[gst-devel] I thought SSRC was a constant

[Wes Miller]

I have two streams feeding into the udpsrc attached to a gstrtpbin.  One
stream is live data and the other is from a audiotestsrc intended to wake up
the pipeline (blocked waiting on the async recv_rtp_src_%d_%d_%d pad to
connect.)  It is not always possible to know the order the streams will
arrive, so either may be "first".





noise stream =======\
                     >>> udpsrc---->gstrtpbin
live stream=========/




When the first stream connects, cb_pad_added in the receiver pipe finishes
the async connection from  the recv_rtp_src_%d_%d_%d pad to the rest of the
receive pipe.  

When the second stream comes online, I get a second callback indicating a
new recv_rtp_src_%d_%d_%d pad has been requested. Makes sense, the second
stream should have a different SSRC.

Wanting to know which stream was which, I added an identity to the pipe
producing the "noise" stream between the payloader and udpsink and connected
a pad_probe to it.  The cb_pad_probe() does nothing more than tell me the
SSRC of the packets.  Figured I could use this info to tell the main
gstrtpbin which connection to keep.





               ,---padprobbe() {print ssrc}
               |
--->encodeer-->identity-->udpsink === noise stream =======\
                                                           >>>
udpsrc---->gstrtpbin
                                      live stream=========/





Well, lo and behold, the SSRC reported from each packet is different!
Siimilar looking numbers, but different.  What I don't get is a message from
the cb_pad_added() in the main pipe telling me each different SSRC is
requesting a new recv_rtp_src_%d_%d_%d pad!

So, friends, why are the SSRCs different and whay does the gstrtpbin see
them as equivalent?  How does it tell the next stream is different? *both
streams have payload type = 96).

I am about to add an identity between the udpsrc and the gstrtpbin to see it
sees the same thing.  Will add that information when  have it.

Warmly,

Wes




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