Order of the Bath

The way Audio Visual playback works on a PC is that your player software of choice looks at that the file and decides what format it is from a 4 character code in the headers. This will tell it what codecs are required (they are separate for video and audio). It will then read the data from the file and pass it to the relevant codec. This will decode and expand the data stream and pass it back to the player software for display. The decoder parts of the codec have standard algorithms so, assuming they have been coded correctly, it doesn’t matter which one you use.

The best known codecs types are

MPEG-1—used on Video CDs.
MPEG-2—used on DVD and SVCD.
MPEG-4—used on HD-DVD and Blu-ray.
Sorenson3—used by Apple QuickTime videos.
WMV—Windows Media Video sponsored by Microsoft.
Realvideo—now used mostly for streaming video.

but there are subdivisions such as mp42 and mpg4 which are both MPEG-4 codecs.

The best known audio codecs are

mp3—the generic and (probably) public domain codec.
WMA—Windows Media Audio which compliments the Microsoft video codec.

Some codecs do other things like the splitter which separate the audio from the video content. There are also surround sound decoders, subtitle extractors, language separators for multilingual files, chroma-key generators and digital signal processors for sound and picture manipulation. Even Audio and Video hardware drivers are considered as codecs by some applications.

Codecs come as installable packages, often in bundles, and are stored in C:\WINDOWS\system32 as .dll or .drv files.

How to find out what you need

AVI Codec Analyser tells you what you have installed and what you need to play any particular file but I can’t relate the two and it doesn’t seem to recognise QuickTime at all.

GSpot is popular doesn’t seem to recognise many for me.

MediaInfo gives similar information in a much more readable format (with many options) and supports QuickTime.

Finding missing codecs

If you find you need a missing codec, the best way is to search for them by name. Many will be found in the K-Lite package from codecguide.com

This entry was posted on 2 Aug 2007 at 08:52 by Rick and is filed under ChurchTech, Technical, Windows. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.