[pulseaudio-discuss] Moving speakers around using AC3

Aurelien Bompard gauret at free.fr
Sat Nov 28 00:29:29 PST 2009

Hi people,

I have a strange use case, and I'd like to know if it's possible to do it 
with PulseAudio :
At home, I have an AC3 amp, a couch and a computer against the wall to the 
left of the couch. The speakers are set up for watching movies sitting in 
the couch. Tentative ASCII art :

  u       CENTER+LFE

 RR       FR
(boy am I untalented with this...)

Now, my problem is the following : when I'm at the computer, I'd like the 
stereo sound to come out from the speakers beside me, which would come down 
to this kind of routing:
front left -> rear left
font right -> front left

I've actually managed to do that using plain ALSA and my SPDIF connector 
with the following config:
# 0: FL
# 1: Center
# 2: LFE
# 3: RL
# 4: FR
# 5: RR
pcm.atdesk {
   type route
   slave.pcm "Filter_A52Encode"
   slave.channels 6
   # FL -> RL (with higher volume)
   ttable.0.3 2
   # FR -> FL
   ttable.1.0 1
   # same thing on the back
   ttable.0.5 1
   ttable.1.4 0.5
   # LFE
   ttable.0.2 0.1
   ttable.1.2 0.5
pcm.Filter_A52Encode {
   type a52
   card 0

It does work, but I have to manually choose the alsa output and the "atdesk" 
driver in mplayer, since and it does not integrate nicely with pulseaudio, 

My dream setup would be to have a profile in pavucontrol's "Configuration" 
tab which would allow me to switch from the normal setup to the routed setup 
at runtime.

I've tried many setups in default.pa to do that, but failed.

Do you think this is possible, or is it too much of a pony ?

Thanks !

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