[BUG] Frequent distortion in sound output

OSS specific Linux discussion (x86/amd64)

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[BUG] Frequent distortion in sound output

Postby fictive » Wed Apr 06, 2011 11:12 am

Distribution: Archlinux 64bit
Motherboard: ASUS P8P67-Pro
Using external (PCI-attached) audio card (SB Live 5.1), because no drivers exist for the motherboard's built-it sound card.

  • The distortion can be clearly heard from the speakers. Front and rear channels exhibit the same symptom.
  • It is only audible during playback
  • It occurs randomly but very often and is audible until audio is stopped.
  • Workaround so far has been to stop and start the software playing the audio a few times.
  • Restarting OSS itself doesn't make any difference.
  • Nibbling with audio settings doesn't make any difference.
Attachments
sysinfo.txt
Command output for 'ossinfo' and 'uname -a'
(1.62 KiB) Downloaded 552 times
sound_samples.zip
Distorted and Undistorted sound samples
(434.22 KiB) Downloaded 553 times
fictive
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Re: [BUG] Frequent distortion in sound output

Postby cesium » Wed Apr 06, 2011 7:56 pm

What happens if you disable vmix? ('vmix_disabled=1' in /usr/lib/oss/osscore.conf, or maybe just set vmix0-enable to OFF in the mixer). Btw, what's wrong with the internal audio?
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Re: [BUG] Frequent distortion in sound output

Postby fictive » Wed Apr 06, 2011 8:58 pm

cesium wrote:What happens if you disable vmix? ('vmix_disabled=1' in /usr/lib/oss/osscore.conf, or maybe just set vmix0-enable to OFF in the mixer).

Disabling the vmix in the config file makes the distortion go away, but audio can only be played in one application at a time after that change. Oddly, disabling the vmix on the mixer does nothing.

cesium wrote:Edit /usr/lib/oss/build/osscore.c and change line 811 to have a '<=' memlimit comparison. Run 'sudo sh install.sh' in the same directory and restart OSS. I don't think it would help here, but I recall it did help someone with a similar issue (which had audigy).

Relinking succeeded and OSS restarted, but the distortions are still present.

cesium wrote:Btw, what's wrong with the internal audio?

Internal audio card just doesn't show up on the ossxmix. It is "Realtek® ALC892 8-Channel Audio CODEC", currently turned OFF from bios.
fictive
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Re: [BUG] Frequent distortion in sound output

Postby cesium » Thu Apr 07, 2011 9:17 pm

Hmm... You can try attaching it manually (disable it and then 'sudo vmixctl attach -M /dev/dsp /dev/dsp_in') and see if that helps. And idea: rebuild OSS from source, providing --config-vmix=FIXEDPOINT argument to configure and test with that.
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Re: [BUG] Frequent distortion in sound output

Postby fictive » Sat Apr 09, 2011 7:58 am

cesium wrote:Hmm... You can try attaching it manually (disable it and then 'sudo vmixctl attach -M /dev/dsp /dev/dsp_in') and see if that helps.

VMIX disabled in osscore.conf. vmixctl with the parameters you gave outputs "/dev/dsp: Device or resource busy"

cesium wrote:And idea: rebuild OSS from source, providing --config-vmix=FIXEDPOINT argument to configure and test with that.

No noticeable change. Distortions still occur.
fictive
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Re: [BUG] Frequent distortion in sound output

Postby cesium » Sun Apr 10, 2011 9:30 am

The /dev/dsp message is because something is using the card. You can check this via "fuser /dev/dsp". Kill it, and try vmixctl again.
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Re: [BUG] Frequent distortion in sound output

Postby fictive » Sun Apr 10, 2011 11:04 am

cesium wrote:The /dev/dsp message is because something is using the card. You can check this via "fuser /dev/dsp". Kill it, and try vmixctl again.

Already checked. The device node is not open by any program and no program has oss libraries loaded.

Code: Select all
$ fuser /dev/dsp
$ fuser /dev/dsp_in
$ lsof -n | grep -i oss
$ lsmod | head -n 3
Module                  Size  Used by
oss_sblive             87994  0
osscore               551852  1 oss_sblive

lsmod also shows that 'osscore' is used only by 'oss_sbline' and 'oss_sblive' is not used by anyone.
fictive
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Re: [BUG] Frequent distortion in sound output

Postby cesium » Tue Apr 12, 2011 2:47 pm

Hmm.. Try 'sudo vmixctl attach -r -M /dev/oss/oss_sblive0/pcm0'
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Re: [BUG] Frequent distortion in sound output

Postby fictive » Tue Apr 12, 2011 8:55 pm

Code: Select all
$ vmixctl attach -r -M /dev/oss/oss_sblive0/pcm0
VMIXCTL_ATTACH: Input/output error

The device referenced exists and is not a symlink.
*Sigh*
fictive
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Re: [BUG] Frequent distortion in sound output

Postby cesium » Tue Apr 12, 2011 9:02 pm

You need root privileges for this, which is why I placed 'sudo'... (The '$' prompt suggest you're doing this as a normal user)
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Re: [BUG] Frequent distortion in sound output

Postby fictive » Wed Apr 13, 2011 6:22 pm

Yes, it was run as root (su -). I have tweaked my PS1 environment variable.
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Re: [BUG] Frequent distortion in sound output

Postby cesium » Fri Apr 15, 2011 6:39 pm

Hmm.. are you sure you disabled vmix before this? You can check this in 'ossinfo -v2' printout...
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Re: [BUG] Frequent distortion in sound output

Postby fictive » Sat Apr 16, 2011 6:39 pm

cesium wrote:Hmm.. are you sure you disabled vmix before this? You can check this in 'ossinfo -v2' printout...

Code: Select all
$ grep -i vmix_disabled /usr/lib/oss/conf/osscore.conf
vmix_disabled=1


Code: Select all
$ ossinfo -v2

Output can be found in the attachment. Only one application can output sound at once but seems the 'Related mixer dev' references 'Mixer device 0'. I haven't a clue how to verify that my mixer is disabled.

fictive wrote:Disabling the vmix in the config file makes the distortion go away, but audio can only be played in one application at a time after that change. Oddly, disabling the vmix on the mixer does nothing.

At first I thought the distortions went away. Now that I have used my computer for quite some time with "vmix_disabled=1", I have witnessed the distortions a few times. They still exists :(
Attachments
ossinfo_-v2.txt
'ossinfo -v2' command output
(4.33 KiB) Downloaded 568 times
fictive
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Re: [BUG] Frequent distortion in sound output

Postby fictive » Thu Apr 21, 2011 3:07 pm

Thanks for the help. Problem fixed. I bought a new sound card.
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