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

Re: Why use time as a unit of measurement?

From: <lists@wiltgen.net>
Date: Wed, 12 Feb 2003 07:05:21 -0800 (PST)
Message-ID: <64242.66.127.210.130.1045062321.squirrel@webmail.wiltgen.net>
To: <public-tt@w3.org>

Michael A. Dolan wrote...

> If exact sync with a frame of video is a requirement, then your clock will
> have to be much more precise than you may be thinking - has to do with how
> analog television timing works (it's not really 30/25Hz frame rates - there
> is an error of 1/1000).

Right, so with this timing model things can be controlled to the
millisecond, so the text may start up to half of one millisecond from the
video or audio frame you're trying to sync it to if the system allows for
that sort of resolution.

I expect that many systems will not handle between-video-frame events, and
will put the text at the nearest frame.

-- Charles Wiltgen
   <http://playbacktime.com/>
Received on Wednesday, 12 February 2003 10:05:09 GMT

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