Hi Richard-

Thanks very much for your reply. Please allow me to answer in reverse order - first in the Wireshark screencap (see link below) the two red arrows are pointing at media packets, not SID. The sequence number advances by 1 but the RTP timestamp advances 640 (should be 320 for AMR-WB).

Second, the stream is not transcoded, but I'm trying to narrow down whether there may be "rate correction" happening, and if so where it's occurring. The carrier says they are not sending media packets with non-matching sequence number and RTP timestamp increments, at least not on a regular basis (i.e. 10 to 15% of a 2 hour call).

-Jeff

Quoting Richard Fuchs via sr-users <[email protected]>:

I don't know if my original reply to this went through to the list or not, so I'm sending it again:

Is this stream actually produced by rtpengine (i.e. from transcoding) or just a relay? Because this looks like just regular DTX behaviour from a normal AMR sender, i.e. send a SID frame and then not transmit anything for up to 200 ms or so. Rtpengine itself doesn't produce DTX streams.

Cheers


On 21/05/2024 12.45, Jeff Brower via sr-users wrote:
Rtpengine support-

I am re-posting again, as I noticed on the SR-USERs web page no HTML or inline images are showing (https://lists.kamailio.org/mailman3/hyperkitty/list/[email protected]/latest?count=200).

The Wireshark screencap that demonstrates the issue is uploaded at:

https://www.signalogic.com/images/rtpengine_wireshark_capture_timestamp_jump.png

all other info remains the same.

Thanks, Jeff

----- Forwarded message from Jeff Brower <[email protected]> -----
   Date: Fri, 17 May 2024 17:10:10 +0000
   From: Jeff Brower <[email protected]>
Subject: Fwd: [SR-Users] rtpengine timestamp jumps
     To: [email protected]

Reposting this. If there is an issue with HTML format and/or wireshark screen cap and I need to upload that separately somewhere else, please let me know. Thanks.

-Jeff

----- Forwarded message from Jeff Brower <[email protected]> -----
   Date: Thu, 09 May 2024 05:32:27 +0000
   From: Jeff Brower <[email protected]>
Subject: [SR-Users] rtpengine timestamp jumps
     To: [email protected]

 Hi rtpengine experts,

We have some customers processing long multi-party call pcaps using mediaMin who are reporting large amounts of packets with timestamp jumps but no packet loss (for instance 10% of packets over a 1 hr 45 min call). For example, in the Wireshark excerpt shown below, packets 6 and 8 sent by rtpengine show a timestamp increment of 640, but sequence number increment of 1:

 [screencap link at https://www.signalogic.com/images/wireshark_capture_timestamp_jump.png]

In the mediaMin output packet log we typically see sections similar to:

   :
   :
Seq num 98584              timestamp = 3902252372, rtp pyld len = 33 media-R
Seq num 98585              timestamp = 3902252692, rtp pyld len = 33 media
Seq num 98586              timestamp = 3902253012, rtp pyld len = 33 media-R
Seq num 98587              timestamp = 3902253332, rtp pyld len = 33 media
Seq num 98588              timestamp = 3902253652, rtp pyld len = 33 media-R
Seq num 98589              timestamp = 3902253972, rtp pyld len = 33 media
Seq num 98590              timestamp = 3902254292, rtp pyld len = 33 media
Seq num 98591              timestamp = 3902254612, rtp pyld len = 33 media-R
Seq num 98592              timestamp = 3902254932, rtp pyld len = 33 media
Seq num 98593              timestamp = 3902255252, rtp pyld len = 33 media
Seq num 98594              timestamp = 3902255572, rtp pyld len = 33 media-R
Seq num 98595              timestamp = 3902255892, rtp pyld len = 33 media
Seq num 98596              timestamp = 3902256212, rtp pyld len = 33 media
Seq num 98597              timestamp = 3902256532, rtp pyld len = 33 media
Seq num 98598              timestamp = 3902256852, rtp pyld len = 33 media-R
Seq num 98599              timestamp = 3902257172, rtp pyld len = 33 media
Seq num 98600              timestamp = 3902257492, rtp pyld len = 33 media-R
Seq num 98601              timestamp = 3902257812, rtp pyld len = 33 media
Seq num 98602              timestamp = 3902258132, rtp pyld len = 33 media
Seq num 98603              timestamp = 3902258452, rtp pyld len = 33 media
Seq num 98604              timestamp = 3902258772, rtp pyld len = 33 media-R
Seq num 98605              timestamp = 3902259092, rtp pyld len = 33 media
   :
   :

where media-R packets are timestamp gap repairs (i.e. frame loss concealment). The behavior tends to be bursty, but once it gets going it goes for a while and seems relatively consistent.

Is this expected behavior for rtpengine ? If so is rptengine in turn dealing with some type of "slow packet rate" issue from a remote sender ?

Thanks, Jeff
----- End forwarded message -----

----- End forwarded message -----




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