[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: 3-PERF REARS HEAD! THOUSANDS FLEE IN PANIC!



Bill Tapazio wrote:

>What are folks out there doing for 3-perf jobs?  I'm not so
>concerned with the actual transfer, but what systems can handle
>the odd pulse counts for timecode generation and how in the world
>can you get a FLEx/KL file from this?  And what about audio synch?

Unfortunately the 64 perf repetition rate of KeyKode does not work well
for 3 perf. In fact there are 21 1/3 frames per barcode, and hence the
reference dot of the KeyKode changes every foot.  Once every three feet,
 you gain an extra frame.  The first method of dealing with 3 perf was
to talk about 'yards and feet' because every three feet the pattern
repeats.  This counting method was awkward for negative cutters for at
least three reasons.  64 frames between count cycles was very awkward to
work with.  Second the counting ' yard part incremented by 3 each time
it changed.  Third there was no easily definable way to identify the
start of a yard.

A couple of years ago several manufacturers met at NAB to discuss the
best way to do 3 perf KeyKode.  A scheme was developed that would retain
the normal KeyKode counting sequence of feet, that would have two 'short
feet' with 21 frames each and one 'long foot' with 22 frames, and that
would identify uniquely where the start of each cycle would be.  We
decided that the foot with the reference dot at the head of the frame
would be called the first short foot, the foot with the reference dot at
the center of the frame would be the second short foot and the foot with
the reference dot at the tail of the frame would be the long foot.  This
information would need to be identified in the 3 line VITC and in the
database so that editing systems and film conforming systems could
accurately track the 3 perf numbering throughout the process and
ultimately make a neg. assembly list accurately.

The 4025 3 perf Kit can be added to any 4025 and adds the necessary
firmware to the 4025 to handle 35mm 3 perf in addition to 16mm/Super
16mm and 35 mm.  An indicator is placed in the KeyKode burn-in window
identifying which foot you are in, and there are bits in the 3 line VITC
that identify this also so that our Afterburner and other devices
reading the VITC can follow the three perf counting cycle.  This
information is also captured in version 1.1 and later of Key-Log and
passed on to Lightworks, AVID and other editing systems that can
understand 3 perf. 

On Rank Telecines you do require a special gate and tach wheel to
generate the correct number of biphase pulses per 3 perf frame.  I
believe Metaspeed can generate the correct pulse rate too.  On newer BTS
telecines, I believe the tach rate is programmable.

For those who are interested, we have a drawing explaining the 3 perf
numbering cycle on our web page (www.evertz.com)

>

--------------------------- Alan Lambshead:  - V.P., Director of
Engineering:   E-mail:  alan at evertz.com --------
--------------------------- Evertz Microsystems Burlington, Ontario,
Canada ------http://www.evertz.com -------- 
--------------------------- Phone: 905-335-3700   Fax: 905-335-3573  
BBS: 905-335-9131-------------------------