Re: Chapter marks not where specified.

Hi Lawrence,

> On Wed, 28 Mar 2012 16:25:50 +0100, Tom Brock wrote:
> 
> > Even with NTSC, I've often wondered which is right, the 29.97 fps
> > figure or the 1.001 fudge factor that is supposed "correct" for its
> > not being exactly 30 fps.
> 
> The answer, as I understand it, is the actual, original broadcast frame
> rate is 30/1.001 fps. However, for timecode purposes, the frame rate is
> taken as exactly 29.97, which means the NTSC timecode clock differs from
> actual time by about one part in a million.

Indeed: the timestamp would need to be implausibly large to get the frame 
number off by one, by using 29.97 fps.  Nevertheless, especially if 
floating-point arithmetic was available, I'd simply use 900000/3003 for the 
frame rate on a DVD, since the PTS clock is 90 kHz and there are 3003 ticks 
per frame.  I really wonder about the 3003, though: I'd always sort of assumed 
that 90 kHz was chosen to be a suitably large common multiple of 30 and 25.

Tom Brock.



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