echo-cancellation plugin advice?

["Robert Brewer" <rwb123@gmail.com>]

I'm writing a small speech input app for my laptop.  My app is
unusable when other sounds are being generated by the laptop, such as
from a music playing app.  For this reason, I'd like to have an echo
cancellation plugin that would cancel out the music played on the
laptop speakers when it is received by the mic.  I think this should
be doable since the music is playing through alsa.  I've done some
poking in the plugin documentation, and it's not clear to me how to
architect this plugin.  Ideally, I would route all my music playing
apps through the echo cancelling plugin.  I would also route the mic
capture stream through the plugin.  So the plugin must handle both
playback and capture streams.  Does the asym plugin hold the answers I
need?  Does anyone have any thoughts on how I might do this?  There
are several open source echo cancellation algorithms available, so I'm
mainly asking for advice on implementing this as an alsa plugin.

Thanks,
Rob
-- 
Robert W. Brewer