[Live-devel] time difference

[Ross Finlayson]

I’m sorry, but I’m not sure that I understand your question.  However, please note that LIVE555 programmers should never have to deal with RTP timestamps directly.  Our software automatically uses RTCP to convert presentation times to RTP timestamps (when transmitting) and back to presentation times (when receiving). Presentation times are all that you need to think about.  (Therefore, please don’t mention the word “timestamp” again; this will lead to unnecessary confusion.)

Also, if you haven’t done so already, please read our FAQ; especially these entries:
	http://live555.com/liveMedia/faq.html#separate-rtp-streams
	http://live555.com/liveMedia/faq.html#rtcp-synchronization-issue

Finally, if you are receiving a RTSP/RTP/RTCP stream (i.e., if you are a RTSP client), then it’s perfectly OK for the presentation time of the received frames (after RTCP synchronization) to be different from ‘wall clock’ time.  This can happen if the sender (i.e., RTSP server) has a clock that is not set to ‘wall clock’ time.  But that’s OK; it’s only the *difference* between successive presentation times that matters (for proper playback, and audio/video synchronization).

(If, however, you are writing a RTSP *server* that uses our code, then the presentation times that it sends (for each of its frames) should be aligned with the server computer’s ‘wall clock’ time (i.e., the time that you’d get by calling “gettimeofday()”.)

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