[Ffmpeg-devel] [PATCH] lpcm 20 and 24 bit support in MPEG PS

Diego Biurrun diego
Mon Oct 16 13:00:56 CEST 2006

Baptiste, patch forgotten?  :)


On Sat, Sep 30, 2006 at 01:49:01PM +0200, Baptiste Coudurier wrote:
> Reimar D?ffinger a ?crit :
> >Hello,
> >On Fri, Sep 29, 2006 at 06:00:04PM +0200, Baptiste Coudurier wrote:
> >>Demuxer is not doing any conversion, it just depack samples correctly.
> >
> >With that argument there is no reason why we should have both big and
> >little endian audio formats either.
> Maybe.
> >>That is a demuxer issue, not a codec one, if demuxer do not depack it
> >>you cannot stream copy,
> >
> >Ok, but why is that so? Does the muxer do packing as well? I also wasn't
> >aware that stream copy does not work with MPlayer for these files.
> Mplayer does the exact decoding treatment as well, but it does not work 
> with mono, and uses a special dvdpcm decoder.
> Stream copy wont work except from PS to PS.
> Yes muxer should pack it, and it muxer's job. Atm Lavf Mpeg PS muxer 
> does not mux 24 bit lpcm.
> >>and there is no reason to put the code in
> >>libavcodec.
> >
> >Well, except that there is lots of similar code there. And that like
> >this you will be doing 20 bit lpcm -> 24 bit PCM -> 16 bit PCM during
> >playback which is a waste of CPU time (and not even such a small one if
> >it was 6 channel 192KHz, 24 bit audio)...
> I agree that it is a waste of cpu time, but it is the correct way to do 
> it. Now it seems the audio API is a bit special.
> Maybe we should start using AVFrame, SampleFormat, and doing conversion 
> only when it is needed. Not only decode_to_16. And finally use 
> Could we go for that for 0.5.0 ?
> >>It looks like PCM_S24DAUD case, which has nothing to do in pcm.c, since
> >>it is 20 bit lpcm.
> >
> >Nobody objected to me placing it there...
> >
> True. I was not following ffmpeg one year ago. Im sorry.

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