Today I tried to convert mkv-file and vlc converts video way too quickly (either few secs if selects mpeg4 1080p and ~15 secs if uses any other format) and size is either 82.8 KB or 82.8 MB and vlc can't play either file and media player hc plays starting music of bigger file but nothing else.
Earlier I have converted mkv-files w/o problems.
If I try to convert for example flv-file converting works fine with same options as with failed mkv-convert.