Subject: RTSP: terminology, time axis

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 05 Mar 1997 19:24:26 -0500

To align with DSM-CC usage, I suggest the use of the terms "normal play
time" (NPT) for the common time line spanning multiple tracks and
"event" (instead of set of streams, presentation, etc.). Also, it should
probably be made clear that that time axis in RTSP should correspond to
the RTP SR time units (NTP timestamps). Otherwise, editing and display
of frame counters becomes difficult.

DSM-CC allows to have nested time axes (contentID), so that a commercial
can have an independent time axis. This would seem to make any type of
counter display and positioning (slider, etc.) at the client very
difficult to implement and greatly complicate the play command (need to
specify contentID as well). Is this necessary, given that a server can
construct a single, uniform play axis easily?

DSM-CC also allows non-zero initial time values. Since the server can
easily reconstruct a zero-based time axis, this only seems to complicate
things, particularly in terms of user interface.

Comments, please.
-- 
Henning Schulzrinne         email: [email-masked]
Dept. of Computer Science   phone: +1 212 939-7042
Columbia University         fax:   +1 212 666-0140
New York, NY 10027          URL:   http://www.cs.columbia.edu/~hgs