avcodec/h264dec: Support skipping frames that used gray gap frames

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/h264dec.c

@@ -939,6 +939,12 @@ static int finalize_frame(H264Context *h, AVFrame *dst, H264Picture *out, int *g
          (h->avctx->flags2 & AV_CODEC_FLAG2_SHOW_ALL) ||
          out->recovered)) {
 
+        if (h->skip_gray > 0 &&
+            h->non_gray && out->gray &&
+            !(h->avctx->flags2 & AV_CODEC_FLAG2_SHOW_ALL)
+        )
+            return 0;
+
         if (!h->avctx->hwaccel &&
             (out->field_poc[0] == INT_MAX ||
              out->field_poc[1] == INT_MAX)
@@ -1091,6 +1097,7 @@ static const AVOption h264_options[] = {
     { "nal_length_size", "nal_length_size", OFFSET(nal_length_size), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 4, VDX },
     { "enable_er", "Enable error resilience on damaged frames (unsafe)", OFFSET(enable_er), AV_OPT_TYPE_BOOL, { .i64 = -1 }, -1, 1, VD },
     { "x264_build", "Assume this x264 version if no x264 version found in any SEI", OFFSET(x264_build), AV_OPT_TYPE_INT, {.i64 = -1}, -1, INT_MAX, VD },
+    { "skip_gray", "Do not return gray gap frames", OFFSET(skip_gray), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 1, VD },
     { "noref_gray", "Avoid using gray gap frames as references", OFFSET(noref_gray), AV_OPT_TYPE_INT, {.i64 = 1}, -1, 1, VD },
     { NULL },
 };

libavcodec/h264dec.h

@@ -572,6 +572,7 @@ typedef struct H264Context {
 
     int non_gray;                       ///< Did we encounter a intra frame after a gray gap frame
     int noref_gray;
+    int skip_gray;
 } H264Context;
 
 extern const uint16_t ff_h264_mb_sizes[4];