[pulseaudio-discuss] Issue connecting a null-sink to a tunnel sink

[Georg Chini]

On 14.10.2015 17:18, Olivier Delbeke wrote:
> Hi all,
>
> I'm struggling with a pulseaudio configuration that I expected to be 
> working out-of-the box (as it seems very simple).
>
> I have :
>  * a null-sink "mynullsink"
>  * a tunnel-sink "mytunnel"
>  * a module-loopback to connect "mynullsink.monitor" to "mytunnel"
>
> Content of /etc/pulse/default.pa <http://default.pa> is here (full 
> content):
>   load-module module-native-protocol-unix
>   load-module module-suspend-on-idle
>   load-module module-null-sink sink_name=mynullsink
>   load-module module-tunnel-sink sink_name=mytunnel 
> server=tcp:192.168.100.3:4713 <http://192.168.100.3:4713> sink=remotesink
>
> Playing a wav file directly to the tunnel works fine, all the time :
>   paplay sample1.wav -d mytunnel
>   => audio sent correctly through the tunnel
>      However, I can see with "pacmd list-sinks" that "mytunnel" has a 
> "current latency" of 0ms. Normal ?
>
> To connect the null-sink and the tunnel, I do this (with either pactl 
> or pacmd) :
>   pacmd load-module module-loopback source=mynullsink.monitor 
> sink=mytunnel
>   => The module is correctly loaded (as I can see with "pacmd 
> list-modules")
>
> But playing audio to the null-sink does not work (i.e., no sound is 
> forwarded to the tunnel by the loopback) :
>   paplay sample1.wav -d mynullsink
>   => NO AUDIO. NO ERROR MESSAGE. VOLUMES AT 100%. STATE RUNNING
>
> With pulseaudio 6.0, I see that the latency calculated by the 
> module-loopback is increased by 10s every 10s :
> D: [pulseaudio] module-loopback.c: Loopback overall latency is 
> 21552.00 ms + 0.00 ms + 0.00 ms = 21552.00 ms
> D: [pulseaudio] module-loopback.c: Should buffer 0 bytes, buffered at 
> minimum 0 bytes
> D: [pulseaudio] module-loopback.c: [mytunnel] Updated sampling rate to 
> 48000 Hz.
> D: [pulseaudio] module-loopback.c: Loopback overall latency is 
> 31524.00 ms + 0.00 ms + 0.00 ms = 31524.00 ms
> D: [pulseaudio] module-loopback.c: Should buffer 0 bytes, buffered at 
> minimum 0 bytes
> D: [pulseaudio] module-loopback.c: [mytunnel] Updated sampling rate to 
> 48000 Hz.
>
> With pulseaudio 4.0, the latency moves around 250ms, but there is also 
> no audio.
>
> There seems to be a very unexpected workaround : loading the loopback 
> module twice ! When I do that, I get audio, but it's slightly 
> disturbed (sounds like an old vinyl record).
>
> What is happening ? Does anyone have a hint ?
> Why can't I chain a null sink to a tunnel sink using a loopback module ?
>
> Thank you and best regards,
>
> Olivier
>
>

Hi Olivier,

I wonder if you also loaded module-native-protocol-tcp somewhere. I 
think you need
it for tunneling. Did you try to use a standard default.pa?

A while ago I tried a similar setup, but instead of tunnel_sink I used 
tunnel_source:

On the source machine (my local network is 192.168.255.0/24):

load-module module-native-protocol-tcp 
auth-ip-acl='127.0.0.1;192.168.255.0/24'
load-module module-null-sink sink_name=my_sink channels=2 rate=44100

Then I played the stream back to my_sink.

On the destination machine:

load-module module-tunnel-source server=192.168.255.x 
source_name=remote_source source=my_sink.monitor
load-module module-loopback source=remote_source

This worked fine and has the advantage that you can easily connect (or 
re-connect) the
same stream from multiple clients. Maybe you can try it this way.

Regards
             Georg


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