Binary package hint: pulseaudio
I have 32-bit Ubuntu 11.04, and Asus P5B Deluxe MB with onboard audio (Intel Corporation 82801H (ICH8 Family) HD Audio Controller rev 02). A few days ago, I bought 5.1 sound system, and after enabling 5.1 setup in preferences, I noticed something weird about sound. After a few hours of fiddling with various controls and googling, here is what I found:
1. Changing Balance, Fade or Subwoofer settings in Sound Preferences/Output makes very heavy distortion of sound from any program (any audio player, mplayer, vlc,...). The distortion is present on all speakers on 5.1 system, and on headphone output on MB also.
2. Changing volume (sound indicator) makes slight metallic distortion (all outputs).
3. Changing sound setup back to Analog Stereo Output makes sound OK again (but, then, 5.1 system isn't working as it is supposed to do).
4. Starting alsamixer and just changing the PCM slider makes sound OK. Also, I had to turn all other sliders except Master to 0db to get good sound (when using sound indicator, it changes Master and PCM settings in alsamixer).
alsamixer makes everything OK, but it is not the way I want to change the volume (I'm used to MM keys for that). Is there a way to make system sound volume to affect alsa's Master control only? This would solve my problem till better solution is found. I tried to restart pulseaudio with PULSE_NO_SIMD=1 (as advised in one bug report), but that didn't solve the problem. Tried to load module-x11-xsmp also (another advice), but also not working.
I suppose that this bug is a duplicate of some other, but I didn't know which one. I saw similar bugs, but none for natty (maybe I didn't search enough).
I must say that I was pleasantly surprised how audio subsystem recognised 5.1 setup and if only wasn't for this distortion, it would be perfect 'plug and play'.
As I was unable to resolve this in a better way, I made a script that resets the PCM volume to 100% every 3 seconds:
#!/bin/bash
#reset PCM volume to 100% (and remove distortion)
while [ 1 ]; do
amixer sset PCM 100%
sleep 3s
done
I put it in a Startup Applications, so I don't forget to start it after login. Now I can use standard controls for volume up/down, and the sound is distorted only for a short time. But, I hope that better solution could be found.