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Re: video use-case

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Mon, 6 Oct 2008 20:01:47 +1100
Message-ID: <2c0e02830810060201l26ebfe2n44c6bc8bb131d1d3@mail.gmail.com>
To: "Jack Jansen" <Jack.Jansen@cwi.nl>
Cc: "Media Fragment" <public-media-fragment@w3.org>

Hi Jack, all,

On Thu, Oct 2, 2008 at 7:55 AM, Jack Jansen <Jack.Jansen@cwi.nl> wrote:
> On 1-Oct-2008, at 17:42 , Pierre-Antoine Champin wrote:
>>> That would be the case for the use cases you explicitly mention here,
>>> but there are other multiplexed videos where this isn't the case, think
>>> of movies in airline  cut/normal cut/directors cut. This means that
>>> timestamps become messy: either "00h:02m:00s:00f" becomes ambiguous
>>> (could be different points depending on track selection), or arithmetic
>>> on timestamps becomes impossible (depending on track selection
>>> "00h:02m:00s:00f" may or may not be 60 seconds after "00h:01m:00s:00f".
>> interesting example, indeed.
>> But, I would rather consider the different "cuts" to be different videos.

I regard them as different Web resources. The addressing of them is
always based on a specific Web resource just like different variants
of Web pages also live under totally different URLs and you can
address to them differently.

>> Indeed, the timeline is, in my view, a fundamental aspect of a video.
> Agreed.

Yes, I agree also - we are only dealing with one fixed timeline per resource.

> But this triggered another question: are we interested in the
> timestamps in the movie? If we ask for a segment of video starting at 30s,
> do we expect the timestamp of the first frame to be "30s"? Do we expect it
> to be "0s"? Do we expect nothing at all? This is going to be important for
> client-side creation of URLs for selecting subparts of videos.
> Sylvia, do Annodex temporal URLs say anything about this?

Yes, Annodex proposes a sophisticated scheme for how to deal with this

As you can see from
http://annodex.net/TR/draft-pfeiffer-annodex-02.html#anchor14 the
Annodex resource that is returned upon a temporal URI request knows
whether it starts at an offset of 30s or not (stored in the
"presentationtime" header field).

describes the protocol aspect of it. If we ask for an offset of 30s we
have to expect the first frame to be at 30s and a 404 otherwise (in
the I-D an additional exception is mentioned for the case where the
server decides to dishonour the query and serve the resource without
the offset).

Received on Monday, 6 October 2008 09:02:24 UTC

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