Very interesting, many thanks. This will at least give us a starting
point.
The VoIP equipment we have is only capable of using one of three codec's
- G711, G723.1 and G729a. We use G711 as the general quality of the
other codecs is not fantastic. However, it has been noted that the
problem is evident no mater what codec is used. This was a quote from
one of the user -
"An intermittent BUZZ occurs at some times and lasts for around 1-6
seconds. The buzz can usually only be heard by one party although
sometimes both parties do hear the buzz, with one party getting the
problem much worse than the other. By altering the CODEC, the buzz can
be transformed into a series of very rapid clicks."
Thanks,
Chris
-----Original Message-----
From: Jacques, Olivier (OpenCall Test Infra)
[mailto:olivier.jacques@xxxxxx]
Sent: 06 October 2006 07:43
To: frnkblk@xxxxxxxxx; Community support list for Wireshark
Subject: Re: [Wireshark-users] VoIP analysis and assessment
> Yes, Wireshark can re-construct the audio, but it's without the
> jitter-buffer of the client device in mind. It merely strings the RTP
> packets together and makes a WAV file. I learned this the hard way.
This is not true anymore. The "VoIP Calls/RTP Player" feature (as
available in latest development releases of Wireshark 0.99.4) allows to
reconstruct the audio _with_ jitter buffer in mind.
It works this way:
- You specify the jitter buffer size (in ms)
- You press "Decode" button: Wireshark re-construct the audio.
- RTP packets with an excessive jitter are dropped
- The number of RTP packets dropped are counted and displayed
- You can listen to resulting audio from within Wireshark
See picture attached.
Of course, this doesn't take into account other client-side parameters
like adaptive jitter buffer, bad clocking, bad RTP implementation, ...
Last warning, RTP player supports G711 A/u law codecs at the moment. It
is possible to add your own codecs, the RTP player feature being well
designed for that, but codecs licensing issues will certainly prevent
many codecs to be included in Wireshark.
Olivier.
