[Asterisk-Users] Are my expectations too high?

[Andrew Kohlsmith]

On Tuesday 23 May 2006 14:54, Cosmin Prund wrote:
> Is there a known "hack" or patch to blow Asterisk's echo canceler up to
> 128ms? Or at least 64 ms?

It's real easy... at least for us code tinkerers.

In the zaptel source tree, in zaptel.c, you will see a call to 
echo_can_create() with a check to validate the number of taps just above.  
256 = 32ms, 512 = 64ms, 1024 = 128ms.  Add the checks for 512 and 1024.

Now in the asterisk source, channels/chan_zap.c has a similar check where it 
looks for and validates the echocancel parameter.  search for "echocancel = 
ast_true" and you'll see the validation just above.  If you don't change this 
here, it'll see your 512 and 1024 declaration and just silently drop it to 
128.

I am not sure if the software echo cancellers are unidirectional tail or 
bidirectional tail, but typically (and Steven Underwood may step in and 
correct me on this) you only need to cancel the tail in one direction -- the 
"echo coming from the "far end".

-A.