Asterisk Voice Quality Problems


#1

Hi,

I am running Asterisk 1.2.1 using Digium TDM 400P with 4FXO lines
to connect to the PSTN world. But, I constantly get clipped voice whenever
there is a call placed using Zap channels.
I have tried it all the recommended solutions
- turned off all non essential services on the machine
- ran fxotune
But nothing works.
The only thing that works is reducing the rxgain to around -20. But
this leads to other issues like the hangup on the PSTN line is not detected
by Asterisk.
Anyone have a clue about how to fix the bad quality problem. Any
help will be highly appreciated.

Thanks,
Shyam


#2

Everything down to like -8 is ok, after that it gets to low (normally) in volume - causing effects you described - and more: DTMF tones can screw up too now… (way to low)

So the “push” of volume must come from somewhere else, making such drastical values needed.

What phones ? Do they have a volume setup ?
Can u lower it for like 6 or 10 dB and raise asterisk to like -6 ?

I dont use FXO cards, but dont they have a milliwatt parameter you can configure in the module load command ? To exactly solve issues like this, where the milliwatt needs to be corrected for such loud devices (aka high voltage output?)

I would try 50% for a start.
If the milliwatt is (just a number) 300 by default, look up if there is a commandline switch like -mw 150 (so the half).

Remember to reload the module and asterisk after making changes.


#3

Richard,

I could not find any such option. The options that I found
after looking at the wctdm source file are :

debug
loopcurrent
reversepolarity
robust
opermode
timingonly
lowpower
boostringer
fastringer
fxshonormode
battdebounce
battthresh
alawoverride

No option for milliwatt is present. Is it any of the above options?
Or are you talking about some other module, I looked at the
options for the wctdm kernel module.

Thanks,
Shyam


#4

Well, i dont know, i dont have this card.

I just thought there should (could/must) be an option to “tune” the sensetivity of the card’s ports ?

Would be a shame if not…

Is there any documentation of this card regarding the sensitivity of the ports ? Maybe there is a solution ?