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From: myers@hpfcdj.HP.COM (Bob Myers)
Newsgroups: comp.graphics
Subject: Re: Frame rate (was: Re: HDTV and ATV Glossary (TN32))
Message-ID: <17400006@hpfcdj.HP.COM>
Date: 18 Aug 89 19:11:22 GMT
References: <13130@well.UUCP>
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 29

>Interlace seems to be an excellent way to cut the bandwidth in half
>while avoiding flicker and motion artifacts.  Other than pressure
>from the movie industry, what are the other arguments for eliminating
>interlace?

Interlace does NOT avoid flicker and motion artifacts; flicker (actually
a host of effects with various names, but let's just do what everybody
does and lump them together under "flicker) is MUCH  worse in an
interlaced display over a non-interlaced display of the same size and
brightness at the same *frame* rate.  You can't avoid it - the price you
pay for reducing the bandwidth required is the fact that each pixel gets
refreshed only half as often as before.  This is particulrly annoying
in images containing narrow horizontal or near-horizontal lines, but even
a plain white raster, if interlaced, will be obviously worse than a
non-interlaced raster, all else being equal.

The effects you mention - regarding panned images, etc. - are certainly
artifacts of the slower refresh rate, and to some degree the 3:2 pulldown
used in going from film to television.  (I also believe that part of the
problem with a pan is psychological - things which you expect to be
"stationary" suddenly start moving, but you're NOT moving your head.
You tend to track differently than you would if you were "panning your eyes.")
But non-interlaced TV would definitely provide a significant performance
improvement over interlaced, assuming that you can afford the bandwidth.


Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
myers%hpfcla@hplabs.hp.com               |  sentient life-form on this planet.