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Reading KC at (25) 24.975/NTSC



Ken Robinson/Imagen Transfer/Santiago   7/1/97 0:54  wrote:

> I have someone here in Chile who has a problem that I know 
> someone out there can solve!!!
> He filmed in the UK  at 25fps including Sound at the same speed.
> Then he flew back to Chile and transferred all the material 
> to NTSC but at 25 fps.  There wasn't any problem syncing the 
> sound but now there is a worry about cutting the negative ...

You are right, the TIG is the best place to alert concerned
engineers about the (25fps) 24.975/NTSC transfers
which are becoming more and more frequent... and a real
headache.  Our P-frame proposition below will only work if
manufacturers upstream and downstream the telecine 
keycode-reader play the same game.   

  * Out of five film images [P A B C D] running at 24.975fps,  
  the 2:2:3:2:3 field repetition pattern delivers twelve 
  fields [P1 P2 A1 A2 B1 B2 B3 C1 C2 D1 D2 D3] which produce 
  six video frames [P1P2 A1A2 B1B2 B3C1 C2D1 D2D3] at 29.97fps.
  We called the sequence *PABCD*, instead of *ABCDE* to avoid 
  confusion between the well known A-frame and the new edit 
  reference which becomes the P-frame.

Which means:
1 - the telecine must deliver a repetitive 2:2:3:2:3 frame 
pulse timing at 24.975/NTSC.
2 - the TK keycode-reader must tag the twelve P1 to D3 fields 
and produce frame accurate lists under this mode. 
3 - the TK edit-controller must insure edits on P-frames like 
it does on A-frames in the 23.98/NTSC world.
4-  and finally, the NLE must handle the '2:2:3:2:3' P-frame 
sequence and deliver EDLs the way it does for '2:3:2:3'.

A conference in Santiago between the '24.975/NTSC willing' 
manufacturers is upon you Ken :)

--jp
_______________________________________________________________
Jean-Pierre Beauviala                      http://www.aaton.com
.

++
thanks to The Post Group for support of the TIG in 1997
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