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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.

  • Try speaker-test with device hw. What is the output of amixer scontents? – CL. Apr 5 '14 at 7:18
  • @CL. Sorry, was out of town for a week for a personal emergency. speaker-test yielded the same result as described in the question (not full channel isolation; rear channels are bleeding through to the front ones). As soon as I can, I will post the output you requested (can't access the system for the next 24 hours). – MaxAxeHax Apr 12 '14 at 18:34

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