[Speex-dev] trouble getting speex_echo_cancel() to work

Kleijn, J.S. de J.S.d.Kleijn at student.tue.nl
Thu Jun 2 07:46:01 PDT 2005

Here http://home.arcor.de/andreadrian/ you can download another echo canceller including a double talk detector. It is open source etc and it's used in Kphone etc. I haven't got it to work well but this should be possible with some tuning.
In my opinion it is easier to use than the echo canceller in speex
PS: the latest source of the echocanceller is included in the intercom program.
Greetings Jeroen de Kleijn

	-----Oorspronkelijk bericht----- 
	Van: speex-dev-bounces at xiph.org namens Thorvald Natvig 
	Verzonden: do 2-6-2005 15:58 
	Aan: speex-dev at xiph.org 
	Onderwerp: Re: [Speex-dev] trouble getting speex_echo_cancel() to work

	> - set sampling rate to 8 kHz (at least for now)
	> - make sure the far end signal in the playback signal is always a bit in
	> advance (never late) compared to the mic signal.
	> - Set the tail length to something around 100 ms.
	> Also, if you're using two different soundcards (as I understand) for the
	> playback and the capture, you're *never* going to get echo canceller to
	> work because the playback and capture need to be *exactly* in sync.
	I did a bit more testing, and ended up creating a set of testsamples, as
	ideal.pcm => me saying "This is what I'd like to hear"
	junk.pcm => me saying "With a bit of luck, this is gone"
	mixdown.pcm => ideal.pcm, with junk.pcm started 7 ms later and 3 dB lower.
	(All of this as 8000 Hz, 16-bit signed)
	I then copied junk.pcm to play.sw, mixdown.pcm to mic.sw and ran testecho.
	The output sounds almost identical to the mixdown, and far from "ideal".
	As a 2nd test, I made play.sw and mic.sw identical (both the mixdown).
	The result is the same as the mixdown, with the volume slowly decaying
	until it's about 15 dB lower at the end of the 8 sec sample.
	Somewhat encouraged by this, I made a much longer set of samples, and in
	the mixdown I inserted the "desired" sound 5 seconds into the mix to let
	the filter have time to adapt. Indeed, after a few seconds,  the echo is
	reduced by about 15 dB, but that will still be loud enough to be annoying
	and distractive when talking.
	Are there any tunable parameters I can set to allow the echo canceller to
	be a bit more aggressive?
	Speex-dev mailing list
	Speex-dev at xiph.org

More information about the Speex-dev mailing list