Subject: [MMUSIC] Re: RTSP 2.0: [ 1701558 ] Pause response to live streams

From: "Joseph Pallas" <[email-masked]>
Date: Fri, 26 Oct 2007 15:37:56 -0700

> To me it should indicate the point the server is ceasing to deliver
> media on. Also the live media have some time line. Either expressed in
> UTC or in NPT since session start. What ever is used needs to be
> reported. I don't think "now-" would be particular good answer. For that
> reason a clearer text on this would be good.

A simple way to do that is to say that "now" can only be used in
requests, not in responses.

> However, this leads me to another issue related to the content being
> played back. It might be time to be more explicit about the content
> properties related to playback.
...
> However, my question is: Should we define a new SDP attribute that
> expresses the contents major properties to allow RTSP clients to know
> what to handle?

It might be wise to separate that into two questions: (1) should there
be a way to express these properties, and (2) should the properties be
expressed in SDP or in RTSP itself.  I'm kind of biased against SDP
here, because it is generally information about how to interpret the
stream, not how to control it.

Just a thought.
joe

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From: Magnus Westerlund <[email-masked]>
Date: Mon, 29 Oct 2007 10:50:14 +0100

> stream, not how to control it.

Hi Joe,

Yes, you are right that it should be split into two questions. Regarding
number two. I agree that we should be as explicit as possible and where
it is suitable. I agree that it is good that we express as much as
possible in RTSP. However, that will create issues. First it makes it
problematic to do optimized pipelined setups unless the client knows
these properties before sending its requests. Secondly, I would notice
that at least most what at least I consider are actually properties of
the content rather than the control session and therefore belongs in the
content description which SDP is one protocol instance of. This of
course leads to the interesting question if one should indicate it in
only one place or both for covering all potential cases?

cheers

Magnus Westerlund

IETF Transport Area Director & TSVWG Chair
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S-164 80 Stockholm, Sweden | mailto: [email-masked]
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From: "Mike Severa" <[email-masked]>
Date: Mon, 29 Oct 2007 13:28:09 -0700

While this may again be something slightly outside the domain of RTSP,
I'll mention it anyway because it may be relevant for this discussion..

I would argue that it is possible to mix content that has different
properties in this regard within a single session. One could always
argue that if that were so then additional SDP should be required (even
if all that changed were this property). However, I could envision
scenarios where the client may not be the one requesting/controlling
this kind of multiplexing and as such there would be nothing but RTSP to
rely on wrt signalling (i.e., at PAUSE, PLAY time). Whether RTSP needs
to provide support for a use case in which it may not be the primary
means of session control (at least related to this very specific
behavior) is an entirely different (and valid) question. 

Again, I'm not sure of the relevance of this other than it relates to
the behavior and signalling associated with the content properties under
discussion in this thread. The use cases will exist imho, whether they
are more appropriately supported by RTSP or some other means is unclear.

Thanks,

Mike

-----Original Message-----
From: Magnus Westerlund [mailto:[email-masked]] 
Sent: Monday, October 29, 2007 2:50 AM
To: Joseph Pallas
Cc: [email-masked]
Subject: Re: [MMUSIC] Re: RTSP 2.0: [ 1701558 ] Pause response to live
streams

Joseph Pallas skrev:
>> media on. Also the live media have some time line. Either expressed 
>> in UTC or in NPT since session start. What ever is used needs to be 
>> reported. I don't think "now-" would be particular good answer. For 
>> that reason a clearer text on this would be good.
> 

Hi Joe,

cheers

Magnus Westerlund