[pulseaudio-discuss] playback from loopback over network fades, dies every few minutes and then comes back

[Georg Chini]

On 14.06.2015 18:54, Nick wrote:
> Greetings PulseAudio folks:
>
> I'm trying to pipe audio between an amateur radio (basically a USB sound
> card) hooked to a Raspberry Pi and my laptop over a local network. I've
> built PulseAudio 6 on a Raspberry Pi B+ and set up module-tunnel-sink
> and module-tunnel-source, and that's all functioning. I can record audio
> on my laptop and it seems to work well. However, I need to be able to
> monitor the sounds coming out of the radio live, so I set up a
> module-loopback with the source set to the USB sound card on the RPi.
>
> Here are the relevant bits in my system.pa config file:
>
> load-module module-tunnel-sink server=laptop sink_name=xps rate=11025
> load-module module-tunnel-source server=laptop source_name=xpss rate=11025
> load-module module-loopback
> source=TI_USB_Audio_CODEC-00-CODEC.analog-stereo latency_msec=100 rate=11025
>
> I've downsampled because I'm trying to minimize bandwidth and don't need
> hi-fi audio (after all, it's a ham radio). This works, but only for a
> few minutes. Then, the audio from the loopback becomes choppy and
> eventually fades out completely. It sits silently for about a minute
> (sometimes more) and then comes back in full quality. A minute or so
> later, the process repeats.
>
> Some interesting tidbits:
> 1) Only the loopback fades. If I'm recording in an application on the
> laptop from the networked tunnel source directly, it holds the signal
> nicely the whole time (even during the fadeouts).
> 2) If I connect to my local network over a VPN, the loopback fading does
> not occur at all.
> 3) The fading happens both on wifi connections and on hard-wired ones.
> 4) If I change the target of the loopback in pavucontrol's Playback tab
> to something else and then back to my laptop speakers, it often stops a
> fadeout and comes back strong for a minute or so (and then fades out
> again).
> 5) The fading occurs both with the downsampled rate set on the loopback
> and with the default.
> 6) This happens on multiple remix methods, including the default and
> trivial.
> 7) This happens on both the Raspberry Pi B+ and on the Raspberry Pi 2.
> CPU on the RPi2 is at about 20%.
> 8) The client (my laptop) has PulseAudio 4.0, not 6.0 like the server.
>
> I've uploaded a recording of the fading phenomenon that you can listen
> to here: http://partofthething.com/upload/pulseaudio-fadeout.mp3
>
> I'm not sure what to do to continue debugging. Any suggestions?
>
> Best regards,
> -Nick
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Hello Nick,

can you send some debug output from your pulseaudio session? It
might help to identify the problem. module-loopback should provide
a state update each adjust_time.

Regards
              Georg