[Live-devel] Restoring ORIGINAL presentation time and duration on client side

[Ross Finlayson]

At 10:30 AM 11/9/2005, you wrote:
>Is it possible to retrieve ORIGINAL presentation time
>and sample duration on the client side?

As I've explained several times already, the "presentationTime" 
passed to a receiver (that reads derives from "RTPSource") *is* the 
'original' presentation time (i.e., the presentation time that was 
specified by the server).  See 
<http://www.live555.com/liveMedia/faq.html#separate-rtp-streams>

As for 'sample duration' - i.e., the "durationInMicroseconds" 
parameter.  Unfortunately "RTPSource" and its subclasses don't set 
this parameter (so it gets the default value of zero).  In general, 
there's no good way for the receiving RTP implementation to compute 
the duration of received data - other than just using the difference 
between successive presentation times.

>The reason why this is important is that exact
>original timestamps and diration make is MUCH easier
>to synchronize multiple streams in DirectShow on
>Windows. If there was a way to pass the original
>DirectShow samples' presentation time and duration to
>the client side- DirectShow would do all the work
>required to synchronize the streams.

As I noted above, the RTPSource's "presentationTime" value will be 
accurate (provided, of course, that you're also implementing 
RTCP).  So, you can (in fact, should) use this for synchronization.


	Ross Finlayson
	Live Networks, Inc. (LIVE555.COM)
	<http://www.live555.com/>