Hello all. I've been following this and other threads in regards to DRC for XBMC, and thought I'd talk about SOME progress I've made on Ubuntu 10.04 (Lucid Lynx).
Please note that this method is temporary and settings will be lost after restarting PulseAudio (i.e. rebooting computer). If somebody knows a better way to do this, feel free to share.
Before you proceed, have a look here:
http://ubuntuforums.org/showthread.php?t=1470407
Follow the above link as a guide, and then install the following additional packages from a terminal (this SHOULD be all you need after following the above link:
apt-get install jack qjackctl jack-rack
After installing the packages above, you will need to startup JACK (qjackctl recommended) and JACK-Rack, then create the PulseAudio to JACK clients from a terminal (NOTE that JACK MUST be running BEFORE you create them):
qjackctl
jack-rack
pactl load-module module-jack-sink
pactl load-module module-jack-source
If the above commands work, you should see the PulseAudio in/out clients connected to the JACK system clients.
Now DISCONNECT ALL inputs and outputs, and start routing the PulseAudio outputs that you want to use, to the JACK-Rack inputs. Finally, connect the JACK-Rack outputs to the system.
That's it! Everything is connected properly to use LADSPA effects. Just fire up XBMC and make sure it's using PulseAudio.
TIP: a combination of Compressor, Noise Gate, and Low-cut (high-pass) filter should handle MOST situations if you want to watch a variety of stuff late at night.
I will post a follow-up when/if I find a more streamlined approach with a script.
Good Luck!
P.S. I would strongly encourage XBMC linux devs to include NATIVE JACK support to avoid this chaotic spaghetti mess with PulseAudio, but for now it's SOMETHING.