FIX: Upstream Annex-B bitstream conversion fix for some BD mkv iso rips

Upstream ref: https://github.com/FFmpeg/FFmpeg/commit/ad91bf854b559f1afc42fc06f8a7dfbb75def5c8
Merge pull request #5042 from koying/fixbitstream

FIX: Upstream Annex-B bitstream conversion fix for some BD mkv iso rips