[Gta04-owner] Routing UMTS sound

NeilBrown neilb at suse.de
Sun Jan 1 10:14:14 CET 2012

On Sat, 31 Dec 2011 05:14:16 +0000 Radek Polak <psonek2 at seznam.cz> wrote:

> Hi,
> now that we have sound in 3.2 kernel, i'd like to do better UMTS<-->sound card 
> routing.
> I am now trying:
> sox -r 8000 -t alsa hw:0 -t alsa -r 8000 hw:1
> sox -r 8000 -t alsa hw:1 -t alsa -r 8000 hw:0
> It works quite good except clicking noises every few seconds. Sox prints this 
> error:
> In:0.00% 00:00:51.71 [00:00:00.00] Out:410k  [ -====|====- ]        Clip:0    
> sox WARN alsa: Input/output error
> I have nearly zero experience with sound. Anyone has ideas what is the 
> problem?

My only guess is that the two devices run with different clocks so you might
get some clock drift which could cause clicks.

I would suggest trying to set up pulseaudio to do the routing.

I've done a bit of exploring and this is where I am at:

1/ install dbus and pulseaudio and related packages (pulseaudio-utils,

2/ Create a non-root user in group 'audio' and use that as pulseaudio doesn't
seem to like running as root.

   eval `dbus-launch --auto-syntax`
   pulseaudio --daemon


  pactl load-module module-loopback   \
       source=alsa_input.platform-soc-audio.0.analog-stereo  \
       sink=alsa_output.platform-soc-audio.1.analog-mono \

  pactl load-module module-loopback \
       source=alsa_input.platform-soc-audio.1.analog-mono \
       sink=alsa_output.platform-soc-audio.0.analog-stereo \

I'm not at all sure that this actually works, but at least it doesn't fail
miserably, and seems to be heading in the right direction.

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