Sidetone Issues


#1

My users are experiencing echo sidetone issues on calls from the PSTN to their Polycom SoundPoint IP phones. Various phone models affected (301, 501, 650).

Tried dahdi-linux versions 2.2.0.2 and 2.4.1.2.
Tried asterisk versions 1.6.2.19 and 1.8.4.4

Done fxotune on the PSTN channels

Does not seem to occur on SIP to SIP internal calls.

Using OSLEC as echo canceller.

The person on the PSTN side does not experience echoing. It is only on the SIP/Polycom side. Users of Polycom phones are hearing their own voice echoing.

HELP!?!


#2

That’s echo, not sidetone. Sidetone is deliberately introduced, with low delay.

Your problem lies at the VoIP to PSTN boundary.


#3

[quote=“david55”]That’s echo, not sidetone. Sidetone is deliberately introduced, with low delay.

Your problem lies at the VoIP to PSTN boundary.[/quote]

Basically at the TDM card?

We seem to have noticed somewhat of an improvement when reverting back to dahdi-linux 2.2.0.2. This issue isn’t on every call either. It is very intermittent.


#4

What analog card are you making use of?


#5

TDM410P
Asterisk 1.8.4.4
Dahdi driver version doesn’t seem to matter.
In users.conf txgain is set to -3.6, rxgain is set to 5.4


#6

Ah, sorry, can’t help you with OSLEC.

Your best bet is to go after the DSP-based echo cancellation module for the TDM410, the VPMOCT032.


#7

Ah, sorry, can’t help you with OSLEC.

Your best bet is to go after the DSP-based echo cancellation module for the TDM410, the VPMOCT032.


#8

[quote=“malcolmd”]Ah, sorry, can’t help you with OSLEC.

Your best bet is to go after the DSP-based echo cancellation module for the TDM410, the VPMOCT032.[/quote]

If you’re referring to the hardware module, I ordered the TDM410 with it. It didn’t work very well at all so I removed it as I had much better experience with OSLEC in the past.

At any rate, I believe I have finally managed to subdue most of the echo.

In users.conf, I have each channel set as:
txgain=-4.2
rxgain=5.6

In chan_dahdi.conf I have:
echocancel=512

With echocancel below 128 echo was quite significant. When I upgraded from 1.6.0.x to 1.8.4 I found that 1.8.4 was no longer reading the txgain and rxgain from the chan_dahdi.conf file. I had the similar settings as I have now in the users.conf, but it wasn’t reading them.