W3C home > Mailing lists > Public > public-media-fragment@w3.org > October 2008

Re: video use-case

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Mon, 6 Oct 2008 23:59:43 +1100
Message-ID: <2c0e02830810060559q296d55e8nf47fcbe7b5d527bf@mail.gmail.com>
To: "Yannick Priť" <yannick.prie@liris.cnrs.fr>
Cc: "Jack Jansen" <Jack.Jansen@cwi.nl>, "Media Fragment" <public-media-fragment@w3.org>

Hi Yannick,

On Mon, Oct 6, 2008 at 11:11 PM, Yannick Priť
<yannick.prie@liris.cnrs.fr> wrote:
> Hi Silvia
>>>> 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?
> Well, I just insisted on the fact that from an applicative point of view, a
> "video" is different from a "video fragment", it is the difference between,
> let's say
> - considering a shot of a video as a plain video by itself (not explicitly
> knowing it is actually a fragment of another video, or generated on the fly,
> or anything else): all I know about it are its video characteristics, all I
> can do is play it as a video and related manipulations,
> - and considering a shot of a video as a fragment of a specific video: I
> know it from its fragment characteristics, ie I know the video it is
> extracted from as a video, and I know the fragment as such. It enables me
> for instance to play the fragment while giving access to the plain video it
> is a fragment of.
> The notion of "fragment in context" and "fragment out of context" seems to
> be a good expression of such difference, though the question is whether I
> could even forget about the fragment being a fragment (from my applicative
> point of view).
> It is possible to say that it is no problem, because users will always
> manipulate video through dedicated user interfaces that can hide / manage
> such differences, or to consider that URI and related mechanisms proposed by
> the group should be made sufficiently clear so as to offer direct
> manipulation inside textual webpages definitions, and somehow reflect these
> differences.

I think it depends on the context of the user whether he cares that
something is a fragment or not.

I think we should always from a browser/URI viewpoint make it clear
that something is a fragment when it is one, and that something is the
whole video when it is. The UA should definitely care and know which
is which and expose that to the user. Whether the user cares is
another matter.

>From the "manipulation" POV, I would say there is no difference
between the two: Whatever I can do within my browser with a full
video, I should be able to do with the fragment.

Received on Monday, 6 October 2008 13:00:21 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 20:52:41 UTC