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Re: ISSUE-2: What is the mime type of a media fragment? What is its relation with its parent resource?

From: Yves Raimond <yves.raimond@gmail.com>
Date: Tue, 27 Jan 2009 15:10:54 +0000
Message-ID: <82593ac00901270710l29dad11co726c0a0c2e7cd009@mail.gmail.com>
To: David Singer <singer@apple.com>
Cc: Michael Hausenblas <michael.hausenblas@deri.org>, Media Fragment <public-media-fragment@w3.org>, RaphaŽl Troncy <Raphael.Troncy@cwi.nl>

On Tue, Jan 27, 2009 at 2:48 PM, David Singer <singer@apple.com> wrote:
> At 14:36  +0000 27/01/09, Michael Hausenblas wrote:
>> Dave,
>>>  a) the MIME type of the requested fragment is the
>>>  same as that of the original resource;  yes, that
>>>  might result in one-frame movies, and so on;
>> Sounds good. Didn't think about this one yet. But how do we technically do
>> this? I fear I don't understand. Could you be more precisely on this
>> option,
>> please?
> Well, I am trying hard to think of a case *in multimedia* where the
> statement
> "the type of a piece of X *cannot* be the same as the type of X"
> would be true.
> The obvious problem area is if you select a time-point in a video track of a
> movie, then a fragment cast as a movie would have zero duration -- it's more
> sensibly a picture.  Unfortunately, zero duration frames are explicitly
> forbidden in MP4, 3GP etc. (since they can make the visual display at a
> given time ambiguous).
> But this gets semantically tricky if there is sound;  what is the correct
> representation of a point in time of a sound track?  It's not right to drop
> it from the fragment (oof, we'd need media-type rules for what types get
> dropped and what don't).
> This is steering me towards wondering if a piece of X, in time, necessarily
> has some extension in time, i.e. a time-point is not a fragment (can you see
> a zero-width character if you meet one in the street?).

I think that raises lots of really interesting questions, and
highlight the need for a debate about what a media fragment actually
is. Is it a bunch of byte (in that case, it makes sense to associate a
mime-type with it), or is it an identifier for a piece of the content?
In other words, does it identify a FRBR item, or a FRBR manifestation?
I would personally go for the latter, which would allow us to use
media fragments for identifying a particular signal sample, a frame in
a video, etc.


Yves Raimond
BBC Audio & Music interactive
Received on Tuesday, 27 January 2009 15:11:36 UTC

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