avformat/av1: support av1C extradata in ff_av1_parse_seq_header()

Fixes dash manifest creation for av1 streams with av1C formatted extradata.

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

libavformat/av1.c

@@ -335,10 +335,43 @@ int ff_av1_parse_seq_header(AV1SequenceParameters *seq, const uint8_t *buf, int
 {
     int64_t obu_size;
     int start_pos, type, temporal_id, spatial_id;
+    int is_av1c;
 
     if (size <= 0)
         return AVERROR_INVALIDDATA;
 
+    is_av1c = !!(buf[0] & 0x80);
+    if (is_av1c) {
+        GetBitContext gb;
+        int ret, version = buf[0] & 0x7F;
+
+        if (version != 1 || size < 4)
+            return AVERROR_INVALIDDATA;
+
+        ret = init_get_bits8(&gb, buf, 4);
+        if (ret < 0)
+            return ret;
+
+        memset(seq, 0, sizeof(*seq));
+
+        skip_bits(&gb, 8);
+        seq->profile    = get_bits(&gb, 3);
+        seq->level      = get_bits(&gb, 5);
+        seq->tier       = get_bits(&gb, 1);
+        seq->bitdepth   = get_bits(&gb, 1) * 2 + 8;
+        seq->bitdepth  += get_bits(&gb, 1) * 2;
+        seq->monochrome               = get_bits(&gb, 1);
+        seq->chroma_subsampling_x     = get_bits(&gb, 1);
+        seq->chroma_subsampling_y     = get_bits(&gb, 1);
+        seq->chroma_sample_position   = get_bits(&gb, 2);
+        seq->color_primaries          = AVCOL_PRI_UNSPECIFIED;
+        seq->transfer_characteristics = AVCOL_TRC_UNSPECIFIED;
+        seq->matrix_coefficients      = AVCOL_SPC_UNSPECIFIED;
+
+        size -= 4;
+        buf  += 4;
+    }
+
     while (size > 0) {
         int len = parse_obu_header(buf, size, &obu_size, &start_pos,
                                    &type, &temporal_id, &spatial_id);
@@ -358,7 +391,7 @@ int ff_av1_parse_seq_header(AV1SequenceParameters *seq, const uint8_t *buf, int
         buf  += len;
     }
 
-    return AVERROR_INVALIDDATA;
+    return is_av1c ? 0 : AVERROR_INVALIDDATA;
 }
 
 int ff_isom_write_av1c(AVIOContext *pb, const uint8_t *buf, int size)