Bug 50510 - Without tsched=0 for module-udev-detect, sound is distorted
Without tsched=0 for module-udev-detect, sound is distorted
Status: NEW
Product: PulseAudio
Classification: Unclassified
Component: core
x86-64 (AMD64) Linux (All)
: medium normal
Assigned To: pulseaudio-bugs
Depends on:
  Show dependency treegraph
Reported: 2012-05-30 11:48 UTC by Josef Hahn
Modified: 2015-10-15 16:08 UTC (History)
5 users (show)

See Also:
i915 platform:
i915 features:

pacmd list (33.57 KB, text/plain)
2012-05-30 11:52 UTC, Josef Hahn
pulseaudio --log-level=4 (258.92 KB, text/plain)
2012-05-30 11:57 UTC, Josef Hahn

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Description Josef Hahn 2012-05-30 11:48:36 UTC
I've had sound distortions at least with many versions of VLC player for a long time. Although mostly VLC was affected, i think other programs randomly had the same issues. The sound is distorted and has an echo component. Fiddling at the pulseaudio volume control for some seconds fixes this problem until the player opens a new stream.

Adding "tsched=0" to the options for the module-udev-detect module prevents the issue here.
Comment 1 Josef Hahn 2012-05-30 11:52:54 UTC
Created attachment 62297 [details]
pacmd list
Comment 2 Josef Hahn 2012-05-30 11:57:36 UTC
Created attachment 62298 [details]
pulseaudio --log-level=4
Comment 3 Diego Viola 2013-06-07 18:34:09 UTC
I'm having this same issue, without "tsched=0" in "load-module module-udev-detect", Skype gives me very choppy/horrible audio quality.

When I have "load-module module-udev-detect tsched=0" in /etc/pulse/default.pa, audio is crystal clear.

I have experienced this issue only in Skype. VLC and mplayer are giving me great audio quality (all of them are using pulseaudio driver).

My system is archlinux x86_64, pulseaudio 4.0.

Comment 4 Diego Viola 2013-06-07 19:50:50 UTC
Ok so I went to #pulseaudio and asked about this issue there.

heftig has replied to me and gave me some helpful suggestions:

14:46:01     heftig | diegoviola: try starting skype with PULSE_LATENCY_MSEC=30
14:46:35     heftig | (and reenable tsched)

So I did that, removed tsched from load-module module-udev-detect in /etc/pulse/default.pa, restarted pulseaudio, and started skype with PULSE_LATENCY_MSEC=30.

Now sound is good again, and I don't notice any other problems with audio anymore.
Comment 5 Diego Viola 2013-06-07 19:57:40 UTC
Anyway, this seems to be a Skype problem, doesn't it?

I don't get any problems with audio with other applications, VLC, mplayer, amarok, etc.

Anyway, thanks to heftig and all the people who have helped.
Comment 6 Josef Schlehofer 2013-10-19 16:08:22 UTC
It's only skype problem
Comment 7 Lara Maia 2015-01-22 17:55:00 UTC
I have same problem with various random applications. But have strange thing...

If I open pavucontrol window the sound play perfectly. When closed pavucontrol window sound distorted again. WHAT?! 

I try with tsched=0 and this prevents the issue.
Comment 8 Josef Hahn 2015-01-22 21:24:36 UTC
just btw: I never have used or even installed skype. here it was with all kinds of programs. vlc player was affected all the time. it is/was definitely _not_ a skype-only issue.
Comment 9 Nikola Šnele 2015-10-12 12:33:04 UTC
On new haswell i3 laptop and kubuntu 14.04.3, viber is literally unusable (sound distortions doesn't go away). Option tsched=0 fixes distortions. I have had distorted sound in skype and viber on different laptop/desktops for years, so I think there are bugs in pulseaudio's glitch free audio implementation.
Comment 10 Raymond 2015-10-15 16:08:15 UTC
Node 0x02 [Audio Output] wcaps 0x41d: Stereo Amp-Out
  Control: name="Speaker Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Device: name="ALC892 Analog", type="Audio", device=0
  Amp-Out caps: ofs=0x40, nsteps=0x40, stepsize=0x03, mute=0
  Amp-Out vals:  [0x40 0x40]

alc892 has 64 steps with 1 dB per step

it is strange that pulseaudio hardware volume at -1.2dB

ulseaudio] alsa-sink.c: Got hardware volume: 0:  96% 1:  96%
D: [pulseaudio] alsa-sink.c:               in dB: 0: -1.20 dB 1: -1.20 dB