W3C home > Mailing lists > Public > public-tt@w3.org > February 2003

Re: Why use time as a unit of measurement? (was: Proposal 0.0)

From: Dave Singer <singer@apple.com>
Date: Thu, 20 Feb 2003 10:54:29 -0800
Message-Id: <p05200e68ba7ad420e45a@[]>
To: Jean-Claude Dufourd <jean-claude.dufourd@enst.fr>
Cc: public-tt@w3.org

At 22:01 +0100 2/19/03, Jean-Claude Dufourd wrote:
>Hi Dave
>Dave Singer wrote:
>and a timecode stream.  If we are talking about discontinuous 'tags' 
>it is much better to talk about it as a timecode stream, in my 
>Using a timecode stream is a solution. I think I am not yet at this 
>level of specificity.
>What is this discontinuity thing ? You just want to specifiy a list 
>of segments to play, period.

Well, that appears to be what happens, but alas, is not.  What you'd 
like to know is "play from 0 to 10 minutes", "play from 12 to 15 
minutes", and so on.  What you actually get is a continuous program 
where those edits have already occurred.

Happily, the timecodes get edited with the video and audio; that's 
why I say that it is a stream.  If you look at the timecodes going 
by, you can work out what edits happened.  If there is a text tag 
with a time-code value of "13 minutes" as its trigger, that will play 
12 minutes in (minute 11 being missing).  If the trigger said "11 
minutes" then that text element will never display as that timecode 
was edited out.

>>>(actually, possibly many audio and subtitles), should be playable 
>>>in sync, whatever part is played in whatever sequence
>>>2- a movie should be playable according to an edit list
>>ah, it's more subtle.  He wants to be able to edit, not the whole 
>>layup, but just the a/v/timecode part, and then lay in the text 
>>stream, and still have it line up with the right timecodes.
>Why is it different from an edit list (using the QT terminology) ? 
>Or a list of segments to play (using the MPEG-4 OD terminology).
>I see 2 very much as a composition (temporal composition) requirement.
>I fully agree, but it is a requirement at the movie level, not at 
>the TT level.

agreed.  composition is a 'movie level' thingy.
David Singer
Apple Computer/QuickTime
Received on Thursday, 20 February 2003 14:07:19 UTC

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