[Speex-dev] AEC in live performance

joel silvestre j.silvestre at wanadoo.fr
Thu Feb 5 04:12:54 PST 2009


I plan to use AEC for a live performance, storytelling for very young
children (and their parents!) in a mongolian yourte . Actually the
storyteller can make vocal loops, there is an omnidirectional microphone
in the center of the yourte, 5 loudspeakers in a circle along the
yourte's wall and Pure Data in a linux box.  And now she wants to make
vocal loops over music and loops over loops... Maybe aec will help her?
I did some testing on a small setup, 2 desktop loudspeakers and have
very good results (20 to 30dB rejection) with mono music and
speex_echo_state_init_mc() set to 1 speaker but nearly no cancellation
with a stereo setup. Initializing echo_state with 2 speakers doesn't
improve but rather degrade cancellation. Also tried decorrelation but no
noticeable effects.
And of course sounds are strongly dynamically panned over the 5
So here are the questions, is there a hope aec can do something for her
or do I am dreaming? do I miss something?
Surely stupid but as the loudspeakers and the microphone are always at
the same place in the yourte I can mesure the impulse response of each
loudspeaker as seen by the central microphone and convolve the 5 "far
end" signal before feeding the eac's adaptative filter. Will it help?

All the best,

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