[pulseaudio-discuss] [SOLVED] usb sound card: PCM has 8 channels, thats too much & cannot submit datapipe for urb 0

Tanu Kaskinen tanuk at iki.fi
Sun Nov 20 02:24:52 PST 2011

On Sat, 2011-11-19 at 22:03 +0100, Martin Steigerwald wrote:
> Am Samstag, 19. November 2011 schrieb Martin Steigerwald:
> > Hi!
> >
> > I saw the soundcard working already with Pulseaudio, but now it
> > doesn´t.
> Forget this. I should tune my hi-fi to the right input in order to hear 
> anything ;). Seems I have been too much into audio troubles.
> Still Pulseaudio only sets volume on the right channel instead of both and 
> the left one is muted, but I will report this properly at some other time.

Ok. The first thing I'd be interested is the verbose log of Pulseaudio.
Instructions for getting the verbose log can be found at

Quoting that page: "Also, make sure to include the verbose output of PA
when this problem happens. For that run "pulseaudio -vvvvv" in a
terminal and try to reproduce your issue. You might need to stop a
running PA first by issuing "pulseaudio -k". If autospawning is enabled
(which it now is by default) you might have to race against it when
restarting PA, so it might be a good idea to issue "pulseaudio -k ;
pulseaudio -vvvvv" in a single command and try a few times. Usually that
should work well enough to win the race. If it doesn't, adding
"autospawn=no" to ~/.pulse/client.conf will disable autospawning."

> At least thats with this sound card and maybe the PCM has 8 channels, 
> thats too much message is the problem here? 

It may be in some way related. The message is printed when checking
whether a "path" is available. A path determines how Pulseaudio uses
hardware volume through alsa. The path availability checking is done by
inspecting what kind of alsa mixer elements exist. The "PCM" mixer
element of some of your sound cards appears to have 8 channels for
volume control, and Pulseaudio doesn't currently support more than two
channels. Apparently we should support more. (This is the first time I
see an alsa driver that provides a volume control element with more than
two channels.)

The consequence of seeing that Pulseaudio error should be at worst that
you won't have hardware volume control. You'll still have volume
control, however, it will just be implemented in software.

Your sound card seems to be a USB card. AFAIK USB doesn't have enough
bandwidth to support uncompressed 8-channel audio, so I wonder if that
error that pulseaudio prints comes from handling some other card than
the USB card. If that's the case, then the pulseaudio error doesn't have
anything to do with the volume problem with the USB card. But since
there's also the kernel error complaining about insufficient bandwidth,
I wonder if the sound card driver is nevertheless trying to use the USB
card in 8-channel mode...


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