[Asterisk-Users] Echo Cancellation (Newbie Qu)

[Andrew Kohlsmith]

> I've tried all the other methods of dispelling the x100p echo mystery
> such as echo training rx tx gain through ztmon and swapping POTS lines
> etc etc. Can someone mail me a step by step guide to changing the echo
> cancellation algorithms such as Mark,Mark2, Steve etc.

There isn't much to the step-by-step -- in the ztconfig.h file you will see 
the various echo cancellation algorithm defines:

/*
 * Pick your echo canceller: MARK2, MARK3, STEVE, or STEVE2 :)
 */
/* #define ECHO_CAN_STEVE */
/* #define ECHO_CAN_STEVE2 */
/* #define ECHO_CAN_MARK */
#define ECHO_CAN_MARK2
/* #define ECHO_CAN_MARK3 */

In the example MARK2's defined.   The general consensus is that MARK2's the 
best, IIRC.

There is also the agressive cancellation code, which I think practically 
everyone wants but it breaks things like POS machines and faxes, although I 
think now if the driver hears a fax tone it will disable the aggressive 
code:

/*
 * Uncomment for aggressive residual echo supression under
 * MARK2 echo canceller
 */
/* #define AGGRESSIVE_SUPPRESSOR */

Once you've made the changes, save 'em and make clean && make && make 
install.

Regards,
Andrew