[asterisk-users] Disabling Echo Cancellation on a per Call basis

[Tobias Wolf]

Olivier schrieb:
> 
> 
> 2009/2/10 Tobias Wolf <tobias.wolf at evision.de 
> <mailto:tobias.wolf at evision.de>>
> 
>     Hello all,
> 
>     i was just made aware on the Bristuff-Mailing list, that it is
>     possible to
>     disable echo cancellation per dialplan application.
> 
>     This comes in very handy, for terminating faxes.
> 
>     But the application seems only to be existing in the bristuff patches.
> 
>     Does there exist a solution for
> 
>     Asterisk 1.6.0.3
>     Digium Wildcard TE110P T1/E1
>     DAHDI Version: 2.1.0.3 Echo Canceller: MG2
> 
>     without any Bristuff?
> 
>     At the Moment i have fax detection enabled.
> 
> 
> Do you mean a given DID receives voice or fax calls ?
> If positive, which app is detecting faxes ?

Since i have a dedicated DID for fax calls, i don't really need the fax 
detection. For this number i simply start the ReceiveFAX-Application and have 
some voodoo around it to name the file correctly.

But if i do this, and look into the channel information from Dahdi i see that 
the fax handled flag is set to no. And this seems wrong to me. I have the 
feeling that the percentage of failed faxes is higher is this flag is set to no 
(or false, can't remember) ...

Since i have a PRI connected to my Asterisk, i use the built-in fax detection of 
DAHDI. I have enabled it for incoming fax calls, in chan_dahdi.conf

faxdetect=incoming

The incoming call is answered and with an included Wait(4) the fax is detected 
and switched to the fax extension, where the ReceiveFAX-App is executed.

Now the fax handled flag is set to yes and i am able to receive most of the fax 
calls. But i have massive problems receiving fax calls from certain people, 
especially from UK (i am in germany). I am not quite sure, if the echo canceller 
is automatically disabled if DAHDI knows that the call is a fax and the channel 
info doesn't indicate otherwise, since it says that echo canceller is active 
even if it says that it handles an fax.

This is the reason why i was so happy to hear, that there seems to be the option 
to control the echo canceller with an dialplan app. But since this seems to be 
an Bristuff-only feature i am a little bit stuck.

Kind regards,

-- 

   Tobias Wolf