lavf/matroska: Support codec ID V_FFV1 for demuxing.

Fixes ticket #6206.

libavformat/matroska.c

@@ -77,6 +77,7 @@ const CodecTags ff_mkv_codec_tags[]={
     {"S_HDMV/TEXTST"    , AV_CODEC_ID_HDMV_TEXT_SUBTITLE},
 
     {"V_DIRAC"          , AV_CODEC_ID_DIRAC},
+    {"V_FFV1"           , AV_CODEC_ID_FFV1},
     {"V_MJPEG"          , AV_CODEC_ID_MJPEG},
     {"V_MPEG1"          , AV_CODEC_ID_MPEG1VIDEO},
     {"V_MPEG2"          , AV_CODEC_ID_MPEG2VIDEO},

libavformat/matroskaenc.c

@@ -1138,7 +1138,7 @@ static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,
         // if none are found, use AVI codes
         if (par->codec_id != AV_CODEC_ID_RAWVIDEO || par->codec_tag) {
             for (j = 0; ff_mkv_codec_tags[j].id != AV_CODEC_ID_NONE; j++) {
-                if (ff_mkv_codec_tags[j].id == par->codec_id) {
+                if (ff_mkv_codec_tags[j].id == par->codec_id && par->codec_id != AV_CODEC_ID_FFV1) {
                     put_ebml_string(pb, MATROSKA_ID_CODECID, ff_mkv_codec_tags[j].str);
                     native_id = 1;
                     break;