Re: [MMUSIC] Range Header In Play Responses

[Magnus Westerlund <magnus.westerlund@era.ericsson.se>]

Hi Thomas,

Some comments below.

Thomas Zeng wrote:

> Hi:
>
> During the Jan 22, 2003 RTSP telecon, we discussed Range header in PLAY
> reponses in the context of option tag play.basic.
> In current draft (draft-ietf-mmusic-rfc2326bis-02.txt), PLAY Range response
> is required for on demand media (see section 10.5).
> It was decided to make this an requirement for live streaming as well. 
> Here is the proposed changes to section 10.5 and section 14 (examples) in
> draft-ietf-mmusic-rfc2326bis-02.txt. Each change is separated by "-----"'s,
> and instructions on how to make the changes are put in square brackets.
>
> Your comments are always welcome.
>
> Thanks
> thomas
>
> ---------------------------------
> [insert the following to Section 10.5, before the paragraph started with
> "For a on-demand stream, the server MUST reply with the actual range...]
>
> [new paragraph] Server MUST include a "Range" header in its Play response.
> When playing live media, the Play response MUST use one, and only one, of
> the two
> Range headers below:
>
> Range: now-
>
> - or -
>
> Range: 0-
>
> Here in live mode "now" happens to mean "0"  in NPT time space for this
> session.
>  
Actually I think at least one more range type attribute is allowed. That 
is the use of clock. It is perfectly all right for a client to ask a 
server to play a live session using the following range header:
Range:clock=20030213T143205Z-

Which means that the server should play out media starting at 13 Feb. 
2003 at 14:32:05. If this stream is live stream the play out can't start 
before that time. There are also a requirement that range responses uses 
the same sort of units as in the request. Therefore also clock responses 
must be allowed. And for being future proof I think the above proposal 
in text needs to be reformulated so it will be possible to use those 
formats. Also what values should be given in SMTP request streams.

--- My proposal for text would be:
Server MUST include a "Range" header in any PLAY response. The response 
MUST use the same format as the request's range header contained. If no 
Range header was in the request, the NPT time format SHOULD be used 
unless the client showed support for other formats. For a session with 
live media streams the Range header MUST also be given, containing a 
valid time indication. It is RECOMMENDED that either "npt=now-" or a UTC 
clock time for the corresponding time is given, i.e. 
"clock=20030213T143205Z-". The UTC clock format SHOULD only be used if 
client has shown support for it.
------ End of proposal ------

The examples must all be updated when we have a stable specification. 
Especially the ones in chapter 14 are out of date.

Best Regards

Magnus

> ----------------------------------------------------------------------------
> --------------------------------------
> [change section 14.2, add the following right before the begining of actual
> RTSP DESCRIBE request]
>
> In this example we assume the length of the presentation is 600 seconds.
>
> [Also in section 14.2, Add a range header to PLAY response]
>
> Range: 0-600
>
>
> -------------------------------------------------------
> [change section 14.3, add the following right before the begining of actual
> RTSP DESCRIBE request]
>
> In this example we assume the length of the presentation is 600 seconds.
>
> [change the example RTSP conversation in section 14.3 to add the following
> "Range" header to PLAY reponse]
>
> Range: 0-600
>
> ------------------------------
>
> ------------------------------
> [change section 14.4 Live Media example, add the following "Range" header to
> PLAY reponse]
>
> Range: now-
>
> ------------------------------
>
>
>
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>  
--

Magnus Westerlund 
Multimedia Technologies, Ericsson Research ERA/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: magnus.westerlund@era.ericsson.se



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