GNOME Bugzilla – Bug 623303
video with 5.1 audio isn't downmixed
Last modified: 2010-07-01 17:12:33 UTC
Using alsasink and try to play http://trailers.apple.com/movies/paramount/ironman2/ironman2-z7r459g-tlr1_480p.mov I don't hear the voices, only the music.
As suggested by Tim, setting playbin2 audio-sink to audio-sink="capsfilter caps=audio/x-raw-int,channels=2 ! alsasink" fixes the issue... So maybe something went wrong in my ALSA setup, not sure.
Yes, that's most likely an issue with your alsa or pulseaudio setup, especially if downmixing by GStreamer works (which means that otherwise you get the 5.1 channels directly passed to your soundcard).