[alsa-devel] VT1708 clicks & pops

Fri Sep 30 04:04:23 CEST 2011

Hi Takashi,

On Wed, Sep 28, 2011 at 05:12:24PM -0400, Forest Bond wrote:
> On Wed, Sep 28, 2011 at 07:33:49AM +0200, Takashi Iwai wrote:
> > At Tue, 27 Sep 2011 17:45:32 -0400, Forest Bond wrote:
> > > On Tue, Sep 27, 2011 at 02:57:16PM +0200, Takashi Iwai wrote:
> > > > At Wed, 21 Sep 2011 13:55:53 -0400, Forest Bond wrote:
> > > > > On Wed, Sep 21, 2011 at 04:43:15PM +0200, Takashi Iwai wrote:
> > > > > > At Wed, 21 Sep 2011 10:35:10 -0400, Forest Bond wrote:
> > > > > > > On Wed, Sep 21, 2011 at 10:39:44AM +0200, Takashi Iwai wrote:
> > > > > > > > At Tue, 20 Sep 2011 15:05:34 -0400, Forest Bond wrote:
> > > > > > > > > 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).
> > > > > > > > > The crackling with PCM volume set to 0 persists with tsched=0.
> > > > > 
> > > > > [...]
> > > > > 
> > > > > > > > Hrm, which PA version are you using?  I remember vaguely a buggy PA
> > > > > > > > SIMD operations in some old PA versions.
> > > > > > > 
> > > > > > > 1:0.9.22+stable-queue-24-g67d18-0ubuntu3 from Ubuntu Lucid.
> > > > > > > 
> > > > > > > > Also, when you mute the mixer (nor the PA's mixer), e.g. via
> > > > > > > > "alsamixer -c0", the noise goes away, right?
> > > > > > > 
> > > > > > > I do not use the PA mixer.  The noise is present with ALSA's PCM control set to
> > > > > > > zero (-51dB).  If I move the PCM control up one tick (to -50.8dB) the noise goes
> > > > > > > away.
> > > > > > 
> > > > > > OK, then it's an issue in the sound driver.
> > > > > > Could you give alsa-info.sh outputs both mute-with-noise and without
> > > > > > noise for comparison?
> > > > > 
> > > > > I guess we can ignore this one for now.  I do not have this problem using a
> > > > > recent alsa-driver snapshot.  The PCM control does not go below -40.25dB with
> > > > > this version.  It's possible the new driver simply doesn't allow the control to
> > > > > be set to a problematic value.
> > > > > 
> > > > > I will note, however, that the master control with the snapshot has a minimum
> > > > > value of 0dB and a maximum of 6.75dB,
> > > > 
> > > > That's odd.
> > > > 
> > > > > and that the audio is barely audible at
> > > > > 0dB.  I have to crank the master control all the way up to get the same volume
> > > > > as the old driver set to 0dB.  Maybe I can come up with a fix for this.
> > > > 
> > > > For debugging, I'd need anyway the alsa-info.sh output from the latest
> > > > alsa-driver snapshot.
> > > 
> > > Okay, here you go:
> > > 
> > >   http://www.alsa-project.org/db/?f=8f3da35bd1b615d199f8e71df8b012fbdf5ff690
> > 
> > This is the working device, right?
> 
> No, this is the one with PA issues and the mixer levels issue I mentioned above.
> I haven't tested the snapshot driver on the working board, so I don't know if it
> is also effected by the mixer levels issue.
> 
> > > > Also, I'm working now on non-snooping mode support, and this might
> > > > help for fixing some problems like yours.  Could you try the patch
> > > > below (with the snapshot version)?
> > > 
> > > Unfortunately, this doesn't seem to help.
> > > 
> > > Given the similarities between the working and non-working boards, I was
> > > wondering if the BIOS is setting up the chips differently and that is the
> > > immediate cause of the problems.  In particular:
> > > 
> > > * There is no set_widgets_power_state function for this chip.  If the BIOS
> > >   enables some power management function on one board but not the other and the
> > >   driver has no way to disable it, could that cause an issue like this one?
> > 
> > No, as default the driver powers up all widgets and power down all
> > again at power-saving.  The VIA codec driver has an advanced
> > implementation to turn off a few unused widgets even in power-up.
> > And this feature is missing in VT1708.  So, it doesn't mean that the
> > driver has no power control.  It has.
> 
> I see.
> 
> > > * I see that the VB8002 has "N/A" listed for "Pin Default" for several
> > >   "Pin Complex" nodes where the EX15000G has "Jack".  Is it possible the
> > >   EX15000G has some nodes configured as AC_JACK_PORT_COMPLEX that should be
> > >   configured as AC_JACK_PORT_NONE?
> > 
> > I don't know.  You need to check whether the pins are really correctly
> > set up.  For example, most of jacks have the detection capability.
> > Then plug/unplug each jack and check the pin-detection e.g. with
> > hda-verb program.
> 
> I probably should have said so earlier, but this board has RCA connectors for
> most outputs.  I'm not sure that pin detection works for these?  In any case,
> the EX15000G and the VB8002 have the exact same the same physical connectors.
> 
> The only 1/8" connector is the front panel headphone jack.  I checked this pin
> with hda-verb, and it appears to be setup correctly.
> 
> > > It should be clear that I do not have a very good understanding of the HDA spec.
> > > I'm assuming the BIOS is responsible for configuring the chip as I've described
> > > above.  Do any of those problems sound possible to you?  If so, are there ways
> > > to work around them in the driver?
> > 
> > Yes, pins can be easily overridden via sysfs or patch option.
> > See Documentation/sound/alsa/HD-Audio.txt.
> 
> Okay, thanks for the info.
> 
> I experimented more and have some additional information that might be
> interesting:
> 
> 1. The clicks and pops sound like they are actually brief snippets of audio that
>    are being played at the wrong time and mixed in with the correct audio.
> 
> 2. With the old driver, when I mute some of the mixer controls the audio stream
>    becomes silent as expected but I still hear the snippets/clicks and pops for
>    a few seconds.  This happens with the Master Front, Headphone, Front,
>    Surround, Center, LFE, and Side elements, although it only seems to happen
>    with the Headphone element when I'm using the rear panel line out (RCA)
>    jacks.  I do not see this with the snapshot driver.
>    
> #2 in particular is puzzling to me, but maybe that is due to not understanding
> the hardware well enough.

FYI, I tracked down the root cause of the clicks and pops and it's a PulseAudio
issue.  I'll follow up with the PA devs.  It's a pretty interesting problem, so
I'll probably Cc you if that's okay.

Please note that the mixer issue affecting the snapshot driver is still
outstanding.  I'm happy to test a fix if that's helpful.  It is not an urgent
matter for me, though, as the older driver version works fine.

Thanks for all of your help!

-Forest
-- 
Forest Bond
http://www.alittletooquiet.net
http://www.rapidrollout.com
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