Nitin,
It is possible for the Gateway to change its SSRC when it is using mixer
or any other different media source.
Please see below.
Section 3 of RFC 1889
=======================
Synchronization source (SSRC): The source of a stream of RTP packets,
identified by a 32-bit numeric SSRC identifier carried in the
RTP header so as not to be dependent upon the network address.
All packets from a synchronization source form part of the same
timing and sequence number space, so a receiver groups packets
by synchronization source for playback. Examples of
synchronization sources include the sender of a stream of
packets derived from a signal source such as a microphone or a
camera, or an RTP mixer (see below). A synchronization source
may change its data format, e.g., audio encoding, over time. The
SSRC identifier is a randomly chosen value meant to be globally
unique within a particular RTP session (see Section 8). A
participant need not use the same SSRC identifier for all the
RTP sessions in a multimedia session; the binding of the SSRC
identifiers is provided through RTCP (see Section 6.4.1). If a
participant generates multiple streams in one RTP session, for
example from separate video cameras, each must be identified as
a different SSRC.
________________________________
From: Nitin Kapoor [mailto:[email protected]]
Sent: Tuesday, December 29, 2009 6:23 PM
To: Uttam Sarkar
Cc: [email protected]
Subject: Re: [Sip-implementors] Two Media Stream in one Dialog
Uttam,
You are correct...i checked the the SDP, and unable to find multiple
m-lines into it, as well as the RTP stream source and destination ip and
port is also same...
The only thing i have noticed that the SSRC are the different in both
the RTP packets which is going from source and which is coming from
destination....
Could you please tell me, what could be the possible reason for this....
i never faced this problem before.....
Thanks,
Nitin Kapoor
2009/12/29 Uttam Sarkar <[email protected]>
Can you please check if the SDP has multiple m-lines or not? Please
check the source and destination IP address (along with port) of RTP
stream. If they are same, probably RTP is changing the SSRC that's why
you might see multiple streams.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
Nitin Kapoor
Sent: Tuesday, December 29, 2009 12:48 PM
To: [email protected]
Subject: [Sip-implementors] Two Media Stream in one Dialog
Hello All,
I am facing the issue with one of my customer where he is getting two
media
streams in one call and they are using SBC(Nextone)
I checked the signaling & RTP traces and everything looks okay to me.
As per the traces one RTP packet is going out and the other is coming
in, *But
whenever i am decoding the packets and trying to hear the conversation
so
both are the different conversation. *
Could you please let me know is it possible where i can have the two
media
streams in one call when this is the not the conference call. And if
this is
possible then what is the scenario where its possible.
Thanks,
Nitin Kapoor
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