[pulseaudio-discuss] Emulate Alsa A52 plugin in pulseaudio ?

Tanu Kaskinen tanuk at iki.fi
Thu Feb 28 12:55:06 PST 2008

On Thu, Feb 28, 2008 at 03:09:45PM -0500, Jim Duda wrote:
> I would like to use pulseaudio on a machine which I have the sound card attached to an digital decoder.  I'm using the 
> alsa A52 plugin to perform a stereoupmix from 2 channels to six channels such that I get the same stereo out of the 
> front and rear speakers.

> Can I use the remap module to copy 2 channels to 4?  The front speaker and sub woofer would be nice too.

Yes you can, but there shouldn't be need for that. Since
0.9.8 PulseAudio has supported automatic up- and downmixing,
which probably does what you want. If you have 0.9.8 and it
still doesn't work, check that you haven't disabled the
feature in daemon.conf by saying disable-remixing=yes.

If I've understood your setup correctly, you would need to
encode the output of PulseAudio to AC-3. I don't have any
experience in that field, so the following is just my best
guess how it would work:

Your new ~/.asoundrc:

pcm.!default {
    type pulse

pcm.a52encode {
    type a52

# What's this for?
pcm.front-spdif {
    type plug
    slave.pcm "iec958"

Comment out module-hal-detect and module-detect in
/etc/pulse/default.pa. Add this line instead:
module-load module-alsa-sink sink_name=ac3_out device=a52encode channels=6 rate=48000

Tanu Kaskinen

More information about the pulseaudio-discuss mailing list