[FFmpeg-devel] [PATCH] avcodec: Add bits_per_raw_sample to AVCodecParameters

[wm4]

On Mon, 11 Apr 2016 03:12:20 +0200
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Sun, Apr 10, 2016 at 11:39:57PM +0000, Kieran Kunhya wrote:
> > On Mon, 11 Apr 2016 at 00:33 Michael Niedermayer <michael at niedermayer.cc>
> > wrote:
> >   
> > > The bits_per_raw_sample represents the number of bits of precission per
> > > sample.
> > >
> > > The field is added at the logical place, not at the end as the code was
> > > just
> > > recently added
> > >
> > > This fixes the regression about loosing the audio sample precission
> > > information
> > >
> > > The change in the fate test checksum un-does the change from the merge
> > >
> > > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > > ---
> > >  libavcodec/avcodec.h |   17 +++++++++++++++++
> > >  libavcodec/utils.c   |    2 ++
> > >  tests/ref/lavf/ffm   |    2 +-
> > >  3 files changed, 20 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> > > index b3655c5..87739d7 100644
> > > --- a/libavcodec/avcodec.h
> > > +++ b/libavcodec/avcodec.h
> > > @@ -3832,9 +3832,26 @@ typedef struct AVCodecParameters {
> > >       */
> > >      int64_t bit_rate;
> > >
> > > +    /**
> > > +     * The number of bits per sample in the codedwords.
> > > +     *
> > > +     * This is basically the bitrate per sample
> > > +     *
> > > +     * This could be for example 4 for ADPCM
> > > +     * For PCM formats this matches bits_per_raw_sample
> > > +     * Can be 0
> > > +     */
> > >      int bits_per_coded_sample;
> > >
> > >      /**
> > > +     * The number of bits of precission in the samples.
> > > +     *
> > > +     * For ADPCM this might be 12 or 16 or similar
> > > +     * Can be 0
> > > +     */
> > > +    int bits_per_raw_sample;
> > >
> > >  
> > Precision spelt wrong. Also needs more clarification as to the difference
> > between the two  
> 
> on one side of a bitstream format there is raw pcm data (raw samples)
> and on the other a compressed bitstream (aka coded samples)
> these 2 where intended to specify the number of bits per sample in
> these 2 representations
> 
> i really dont know how to word this so that its clear and everyone
> understands it
> 
> 
> > - I have no idea what the difference is or why one would
> > use bits_per_coded_sample for anything.  
> 
> bits_per_coded_sample is used by several codecs (huffyuv, ima adpcm,
> ...) in avi as a single byte extradata. so it must be transported from
> the demuxer (avi headers) to the decoder and encoder to muxer
> to make this worse, in some of these codecs it matches the
> bits_per_raw_sample, in some it does not

I still don't understand. bits_per_coded_sample is part of the
AVCodecParameters struct. So what's the difference between per_coded
and per_raw?