RE: [Wireshark-users] RTP stats explaination

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Hi,

Are you using some sort of silence suppression (or voice activity detection) ?
If not, then the packets of your stream should be evenly spaced over time, i.e. "Max delta" should not be very different from the RTP packetization time. Go to the packets with high "Delta" and verify that you have gaps in your RTP stream. It seems you have some timing issues with your app.

Lars



-----Original Message-----
From: wireshark-users-bounces@xxxxxxxxxxxxx [mailto:wireshark-users-bounces@xxxxxxxxxxxxx] On Behalf Of Arif Hossain
Sent: vendredi 18 mai 2012 12:22
To: wireshark-users@xxxxxxxxxxxxx; netfilter-devel@xxxxxxxxxxxxxxx; netfilter@xxxxxxxxxxxxxxx; CentOS mailing list; debian-user@xxxxxxxxxxxxxxxx
Subject: [Wireshark-users] RTP stats explaination

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Hi all,
We are getting very poor quality of voice during testing of a new filtering application of us.

The application receives packets from kernel using netfilter_queue library. Then insert the packets into a new user managed queue and does some transformations on it, like concatenation of udp payload.

The network is healthy. Its inside our lab. And it does not drop packets or anything .

In our app we do not forward packet immediately. After enough packet received to increase rtp packetization time (ptime) the we forward the message over raw socket and set dscp to be 10 so that this time packets can escape iptable rules.

>From client side the RTP stream analysis shows nearly every stream as problematic. summery for some streams are given below :

Stream 1:

Max delta = 1758.72 ms at packet no. 40506 Max jitter = 231.07 ms. Mean jitter = 9.27 ms.
Max skew = -2066.18 ms.
Total RTP packets = 468   (expected 468)   Lost RTP packets = 0
(0.00%)   Sequence errors = 0
Duration 23.45 s (-22628 ms clock drift, corresponding to 281 Hz (-96.49%)

Stream 2:

Max delta = 1750.96 ms at packet no. 45453 Max jitter = 230.90 ms. Mean jitter = 7.50 ms.
Max skew = -2076.96 ms.
Total RTP packets = 468   (expected 468)   Lost RTP packets = 0
(0.00%)   Sequence errors = 0
Duration 23.46 s (-22715 ms clock drift, corresponding to 253 Hz (-96.84%)

Stream 3:

Max delta = 71.47 ms at packet no. 25009 Max jitter = 6.05 ms. Mean jitter = 2.33 ms.
Max skew = -29.09 ms.
Total RTP packets = 258   (expected 258)   Lost RTP packets = 0
(0.00%)   Sequence errors = 0
Duration 10.28 s (-10181 ms clock drift, corresponding to 76 Hz (-99.05%)

Any idea where should we look for the problem?


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- -aft
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