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<DIV dir=ltr align=left><SPAN class=284551022-04012011><FONT face="Courier New"
size=2>Hi Omer,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=284551022-04012011><FONT face="Courier New"
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=284551022-04012011><FONT face="Courier New"
size=2>I think we've experienced something similar. We sometimes hear what
sounds like bursts of noise (very ugly) if the microphone is
clipped. I haven't had a chance to investigate further
though.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=284551022-04012011><FONT face="Courier New"
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=284551022-04012011><FONT face="Courier New"
size=2>-Stef</FONT></SPAN></DIV><BR>
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<FONT face=Tahoma size=2><B>From:</B> speex-dev-bounces@xiph.org
[mailto:speex-dev-bounces@xiph.org] <B>On Behalf Of </B>Omer
Gilad<BR><B>Sent:</B> Monday, January 3, 2011 08:31<BR><B>To:</B>
speex-dev@xiph.org; jmvalin@jmvalin.ca<BR><B>Subject:</B> [Speex-dev]
Distorted output in fixed-point AEC<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=ltr>Hi,
<DIV>I couldn't find a discussion that specifically addresses this, so here it
is.</DIV>
<DIV><BR></DIV>
<DIV>I'm using Speex AEC in my mobile VoIP application to cancel speaker echo.
The used version is 1.2rc1 from the website, and I'm compiling with
fixed-point.</DIV>
<DIV>On most occasions, the AEC works very well and cancels most of the echo
(combined with the preprocessor).</DIV>
<DIV>On some devices, where the microphone signal gets a bit distorted
(because of sensitivity or some internal AGC pass), the AEC outputs distorted
and unacceptable voice, while only augmenting the echo signal instead of
cancelling it.</DIV>
<DIV>I have tried a few things:</DIV>
<DIV><BR></DIV>
<DIV>1. Compile in floating point - solves it, but irrelevant to some devices
which don't have an FPU and can't handle this. I actually use the FP version
on devices that DO support it.</DIV>
<DIV>2. Check where it reproduces - on any device where the recording gets
clipped every now and then, and also on devices that normalize their mic
input.</DIV>
<DIV><BR></DIV>
<DIV>I'm a bit desperate about this, and almost getting to the point of
debugging the AEC itself - my guess is that it's a lot of integer
overflows.</DIV>
<DIV>I'm willing to send voice samples that reproduce the problem.</DIV>
<DIV><BR></DIV>
<DIV>Did anyone experience that or has some insight?</DIV>
<DIV><BR></DIV>
<DIV>Thanks ahead,</DIV>
<DIV>Omer</DIV></DIV></BLOCKQUOTE></BODY></HTML>