[FFmpeg-devel] [PATCH v2 4/5] tinterlace: Properly preserve CEA-708 closed captions

[Lance Wang]

On Sat, Apr 8, 2023 at 5:04 AM Devin Heitmueller <
devin.heitmueller at ltnglobal.com> wrote:

> Because the interlacing filter halves the effective framerate, we
> need to ensure that no CEA-708 data is lost as frames are merged.
>
> Make use of the new ccfifo mechanism to ensure that caption data
> is properly preserved as frames pass through the filter.
>
> Thanks to Thomas Mundt for review and noticing a couple of
> missed codepaths for injection on output.
>
> Signed-off-by: Devin Heitmueller <dheitmueller at ltnglobal.com>
> ---
>  libavfilter/tinterlace.h    | 2 ++
>  libavfilter/vf_tinterlace.c | 8 ++++++++
>  2 files changed, 10 insertions(+)
>
> diff --git a/libavfilter/tinterlace.h b/libavfilter/tinterlace.h
> index 37b6c10..9f5ce7e 100644
> --- a/libavfilter/tinterlace.h
> +++ b/libavfilter/tinterlace.h
> @@ -32,6 +32,7 @@
>  #include "libavutil/pixdesc.h"
>  #include "drawutils.h"
>  #include "avfilter.h"
> +#include "ccfifo.h"
>
>  #define TINTERLACE_FLAG_VLPF 01
>  #define TINTERLACE_FLAG_CVLPF 2
> @@ -77,6 +78,7 @@ typedef struct TInterlaceContext {
>      const AVPixFmtDescriptor *csp;
>      void (*lowpass_line)(uint8_t *dstp, ptrdiff_t width, const uint8_t
> *srcp,
>                           ptrdiff_t mref, ptrdiff_t pref, int clip_max);
> +    AVCCFifo *cc_fifo;
>  } TInterlaceContext;
>
>  void ff_tinterlace_init_x86(TInterlaceContext *interlace);
> diff --git a/libavfilter/vf_tinterlace.c b/libavfilter/vf_tinterlace.c
> index 0326292..226983c 100644
> --- a/libavfilter/vf_tinterlace.c
> +++ b/libavfilter/vf_tinterlace.c
> @@ -291,6 +291,9 @@ static int config_out_props(AVFilterLink *outlink)
>  #endif
>      }
>
> +    if (!(tinterlace->cc_fifo = av_ccfifo_alloc(&outlink->frame_rate,
> ctx)))
> +        av_log(ctx, AV_LOG_VERBOSE, "Failure to setup CC FIFO queue.
> Captions will be passed through\n");
> +
>

free cc_fifo?


>      av_log(ctx, AV_LOG_VERBOSE, "mode:%d filter:%s h:%d -> h:%d\n",
> tinterlace->mode,
>             (tinterlace->flags & TINTERLACE_FLAG_CVLPF) ? "complex" :
>             (tinterlace->flags & TINTERLACE_FLAG_VLPF) ? "linear" : "off",
> @@ -375,6 +378,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame
> *picref)
>      tinterlace->cur  = tinterlace->next;
>      tinterlace->next = picref;
>
> +    av_ccfifo_extract(tinterlace->cc_fifo, picref);
> +
>      cur = tinterlace->cur;
>      next = tinterlace->next;
>      /* we need at least two frames */
> @@ -451,6 +456,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame
> *picref)
>              if (!out)
>                  return AVERROR(ENOMEM);
>              out->pts /= 2;  // adjust pts to new framerate
> +            av_ccfifo_inject(tinterlace->cc_fifo, out);
>              ret = ff_filter_frame(outlink, out);
>              return ret;
>          }
> @@ -486,6 +492,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame
> *picref)
>              out->pts = cur->pts*2;
>
>          out->pts = av_rescale_q(out->pts, tinterlace->preout_time_base,
> outlink->time_base);
> +        av_ccfifo_inject(tinterlace->cc_fifo, out);
>          if ((ret = ff_filter_frame(outlink, out)) < 0)
>              return ret;
>
> @@ -521,6 +528,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame
> *picref)
>
>      out->pts = av_rescale_q(out->pts, tinterlace->preout_time_base,
> outlink->time_base);
>      out->duration = av_rescale_q(1, av_inv_q(outlink->frame_rate),
> outlink->time_base);
> +    av_ccfifo_inject(tinterlace->cc_fifo, out);
>      ret = ff_filter_frame(outlink, out);
>
>      return ret;
> --
> 1.8.3.1
>
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