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RTP telephony stream shows 0 jitter

asked 2022-06-09 15:48:32 +0000

I have a capture file of an RTP stream and wanted to check my jitter levels. However when i used the RTP->RTP Streams option under telephony these are the jitter values displayed: Min Jitter = -1 Mean Jitter = 0 Max Jitter = 0 I know for a fact that these values cannot be correct as there is a variance in delay so the mean can't be 0. I've seen some people suggesting that it could be a clock synchronization problem but I have no idea how to solve it. Any help is much appreciated!

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Please add the Wireshark version info to the question.
(wireshark -v or Help->About Wireshark:Wireshark)

Chuckc gravatar imageChuckc ( 2022-06-09 19:50:07 +0000 )edit
Chuckc gravatar imageChuckc ( 2022-06-09 19:56:42 +0000 )edit

Wireshark 3.6.3 (v3.6.3-0-g6d348e4611e2)

UniStudent122222 gravatar imageUniStudent122222 ( 2022-06-09 20:17:27 +0000 )edit

Can you share a packet capture on a public file share and add a link to it in the question above?

If clock_rate is not set (tap-rtp-analysis.c) min_jitter is not calculated.
clock_rate is set based on the payload type.

Chuckc gravatar imageChuckc ( 2022-06-10 16:59:40 +0000 )edit here is a google drive link with the capture file. Thank you for your help!!

UniStudent122222 gravatar imageUniStudent122222 ( 2022-06-11 10:53:38 +0000 )edit

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answered 2022-06-11 15:54:33 +0000

Chuckc gravatar image

I have not been able to find a sample capture with dynamic payload that is not DTLS.
The clock rate for dynamic payloads is extracted from a string in the packet (tap-rtp-analysis.c) that is not available due to the encryption.
Here is a similar issue: 17905 - RTCP compound packets not shown (closed)

All of the malformed packets in the capture are worth opening a new issue - Wireshark Gitlab Issues
(ReportingBugs, Wishlist - select Bug). Please add a link to it that points back to this question and link to the sample capture in the Gitlab Issue.

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Assuming this is SRTP/SRTCP these are not malformed, just not decrypted.

Jaap gravatar imageJaap ( 2022-06-11 16:08:05 +0000 )edit

There is a mix of [Encrypted RTCP Payload - not dissected] and [Malformed Packet (Exception occurred)]. Maybe not recognizing as encrypted sometimes?

Chuckc gravatar imageChuckc ( 2022-06-11 16:14:41 +0000 )edit

Without the associated signalling it's hard to tell from the packet content alone.

Jaap gravatar imageJaap ( 2022-06-12 05:22:08 +0000 )edit

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Asked: 2022-06-09 15:48:32 +0000

Seen: 238 times

Last updated: Jun 11 '22