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Posted by Jan Panteltje on 10/17/07 19:34
On a sunny day (Wed, 17 Oct 2007 18:40:25 GMT) it happened "Neil Smith [MVP
Digital Media]" <neil@nospam.com> wrote in
<d8mch3t026sp8lkjsacnhrs8m8egcu19ji@4ax.com>:
>On Wed, 17 Oct 2007 04:49:32 -0700, "ÑÏÍû" <bobby_yan@msn.com> wrote:
>
>>If there's any, please list some. Thx.
>
>
>Your question doesn't make sense.
>
>A codec is a small portion of program code designed to encode or
>decode specific video formats. A codec in isolation is no use, it has
>to be combined with a player or encoding application.
Thisis not correct.
A 'codec' is short for [en]coder-decoder.
Both the [en]coder and the decoder can take a simple file in some specified format as input,
and produce some format as output.
For example, ffmpeg, that I mentioned, will so something like this:
cat mymovie.yuv | ffmpeg -f yuv4mpegpipe -i - -f avi -vcodec mpeg4 -b 800 -g 300 -bf 2 -y mymovie.avi
In this example a mjpegtools yuv format file is encoded to mpeg4 avi file.
mplayer is, among other things, based on ffmpeg btw.
But ffmpeg has its own player too: ffplay.
xine is also based of ffmpeg.
So, an encoder accepts some input format, and encodes to some specified outputformat.
Some codecs accept more then one input format and support more then one output formats (as does ffmpeg).
Your player 'mplayer' simply sends the stream in the specified format to the decoder part of the ffmpeg codec,
that decoder part then provides YUV that is converted to RGB for or by the display driver.
In the above example 'avi' is the container, and 'mpeg4' the format of the steam in it.
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