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

[wm4]

On Tue, 12 Apr 2016 13:10:09 +0200
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Mon, Apr 11, 2016 at 01:32:07AM +0200, Michael Niedermayer 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(-)  
> 
> new version of this with improved documentation
> I intend to apply this soon if noone is against
> 
> 
> From e500d2222d31368b760144b1e2b5b094f73b571b Mon Sep 17 00:00:00 2001
> From: Michael Niedermayer <michael at niedermayer.cc>
> Date: Mon, 11 Apr 2016 00:52:21 +0200
> Subject: [PATCH] avcodec: Add bits_per_raw_sample to AVCodecParameters
> 
> 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 |   21 +++++++++++++++++++++
>  libavcodec/utils.c   |    2 ++
>  tests/ref/lavf/ffm   |    2 +-
>  3 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index b3655c5..99cbf88 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -3832,9 +3832,30 @@ typedef struct AVCodecParameters {
>       */
>      int64_t bit_rate;
> 
> +    /**
> +     * The number of bits per sample in the codedwords.
> +     *
> +     * This is basically the bitrate per sample, it is mandatory for a bunch of
> +     * formats to actually decode them, its the number of bits for one sample in

"It's". Also, add more full stops instead of creating long sentences.

> +     * the actual coded bitstream.
> +     *
> +     * 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.

Precision. Just get a spellchecker.

> +     *
> +     * These are the bits in a decoded (raw) sample.

Maybe: "This is the number of valid bits in each output sample. If the
sample format has more bits, the least significant bits are additional
padding bits, which are always 0. Use right shifts to reduce the sample
to its actual size. For example, audio formats with 24 bit samples will
have bits_per_raw_sample set to 24, and format set to AV_SAMPLEFMT_S32.
To get the original sample use "(uint32_t)sample >> 8"."

Don't know if this is good. (Also is it even correct? I forgot whether
audio sample data uses negative values too.) Maybe this should be added
to AVCodecContext too. It's a common point of confusion.

> +     *
> +     * For ADPCM this might be 12 or 16 or similar
> +     * Can be 0
> +     */
> +    int bits_per_raw_sample;
> +
> +    /**
>       * Codec-specific bitstream restrictions that the stream conforms to.
>       */
>      int profile;
> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> index c1f8e22..e0edce3 100644
> --- a/libavcodec/utils.c
> +++ b/libavcodec/utils.c
> @@ -3771,6 +3771,7 @@ int avcodec_parameters_from_context(AVCodecParameters *par,
> 
>      par->bit_rate              = codec->bit_rate;
>      par->bits_per_coded_sample = codec->bits_per_coded_sample;
> +    par->bits_per_raw_sample   = codec->bits_per_raw_sample;
>      par->profile               = codec->profile;
>      par->level                 = codec->level;
> 
> @@ -3824,6 +3825,7 @@ int avcodec_parameters_to_context(AVCodecContext *codec,
> 
>      codec->bit_rate              = par->bit_rate;
>      codec->bits_per_coded_sample = par->bits_per_coded_sample;
> +    codec->bits_per_raw_sample   = par->bits_per_raw_sample;
>      codec->profile               = par->profile;
>      codec->level                 = par->level;
> 
> diff --git a/tests/ref/lavf/ffm b/tests/ref/lavf/ffm
> index e45ef08..c4d7e1f 100644
> --- a/tests/ref/lavf/ffm
> +++ b/tests/ref/lavf/ffm
> @@ -1,3 +1,3 @@
> -79674a5219d00e1d2221a29157b35eb4 *./tests/data/lavf/lavf.ffm
> +e63c16b5f0ad5015304fc4009fdb33ca *./tests/data/lavf/lavf.ffm
>  376832 ./tests/data/lavf/lavf.ffm
>  ./tests/data/lavf/lavf.ffm CRC=0x000e23ae
> --
> 1.7.9.5
> 
> [...]