Subject: [MMUSIC] RTSP: RTP timestamps when playing after pause

From: Magnus Westerlund <[email-masked]>
Date: Fri, 18 Jan 2002 08:33:27 +0100

Hi,

At the RTSP teleconference last week we discussed what to do with RTP
timestamps when you PAUSE, waits some time then do PLAY. I thought there
was going to be a new bug report on sourceForge, has somebody forgotten?

The following was my interpretation of the proposal for a solution. The
RTP timestamp is equal to display time. So it you do pause, wait five
seconds and then press play the timestamp will be 5 seconds later for
the first packet when resuming.

This behavior works fine when the play contains a range, for queued play
following after each other, but not for resuming play. The reason is the
delay between a user on the client side pressing pause and until the
client stops receiving data packets. If the client then does resume
play, i.e. play without range, the server will continue after the last
packet sent. In this case the client needs to show first the packet
arriving directly after pressing pause (which according to the used
model is past time), and then correctly synchronize the new packet which
has a significant offset in timestamp corresponding to the period of
pause the server has seen. The solution to this is to not use resume
play and instead say play from the point where user pressed pause.

On the other side I don't believe any other model will not have worse
problems.

Regards

Magnus Westerlund

Audio Technology, Ericsson Research
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Ericsson Radio Systems AB  | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email-masked]

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