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

[Eric "ManxPower" Wieling]

Christian wrote:
> a ping in a LAN takes around 1ms ..  zaptel reads buffers of 160bytes = 
> 20ms from the driver. i don't think a LAN has so much latency
> 
> i would think, the latency might change during a session, so the 
> Echocanceler needs to be good at adaption.

You have many places where latency happens (in order, I think).

PSTN interface (zaptel)
Codec conversion (asterisk)
Packetization (asterisk)
Network (ping)
De-Packetization (IP phone)
Jitter Buffering (IP phone)
Codec Conversion (IP phone)

As far as I know there are no products out there that do EC on a VoIP 
audio stream.  Not from Digium, not from Cisco, not from Avaya, not from 
anyone.  EC on a VoIP link would take such a high amount of CPU to 
handle such long echo tails it would not be worth it.

Most of the EC devices out there that I have seen have 16ms or 32ms of EC.