[asterisk-users] Help - Poor Voice Quality

[Bryan M. Johns]

Run mtr on your server against the registration server at Teliax and  
look for bad hops on your route to and fro.

If you don't find anything there, you may want to fire up ethereal  
and capture packets on a few calls and look through them for error  
data that may be contributing to bad voice quality.

I hope this is helpful.

Bryan M. Johns
Partner
Shelton | Johns Technology Group
office: 678:248:2637 x:1500
direct: 678:229:1809
mobile: 404.259.9216
iaxtel: 700:248:2637 x:1500
http://www.sheltonjohns.com


On Feb 6, 2007, at 8:09 PM, Jim Duda wrote:

> I'm struggling to get my VOIP installation to be acceptable.  I'm  
> looking for advice on what else I can look for.
>
> My system:
> o Teliax VOIP service, voip-ny1 proxy
> o RCN Cable Internet Service (3Mbps download, 500kbps upload, 6ms  
> average jitter)
> o 3.2 GHZ P4 Server (runs asterisk, firewall, other stuff)
> o server lightly loaded
> o Linux kernel 2.6.19.2
> o Shorewall Firewall software with QOS configured for VOIP P1
> o Asterisk 1.4.0
> o Sipura SPA-2000
> o Grandstream GXP-2000
> o IAX connection to teliax
>
> Outbound voice quality is many times horrible, to the point where  
> ppl say they cannot hear me.  The voice often drops out.  Inbound  
> quality seems to cut in and out too.
>
> I downloaded the myVoipSpeed VOIP analyzer.  It indicates that I  
> have plenty of download and upload bandwidth.  I also have good  
> jitter.  The tool doeesn't find any packet loss whatsoever.
>
> My RCN cable company cannot find anything wrong with my cable  
> modem.  No packet loss.  I'm supposed to be paying for 10M bit  
> downloads, but only getting 3M bit.
>
> I've been on the shorewall firewall and confirmed that I have the  
> firewall configured properly for VOIP QOS.
>
> I'm using the basic asterisk iax.conf setup with only those changes  
> required to interface with the teliax service.
>
> I have the same issues with both the Sipura Adapter and the  
> Grandstream phones, however, I do believe the Grandstream appears  
> worse at times.
>
> I've attempted to analyze the IAX traffic using the Wireshark  
> ethernet protocol analyzer.  Everything looks okay best I can tell.
>
> What else can I do to analyze why the voice quality is so bad?
> What can I do in Asterisk to help track down where the problem is?
>
> I want to make this VOIP work.
>
> Thanks for any help.
>
> Jim
>
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