Ramesh,
On 5/22/17 3:00 PM, Ramesh Kuppili wrote:
SIP Gurus,
I have a situation where I am receiving multiple RTP stream from the
same IP address and port number. But with different SSRC. The media in
the both streams is the same (audio, more precisely ringback tone). How
should I handle this scenario.
1. Should I accept one stream and ignore the other. If so, which stream
should I prefer.
2. Should I mix both the streams and play on the endpoint. I am almost
certain that mixing both the audio streams will result in undesirable
ringback like tone.
Is there a any standard that specifies how I should handle this case.
Any pointers in this regard is really appreciated.
I'm not an expert in media processing, but I'll try to provide some context.
First can you confirm that you are talking about media associated with a
single 5-tuple negotiated via a single m-line in SDP?
Historically SIP didn't talk about this. In the primary usage for simple
VOIP I think the expectation has been that only a single RTP stream will
used at any one time. But that stream may change over time. (For
instance when transitioning from in-band ringback to media from the
callee.) So I think it has been fairly typical to simply play out what
is received without regard to SSRC.
However more advanced uses of SIP have used multiple SSRCs. There was
never any formal prohibition against doing this, but because there was
no standardization about how it should be processed there have been no
guarantees of interoperable behavior when doing so.
Some of the other people who post here can probably give you better
advice on how best to cope when receiving from multiple SSRCs.
More recently there has been explicit work to standardize such usage. In
particular:
https://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-38
This results in using multiple m-lines, each describing an RTP stream
but all sharing the same 5-tuple. Presumably that isn't your case.
Thanks,
Paul
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