There are several kinds of video and audio compression formats, also known as codecs. Many of them have been standardized by one of two major organizations.
The ISO/IEC, or International Organization for Standardization and the International Electrotechnical Commission, have a group called the Moving Pictures Experts Group or MPEG. MPEG is responsible, for example, for the familiar compression formats MPEG-1, MPEG-2 and MPEG-4.
The ITU-T standardizes formats for the International Telecommunications Union, a United Nations Organization. Some popular ITU-T compression formats include the H.261 and H.264 formats.
There are other compression formats, such as Intel Indeo and RealVideo (based on the ITU-T H.263 codec). These are just as useful as the ones standardized by the international groups, although some video sharing websites won’t accept them.
It’s important not to get video compression formats mixed up with media container formats.
A media container is a file format that contains data that had been compressed using a video compression format. So the media container is the end product of video compression.
‘Codec’
Codec is a short name for coder-decoder, the software that takes a raw data file and turns it into a compressed file. Because compressed files only contain some of the data found in the original file, the codec is the necessary “translator” that decides what data makes it in to the compressed version and what data gets discarded.
Different codecs translate in different ways, so a video file compressed using the Intel Indeo codec will be different from a file compressed using the Cinepak codec, for example. Sometimes the difference is noticeable, sometimes not, but it’s good to be aware of what codecs are best for what you’re trying to do in order to maintain the best ratio of file size to quality.
Media container formats
A media container format is a format that can contain several types of data, such as audio and video. The video file formats we’re familiar with, such as Quicktime movies (.mov), are media container formats. They contain data that has been compressed using a video compression format or codec.
Some container formats just contain audio, like WAV files for Windows or AIFF files for Macs. Others contain audio and video, such as ASF files for Windows, which contain audio compressed with the WAV codec and video compressed with the WMV codec. Still others are exclusive to still images.
There are dozens of these container formats. If you’re uploading a video to an online sharing site, check to see what formats the site supports. Sometimes this can be confusing because the list of accepted formats may have both compression formats like MPEG-4 and container formats like .mov listed. All this means is the site accepts files compressed with those codecs in those final file formats.
By Gretchen Siegchrist, About.com
