no thumbnail display with opus or vorbis with covert art pic in mkv

1/ Put test files into some directory, for example TEST

2/ Open Thunar 4.16.1

3/ View in icons mode this test directory.

4/ notice there are no image thumbnails for files in opus or vorbis coded (ffmpeg encoded), but well with aac

Container: MKV Seems to be OK with webM container.

aacWITH_COVER.mkv opus_WITH_COVER.mkvvorbisWITH_COVER.mkv