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: Luke-Jr <Luke7Jr@yahoo.com>
Date: Wed, 12 Feb 2003 23:03:36 -0500
Message-ID: <3E4B1918.7090500@yahoo.com>
To: public-tt@w3.org
One idea I just thought of that sounded possible was to use percentages
between scenes. A possible problem with this would be that all
players/encoders would need the same (or very similar) definition of a
scene change... or perhaps have it be a vague definition made more
specific by a setting in the TT stream/file. Another problem would be
that it could take a while for some applications to calculate the length
of a scene especially for streaming. And the possibility of a endless
stream would also need a solution.


Luke-Jr wrote:

> I haven't had much time to read/contribute to this ML yet, but I just
> thought it would be important to point out that using a time standard
> (such as English time) would be a mistake since there are more than
> one time standard (I myself have been recently switching over to use
> the hexadecimal time standard). Yet using frame numbers would also be
> a problem as the TT script might be used with different video
> files/streams which have different framerates. I'm not sure what
> alternative is left over, but those are two important things to
> consider...
>
> lists@wiltgen.net wrote:
>
>>Johnb@screen.subtitling.com wrote...
>>
>>  
>>
>>>FileX is indexed against the timecode that is stored as VBI data on TapeX.
>>>So unlike SMIL - the media are separate - subtitles in one - video and
>>>audio on another.
>>>    
>>>
>>
>>You can forget about SMIL, although I think that understanding what it is
>>a useful prerequisite for anyone who wants to contribute.
>>
>>Unless I'm missing something, Proposal 0.0 works just the way you would like
>>-- subtitles in one file, video and audio in another.
>>
>>  
>>
>>>In practice, the broadcaster will want to show adverts. These can occur
>>>at **any time** during the broadcast, and may differ from showing to
>>>showing...
>>>    
>>>
>>
>>In my previous post I described how this would work.  (Please let me know
>>if the explanation didn't make seise.)
>>
>>  
>>
>>>Subtitles are frame accurate for lip synching.
>>>    
>>>
>>
>>I've explained a few times why time (rather than frame-based timecode)
>>must be used.  As two examples, the TT should still work when taking a
>>24fps film source to NTSC, or to the web via a QuickTime movie with a
>>default timebase of 600 units/second whose video content is encoded at
>>12fps.
>>
>>  
>>
>>>I can conceive of other situations where the assumption of 1 sec per sec
>>>is invalid.
>>>    
>>>
>>
>>I know you're not serious, but I don't get the joke.
>>
>>  
>>
>>>...timebases can always be converted into a single format.
>>>    
>>>
>>
>>Exactly, and that single format is time.
>>
>>-- Charles Wiltgen
>>   <http://playbacktime.com/>
>>
>>
>>
>>
>>  
>>
>
Received on Wednesday, 12 February 2003 23:03:41 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 2 November 2009 22:41:26 GMT