[Live-devel] Problem with NTP timestamps in SR packets with Flir A320 camera source

Ross Finlayson finlayson at live555.com
Sat Jan 9 02:02:46 PST 2010

>The problem is the camera is using the time since the camera was 
>last rebooted for the NTP time values in the SR reports (which in my 
>case was about 30 hours and now is about 10 min).

This is legal (although unusual).  The NTP timestamps don't have to 
actually be set to the 'true' time using the NTP protocol.

>I don't know if this points to a bug in the SR handling code in LiveMedia.


>   In RTPReceptionStats::noteIncomingSR() 0x83AA7E80 is always 
>subtracted from theNTP seconds value and this caused the reported 
>presentation time value to wrap around and report something way out 
>in the future (around 2038).

That's fine.  The presentation times are still valid, even though 
they don't correspond to the 'true' time.  Just remember to have your 
client call "RTPSource::hasBeenSynchronizedUsingRTCP()" to check when 
the presentation times have become RTCP-synced, and compensate 


Ross Finlayson
Live Networks, Inc.

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