[Gta04-owner] Echo cancellation
psonek2 at seznam.cz
Mon Feb 20 11:03:07 CET 2012
i have started working on echo cancellation in the gsm voice routing program
Why do we need this? If you try e.g. QtMoko v40 you will notice that the
speaker and mic volumes are very low during call. I have been experimenting
with higher volumes, but then the other party starts hearing herself which is
very annoying. And current low volumes are usable only indoors. Btw same
problem was on Freerunner. Freerunner has special AT commands for this and it
was all handled by modem firmware then.
So I have added two new defines in the voice routing program:
If you enable first one, it will use simple algorithm which lowers mic volume
and increases speaker volume when the other party is speaking and does the
opposite when you are speaking.
Second define uses speex library which has echo cancellation algorithm for VOIP
calls. You can find some info about it here.
I have not tested it very much yet, but the walkie talkie algorithm seems to
work quite good. Using speex does not work for me yet - maybe i am doing
I am leaving home until Sunday so i will not work on this now.
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