Posted by Neil Smith [MVP Digital Media] on 10/17/07 21:38

On Wed, 17 Oct 2007 19:34:31 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

>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.


I know what it stands for, thankyou. I was trying to frame the
response in a simplified way the confused OP could understand.


>Both the [en]coder and the decoder can take a simple file in some specified format as input,
>and produce some format as output.

Yes, but they expose "interfaces" to do that. You don't pipe content
directly to a codec, you send it via a uniform handler such as a
player or ffmpeg

>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


Yes ? And you're not piping it directly to the "mpeg4 codec" are you -
you're piping the raw data frames to ffmpeg, which encapsulates them
and provides the uniform programmatic hook to the interface which the
codec exposes.


>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,

FFMPEG is *not* a codec of itself :
http://en.wikipedia.org/wiki/FFmpeg

"FFmpeg is a collection of software libraries that can record, convert
and stream digital audio and video in numerous formats. It includes
libavcodec, an audio/video codec library used by several other
projects, and libavformat, an audio/video container mux and demux
library"

Codec Library, FFMPEG is not "the 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.

OK we're agreed on that part ;-)

Cheers - Neil
------------------------------------------------
Digital Media MVP : 2004-2007
http://mvp.support.microsoft.com/mvpfaqs

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