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Re: video use-case

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Mon, 6 Oct 2008 20:05:37 +1100
Message-ID: <2c0e02830810060205q787223chadf22c17ab8c43d4@mail.gmail.com>
To: "Yannick Prié" <yannick.prie@liris.cnrs.fr>
Cc: "Jack Jansen" <Jack.Jansen@cwi.nl>, "Media Fragment" <public-media-fragment@w3.org>

Hi Yannick,

On Thu, Oct 2, 2008 at 8:13 AM, Yannick Prié <yannick.prie@liris.cnrs.fr> wrote:
> Le 1 oct. 08 à 22:55, Jack Jansen a écrit :
>> 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.
>>> Indeed, the timeline is, in my view, a fundamental aspect of a video.
>> Agreed. 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.
> I can consider a fragment of a video as a video, and I do not care about the
> architecture that allows me to see it, download it, etc. as a video. It
> begins at 0s.

Actually, if I request a video from 30sec offset, I expect it to start
at 30sec. Otherwise I will be confused and wonder whether the offset
has actually worked. If I download it, the video may have forgotten
that it was originally started at 30sec offset (this is particularly
the case where the video format does not offer storage of an offset).
In that case (i.e. an offline video player) it's probably ok to run it
with a 0sec offset, even though it's generally wrong.

> I can consider a fragment of a video as a fragment of a video. In that case
> it begins at 30s, I can explicitly manipulate both the fragment and the
> video (e.g. jump to a frame before the fragment beginning, let's say at
> 20s).
> I think both cases should be considered. I do not manipulate a "video" and a
> "fragment of a video" in the same way, even if their playing can result in
> the same rendering (eg. 5 seconds of video in a web page).

I'm curious: how would you manipulate a "video" and a "fragment of a
video" differently? Can you explain?

Received on Monday, 6 October 2008 09:06:14 UTC

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