[Live-devel] Synchronize the "RTCP" time using RTSP Range ?

[Jeff Shanab]

I record video from a security camera. I do not want to throw away up to the first 2 seconds so I measure the offset and adjust my timestamps to the timebase of the machine. When I get the sync notification I adjust the adjustment. This adjustment is continually applied to all timestamps.

It is not the ntp time of the server, but it is an exact offset from the beginning of the hour of a ntp syned machine, we split our video on the hour boundry.
We let the camera independently sync to a ntp server and it all stays very close.






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From: live-devel-bounces at ns.live555.com [mailto:live-devel-bounces at ns.live555.com] On Behalf Of Ross Finlayson
Sent: Monday, March 18, 2013 3:57 PM
To: LIVE555 Streaming Media - development & use
Subject: Re: [Live-devel] Synchronize the "RTCP" time using RTSP Range ?

What I was suggesting is this "missing" NTP information (before RTCP "SR") could perhaps be computed from RTSP PLAY answer.
It is quite annoying to drop data waiting for RTCP "SR" because we cannot send the timestamp through RTSP/RTP/RTCP mechanism.

What I can probably do is upgrade our server code so that it sends a RTCP "SR" packet immediately upon handling a "PLAY" command (before the first RTP packet is sent).  (I think this is actually prescribed in one of the IETF RFCs.)  That won't be 100% reliable (because this first RTCP packet may get lost, but most of the time it will eliminate the delay before RTCP synchronization occurs.

Yes, it would be nice if the "RTP-Info:" data included a NTP-format time (the same as in RTCP "SR"s), but unfortunately that's not in the standard.

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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