[Ffmpeg-devel] [PATCH] THP PCM decoder (GSoC Qualification)

[Michael Niedermayer]

Hi

On Tue, Apr 03, 2007 at 08:59:31PM +0200, Marco Gerards wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> 
> > Hi
> >
> > On Tue, Apr 03, 2007 at 03:21:56PM +0200, Marco Gerards wrote:
> > [...]
> >> In this new patch there are still two issues.  For some reason the
> >> quality of the sound was not that good.  It wasn't as bad as someone
> >> reported, for example he said that there were issues with mono sound.
> >> I can not reproduce this.
> >> 
> >> The problem is in stereo sound.  I have disabled stereo in this patch
> >> and the sound is just fine now.  To be honest, I am not sure what the
> >> problem is.  I have tried all kinds of things without much success.
> >> Perhaps it is better to commit this first.  After that I can fix this
> >> with another patch.
> >
> > hmm did you properly interleave right and left channel samples? that is
> > does it work if you decode just the other channel?
> > could it be that the encoding is R+L,R-L ? instead of R,L
> 
> I tried about anything.  This is the first time I am working with
> audio, so I perhaps made a silly mistake.
> 
> What I tried was interleaving the data send to the output buffer.  The
> PCM data in the THP files is stored in packets.  First x samples for
> the first channel are stored, after that x samples for the second
> channel.
> 
> When I decode the other channel it seems to work as well.  So I assume
> the problem is in how I fill the output buffer and how I tell ffmpeg
> the format (stereo, interleaved samples) of this data.  How does one
> in general deal with stereo from a decoder?

stereo in ffmpeg is always
channel0-sample0, channel1-sample0, channel0-sample1, channel1-sample1, channel0-sample2, channel1-sample2, ...


> 
> [...]
> 
> >> Index: libavcodec/allcodecs.c
> >> ===================================================================
> >> --- libavcodec/allcodecs.c	(revision 8605)
> >> +++ libavcodec/allcodecs.c	(working copy)
> >> @@ -242,6 +242,7 @@
> >>      REGISTER_ENCDEC (ADPCM_SBPRO_3, adpcm_sbpro_3);
> >>      REGISTER_ENCDEC (ADPCM_SBPRO_4, adpcm_sbpro_4);
> >>      REGISTER_ENCDEC (ADPCM_SWF, adpcm_swf);
> >> +    REGISTER_ENCDEC (ADPCM_THP, adpcm_thp);
> >
> > ENCDEC ?
> 
> 
> Baptiste said "use CODEC and dummy return -1 to stay in conformance
> with others (see IMA_QT)".  I assumed it also applied to allcodecs.c.
> Should I change this to REGISTER_DECODER?

yes and flame baptiste ;)


>
> >>      REGISTER_ENCDEC (ADPCM_XA, adpcm_xa);
> >>      REGISTER_ENCDEC (ADPCM_YAMAHA, adpcm_yamaha);
> >>  
> >> Index: libavcodec/Makefile
> >> ===================================================================
> >> --- libavcodec/Makefile	(revision 8605)
> >> +++ libavcodec/Makefile	(working copy)
> >> @@ -246,6 +246,8 @@
> >>  OBJS-$(CONFIG_ADPCM_SBPRO_4_ENCODER)   += adpcm.o
> >>  OBJS-$(CONFIG_ADPCM_SWF_DECODER)       += adpcm.o
> >>  OBJS-$(CONFIG_ADPCM_SWF_ENCODER)       += adpcm.o
> >> +OBJS-$(CONFIG_ADPCM_THP_DECODER)       += adpcm.o
> >> +OBJS-$(CONFIG_ADPCM_THP_ENCODER)       += adpcm.o
> >>  OBJS-$(CONFIG_ADPCM_XA_DECODER)        += adpcm.o
> >
> > unless you write an ADPCM_THP encoder there shouldnt be
> > a CONFIG_ADPCM_THP_ENCODER ...
> 
> Same as above.  Should I remove this?

yes


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

I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates
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