[Freeswitch-users] echo cancellation on PRI cards

[Steve Underwood]

Wasim Baig wrote:
> 2009/3/17 Anthony Knight <tntknight at gmail.com 
> <mailto:tntknight at gmail.com>>
>
>     I'm thinking about doing a project that would use FreeSWITCH as an
>     IVR, with callers being routed in by both ISDN PRI, and also SIP
>     trunks, with occasional bridge calls between callers.
>
>     I'm wondering in what use cases hardware echo cancellation on the
>     PRI cards is needed.
>
>
> When there is Echo being generated from the far end, usually in a 
> bridged call. If you application is just an IVR, with no far end 
> connectivity, then you shouldn't need an echo can. If you are bridging 
> calls, then at some point you may need it, depending on what else is 
> in the loop.
This is VERY VERY WRONG. IVRs badly need echo cancellation. Without it 
they give very poor reliability detecting DTMF while the prompts are 
playing. If the system uses voice recognition, its reliability will be 
even worse.
>   And does hardware echo cancellation work with OpenZap/FreeSWITCH? 
>
>
> Yes, it really has nothing to do with the software then, its handled 
> by the card and its hardware driver. In Sangoma's case, by Wanpipe.
>  
>
>     It looks like all the major cards (Sangoma, Digium, etc..) use
>     Octasic Echo cancellation add-on cards.  Is there any difference
>     between brands?
>
>
> Sangoma has 1024 tap Octasic Echo Cans. Very nice they are indeed.
>  
>
>     Any recommendations on PRI boards and whether I need to pay for
>     echo cancellation are appreciated
>
>
> Unashamedly, Sangoma's. 100% of the cases where our customers have 
> used Sangoma A10Xd vs A10X, they've been much happier with the quality 
> on the line. Its a tad bit more $, but well worth it (especially in 
> places with bad copper).

If you use Sangoma make sure everything is up to date. People have had a 
lot of DTMF detection trouble with some revisions of the driver, or on 
board firmware, or possibly both. Clearly DTMF trouble would be pretty 
bad for an IVR. I didn't manage to trace which were the offending 
versions, but the current stuff is apparently OK.

Steve