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Re: video use-case

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 8 Oct 2008 10:27:01 +1100
Message-ID: <2c0e02830810071627p739631a8if6efce975d171d55@mail.gmail.com>
To: "Yves Lafon" <ylafon@w3.org>
Cc: "Jack Jansen" <Jack.Jansen@cwi.nl>, "Yannick Priť" <yannick.prie@liris.cnrs.fr>, "Media Fragment" <public-media-fragment@w3.org>

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).


>> So, the only way in which I can see this working is that the UA
>> displays full-context for a screen display (as is customary), but when
>> dealing with braille it strips out only the relevant part. Is that how
>> it works?
>>
>> I'm asking this because with media we cannot work in this way, since
>> we may not want the full video to download to the UA in order to apply
>> the fragment offset. This is the reason why we were not able to use
>> the "#" URI fragment for specifying temporal URIs, but had to use the
>> "?" URI query mechanism.
>
> # 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.

Regards,
Silvia.
Received on Tuesday, 7 October 2008 23:27:51 GMT

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