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Re: video use-case

From: Yves Lafon <ylafon@w3.org>
Date: Wed, 8 Oct 2008 07:52:12 -0400 (EDT)
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
cc: Jack Jansen <Jack.Jansen@cwi.nl>, Yannick Prié <yannick.prie@liris.cnrs.fr>, Media Fragment <public-media-fragment@w3.org>
Message-ID: <Pine.LNX.4.64.0810080747260.7736@ubzre.j3.bet>

On Wed, 8 Oct 2008, Silvia Pfeiffer wrote:

> Hi Yves,
>
> On Tue, Oct 7, 2008 at 6:10 PM, Yves Lafon <ylafon@w3.org> wrote:
>> On Mon, 6 Oct 2008, Silvia Pfeiffer wrote:
>>
>>> My understanding of the URI RFC (now at
>>> http://www.ietf.org/rfc/rfc3986.txt) is that a fragment is a secondary
>>> resource that is addressed through the primary resource. For something
>>> like http://www.example.com/text.html#id12345 the primary resource is
>>> a html page. Seeing as the URI RFC states that the fragment is not
>>> being communicated to the Web server, but only handled within the UA,
>>> this request will always mean that a Web server will return the full
>>> html page and the UA has to do something with the fragment.
>>
>> But what prevent the client to issue a something like a range request, if it
>> is easy to figure out a way to request the fragment you need?
>
> After the time range has been communicated to the server and the
> server has told the User Agent which byte ranges to get, it is indeed
> possible to get the fragment through a range request. However, we
> first need to communicate the time range to the server (as discussed
> with Dave).

Well, Range requests are for now defined as using byte ranges, but it is 
extensible, nothing prevents the creation of custom range units, like 
seconds, absolute time ranges, or whatever useful.

>> # can work, but the UA has to be aware it is dealing with video and a
>> fragment inside this video, in that case it can optimize its requests to the
>> server.
>
> "#" cannot work for communicating the time range to the server. "#" is
> stripped off before it reaches the server. "#" only works in
> communicating a time range to the UA. As explained above and in the
> long discussion with Dave, that is insufficient.

No, but the UA can see there is a #, and using the context of the request, 
do the relevant HTTP request to get only what's needed. There is no need 
to always delegate the processing to the server, one because it avoids a 
round trip, second because you still have to process something client-side 
(in that case parse a custom header to generate an HTTP byte range 
request), if you are using the two requests solution.

-- 
Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves
Received on Wednesday, 8 October 2008 11:52:20 GMT

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