[asterisk-users] Dropouts and echo

[Steve Totaro]

Tom Lanyon wrote:
> Hi all,
>
> Can I ask that you please keep my personal address in the To: or CC:  
> in this thread as for some reason I'm only getting half of the list  
> emails coming through, and they're not showing up on the digium  
> pipermail archive either. The list archive on http://marc.info seems  
> to have the whole thread though.
>
>   
>> Have you tried changing the RTP packet size on the phones from
>> .30(default I believe) to .20?
>>     
>
> The RTP packet size is currently "0.030" which is the default (I  
> wasn't aware we could change it). Would changing to 0.020 help?
>   
Why don't you try it?  Echo and drop outs usually require trying many 
different things (especially echo).  That is a place to start.  Make 
sure you document your changes and so you can easily roll them back.  
Finding your actual problem will most likely be a trial and error 
process, so start trying.
>> Turn OFF CDP on the phones.
>>     
>
> The phones don't support CDP as far as I can find; I know Linksys is  
> a subdivision of Cisco, but these phones are actually made by Sipura.
>
>   
>> As for Echo Canceling, that is the job of the device that
>> does VoIP/PSTN gateway functions.
>>     
>
> As mentioned before, this is SIP <-> SIP, so the echo isn't  
> introduced by the PSTN. I'll keep experimenting with volume levels  
> and environmental issues to try and fix the echo.
>   
Depending on how you define echo, you can try different things with the 
phones such as pressing mute, stuffing the handset with something to 
dampen the sound, have both parties speak softly and then try loud.  
Again, document your results.
>> What kind of switch are you connecting the phones to? I've seen that
>> behaviour with cheap Repotec switches (24+2Gigabit). Just replacing it
>> with a different one fixed the problem.
>>     
>
> The switch is indeed a poor quality one. My next step is to replace  
> it with something decent and see if it helps. I wasn't sure whether  
> this could be the cause so it's good to have your input.
>   
A switch could cause drop outs but I doubt echo so much.  While the 
first thing you should do is have decent quality gear on your network, I 
would also look at timing issues on your box and change RTP from packet 
size to 20.  Make sure ZAPTEL or ZTDUMMY is loaded, make sure your 
system is using RTC and no HPET.


Thanks,
Steve