Subject: [MMUSIC] RTSP: Range response when PLAY request fails

From: Magnus Westerlund <[email-masked]>
Date: Mon, 03 Nov 2008 15:51:34 +0100

Hi,

This is for discussing the following RTSP 2.0 issue raised by Christian
Haas:
https://sourceforge.net/tracker2/?func=detail&aid=2038457&group_id=23194&atid=377744

The issue is the following text in Section 13.4.1:

Server MUST include a "Range" header in any PLAY response.

So what is returned when the response becomes "457 Invalid range" when
playing? Please clarify this.

My suggestion for a fix is the following.

The first pargraph is already exist, the second is added:

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 format used in any previous PLAY
request within the session SHOULD be used. If no format has been
indicated in a previous request the server MAY use any time format
supported by the media and indicated in the Accept-Ranges header in the
SETUP respone. It is RECOMMENDED that NPT is used if supported by the
media.

For any error response to a PLAY request, the server's response depends
on the current session state. If the session is in ready state, the
current pause-point is returned. For time-progressing content where the
pause-point moves with real-time due to limited retention, the current
resume point is returned. For sessions in playing state, the current
playout point and the remaining parts of the range request is returned.

Cheers

Magnus Westerlund

IETF Transport Area Director & TSVWG Chair
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From: "Rémi Denis-Courmont" <[email-masked]>
Date: Mon, 3 Nov 2008 17:02:45 +0200

On Monday 03 November 2008 16:51:34 ext Magnus Westerlund, you wrote:
> If no Range header was in the request, the format used in any previous
> PLAY request within the session SHOULD be used.

and

> It is RECOMMENDED that NPT is used if supported by the media.

reads contradictory to me. Is it so that the last sentence only applies to the 
case that no format has ever been used?

Also, how to ensure that the client will understand the format? I'd rather 
have MUST use the same format as the PLAY request, MUST use NPT if no Range 
in the request. If the client wants something other than NPT, it can always 
put the right format in the request.

And if the client uses a format that the server does not understand, the 
client is buggy.

-- 
Rémi Denis-Courmont
Maemo Software, Nokia Devices R&D
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From: Magnus Westerlund <[email-masked]>
Date: Mon, 03 Nov 2008 16:34:59 +0100

> case that no format has ever been used?

Yes, that is the intention. Note that I have made no changes to the
first paragraph. But if there is unclear text it should be fixed.

> put the right format in the request.

I agree that changing the SHOULD to a MUST would be an improvement here.
 However, if no format has been indicated then using any of the ones in
the Accept-Ranges header would be suitable. I can agree that a
recommendation for NPT is fine in this case. Do note that there is a
requirement to include this header in the SETUP request.

> And if the client uses a format that the server does not understand, the 
Yes, this text doesn't discuss this at all as this is covered in an
other place.

Cheers

Magnus Westerlund