Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!ucsd!nosc!helios.ee.lbl.gov!pasteur!ames!oliveb!tymix!antares!jms
From: jms@antares.UUCP (joe smith)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Message from designer of FlickerFixer
Summary: Film + video = mismatched frames
Message-ID: <142@antares.UUCP>
Date: 31 Aug 88 08:05:32 GMT
References: <3379@crash.cts.com>
Reply-To: jms@antares.UUCP (joe smith)
Followup-To: <3379@crash.cts.com>
Organization: Tymnet QSATS, San Jose CA
Lines: 48

In article <3379@crash.cts.com> haitex@pnet01.cts.com (Wade Bickel) writes:
>I don't know what you guys are talking about.  I have a minor in Video and
>I've spent a lot of time doing frame editing.  On a video display frames are
>NEVER mismatched the way the are by the FlickerFixer.
>
>What is particularely disturbing is when the second feild of a frame is
>overlayed with the first feild of the next frame to form a non interlaced
>screen.  This never happens with video tape or transmitted signals.  In fact,
>if it did, it would be very disturbing.

The mismatch between frames ALWAYS happens whenever a theatrical film is
shown on TV.  It's called the "5 to 2 pulldown", I'm suprised you didn't
mention that.  It is because film runs at 24 frames per second and television
runs at 30 frames per second (60 fields per second).  One twelfth second
lasts 2 film frames or 5 TV fields.  By transmitting 1 film frame as 2
TV fields and the next film frame as 3 TV fields, the 5 to 2 ratio is used.

The symptom is visible on any VCR with a frame-by-frame advance button.
If you single-frame thru a movie that was recorded on film (not a made
for TV movie), you will notice a pattern of 3 good frames and 2 mismatched
frames. 

Frame   A  A  B  B  B  C  C  D  D  D  E  E  F  F  F  G  G  H  H  H
Field  00,01 02,03 04,05 06,07 08,09 10,11 12,13 14,15 16,17 18,19
        good  good  blur  blur  good  good  good  blur  blur  good

The good freeze-frames occur when an even numbered video field matches
with the next higher odd numbered video frame.  The blurry freeze-frames
occur when video frame 2N does not match 2N+1, WHICH OCCURS TWO OUT OF
EVERY FIVE FRAMES DURING THE MOVIE!

>Perhaps someone can give some example of how they think this happens.  Lets
>consider a basketball moveing diagnally accross the screen.  When are scan
>lines drawn with the basketball appearing in two different positions at once?
>(ie: in the same pass of the beam).
>
>ARPA: crash!pnet01!haitex@nosc.mil
>INET: haitex@pnet01.CTS.COM
>Opionions expressed are mine, and not necessarily those of my employer.

In my experience, the answer is yes.  If the basketball moves between
field 2N and field 2N+1 and you are not using a slo-mo-cam, then you will
get a combined frame that has the ball appearing in two different places.
-- 
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