[SIPForum-discussion] RTP ssrc change during a call

Maciej Wasiel Maciej.Wasiel at dialogic.com
Fri Aug 19 00:48:37 UTC 2011

Was the timestamp restarted? If not, then this is not a stream re-start and you should treat the new audio as part of the original stream.

Maciej Wasiel
Software Engineer, Dialogic Research Inc | Address: 15 Crawford Street, Needham, MA 02494 | Phone: (781) 433 9771 | Mobile: (508) 740-2641 | Fax: (781) 433 9255
Email: maciej.wasiel at dialogic.com

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Raghul Prasanna
Sent: Thursday, August 18, 2011 10:21 AM
To: HM Kias; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] RTP ssrc change during a call


nope source had different ssrc..


--- On Thu, 18/8/11, HM Kias <hmkias at gmail.com> wrote:

From: HM Kias <hmkias at gmail.com>
Subject: Re: [SIPForum-discussion] RTP ssrc change during a call
To: "Raghul Prasanna" <raghul82 at yahoo.co.uk>
Cc: discussion at sipforum.org
Date: Thursday, 18 August, 2011, 7:42
Hi Rahul,

This is one kind on scenario for  SSRC.

At the start of an RTP session, the sender randomly chooses an initial value of the timestamp and SSRC. If both the sender and receiver happen to choose the same SSRC, both sides choose again to ensure each have a different SSRC.

Does this happen?


On Fri, Aug 12, 2011 at 2:06 PM, Raghul Prasanna <raghul82 at yahoo.co.uk</mc/compose?to=raghul82 at yahoo.co.uk>> wrote:
Hello All,

I have seen a call where the far end initially starts with a SSRC and then the next rtp from the same source has different ssrc field, I am looking for the wireshark I had so that  I can share it with you guys, will post it if I find that.

Is this acceptable? I remember the user saying one way audio or something like that.

This is not a conference call, because I was wondering if the far end was a mixer and the rtp was actually coming from different source, but then realised that it will have CSRC if it was from a mixer to identify the actual source.

Anyways is it OK to change SSRC by a source during a call, if it can what will be effect on the call?


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HM Kias

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