[Cin] May be I fixed vorbis for webm/mkv with ffmpeg 7/6

[Andrea paz]

I don't remember the Vorbis problem very well. I ran renders of:
Ogg/Vorbis; ffmpeg/Ogg (vorbis); ffmpeg/Ogg (flac); ffmpeg/webm
(vorbis); ffmpeg/mkv (vorbis) and ffmpeg/mkv (flac). In all cases the
sound was clean and correct.