W3C home > Mailing lists > Public > public-media-fragment@w3.org > January 2009

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

From: David Singer <singer@apple.com>
Date: Tue, 27 Jan 2009 15:48:31 +0100
Message-Id: <p06240845c5a4cd72d822@[]>
To: Michael Hausenblas <michael.hausenblas@deri.org>
Cc: Media Fragment <public-media-fragment@w3.org>, RaphaŽl Troncy <Raphael.Troncy@cwi.nl>

At 14:36  +0000 27/01/09, Michael Hausenblas wrote:
>>  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,

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 
David Singer
Multimedia Standards, Apple Inc.
Received on Tuesday, 27 January 2009 14:50:56 UTC

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