[asterisk-users] Echo problem in VoIP-calls

[Gareth Blades]

Jonas Kellens wrote:
> Internet Telephony Service Provider = SIP provider. The company that 
> connects the Asterisk-server via a SIP trunk with the other networks 
> like GSM, analogue carriers...
> 
> 
> Jonas.
> 
>> By ITSP do you mean a SIP provider?
>>   
Thats where I believe the problem lies. You are sending audio to them 
and they are putting it onto the PSTN network. When the audio comes back 
from the PSTN it has echo on it. They are not performing echo cancellation.
If it is an international call from the ITSP's perspective then teh 
network operator should be performing echo cancelation anyway. If its a 
national call then the telco doesnt perform echo cancelation but the 
ITSP should do it themselves. The only time this is not needed is if the 
phones have a very low delay to the ITSP but since this is normally not 
the case echo cancelation must be performed at this point.