[asterisk-dev] Tuning Software Echo Cancellers

[Andrew Kohlsmith]

On Sunday 06 August 2006 22:36, Rich Adamson wrote:
> The echotraining parameter was originally created for analog pstn lines,
> adding a delay (in the above example, 800 milliseconds) to allow analog
> central office equipment to settle down before the s/w echo can routines
> pulsed the line. The reflective energy from the pulse was then used to
> preload the echo can routines.  Doubtful this parameter should be
> anything other then =yes on a PRI.

I was under the impression that echo training in zaptel was used at the 
beginning of a call to help the echo cancellers train more quickly by muting 
audio from Asterisk, sending an impulse down the line and measuring the 
response before unmuting audio and allowing the parties to speak.  Having a 
known and simple impulse helps the echo canceller train more quickly, which 
has the effect of reducing the length of time needed to converge.

> The rxgain and txgain values need only be expressed in units; the
> numbers after the decimal point have no practical value.

Again, I thought that integer values were interpreted as percentages, while 
real numbers were interpreted as decibel values?  Has this changed?  The code 
seems to indicate that it does indeed accept and use decimal values, but that 
the use of percentages in gain setting is no longer available.

-A.