avformat/vpcc: fix VP9 metadata in FLV and RTMP

In order to send VP9 tracks with FLV or RTMP, the enhanced RTMP
specification tells that VPCodecConfigurationRecord, a.k.a. vpcC
ISO-BMFF box, must be inserted into a metadata message. However, the
function responsible for generating vpcCs currently returns invalid
boxes, that are lacking the Version and Flag fields, inherited from
FullBox. For some reason, both flags were being added manually in
movenc. This patch fixes the issue.

Signed-off-by: Alessandro Ros <aler9.dev@gmail.com>
Reviewed-by: Steven Liu <lingjiujianke@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/movenc.c

@@ -1441,10 +1441,7 @@ static int mov_write_vpcc_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
 
     avio_wb32(pb, 0);
     ffio_wfourcc(pb, "vpcC");
-    avio_w8(pb, 1); /* version */
-    avio_wb24(pb, 0); /* flags */
     ff_isom_write_vpcc(s, pb, track->vos_data, track->vos_len, track->par);
-
     return update_size(pb, pos);
 }
 

libavformat/vpcc.c

@@ -208,6 +208,8 @@ int ff_isom_write_vpcc(AVFormatContext *s, AVIOContext *pb,
     if (ret < 0)
         return ret;
 
+    avio_w8(pb, 1); /* version */
+    avio_wb24(pb, 0); /* flags */
     avio_w8(pb, vpcc.profile);
     avio_w8(pb, vpcc.level);
     avio_w8(pb, (vpcc.bitdepth << 4) | (vpcc.chroma_subsampling << 1) | vpcc.full_range_flag);