[FFmpeg-devel] MPEG Audio encoding

[Michael Niedermayer]

On Fri, Jan 25, 2008 at 10:51:13AM +0100, John Sigler wrote:
> [ This message was originally posted to ffmpeg-user ]

you want to send a patch? if not its the wrong list ...


> 
> Hello,
> 
> I have a few questions concerning the MPEG Audio encoder in ffmpeg.
> ( mpegaudioenc.c )
> 
> (I've been reading the corresponding Wikipedia articles.)
> http://en.wikipedia.org/wiki/MPEG-1_Audio_Layer_I
> http://en.wikipedia.org/wiki/MPEG-1_Audio_Layer_II
> 
> AFAICT mpegaudioenc.c implements MPEG-2 Layer II (i.e. MP2).
> 
> Is there support for MPEG Audio Layer I in libavcodec?

why do you want "mp1" ?


[...]
> On a related subject, the Wikipedia article states:
> 
> The format is based on successive digital frames of 1152 sampling
> intervals with four possible formats:
> 
>      * mono format
>      * stereo format
>      * joint stereo format (stereo irrelevance)
>      * dual channel (uncorrelated) format
> 
> http://en.wikipedia.org/wiki/Joint_stereo
> 
> And mpegaudio.h defines
> 
> #define MPA_STEREO  0
> #define MPA_JSTEREO 1
> #define MPA_DUAL    2
> #define MPA_MONO    3
> 
> But joint stereo and dual mono do not seem (??) to be supported by
> the encoder. Is that correct?

could be, if so send a patch implementing them!


> 
> Were joint stereo and dual mono actually defined for Layer II,
> or did they only show up later in Layer III?

greping the draft ...
"Joint Stereo coding can be added as an additional feature to any of the
layers."

I suggest you read it yourself next time instead of asking. You will
have to read it anyway to implement it and send a patch.


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you really think that XML is the answer, then you definitly missunderstood
the question -- Attila Kinali
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