[Freeswitch-users] echo cancellation on PRI cards

[David Knell]

Steve Underwood wrote:
>> 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.
>   
With respect, this is at best half true.  DTMF detection has always 
worked just fine
without echo cancellation - the Dialogic, Aculab and Rhetorex cards 
which I used
in the late 1990s managed it perfectly well; if the DTMF detection code 
in * and FS
can't, then maybe that's something for its author to look at ;-)

ASR - yes, maybe, but L&H's ASR1500 used to work perfectly well on the same
hardware above back in the day.  I'd be interested to see results of 
testing an ASR
engine in with echo; unfortunately, most vendors appear to prohibit the 
publication
of test results in their licensing.

--Dave
 
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