[Openal] echo cancellation

[danflu at uninet.com.br]

Hello,

I'm using the latest openal-soft version (OpenAL Soft
1.6.372) and I've been studing the huge list of capabilities
for sound effects that come with openal, but I could'nt find
anything related to echo cancellation (this should occur
when capturing, I guess...) is there any built-in support
for doing this? 

If there is no built-in suport I could just use some audio
codec API (like speex, any other ideas ?) that comes with
echo-cancellation support and use its funcions to strip the
echo out from the input samples, but there is a problem... 
How could I get the sound samples from the speakers at the
moment it gets played in order to subtract it from the
incoming samples from microphone ? (subtract means
cancelling the echo component from the input) 

Is it too "low level" for doing with openal ? Should I try
using alsa directly ? If so, could you please guive me some
directions at how i could do that ???

Thank you very much,
Daniel