[pulseaudio-discuss] Audio degradation and Underruns when changing sinks on a 'live stream'

[Alejandro Gonzalez]

Hi there, 

I'm new to PA so please forgive me if what I said have no much sense.

I'm using PA 0.9.22 + UCM patches from Margarita Olaya in an Ubuntu
Maverik FS. And I have an alsa UCM profile that sets the playback
controls and define 2 devices (Headset and Handset), so I can manually
change between these two profiles using gnome-sound-preferences. PA
shows them as different profiles Playback__Handset and
Playback__Headset.

The issue is that if I change profiles on a 'live stream' the audio is
correctly routed every time, but after a couple of tries it starts to
get distorted and I can see a lot of buffer underruns and 'Requested to
rewind'. 

I know there is a 'module-rescue-streams' that does the stream
're-routing' when the sink it is playing at dies, and this is exactly
what happens when I do change profiles, the old-sink is deleted and a
new sink is created, both have the same properties but a different name
and each one set different alsa controls. 

D: sink.c: Processing rewind...
D: sink-input.c: Have to rewind 208 bytes on render memblockq.
D: sink-input.c: Have to rewind 184 bytes on implementor.
D: source.c: Processing rewind...
E: protocol-native.c: handle_seek: 0 -- 1
D: protocol-native.c: Requesting rewind due to rewrite.
D: alsa-sink.c: Requested to rewind 1360 bytes.
D: alsa-sink.c: Limited to 1360 bytes.
D: alsa-sink.c: before: 170
D: alsa-sink.c: after: 170
D: alsa-sink.c: Rewound 1360 bytes.
D: sink.c: Processing rewind...
D: sink-input.c: Have to rewind 1360 bytes on render memblockq.
D: sink-input.c: Have to rewind 1256 bytes on implementor.


I'm playing the file with a simple gstreamer pipeline:

gst-launch playbin2
uri=file:///home/ubuntu/DaftPunk_Homework_AroundTheWorld.mp3

So my questions are:
Can I fix the 'Underruns' increasing the default latency or buffer size?
if so, Can I do this through a configuration parameter in
default.pa/daemon.conf/client.conf?

Or is this 'on-the-fly' sink change simply not supported?
and the 'module-rescue-streams' is not really a feature but a 'security
harness'?

Thanks and regards, 

Alejandro.