[Freeswitch-users] echo cancelation

[Sergey Safarov]

Tamas not only mod_portaudio.
In my case used one leg terminated to FXS gateway, other leg terminated to
PSTN via ISDN PRI/E1 gateway.
Echo is observed for some calls. I think the echo is formed on the side of
the subscriber connected to PSTN.
I counted that the echo comes back with a delay of 44-64 ms or more (more
detail http://www.adaptivedigital.com/product/echo_cancel/echo_explain.htm).
Where:

   1. 20-30 ms - packetization time on a-leg
   2. ~1 ms - VoIP packet delivery
   3. ~ 1 ms - PSTN network signal delivery
   4. ~ 1 ms - PSTN network return signal delivery
   5. 20-30 ms - packetization time on ISDN PRI gateway
   6. ~1 ms - VoIP return RTP packet delivery

If FS will apply echo canceller then is required compensate 22-32 ms echo
for each leg.

Sergey



On Sun, Apr 19, 2015 at 9:11 AM, Tamas Jalsovszky <jalsot at gmail.com> wrote:

> On Sat, Apr 18, 2015 at 11:39 AM, Steve Underwood <steveu at coppice.org>
> wrote:
>
>> > Could you help me understand that prevents the use echo cancellation in
>> FS
>> How would you expect to use echo cancellation in FS?
>>
> It could be useful with for example mod_portaudio, IMO
>
> Regards,
>    Jalsot
>
>
>> Regards,
>> Steve
>>
>>
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