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[Ccrtp-devel] How to send a RTCP SR packet first?


From: Martin Runge
Subject: [Ccrtp-devel] How to send a RTCP SR packet first?
Date: Mon, 1 Oct 2007 10:04:12 +0200
User-agent: KMail/1.9.7

Hi .*,

I am evaluating ccrtp for an audio streaming solution (muroa.berlios.de). So 
far, I found all the features I need in ccrtp (1.5.1), but there is one thing 
left:

How can I make the sender send a RTCP SR right at the start? I need it, to 
have the RTP-NTP timestamp correlation to start playback on the client 
synchronously to other clients.

Background: What I want do do is start a new session with a burst, so the 
client can start playback immediately with the first data packet and gets its 
receive buffer filled anyway. I managed to tell ccrtp to perform a burst in 
starting the RTP timestamp at negative numbers, so all data packets with RTP 
timestamp < 0 will be sent immediately. All packets with RTP ts > 0 will be 
correctly scheduled.

With that burst, the client can start playback immediately after receiving the 
first packet. The problem is, that I need the first SR early. I have seen in 
the source, the first RTCP packet will be a RR, because no data packets have 
been sent yet. The second RTCP packet is a SR (data has been sent in the 
meanwhile), but it arrives after ~20 RTP data packets (5% bandwidth for 
control).

Any ideas, how to get a SR packet out of an unmodified ccrtp stack at before 
or directly after the first data packet?

By the way: where to specify the NTP timestamp in the API?

I would be thankful for any tips or ideas regarding this topic.

Thanks in advance,
Regards, 

Martin




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