I have a strange issue with ALSA since 1.0.27 and VLC : VLC does not downmix 5.1 audio to stereo anymore with recent git pulls.
I have a self compiled VLC git package made in april that works well. Slackware upgraded to 1.0.27 in may and then to 18.104.22.168 in june. Any newer VLC package I create do not apply downmix.
I asked for help on the VLC forums and the VLC developpers told me channel mapping was an addition to alsa-lib 1.0.27 whose support was added to VLC in december 2012.
Basically, my audio (HDA ATI SB) is now claiming that it is a 6 channels chip and so VLC applies a 6-channels setting, even though I only have two speakers. Which means I basically have only two channels being played and thus weird results (disappearing voices, missing sounds, etc.)
I tried to force alsa to downmix by adding the following lines to /etc/asound.conf :
but it didn't solve my problem.
If anybody has a clue, I'm interested.