[vlc-devel] [PATCH V2 2/4] aout: handle audio filters discontinuity

[Thomas Guillem]

On Fri, Mar 1, 2019, at 12:42, Thomas Guillem wrote:
> In case of a filter discontinuity from aout_filters_t, flush the pipeline and
> return vlc_block_discontinuity.
> ---
>  include/vlc_filter.h       |  8 +++++++-
>  src/audio_output/dec.c     |  3 +++
>  src/audio_output/filters.c | 32 +++++++++++++++++++++++++++++---
>  3 files changed, 39 insertions(+), 4 deletions(-)
> 
> diff --git a/include/vlc_filter.h b/include/vlc_filter.h
> index b2a8f871a4..3e2d8dbe90 100644
> --- a/include/vlc_filter.h
> +++ b/include/vlc_filter.h
> @@ -88,7 +88,13 @@ struct filter_t
>          /** Filter a picture (video filter) */
>          picture_t * (*pf_video_filter)( filter_t *, picture_t * );
>  
> -        /** Filter an audio block (audio filter) */
> +        /**
> +         * Filter an audio block (audio filter)
> +         *
> +         * @return a valid output block, NULL if the module need more data to
> +         * output a block, or vlc_block_discontinuity in case of
> +         * discontinuity/error.
> +         */
>          block_t * (*pf_audio_filter)( filter_t *, block_t * );
>  
>          /** Blend a subpicture onto a picture (blend) */
> diff --git a/src/audio_output/dec.c b/src/audio_output/dec.c
> index 0898487668..462ea534e0 100644
> --- a/src/audio_output/dec.c
> +++ b/src/audio_output/dec.c
> @@ -363,6 +363,8 @@ int aout_DecPlay(audio_output_t *aout, block_t *block)
>      }
>  
>      block = aout_FiltersPlay(owner->filters, block, owner->sync.rate);
> +    if (unlikely(block == vlc_block_discontinuity))
> +        goto lost;
>      if (block == NULL)
>          return ret;
>  
> @@ -380,6 +382,7 @@ int aout_DecPlay(audio_output_t *aout, block_t *block)
>  drop:
>      owner->sync.discontinuity = true;
>      block_Release (block);
> +lost:
>      atomic_fetch_add_explicit(&owner->buffers_lost, 1, memory_order_relaxed);
>      return ret;
>  }
> diff --git a/src/audio_output/filters.c b/src/audio_output/filters.c
> index b62cf93f04..54c6282b62 100644
> --- a/src/audio_output/filters.c
> +++ b/src/audio_output/filters.c
> @@ -271,6 +271,13 @@ error:
>      return -1;
>  }
>  
> +static inline block_t *
> +aout_FiltersOnDiscontinuity(aout_filters_t *filters, block_t *block)
> +{
> +    aout_FiltersFlush(filters);
> +    return block;
> +}
> +
>  /**
>   * Filters an audio buffer through a chain of filters.
>   */
> @@ -285,6 +292,8 @@ static block_t *aout_FiltersPipelinePlay(filter_t 
> *const *filters,
>          /* Please note that p_block->i_nb_samples & i_buffer
>           * shall be set by the filter plug-in. */
>          block = filter->pf_audio_filter (filter, block);
> +        if (unlikely(block == vlc_block_discontinuity))
> +            return block;
>      }
>      return block;
>  }
> @@ -305,11 +314,16 @@ static block_t 
> *aout_FiltersPipelineDrain(filter_t *const *filters,
>          block_t *block = filter_DrainAudio (filter);
>          if (block)
>          {
> +            if (unlikely(block == vlc_block_discontinuity))
> +                return block;
> +
>              /* If there is a drained block, filter it through the 
> following
>               * chain of filters  */
>              if (i + 1 < count)
>                  block = aout_FiltersPipelinePlay (&filters[i + 1],
>                                                    count - i - 1, 
> block);
> +            if (unlikely(block == vlc_block_discontinuity))
> +                return block;
>              if (block)
>                  block_ChainAppend (&chain, block);
>          }
> @@ -699,7 +713,7 @@ block_t *aout_FiltersPlay(aout_filters_t *filters, 
> block_t *block, float rate)
>      }
>  
>      block = aout_FiltersPipelinePlay (filters->tab, filters->count, 
> block);
> -    if (filters->resampler != NULL)
> +    if (filters->resampler != NULL && block != vlc_block_discontinuity)
>      {   /* NOTE: the resampler needs to run even if resampling is 0.
>           * The decoder and output rates can still be different. */
>          filters->resampler->fmt_in.audio.i_rate += filters->resampling;
> @@ -712,6 +726,8 @@ block_t *aout_FiltersPlay(aout_filters_t *filters, 
> block_t *block, float rate)
>          assert (filters->rate_filter != NULL);
>          filters->rate_filter->fmt_in.audio.i_rate = nominal_rate;
>      }
> +    if (unlikely(block == vlc_block_discontinuity))
> +        return aout_FiltersOnDiscontinuity(filters, block);
>      return block;
>  
>  drop:
> @@ -723,6 +739,8 @@ block_t *aout_FiltersDrain (aout_filters_t *filters)
>  {
>      /* Drain the filters pipeline */
>      block_t *block = aout_FiltersPipelineDrain (filters->tab, filters->count);
> +    if (unlikely(block == vlc_block_discontinuity))
> +        return aout_FiltersOnDiscontinuity(filters, block);
>  
>      if (filters->resampler != NULL)
>      {
> @@ -734,17 +752,25 @@ block_t *aout_FiltersDrain (aout_filters_t *filters)
>          {
>              /* Resample the drained block from the filters pipeline */
>              block = aout_FiltersPipelinePlay (&filters->resampler, 1, block);
> +            if (unlikely(block == vlc_block_discontinuity))
> +            {
> +                filters->resampler->fmt_in.audio.i_rate -= filters->resampling;
> +                return aout_FiltersOnDiscontinuity(filters, block);
> +            }
>              if (block)
>                  block_ChainAppend (&chain, block);
>          }
>  
>          /* Drain the resampler filter */
>          block = aout_FiltersPipelineDrain (&filters->resampler, 1);
> +        filters->resampler->fmt_in.audio.i_rate -= filters->resampling;
> +
> +        if (unlikely(block == vlc_block_discontinuity))
> +            return aout_FiltersOnDiscontinuity(filters, block);
> +

I think it's better to return NULL from aout_FiltersDrain in case of discontinuity.

>          if (block)
>              block_ChainAppend (&chain, block);
>  
> -        filters->resampler->fmt_in.audio.i_rate -= filters->resampling;
> -
>          return chain ? block_ChainGather (chain) : NULL;
>      }
>      else
> -- 
> 2.20.1
> 
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