[pulseaudio-discuss] Stuttering when sending vbr stream via tunnel sink

[Joe (Yu) Zhou]

Hi,

I'm trying to stream some bluetooth audio via ethernet to another
pulseaudio server. I'm using module-tunnel-sink-new with TCP connection. On
the sender computer I have a bluetooth stream generating a variable bit
rate sink-input (around 44.4KHz on average), which I then move to the
tunnel sink with 44.1KHz sample rate. What I noticed is the audio on the
receiver side would stutter every ~6 seconds, and it's very consistent. And
when it stutters, I observe the following log on the sender side:

(15031.656|   0.351) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.664|   0.007) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.672|   0.008) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.680|   0.007) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.688|   0.008) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.696|   0.007) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.704|   0.007) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.712|   0.007) I: [tunnel-sink] module-loopback.c: Could not peek
into queue
(15031.720|   0.008) D: [pulseaudio] module-loopback.c: Underrun detected,
counter incremented to 6

And then the sample rate would change.

I tried the following:

 - Changing sampling method doesn't seem to make a difference.
 - Tried moving the bluetooth stream to a local sink with 44.1KHz sampling
rate, and no stutter was observed.
 - Tried adding --realtime=yes and --high-priority=yes options on the
sender pulseaudio server, no difference.
 - Tried creating additional remap sinks between the bluetooth stream and
the TCP tunnel sink, no difference.
 - Tried moving a constant bit rate stream of 44.1KHz to the tunnel sink,
no stuttering was observed on the receiving end.

I'm wondering, is this caused by some weird interaction between resampling
and the tunnel sink? Any suggestions how this kind of problem can be
debugged? Thank you!
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