I built a small home server recently. It runs Ubuntu Server 12.04 and has a sound card (Via VT1708) with 3 audio jacks - which I want to use as 3 independent stereo outputs to play back (potentially different) audio in different parts of my home. To do this, I am mixing all application audio into a 6-channel stream; this stream has 2 channels of target audio for each location playback should be possible in.
Each jack should then output one of the stereo streams independently of the other channels. Herein lies the problem.
I have managed to play back a 6-channel audio file almost exactly in the desired way. I am using this file (the 5.1/6-channel version) for testing the 'isolation' of every channel. On a different computer, the output worked as expected: when playing back the test file, I'd hear one number exclusively on one of the 6 speakers. I wasn't so lucky on the target machine, though.
Sound is played on speakers connected to all three jacks. However, the sound from the rear left/right channels is also heard on the front left/right channels respectively, although slightly quieter.
I have been trying to go from there, but without any success. I would be thankful for any pointers on how to proceed, what to test, etc.
Some (hopefully) useful console outputs with system details:
$ aplay -l
**** List of PLAYBACK Hardware Devices **** card 0: VT82xx [HDA VIA VT82xx], device 0: VT1708 Analog [VT1708 Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: VT82xx [HDA VIA VT82xx], device 1: VT1708 Digital [VT1708 Digital] Subdevices: 1/1 Subdevice #0: subdevice #0
$ cat /proc/asound/cards
0 [VT82xx ]: HDA-Intel - HDA VIA VT82xx HDA VIA VT82xx at 0xfebfc000 irq 17
$ lsmod | grep snd
snd_hda_codec_via 23198 1 snd_hda_intel 43326 1 snd_hda_codec 169608 2 snd_hda_codec_via,snd_hda_intel snd_hwdep 13276 1 snd_hda_codec snd_pcm 94597 2 snd_hda_intel,snd_hda_codec snd_seq_midi 13132 0 snd_rawmidi 25157 1 snd_seq_midi snd_seq_midi_event 14475 1 snd_seq_midi snd_seq 55716 2 snd_seq_midi,snd_seq_midi_event snd_timer 28930 2 snd_pcm,snd_seq snd_seq_device 14137 3 snd_seq_midi,snd_rawmidi,snd_seq snd 61270 12 snd_hda_codec_via,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_seq_midi,snd_rawmidi,snd_seq,snd_timer,snd_seq_device soundcore 12600 1 snd snd_page_alloc 18398 2 snd_hda_intel,snd_pcm
My ~/.asoundrc is empty.
Please tell me if you need more information.