Garbled Audio with Pulse-loopback

Question

Okay, so I have a relatively delicate PulseAudio setup, where I have a null-sink with two loopbacks from recording devices;
The setup is configured like this:
Default Audio Output Monitor -> Loopback module -> Null-Sink (Output)
Default Audio Input -> Loopback module->  Null-Sink (Output)
This, in theory (and in practice) Mixes the master audio output and master audio input into a single audio stream (for example, if I am talking, and I have music playing, you hear both my voice and the music, at appropriate levels)
This is all fine and dandy, except that when I use the Null-Sink's monitor for audio recording (the whole purpose of this) I get decent audio for a period of time, and then the audio turns into a garbled mess.
Is there any simple workaround to this? Is this intended functionality?
default.pa:
#!/usr/bin/pulseaudio -nF
# This file is part of PulseAudio.
# PulseAudio is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# PulseAudio is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with PulseAudio; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
# This startup script is used only if PulseAudio is started per-user
# (i.e. not in system mode)
.nofail
### Load something into the sample cache
#load-sample-lazy x11-bell /usr/share/sounds/gtk-events/activate.wav
#load-sample-lazy pulse-hotplug /usr/share/sounds/startup3.wav
#load-sample-lazy pulse-coldplug /usr/share/sounds/startup3.wav
#load-sample-lazy pulse-access /usr/share/sounds/generic.wav
.fail
### Automatically restore the volume of streams and devices
load-module module-device-restore
load-module module-stream-restore
load-module module-card-restore
### Automatically augment property information from .desktop files
### stored in /usr/share/application
load-module module-augment-properties
### Load audio drivers statically
### (it's probably better to not load these drivers manually, but instead
### use module-udev-detect -- see below -- for doing this automatically)
#load-module module-alsa-sink
#load-module module-alsa-source device=hw:1,0
#load-module module-oss device="/dev/dsp" sink_name=output source_name=input
#load-module module-oss-mmap device="/dev/dsp" sink_name=output source_name=input
load-module module-null-sink sink_name=pamix
load-module module-loopback latency_msec=2 sink=pamix
load-module module-loopback latency_msec=2 sink=pamix
#load-module module-pipe-sink
### Automatically load driver modules depending on the hardware available
.ifexists module-udev-detect.so
load-module module-udev-detect
.else
### Use the static hardware detection module (for systems that lack udev/hal support)
load-module module-detect
.endif
### Automatically connect sink and source if JACK server is present
.ifexists module-jackdbus-detect.so
.nofail
load-module module-jackdbus-detect
.fail
.endif
### Automatically load driver modules for Bluetooth hardware
.ifexists module-bluetooth-discover.so
load-module module-bluetooth-discover
.endif
### Load several protocols
.ifexists module-esound-protocol-unix.so
load-module module-esound-protocol-unix
.endif
load-module module-native-protocol-unix
### Network access (may be configured with paprefs, so leave this commented
### here if you plan to use paprefs)
#load-module module-esound-protocol-tcp
#load-module module-native-protocol-tcp
#load-module module-zeroconf-publish
### Load the RTP receiver module (also configured via paprefs, see above)
#load-module module-rtp-recv
### Load the RTP sender module (also configured via paprefs, see above)
#load-module module-null-sink sink_name=rtp format=s16be channels=2 rate=44100 sink_properties="device.description='RTP Multicast Sink'"
#load-module module-rtp-send source=rtp.monitor
### Load additional modules from GConf settings. This can be configured with the paprefs tool.
### Please keep in mind that the modules configured by paprefs might conflict with manually
### loaded modules.
.ifexists module-gconf.so
.nofail
load-module module-gconf
.fail
.endif
### Automatically restore the default sink/source when changed by the user
### during runtime
### NOTE: This should be loaded as early as possible so that subsequent modules
### that look up the default sink/source get the right value
load-module module-default-device-restore
### Automatically move streams to the default sink if the sink they are
### connected to dies, similar for sources
load-module module-rescue-streams
### Make sure we always have a sink around, even if it is a null sink.
load-module module-always-sink
### Honour intended role device property
load-module module-intended-roles
### Automatically suspend sinks/sources that become idle for too long
load-module module-suspend-on-idle
### If autoexit on idle is enabled we want to make sure we only quit
### when no local session needs us anymore.
.ifexists module-console-kit.so
.nofail
load-module module-console-kit
.fail
.endif
.ifexists module-systemd-login.so
load-module module-systemd-login
.endif
### Enable positioned event sounds
load-module module-position-event-sounds
### Cork music/video streams when a phone stream is active
#load-module module-role-cork
### Modules to allow autoloading of filters (such as echo cancellation)
### on demand. module-filter-heuristics tries to determine what filters
### make sense, and module-filter-apply does the heavy-lifting of
### loading modules and rerouting streams.
load-module module-filter-heuristics
load-module module-filter-apply
### Load DBus protocol
.ifexists module-dbus-protocol.so
load-module module-dbus-protocol
.endif
# X11 modules should not be started from default.pa so that one daemon
# can be shared by multiple sessions.
### Load X11 bell module
#load-module module-x11-bell sample=bell-windowing-system
### Register ourselves in the X11 session manager
#load-module module-x11-xsmp
### Publish connection data in the X11 root window
#.ifexists module-x11-publish.so
#.nofail
#load-module module-x11-publish
#.fail
#.endif
load-module module-switch-on-port-available
### Make some devices default
#set-default-sink output
#set-default-source input
If any additional information could be helpful, please let me know.
I found a related post on this topic, marked as solved - but I'm unsure how to accomplish the same result, I'm not very familiar with JACK, and I don't really think that is truly a solution.
https://bbs.archlinux.org/viewtopic.php?id=147060
Last edited by Xaero252 (2012-10-24 05:20:29)

Answer 1

I get a bit of garble now and then, for seemingly no reason. Signal strength is good. I haven't noticed with any regularity. I have a feeling it's an AT&T thing, and perhaps something to do with network load. Maybe start logging your issues...time, place, etc. It could help you see a pattern, and might be helpful to AT&T should you decide to contact them.