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From: ntt@dciem.UUCP (Mark Brader)
Newsgroups: net.video
Subject: Re: converting film to video
Message-ID: <891@dciem.UUCP>
Date: Wed, 25-Apr-84 14:38:12 EST
Article-I.D.: dciem.891
Posted: Wed Apr 25 14:38:12 1984
Date-Received: Wed, 25-Apr-84 19:17:45 EST
References: <2432@watcgl.UUCP>
Organization: NTT Systems Inc., Toronto, Canada
Lines: 20

[Just in case.]
	The film chains which transfer film to NTSC video do not usually show
	some frames once and some twice.  NTSC uses 30 frames per second, but
	60 fields per second.  The film chain will hold one frame of the film
	in position for 2 fields (=1 TV frame) and then hold the next film
	frame in position for 3 fields (=1.5 TV frame).  The net result is
	24 film frames/sec matches 60 TV fields/sec, while the motion isn't
	much disrupted.

Equipment is now available which will substitute various alternative frame
patterns for the normal 1-1-2-2-2-repeat described above.  The result is
that the movie still shows smoothly on TV, but occupies a different length
of time from what it did before.  For instance, a frame pattern of
1-1-2-2-2-3-3-4-4-4-5-5-6-6-repeat would result in a playback 1/15 faster
than the original.  This has been used to fit movies into the available
time slots without the need for a lot of editing or for excess minutes
slopping over the end.  The only particular show I have heard of this
being done to was "Chinatown", but I expect it is becoming standard practice.

Mark Brader