[Live-devel] [PATCH] Provide access to the full time mapping in the last received sender report

[Ross Finlayson]

> The attached patch allows access to the last received sender report RTP timestamp, making it possible to get the full NTP/RTP time mapping currently in effect (since it was already possible to get the last received NTP timestamp).
>  
> This information can be used to calculate the wallclock timestamp of each sample in a live stream sent by an IP camera, according to the camera’s clock.

I think you may not realize that our software already does this automatically!  Whenever each frame of data is received (from a "RTPSource" subclass), then the "presentationTime" value will automatically get set to the value calculated from RTCP's 'RTP timestamp-to-NTP' mapping, as long as it has received at least one RTCP "SR" packet.

In other words, receiving application software should never need to look at RTP timestamps (or RTCP-reported NTP times) directly.  Instead, it just needs to look at the "presentation time" values for each received frame.

For more information see
	http://www.live555.com/liveMedia/faq.html#separate-rtp-streams
and
	http://www.live555.com/liveMedia/faq.html#rtcp-synchronization-issue

(Therefore, I won't be applying your patch, unless you can demonstrate a clear need for it.)

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

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