Re: [Ekiga-list] wired VOIP problem and how to playback rtp data under linux

[Damien Sandras <dsandras seconix com>]

Hi,


I would suggest that you make sure it is not a soundcard problem.
Also try other codecs than iLBC, iLBC had been buggy in the past in
Asterisk.

Le mardi 24 octobre 2006 à 20:50 +0200, Konrad Karl a écrit :
> Hi,
> 
> the following VOIP problem is giving me headaches..:
> 
> 3 machines connected via VPN  A---Z---B
> Z is a openvpn server and also runs asterisk.
> The ping times from A to B are in the range of about 30 msec.
> All calls are made via the asterisk server using ILBC.
> 
> I want to track down a wierd problem: when talking
> from A to B (client software does not seem to matter, I
> tried ekiga under linux, X-lite under windows XP)
> then the sound starts to get distorted after about one minute
> and totally unintelligible after about 2 minutes.
> 
> A redial gives again clear sound for about 1 minute (perhaps even less)
> 
> Then I made tcpdump traces on machine Z capturing all RTP traffic and
> it seems that the timestamps of machine B are getting offset over the
> time - the samplerate seems to be 8000.25 Hz or so - while machine
> A keeps perfect time. B is a Laptop, a new Quanta machine,
> exact name escapes me for the moment, with Intel ICH6 
> chipset and Realtek ALC880 sound system. Before I updated the sound
> driver, the times were differing by 5 seconds after a 30 seconds call
> and I could hardly understand the other party during a few seconds
> at the beginning.
> 
> Now I want to listen to the captured RTP traffic to see if it is 
> already distorted before entering the asterisk server.
> (preferably under Linux) 
> 
> Hints about how to do this would be very much appreciated.

You can do it with ethereal, using PCMU or PCMA, but nto any other
codec.

> 
> NB. today I bought a USB headset, perhaps it will cure this problem
> but I am still curious.
> 
> Best greetings,
> Konrad
> 
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 _      Damien Sandras
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