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

[Devin Heitmueller]

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 37b6c10c08..30574c2ebf 100644
--- a/libavfilter/tinterlace.h
+++ b/libavfilter/tinterlace.h
@@ -30,6 +30,7 @@
 #include "libavutil/bswap.h"
 #include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
+#include "libavutil/ccfifo.h"
 #include "drawutils.h"
 #include "avfilter.h"
 
@@ -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 032629279a..226983c645 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");
+
     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;
-- 
2.35.1.655.ga68dfadae5