Re: mumble issues with pulseaudio

[Florian Paul Schmidt]

On 04/02/2017 11:33 AM, Florian Paul Schmidt wrote:
> > PulseAudio: Starting input alsa_input.pci-0000_00_1b.0.analog-stereo
> > PulseAudio: Starting output: alsa_output.pci-0000_00_1b.0.analog-stereo
> > AudioOutput: Initialized 1 channel 44100 hz mixer
> > AudioInput: Initialized mixer for 1 channel 44100 hz mic and 0 channel
> > 48000 hz echo

Oops and I misread this output. Yes, it seems mumble uses PA natively 
here. So the first sentence in my reply below was wrong. The rest of the 
reply still standts as being possibly helpful in understanding what can 
go wrong in other scenarios.

Note though that I found the native PA support in mumble usually working 
worse than using the PA virtual ALSA PCM device.

> Yes, this looks like mumble has opened an ALSA |PCM device that's not
> the default device called "default". If it's a PCM device that is going
> directly to a hardware device that does not provide stream mixing, then
> this will make other calls to ALSA to open that device (either directly
> or indirectly through another PCM device) _block_ until mumble has
> released the device again. Also, if the device is used by e.g. PA before
> mumble tries to open it, mumble's call to ALSA will _block_ until PA
> released the device.
>
> This is a longstanding bug in the ALSA API, that the ALSA devs do not
> consider a bug so it will never be fixed. There have been many
> discussions about how the call to ALSA should rather _fail_ than _block_
> in case of the device being busy (there's a sublety here that the
> failing behaviour is available, but nobody uses it, so you get this
> super annoying behaviour of calls to ALSA _blocking_)..
>
> If the PulseAudio installation shipped with GuixSD is "sane" then it
> will provide a virtual ALSA pcm device and will globally route the pcm
> device called "default" to this virtual PCM device. This device will
> provide stream mixing, etc..
>
> So any ALSA application that just uses the "default" PCM device should
> work out of the box with a sane PA installation since this "default" PCM
> device is just a name for the virtual PCM device provided by PA.
>
> Mumble additionally also has "native" PA support which you can build in.
> So to make mumble work on a PA system either
>
> 1] use the PA provided virtual PCM device "default"
>
> or
>
> 2] build mumble with native PA support and enable it in the preferences.

Flo


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