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Re: Forcing A Frames





Jeff "don't wanna miss that A frame" Kreines wrote:

>What I am trying to do us use a Bosch FDL60 (w/DaVinci Classic and Keylink)
>to generate tapes and Flex files for use with either Avid Film Composers or
>Lightworks -- cutting 24 fps film for film matchback.  I believe (might be
>wrong on this) that the Avid wants the A frame to hit on a zero or five,
>timecode-wise.  
>
>So my objective is to establish where in relation to timecode the A frame
>hits, and maintain that relationship even when starting and stopping the
>teleine/recorder.
>

Jeff,

First, just to get your hopes up, daVinci used to have a 2:3 editor built
into their system and may provide what you need if  it's available for your
system.

Secondly, The A frame is defined as a sequence where an artitrary film frame
is recorded as a two field sequence, where the first field is odd dominant
and then the next film frame is recorded as a 3 field sequence (a B frame),
the C frame is a two sequence, even dominance and the the D frame is a three
field sequence even dominance.  The sequence repeats the cycle ending up at
an A frame again.  It doesn't necessarily have to be a zero or five frame,
it just has to be a multiple of five.   The tricky part is when you
terminate an edit and want to do a pickup for a continuous field sequence
and record every frame of film.  Unless you have some kind of device that
keeps track of the next tape in-point and the last film frame recorded, the
process it more miss than hit.  That is, it will be pure luck.  

 It happens to work out in a TLC-like editor that you tell the editor to
record this film frame (a hole punch on a zero KeyKode footage count e.g) to
that time code address, (usually an even numbered frame, odd dominant).   If
you decide that the sequence should start as an A-frame, then the "A" frame
will be in the gate when the editor turns on,  (don't worry about how-it's
magic).  Thereafter, the editor is responsible for determining the new
IN-point for the next edit event and will continue the unbroken sequence on
the tape.  If necessary, the editor will automatically truncate the last out
point that you manually selected to guarantee the the sequence will be
continuous.  As a matter of conveinence, you decide that the "A" frame is to
begin with an even frame, like :00 and every edit thereafter will fall on a
multiple of five, like :00, :05, :10, :15, :20, :25.    

In short, there is no way to do what you are required to do without some
kind of syncronizing device, like a TLC, ASTEC, or possibly the vintage
daVinci editor, or some other as yet unknown quantity.

Dean Humphus