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Re: Keycode number fields



Don't despair . . . until you get it, it can be a little vexing.

Instead of concentrating on what the alpha numeric description is at the
end of each video frame, instead observe the differences of how the
sequence of each each of the four letters crosses the video fields.

The SMPTE provides a desription of the pattern of these sequences, which
describes SMPTE-A sequences and SMPTE sequences (I'm not sure if they went
on to define the remaining two sequences, which we call <yup> SMPTE-C and
SMPTE-D sequences).

The neccessity for these distinctions is to describe how film,
that is transferred at 24fps, is laid to tape running at 30fps.  Draw on a
piece of paper two horizontal strips, calling the top one film
and the bottom one tape, and then break them down into their smallest
components (frames for film & fields for tape), then drawing guidelines
and marrying successive frames of film to successive fields of tape in a
2-field, 3-field, 2-field, 3-field, etc. sequence.  The first frame of
film is transferred to video fields 1 & 2 (this is a SMPTE-A sequence).
The second frame of film is transferred to the subsequent video fields 1,
2 & 1 (this is a SMPTE-B sequence).  The third frame of film is
transferred to the subsequent video fields 2 & 1 (this is a SMPTE-C
sequence).  And finally the fourth frame of film is transferred to the
subsequent video fields 2, 1 & 2 (this is a SMPTE-D sequence).  From here
one the pattern repeats itself.

Hope this helps!

Tim Bond

On Tue, 17 Sep 1996, PWACKER wrote:

> I have received my first telecine with Keycode windows and I am
> unclear as to what is the precise information conveyed in the last
> alpha-numeric field of the Keycode number.  I know that it is related
> to postion in the pull-down sequence, but I was a bit confused when
> reading the sequence frame to frame on the video.  Each five video
> frame sequence of Keycode numbers ends A1  B1  B3  C2  D2, with each
> value appearing to be the same for both fields of a specific video
> frame.  
> -- 
> Phillip J. Wacker-Hoeflin             pwacker at oa.ithaca.edu
> Post Production Facilities Supervisor                   
> Ithaca College, Roy H. Park School of Communications           
> Ithaca, NY  14850-7256                Phone: 607-274-1973
> 
> ----- 
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> inquiries to rob at alegria.com...http://www.alegria.com/telecinehome.html  
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>