[alsa-devel] VT1708 clicks & pops
forest at alittletooquiet.net
Tue Sep 20 21:05:34 CEST 2011
Thanks for your response.
On Tue, Sep 20, 2011 at 09:22:23AM +0200, Takashi Iwai wrote:
> At Mon, 19 Sep 2011 19:14:13 -0400,
> Forest Bond wrote:
> > 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?
Heh, I guess I'm probably not going to be able to do that very easily.
> > 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.
No, the issue occurs with both driver versions.
> 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.
Using tsched=0 fixes the pops and clicks on the EX15000G. Any idea why I might
see problems on one board but not the other given how similar they are?
The crackling with PCM volume set to 0 persists with tsched=0. It seems
unlikely that this isn't driver or hardware issue. But fixing the pops and
clicks without using tsched=0 is more important to me. If you can provide
suggestions as to where I might start looking, I would be happy to try and come
up with a fix.
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