[pulseaudio-tickets] [Bug 67781] New: heavily distorted sound when using module-loopback with module-tunnel-sink

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=67781

          Priority: medium
            Bug ID: 67781
                CC: lennart at poettering.net
          Assignee: pulseaudio-bugs at lists.freedesktop.org
           Summary: heavily distorted sound when using module-loopback
                    with module-tunnel-sink
        QA Contact: pulseaudio-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: zrin+pa at ziborski.net
          Hardware: x86 (IA32)
            Status: NEW
           Version: unspecified
         Component: modules
           Product: PulseAudio

PulseAudio version: 4.0

When I use module-loopback to connect audio input (line-in) to a sink
provided by module-tunnel-sink, I get chopped sound on the receiving
side. The sound output is missing parts and it gets worse over time.
I've made following observations:

- typical debug output (sending side) that probably correlates with
this problem is
...
D: [pulseaudio] module-loopback.c: Should buffer 0 bytes, buffered at
minimum 0 bytes
D: [pulseaudio] module-loopback.c: [usbol] Updated sampling rate to 44100
Hz.
D: [pulseaudio] module-loopback.c: Loopback overall latency is 149.26 ms +
10.50 ms + 1.01 ms = 160.77 ms
...
this is repeated in the output and the chopping gets worse with the time

- debug output on the receiving side during output
...
D: [alsa-sink-USB Audio] memblock.c: Pool full
D: [pulseaudio] memblock.c: Pool full
D: [pulseaudio] memblock.c: Pool full
D: [alsa-sink-USB Audio] memblock.c: Pool full
D: [alsa-sink-USB Audio] memblock.c: Pool full
... repeated ...
D: [alsa-sink-USB Audio] memblock.c: Pool full
D: [alsa-sink-USB Audio] ratelimit.c: 25 events suppressed
D: [alsa-sink-USB Audio] alsa-sink.c: Wakeup from ALSA!
D: [alsa-sink-USB Audio] alsa-sink.c: Wakeup from ALSA!
D: [alsa-sink-USB Audio] flist.c: pulsecore/memblockq.c: list_items flist
is full (don't worry)
D: [alsa-sink-USB Audio] flist.c: pulsecore/memblockq.c: list_items flist
is full (don't worry)
... repeated ...
D: [alsa-sink-USB Audio] flist.c: pulsecore/memblockq.c: list_items flist
is full (don't worry)
D: [alsa-sink-USB Audio] ratelimit.c: 73 events suppressed
D: [alsa-sink-USB Audio] flist.c: pulsecore/memblockq.c: list_items flist
is full (don't worry)
...

- chopping gets worse over time, and within few minutes there is no
(hearable) sound output any more

- the chopping depends on latency_msec passed to the module-loopback,
but it is always there and gets worse over time. (Lower latency gives
less (hearable) chopping at the start.)

- at the same time, I can paplay or play-sample in parallel to the output
from module-loopback to the same sink without problems

- If I suspend the sink on the receiving side and the resume it again,
then there is huge latency (the sending side seems to be unaware?),
but for some time the sound output is without (AFAIC hear) distortions.
module-loopback outputs (debug log) messages about sampling rate
adjustment. After some time, the latency gets reduced, but then
D: [pulseaudio] module-loopback.c: Should buffer 0 bytes, buffered at
minimum 0 bytes
appears again and the sound gets chopped.

- local loopback from audio-in to audio-out is ok


The setup consists of two almost identical systems with a minimal Debian
testing install.
There is no "desktop environment" - no Gnome or similar.
I've tried to run PA both as system instance and user's instance - both
with root privileges - there is no difference.

Examples of full debug log:
Client side (sending): http://pastebin.com/xwP4Qhwa
Server side (receiving): http://pastebin.com/U3h55jmN
Local loopback: http://pastebin.com/S7VT8UZ7

Config (both sides):
log-level=debug
exit-idle-time = -1

Init (both sides):
load-module module-udev-detect
load-module module-native-protocol-unix auth-anonymous=1
load-module module-native-protocol-tcp auth-ip-acl=192.168.0.0/24
.ifexists module-dbus-protocol.so
load-module module-dbus-protocol access=local
.endif
load-module module-always-sink
load-module module-suspend-on-idle
load-module module-cli-protocol-unix

Thank you!

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