[asterisk-dev] Adding Octastic Soft-Echo to external SIP adapters

[Eric "ManxPower" Wieling]

syd wonder wrote:
> Hi all.  I'm trying to hook into a chan_zap.c function that enables echo 
> cancellation.  I think I've identified the spots to hook into but am 
> wondering if someone can answer a few questions or provide some guidance.
> 
> 1 - I'm using an external device (Sipura SPA3000 FXS/FXO) configured as 
> a SIP trunk.  I'm hoping  that along with the Chan_Sip.C file, that the 
> Chan_Zap.c file is used to setup some of the functionality, namely - 
> whether echo cancellation should be enabled
> 2 - With item 1 being true, the reason why echo cancelling is not being 
> enabled is because the external device is being recognized as a digital 
> channel.
> 
> Anyone have a suggestion as to whether these assumptions are true?  If 
> not, any suggestions how I can add the echo cancellation functions to 
> non-zap devices.  This is something a bit more interesting now that 
> Octastic has released their SoftEcho software.   Thanks.. Syd

Generally, once the audio is converted to VoIP audio latency is far too 
high for echo canceling to work.  Echo needs to be canceled BEFORE the 
call is converted to VoIP.