Re: Format of RTSP URLs

Bill Simpson-Young <bill@syd.dit.csiro.au> Tue, 15 July 1997 04:00 UTC

Received: from cnri by ietf.org id aa05265; 15 Jul 97 0:00 EDT
Received: from services.bunyip.com (services.Bunyip.Com [192.77.55.2]) by cnri.reston.va.us (8.8.5/8.7.3) with ESMTPid XAA03165; Mon, 14 Jul 1997 23:58:59 -0400 (EDT)
Received: (from daemon@localhost) by services.bunyip.com (8.8.5/8.8.5) id XAA20467 for uri-out; Mon, 14 Jul 1997 23:44:56 -0400 (EDT)
Received: from mocha.bunyip.com (mocha.Bunyip.Com [192.197.208.1]) by services.bunyip.com (8.8.5/8.8.5) with ESMTP id XAA20462 for <uri@services.bunyip.com>; Mon, 14 Jul 1997 23:44:51 -0400 (EDT)
Received: (from daemon@localhost) by mocha.bunyip.com (8.8.5/8.8.5) id XAA21743 for uri@services; Mon, 14 Jul 1997 23:44:50 -0400 (EDT)
Received: from alba.syd.dit.CSIRO.AU (alba.syd.dit.csiro.au [130.155.20.1]) by mocha.bunyip.com (8.8.5/8.8.5) with SMTP id XAA21740 for <uri@bunyip.com>; Mon, 14 Jul 1997 23:44:44 -0400 (EDT)
Received: from syd.dit.csiro.au by alba.syd.dit.CSIRO.AU (8.6.12/1.06S) id NAA17324; Tue, 15 Jul 1997 13:44:34 +1000
Message-Id: <199707150344.NAA17324@alba.syd.dit.CSIRO.AU>
X-Mailer: exmh version 1.6.9 8/22/96
To: Rob Lanphier <robla@prognet.com>
Subject: Re: Format of RTSP URLs
cc: www-talk@w3.org, uri@bunyip.com, confctrl@isi.edu
Reply-To: Bill Simpson-Young <bill.simpson-young@cmis.csiro.au>
In-reply-to: Your message of Mon, 14 Jul 1997 20:07:26 -0700. <3.0.32.19970714200724.011aeb24@mail.prognet.com>
X-Internet: bill.simpson-young@cmis.csiro.au
X-Snail: CSIRO DIT, Locked Bag 17, North Ryde NSW 2113, Australia
X-Phone: (+61 2) 325-3155 Fax: (+61 2) 325-3200
X-uri: http://www.syd.dit.csiro.au/staff/bill
X-face: "GS>_j9\.pW; Cs*01=u*o'&mic%_7Hxyz&_UR6{$Ai95Hc5,xn-jf-Z7"njhC<(@`Vr%Nrl &x/|0G%DtL\XmNdIo|eMF,W"ci_a\Z=#aSs+&$5Ia:/$@{'i:T.U]^2l!NarQF+Ldb.
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Date: Tue, 15 Jul 1997 13:44:24 +1000
From: Bill Simpson-Young <bill@syd.dit.csiro.au>
Sender: owner-uri@bunyip.com
Precedence: bulk

Rob,

> A promenent proposal for achieving this is as follows:
> Full Container file:
> rtsp://foo.com/example.mov

Ideally, people won't do this but would do rtsp://foo.com/example and 
leave the type up to content negotiation.

> 
> Individual Track within container file:
> rtsp://foo.com/example.mov?track=1
> (the "track=1" portion is file format specific, the "?" is the consistant
> part).

If format-specific info is to be included in a specific RTSP URL, then it 
makes sense to allow an HTTP-style query part for the specification of 
this but the internal syntax of that part should be outside the scope of 
the scheme.  However, I think there is a need for the standardisation of 
some RTSP scheme- dependent semantics for commonly-used properties so that 
it is rarely necessary to resort to format-dependent references.  Eg in 
this case, one should probably use something like "track=audio1" (but this 
wouldn't be in the query part of the URL - see below).

> ...
>
> The URL scheme, taken from Roy Fielding's draft on the subject
> (draft-fielding-url-syntax-05.txt) is something we'll have to consider very
> seriously in all of this.  The URL syntax there is:
> <scheme>://<site>/<path>?<query>#<fragmentid>
> 
> The problem with that scheme is that "fragmentid" is really "client-side
> fragment id".  What we really need is a server side fragment id as well.
> 
> <scheme>://<site>/<path>?<query>:<ssfrag>#<fragmentid>

In RFC 1808, the URL syntax is 

<scheme>://<net_loc>/<path>;<params>?<query>#<fragment>

where "params   ::= object parameters (e.g., ";type=a" as in
                       Section 3.2.2 of RFC 1738 [2])."

Why not use params which is intended for this purpose?  I know the 
"params" isn't used in the HTTP scheme but the disadvantages of using ? 
and # are great enough that it's better to use params than stay close to 
the HTTP scheme.

> The point here is to make it as simple as possible for a server to add and
> subtract fragments from the server-side fragment portion.  If this is
> buried in the query, it's very difficult.  If it is clearly delimited and
> hanging off of the end, it's really straightforward.

I agree.


Bill