libavcodec/h264_parser.c: treat an I frame as rap if SPS&PPS proceeds it

Hopefully, this should fix AkarinVS/L-SMASH-Works#24. Signed-off-by: akarin <i@akarin.info>
AkarinVS · Dec 14, 2022 · 96da5fb · 96da5fb
1 parent 587bde3
commit 96da5fb
Showing 1 changed file with 9 additions and 1 deletion.
diff --git a/libavcodec/h264_parser.c b/libavcodec/h264_parser.c
@@ -255,6 +255,8 @@ static inline int parse_nal_units(AVCodecParserContext *s,
     int field_poc[2];
     int ret;
 
+    int has_sps = 0, has_pps = 0;
+
     /* set some sane default values */
     s->pict_type         = AV_PICTURE_TYPE_I;
     s->key_frame         = 0;
@@ -322,9 +324,11 @@ static inline int parse_nal_units(AVCodecParserContext *s,
 
         switch (nal.type) {
         case H264_NAL_SPS:
+            has_sps = 1;
             ff_h264_decode_seq_parameter_set(&nal.gb, avctx, &p->ps, 0);
             break;
         case H264_NAL_PPS:
+            has_pps = 1;
             ff_h264_decode_picture_parameter_set(&nal.gb, avctx, &p->ps,
                                                  nal.size_bits);
             break;
@@ -346,7 +350,11 @@ static inline int parse_nal_units(AVCodecParserContext *s,
             if (p->sei.recovery_point.recovery_frame_cnt >= 0) {
                 /* key frame, since recovery_frame_cnt is set */
                 /* Some incorrectly encoded m2ts contains SEI recovery point labeled non-IDR I-slices */
-                if (s->key_frame) s->key_frame = 2;
+                if (s->key_frame ||
+                    /* Unfortunately, not all streams use H264_NAL_IDR_SLICE, so instead we also see
+                       if SPS&PPS are present before the I slice. */
+                    (s->pict_type == AV_PICTURE_TYPE_I && has_sps && has_pps))
+                    s->key_frame = 2;
             }
             pps_id = get_ue_golomb(&nal.gb);
             if (pps_id >= MAX_PPS_COUNT) {