[pulseaudio-discuss] Pops/Crackles Messing up my audio...

[Colin Guthrie]

'Twas brillig, and Nasa at 07/08/11 21:26 did gyre and gimble:
> Hi, 
> 
> I was hoping I could get some help troubleshooting some audio quality issues I am running into.  
> Specifically, I am getting a lot of *pops/crackles* when I play audio files.  It shows up when I 
> move from 2-channel to 4/5 channel audio (via pauvcontrol) - I am using a USB X-FI sound-card with
> the Meego IVI.  
> 
> I have tried changing the resample method (going from ffmpeg to high-quality) and setting tsched=0, 
> neither making any noticeable difference.
> 
> The only things I saw in /var/log/messages that seemed relevant was:
> messages:Aug  6 16:59:26 localhost pulseaudio[570]: alsa-sink.c: ALSA woke us up to write new data to the device, but there was actually nothing to write!
> messages:Aug  6 16:59:26 localhost pulseaudio[570]: alsa-sink.c: Most likely this is a bug in the ALSA driver 'snd_usb_audio'. Please report this issue to the ALSA developers.
> messages:Aug  6 16:59:26 localhost pulseaudio[570]: alsa-sink.c: We were woken up with POLLOUT set -- however a subsequent snd_pcm_avail() returned 0 or another value < min_avail.
> 
> And this was spout out of dmesg
> [   21.857184] ALSA sound/usb/mixer.c:2110: status interrupt: c0 00
> [   21.897058] ALSA sound/usb/mixer.c:2110: status interrupt: c0 00
> [   21.961062] ALSA sound/usb/mixer.c:2110: status interrupt: c0 00
> 
> I have already eliminated the speakers and the amp (played music from a different source and
> they sounded fine).
> 
> Let me know what else I should post (I could record the sound, if that would be useful).
> 
> Thanks in advance,

While this could be an issue in the alsa driver itself, can I ask if
you're applying any volume changes to your streams or sink?

There could be a problem with optimized paths for software volume
adjustments. You can disable these optimisations via a special
environment var: PULSE_NO_SIMD=1

It's worth checking this to see if it's that area that's at fault.

Col


-- 

Colin Guthrie
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http://colin.guthr.ie/

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