF: music (Macintosh)

- AU: music (Sun)

- MP3: music (Fraunhofer IIS)

- Ogg Vorbis: music (open source standard)

- RA, RAM: music (RealNetworks streaming)

- WMA: music (Microsoft)


- µ-Law PCM: telephone circuit (U.S.)

- general speech (VoiceAge)

- ACELP.wide: high quality (VoiceAge)

- A-Law PCM: telephone circuit (Europe)

- AMR-NB: GSM, 3GPP (ETSI narrowband)

- AMR-WB: GSM, 3GPP (ETSI wideband)

- DV Audio: MiniDV, audio

- G.711: audio/videoconferencing (ITU)

- G.722: audio/videoconferencing (ITU)

- G.723.1: VoIP, audio/videoconferencing (ITU)

- G.728: audio/videoconferencing (ITU)

- G.729: audio/videoconferencing (ITU)

- GSM 06.10: GSM, cellphone (unknown)


- AVI: movies (Microsoft)

- Cinepak: movies (SuperMac Technologies)

- H.261: videoconferencing (ITU)

- H.263: videoconferencing (ITU)

- H.264: videoconferencing (ITU)

- Indeo: movies (Intel)

- MPEG-1: movies (Moving Pictures Experts Group)

- MPEG-2: movies (Moving Pictures Experts Group)

- MPEG-4: movies (Moving Pictures Experts Group)

- RM, RV: movies and streaming (RealNetworks)

- Sorenson: movies (Sorenson Media)

- WMV: movies and streaming (Microsoft)



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