[FFmpeg-devel] [PATCH] Add af_resample - sample fmt and channel layout conversion filter

[Michael Niedermayer]

On Sun, Sep 12, 2010 at 02:50:00PM -0700, S.N. Hemanth Meenakshisundaram wrote:
> 
> Now modified af_resample to wrap the channel mix functions in
> lavc/resample.c the way Stefano wanted - exposing the channel mix
> routines as ff_* functions.
> 
> With this af_resample has no duplicate code, calls lavc routines for
> both sample format conversion and channel mixing.
> 
> This patch contains the extra resample_internal.h header and
> audioconvert functions required to represent the channel conversion
> required as a number.
> 
> The patch isn't well split now, but once any changes required to this
> are done, I will split it properly. Please review and comment.
> 
> af_resample is required for ffmpeg.c integration and many other lavfi
> audio filters to work.
> 
> Regards,
> 
> ---
>  libavcodec/audioconvert.c      |   17 ++
>  libavcodec/audioconvert.h      |   10 +
>  libavcodec/resample.c          |   21 ++-
>  libavcodec/resample_internal.h |   36 ++++
>  libavfilter/Makefile           |    1 +
>  libavfilter/af_resample.c      |  378 ++++++++++++++++++++++++++++++++++++++++
>  libavfilter/allfilters.c       |    1 +
>  7 files changed, 454 insertions(+), 10 deletions(-)
>  create mode 100644 libavcodec/resample_internal.h
>  create mode 100644 libavfilter/af_resample.c
> 
> 
> 

>  libavcodec/audioconvert.c      |   17 +
>  libavcodec/audioconvert.h      |   10 +
>  libavcodec/resample.c          |   21 +-
>  libavcodec/resample_internal.h |   36 +++
>  libavfilter/Makefile           |    1 
>  libavfilter/af_resample.c      |  378 +++++++++++++++++++++++++++++++++++++++++
>  libavfilter/allfilters.c       |    1 
>  7 files changed, 454 insertions(+), 10 deletions(-)
> 331672e66f98cef708612cf26bbc18562a188c7f  0001-Add-af_resample-sample-fmt-and-channel-layout-conver.patch
> diff --git a/libavcodec/audioconvert.c b/libavcodec/audioconvert.c
> index c6dc1b1..17fa19a 100644
> --- a/libavcodec/audioconvert.c
> +++ b/libavcodec/audioconvert.c
> @@ -121,6 +121,11 @@ static const struct {
>      { 0 }
>  };
>  
> +int avcodec_get_num_channel_layouts(void)
> +{
> +    return (sizeof(channel_layout_map)/sizeof(channel_layout_map[0]));
> +}

the number is something close to 2^channels


> +
>  int64_t avcodec_get_channel_layout(const char *name)
>  {
>      int i = 0;
> @@ -162,6 +167,18 @@ void avcodec_get_channel_layout_string(char *buf, int buf_size, int nb_channels,
>      }
>  }
>  
> +int avcodec_get_channel_layout_index(int64_t channel_layout)
> +{
> +    int i = 1;
> +    do {
> +        if (channel_layout_map[i].layout == channel_layout)
> +            return i;
> +        i++;
> +    } while (channel_layout_map[i].name);
> +
> +    return 0;
> +}

there are more layouts besides neither of these functions belong to public api


[...]
> @@ -53,7 +54,7 @@ struct ReSampleContext {
>  };
>  
>  /* n1: number of samples */
> -static void stereo_to_mono(short *output, short *input, int n1)
> +void ff_stereo_to_mono(short *output, short *input, int n1)
>  {
>      short *p, *q;
>      int n = n1;

the functions belong to libavfilter
what is the plan to move them there?
maybe iam missing something but these added dependancies dont seem to make
that easier


[...]
> +static void filter_samples(AVFilterLink *link, AVFilterBufferRef *samplesref)
> +{
> +    ResampleContext *resample = link->dst->priv;
> +    AVFilterLink *outlink = link->dst->outputs[0];
> +    short samples_nb_changed = 0;
> +
> +   /**
> +    * If input data of this buffer differs from the earlier buffer/s, set flag
> +    * to reconfigure the channel and sample format conversions.
> +    */
> +
> +    samples_nb_changed = (samplesref->audio->samples_nb != resample->in_samples_nb);
> +    resample->in_samples_nb = samplesref->audio->samples_nb;
> +    resample->reconfig_sample_fmt = (samplesref->format != resample->in_sample_fmt) || samples_nb_changed;
> +    resample->in_sample_fmt = samplesref->format;
> +    resample->reconfig_channel_layout = (samplesref->audio->channel_layout != resample->in_channel_layout) || samples_nb_changed;
> +    resample->in_channel_layout = samplesref->audio->channel_layout;
> +
> +    /* Convert to s16 sample format first, then to desired channel layout  and finally to desired sample format */

we need a float path at some point

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

No human being will ever know the Truth, for even if they happen to say it
by chance, they would not even known they had done so. -- Xenophanes
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