The RTCP SR NTP timestamp is only valid in direct comparison with a NTP timestamp from another stream of the same reference clock. So you can use it to synchronize the presentation times of multiple streams in the same session. You're not supposed to use it to directly generate a presentation time since you have no guarantee that you and the sender share a reference clock.
This is incorrect. The information in incoming RTCP "SR" packets is used to generate presentation times from incoming RTP packets' timestamps. These presentation times - like the RTP timestamps themselves - are (necessarily) based on the sender's clock (because that was the only clock available to the entity (the sender) that created the presentation times).
(Yes, it's true that receivers' clocks will typically drift somewhat relative to the sender's. There are a number of medium-specific techniques (e.g dropping/repeating audio samples and/or video frames) that receivers can use to compensate for this, over time. But the presentation times - even though based on the sender's clock - remain valid, and necessary.)
-- Ross Finlayson Live Networks, Inc. http://www.live555.com/ _______________________________________________ live-devel mailing list live-devel@lists.live555.com http://lists.live555.com/mailman/listinfo/live-devel
