The player's default track selection picks the first probed audio
track, but the substream the disc's current PGC actually plays is
decided by the DVD VM and may be a different one. On discs whose menu
domain plays LPCM while the mux also carries an (unreferenced) AC3
substream, mpv selected the AC3 track, which has no data. We have to
keep track of what VM wants to output and what LAVF expects.
Kacper Michajłow
4109805d0c