[Ffmpeg-devel] [PATCH] GSM-MS decoder and encoder

[Michael Niedermayer]

Hi

On Mon, Feb 19, 2007 at 11:59:14AM +0100, Michel Bardiaux wrote:
> Michael Niedermayer wrote:
> >Hi
> >
> >On Sat, Feb 17, 2007 at 03:42:52PM +0100, Michel Bardiaux wrote:
> >>Michael Niedermayer wrote:
> >>>Hi
> [snip]
> >>>
> >>>is 13000 exactly correct isnt it 13200 for CODEC_ID_GSM?
> >>Yes and no. The last 4 bits of each frame are not actually used, they
> >>come on stage only because we (both libgsm and lavc) use a byte-oriented
> >>API, and files made of bytes. They should be considered as container
> >>overhead in TOAST files, hence not part of the codec bitrate.
> >
> >but with this argumentation we would have to subtract the padding bits from
> >mpeg from the bitrate too and thats something we dont 
> 
> I think you're talking codec-level padding here, but I wrote of 
> container overhead.
> 
> >also it would cause
> >problems for containers which expect the bitrate well to be the bitrate of
> >what they get, not to be slightly less due to some padding bits they dont
> >know about ...
> 
> AFAIK currently only some MS containers (AVI, WAV) accept GSM, and then 
> only MS-GSM, which does not have the problem. The only container for 
> non-MS-GSM is TOAST (currently not implemented) and that one knows about 
> the 4 extra bytes.

well a grep for gsm shows a hit in aiff.c so it seems it is supported in a
non toast format currently and as there is no gsm specific code in it i would
guess it will end with 13200 as bitrate

anyway i wont fight about this appl the patch, i will remove the 13000 check
when it breaks something

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

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle
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