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Re: The history of 29.994



Phil Budden on 2/13/98 1:54 PM wrote:

>Not wanting to appear too ignorant but could one of you on the other side
>of the Pond please tell me the history behind running NTSC at 29.994? 
>Also, when do you use simply 30 f.p.s. instead of 29.994 and when do you
>drop frames and so on ... and on ...

The lurking audio geek takes off his headphones for a moment to respond:

Having successfully implemented a plan to saddle the entire professional 
audio community with tiny lo-fi speakers in every television sold in the 
United States, a group of engineers noticed the audio gurus with their 
shirt pockets intact (no protecters for those guys!), donut in hand, and 
soft chairs in front of a bunch of knobs and decided that more misery 
should be cast upon the folks with the big ears. Being engineers, a 
mathematical formula was quickly derived:

ratio of actual hours worked by audio engineers to time paid (8 hour day) 
=  4.74/8

multiplied by

coffee breaks (3) times the average number of donuts in a coffee break 
(3.67)

multiplied by the ratio of video engineers to audio engineers (4/1)

plus the current frame rate (30) divided by the audio geek arrogance 
factor (10)

thus: ( (4.74/8) * (3*3.67) * (4/1)) + (30/10) = 29.0937

Then they said, "hell, just jumble up the decimal places and _drop_ a 
couple of numbers and those audio bastards will never figure out how we 
came up with this."

Therefore: 29.97 and the insider term "29.97 drop"

Since then, maintaining audio sync has been a headache for the entire 
audio profession. THAT'S what I heard and it seems as logically thought 
out as any other explanation.

BTW: the use of the term "3:2 pulldown" in proximity to the term "29.97 
pulldown" more often than not leads to a torturous attempt to explain 
both concepts and how they do and do not relate.

returning to lurk mode, jrm




John McDaniel <johnmcd at iac.net> Sonic Arts Digital Audio Srvcs, Inc.
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