[asterisk-users] The High Performance Echo Canceller (HPEC)

[Nic Bellamy]

Bill Gibbs wrote:
> Will this work with SIP channels?  I get zero echo out the PRI but I do
> get it occasionally on a LD provider (SIP) we use.  The stock * install
> doesn't appear to be doing anything stopping echo on those channels.
>   
Nope, it won't help - echo cancellation needs to be performed as close 
to the source of the echo as possible. When you've got SIP in the mix, 
you've got variable network delays, packet loss, jitter buffer 
interpolation and various other things to think about, and this would 
make an echo cancellers job orders of magnitude harder (and it's already 
a pretty hard problem).

While it would be technically possible to echo-cancel SIP channels, it'd 
be _extremely_ CPU intensive (you'd need massive tail coverage) and 
probably not do a very good job.

If you're getting echo from a VoIP->PSTN provider, they need to do 
something about it themselves - by the time it gets to you, it's too late.

Cheers,
    Nic.
> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com
> [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Nic
> Bellamy
> Sent: Tuesday, February 13, 2007 3:41 PM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [asterisk-users] The High Performance Echo Canceller (HPEC)
>
> Larry Shields wrote:
>   
>> I recently read about the following new technologies from Digium.  Has
>>     
>
>   
>> anyone tried the new HPEC or knows when it will be available?
>>     
> It's out now, and I've tried it - the difference between HPEC and MG2 
> from trunk is stunning - in situations with bad echo where MG2 can take 
> ten or more seconds to converge to a reasonable degree, HPEC does it in 
> perhaps 300ms - converging on my intake of breath before I say "hello", 
> and absolutely no echo after that unless I purposefully go out of my way
>
> to screw it up (whistling/blowing into the handpiece for instance - even
>
> then, the malfunction is minimal).
>
> You can now buy it from the Digium website (US$10 per channel), or if 
> you have an in-warranty Digium card, email through the serial numbers to
>
> Digium support and they'll give you a key (this is what I did).
>
> You'll need Zaptel 1.2.13 to make it go.
>
> It does take quite a bit of CPU though - perhaps 70% more compared to 
> MG2-trunk for the same number of taps from my rough measurements.
>
> Cheers,
>     Nic.
>
>   


-- 
Nic Bellamy,
Head Of Engineering, Vadacom Ltd - http://www.vadacom.co.nz/