[Asterisk-Users] Reducing echo on FXS port

[Aryanto Rachmad]

Hello Giovanni and everybody,

Thanks a lot for your suggestion.

Unfortunately, that does not help. With READ_SIZE=16, I got vibrating voice on the speaker phone. With READ_SIZE=80, the voice came back to normal and the echo is more reduced but still noticeable. I finally changed it back to 160 as it seems to affect a lot of things in chan_zap.

I am sorry that I didn't properly explain the setup I have. I think this issue happens because I use wireless handset. Here is my actual setup:

                                                         ---------------  out ------------
                                                         |             | <--- |          |
Wireless handset <--> Base phone <--> FXS (TDM400P) <--> | ZAP Channel |      | Asterisk |
  (Mic muted)                                            |             | ---> |          |
                                                         ---------------  in  ------------
                                                                           ^
                                                                        Monitor()

The delay between the original voice going out from asterisk to the phone, and its echo coming back to asterisk is about 104 ms, assuming that Monitor() application wrote both files at exactly the same time. How did I find that? I loaded the "in" and "out" files created by Monitor() application into Audacity (audacity.sourceforge.net). I could not find any other method to find this delay. Does anyone know a better and more accurate method?

When I did the same thing using X-Lite with below setup:

                 ---------------  out ------------
                 |             | <--- |          |
PC (X-Lite) <--> | SIP Channel |      | Asterisk |
(Mic muted)      |             | ---> |          |
                 ---------------  in  ------------
                                   ^
                                Monitor()

There is no sound at all on the "in" file created by Monitor() application, indicating that there is no echo at all as the microphone on X-Lite was muted.

Since the echo on FXS is consistent, there must be a way to eliminate it. The question is how? I think it can not be done only by changing the configuration parameters related to echo, especially with this huge delay.

Do you have any other suggestions?

Cheers,

Anto
  ----- Original Message ----- 
  From: Giovanni Miano 
  To: Asterisk Users Mailing List - Non-Commercial Discussion 
  Sent: Sunday, January 15, 2006 2:27 PM
  Subject: Re: [Asterisk-Users] Reducing echo on FXS port


  Try

  In chan_zap.c change the following line:

  #define READ_SIZE 160

  to

  #define READ_SIZE 16

  In zapata.conf

  jitterbuffers=40

  This will also increase system load by a factor of 10. 
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