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UDP/RTP stream analysis PL type 96

asked 2021-05-21 12:07:11 +0000

sporex gravatar image

Hello, I am analyzing a UDP/RTP stream with PL type 96 (payload is OPUS). The RTP analysis shows MaxJitter=0, ForwardDifference=0. Only forward Delta has realistic values.

Earlier on, I was setting the PL type in the stream equal to zero (with the same OPUS PL) and I got realistic results for jitter and forward difference. The values for ForwardDifference beeing the same as with PL=96.

Can anyone explain this?

PS: there is no SIP involved.

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answered 2021-05-24 06:48:42 +0000

Anders gravatar image

Hi, I think that as paload type 96 is dynamic meaning that the actual payload type is signaled in the set up protocol SIP/SDP. Without this info there is no way to know the cloack rate or frequency. I guess we ought to have a way to set this manually. What version of Wireshark are you using? I think we may have defaulted to 8000Hz. Payload type 0 is defined so the values for that payload type will be used in that case, PCMA if memorty serves, clockrate 8kHZ.

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Hi, thx for your response. For me it's not a real problem. I was just asking out of curiosity.For me it's only important to see the forward difference in order to adjust jitter buffers. BTW I am using TShark on a debian system (latest apt-get)

sporex gravatar imagesporex ( 2021-05-24 13:05:34 +0000 )edit

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Asked: 2021-05-21 12:07:11 +0000

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Last updated: May 24 '21