avcodec/mlp_parser: mark sync frames as key frames

Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/mlp_parser.c

@@ -61,6 +61,8 @@ static int mlp_parse(AVCodecParserContext *s,
     int ret;
     int i, p = 0;
 
+    s->key_frame = 0;
+
     *poutbuf_size = 0;
     if (buf_size == 0)
         return 0;
@@ -136,6 +138,8 @@ static int mlp_parse(AVCodecParserContext *s,
          * access unit header and all the 2- or 4-byte substream headers. */
         // Only check when this isn't a sync frame - syncs have a checksum.
 
+        s->key_frame = 0;
+
         parity_bits = 0;
         for (i = -1; i < mp->num_substreams; i++) {
             parity_bits ^= buf[p++];
@@ -159,6 +163,8 @@ static int mlp_parse(AVCodecParserContext *s,
         if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
             goto lost_sync;
 
+        s->key_frame = 1;
+
         avctx->bits_per_raw_sample = mh.group1_bits;
         if (avctx->bits_per_raw_sample > 16)
             avctx->sample_fmt = AV_SAMPLE_FMT_S32;