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Thanks for both of the responses. I have 2 questions now, is there a better codec to use? I know if I can limit the voip delay that exists, it might help the problem some. 20ms is what is current but maybe 10 would help. What would be best, bandwidth is not an issue currently. This doesn't fix the wctdm issue obviously, which makes perfectly good sense, but might would help.<BR>
<BR>
Second question, what about a chennel bank? I here people talking about the adit 600 but from what I read, it seems more like it requires a T1 as it's a DSU if I'm correct. This would bypass the tdm boards and everybody says it has great echo cancellation. I'm recompiling the drivers right now and turning on the MMX optimizations hoping it might help the issue (a man can dream can't he). I'm getting desperate here because the system works great except for the echo which the users are getting irritable with it and I agree with them they should.<BR>
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Once again thanks. We've been running full steam with asterisk for over 2 months now.<BR>
<BR>
On Mon, 2005-03-07 at 18:14, Steve Underwood wrote:
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<PRE><FONT COLOR="#737373"><I>Steve Kann wrote:
> What he describes is echo suppression. Because an echo canceller can,
> generally, only remove some part of an echo, not the entire echo,
> systems are generally designed to suppress the residual echo in some
> circumstances. Old speakerphones had poor on no echo cancellation, so
> the suppression kicked in like that, because it was the only choice.
> In modern systems, the echo cancellation is much better, so
> suppression is not needed as much, and when it is used, it's probably
> done much more imperceptibly (with comfort-noise and stuff like this).
Only a very few high end conferencing speakerphones have ever used echo
cancellation. Even most expensive digital phones on PBXs merely do echo
suppression in speakerphone mode.
The nature of A-law/u-law limits the performance of an echo canceller
across the PSTN to about 30dB of echo improvement. If you look at the
behaviour of those codecs, you will see they give a roughly contant 30dB
of instantaneous dynamic range, and the echo cancellation enhancement
will never exceed that dynamic range. There is still enough residual
echo that good quality cancellers have to perform non-linear suppression
to eliminate it, and substitute comfort noise. 30dB, on top of the
minimum of at least 12-15dB of echo suppression the hybrids give, means
the echo should be rather quiet. It is still enough to annoy people,
though, and suppression is standard practice. It is specified in G.168.
Regards,
Steve
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