[alsa-devel] VT1708 clicks & pops

Takashi Iwai tiwai at suse.de
Tue Sep 20 09:22:23 CEST 2011

At Mon, 19 Sep 2011 19:14:13 -0400,
Forest Bond wrote:
> Hi,
> On Fri, Sep 16, 2011 at 04:36:01PM -0400, Forest Bond wrote:
> > I have two boards with a VT1708:
> > 
> > * VIA EPIA EX15000G
> > * VIA VB8002
> > 
> > I'm using VLC to play audio via PulseAudio to the analog outputs.  The VB8002
> > sounds great, but the EX15000G has random pops and clicks in the output.  Both
> > machines are running exactly the same configuration (they are using the same
> > pre-built OS image).
> Maybe this issue would be more approachable if I could produce it without
> PulseAudio involved?


> Incidentally, these boards both produce a crackling/static sound when PulseAudio
> is playing and the PCM mixer is turned all the way down.  I have seen scattered
> reports of this in various bug trackers.  The problem does not occur when
> playing via alsa directly.  One thing I have noticed is that the crackling noise
> follows the rhythm of the music being played.  It actually sounds like the music
> has been heavily distorted (i.e. via extreme digital clipping) and then
> attenuated significantly.
> It seems likely that there are driver issues that PulseAudio is exposing.  What
> can I do to track them down?

Is the problem related with the driver version?  You mentioned the
difference of drivers installed on your systems.
If it's a regression of the driver, it'd be easier to figure out.

Other than that, I'd try to adjust PA, e.g. try tsched=0.  Usually
this kind of problem is because of inaccurate playback position
reporting from the hardware.  PA relies (too much) on the playback
position as default.


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