[Asterisk-Users] BAD/GOOD Echo Cancel

[trixter aka Bret McDanel]

On Mon, 2006-02-06 at 04:01 -0800, asterisk at anime.net wrote:
> On Mon, 6 Feb 2006, trixter aka Bret McDanel wrote:
> > Again, I know Sangoma is a sore subject with some on this list, but the
> > echo cancelation stuff I heard while presented by a Sangoma employee was
> > not Sangoma specific, although it did include some research into
> > different hardware/software based cancelers.
> 
> digium licenses g729 codec, wonder if digium could license a good 
> G.168 echo canceller from someone.

They can license anything that is on the market, the catch is whether it
would be cost effective to do that.  

I also remember what the sangoma guy was talking about a little more
now.  It had to do with the ticks, hardware cancelers typically have a
much higher amount becuase they are specialized to do that.  As such
they can do more processing. The second echo that he talked about was
muted but present and out of the range of most software based echo
cancelers.

He said that their results were that software echo cancelation was about
30MHz per channel.  Now he didnt quantify what cpu that was, 30MHz on a
486 is far different from 30MHz off a Xeon, as such I personally dont
like such arbitrary numbers, but be that as it may be did say that intel
rated the G.729 codec at about the same 30MHz per channel, which I would
assume was based on the same series cpu.  If that is true that gives you
some scope of how much cpu you need, and why it may be better to do echo
cancelation in hardware vs software.

As I said earlier I missed the whole presentation, but do notthink he
compared different vendors hardware echo cancelers, there are certainly
good ones and bad ones, without some real data on each its hard to
say ...


-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
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