[FFmpeg-devel] [RFC 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.

Signed-off-by: Devin Heitmueller <dheitmueller at ltnglobal.com>
---
 libavfilter/tinterlace.h    |  2 ++
 libavfilter/vf_tinterlace.c | 10 ++++++++++
 2 files changed, 12 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..260386a889 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 */
@@ -390,6 +395,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *picref)
         if (!out)
             return AVERROR(ENOMEM);
         av_frame_copy_props(out, cur);
+        av_ccfifo_inject(tinterlace->cc_fifo, out);
         out->height = outlink->h;
         out->interlaced_frame = 1;
         out->top_field_first = 1;
@@ -423,6 +429,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *picref)
         if (!out)
             return AVERROR(ENOMEM);
         av_frame_copy_props(out, cur);
+        av_ccfifo_inject(tinterlace->cc_fifo, out);
         out->height = outlink->h;
         out->sample_aspect_ratio = av_mul_q(cur->sample_aspect_ratio, av_make_q(2, 1));
 
@@ -459,6 +466,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *picref)
         if (!out)
             return AVERROR(ENOMEM);
         av_frame_copy_props(out, cur);
+        av_ccfifo_inject(tinterlace->cc_fifo, out);
         out->interlaced_frame = 1;
         out->top_field_first = tff;
 
@@ -481,6 +489,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *picref)
         out = av_frame_clone(cur);
         if (!out)
             return AVERROR(ENOMEM);
+        av_ccfifo_inject(tinterlace->cc_fifo, out);
         out->interlaced_frame = 1;
         if (cur->pts != AV_NOPTS_VALUE)
             out->pts = cur->pts*2;
@@ -495,6 +504,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *picref)
         if (!out)
             return AVERROR(ENOMEM);
         av_frame_copy_props(out, next);
+        av_ccfifo_inject(tinterlace->cc_fifo, out);
         out->interlaced_frame = 1;
         out->top_field_first = !tff;
 
-- 
2.35.1.655.ga68dfadae5