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Clockit Jamming 23.98

Published : 18th August 2003


>>>The only thing I could think of would be if the Clockit was jamming at 29.97 into a 23.98 Camera. Has anyone else seen this or has any suggestions as to how this mistake could have been made that would cause the problem to occur<<<

I don't use a Clockit Box

But I was asked by a producer that told me about a problem
that she had on a HD Shoot.

Post said that Timecode was being laid down but it was jumping and skipping frames :01, :03, :05, :07, etc

Only thing I could think of would be if the Clockit was jamming at 29.97 into a 23.98 Camera. Has anyone else seen this or has any suggestions as to how this mistake could have been made that would cause the problem to occur.

I suggested to Clone the Tapes with New Timecode, That is what they will be doing to fix it.

B. Sean Fairburn SOC
Director of Photography
Castaic Ca



>The only thing I could think of would be if the Clockit was jamming at >29.97 into a 23.98 Camera. Has anyone else seen this or has any >suggestions as to how this mistake could have been made that would >cause the problem to occur.

To the best of my knowledge "23.97" and "23.98" are the same thing. That is, the actual frame rate is close to halfway between 23.97 and 23.98, and is therefore randomly referred to in technical literature as both "23.97" and/or "23.98"

Lew Comenetz - Video Engineer, USA.

(I forgot the exact frequency. Perhaps someone else could write in with it? Its a big long fraction, as in: "23.975465454 etc.") LC.



>Post said that Timecode was being laid down but it was jumping and >skipping frames :01, :03, :05, :07, etc

Sean,

Is it skipping every other frame consistently, or is it seemingly random?

Lucas Wilson
--------------------
Master of Widgets
Los Angeles



Sadly, Americans and Japanese already know this stuff, but for the rest of the world that wonders why in the hell NTSC is the way it is...

[bizarre NTSC history lesson on]

In NTSC, the color subcarrier frequency is 3.579545... MHz. There are 227.5 subcarrier cycles per video line. Where Fsc is the color subcarrier, the horizontal line frequency (Fh) is 2/455 * Fsc.

2/455 * Fsc = 15,734.265... Hz

The field frequency is 2/525 * Fh = 59.94005994...

This can also be represented as 60 * (1000/1001)

Originally, NTSC B&W TV was locked to the power frequency of 60Hz. When Color TV came along, the amount of information that needed to be added to the signal came out to be 1/1000 bigger than 60hz, resulting in a slightly slower framerate.

Applying the same math to 24fps...

24 * (1000/1001) = 23.0976023976...

[bizarre NTSC history lesson off]

sigh. Maybe if I click my heels 3 times, everybody in the world will use 24fps as a standard and all this NTSC nonsense will go away...

Lucas Wilson
HD/2K Online
Los Angeles



>24 * (1000/1001) = 23.0976023976...

I think you meant 23.976... fps? (it's confusing enough without typos!)

Tim Sassoon
Sassoon Film Design



Argh... yes, of course. thanks...

Lucas
---------
2K/4K/8K a dollar...
Los Angeles