[alsa-devel] How to reduce delay between playback and capture for echo canceller

Cliff Cai xcahua at hotmail.com
Tue Apr 1 16:17:33 CEST 2008

Hi all,
  I'm playing a linphone based VOIP demo board these days,the board can connect different soundcard daughter board 
as playback and capture devices through  I2S or AC97.Then I experience a bad echo on my PC(using liphone and headset) when 
talk with the board (with speaker and MIC on board).So I enable the echo canceller (based on speex) for it.
One of my sound card (connected by I2S) works pretty well,but the other one (connected by AC97) doesn't work.
Through the diagnostic tool provided by speex I find that the ac97 one has a big delay between played signal(reference signal)
and captured signal.Just the delay make echo canceller don't work as expectation.So I think the driver for the AC97 soundcard
need some improvement to reduce the delay.
Has anyone a usefull direction for me? Thanks in advance,Best Regards
Cliff Cai
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