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From: poynton@vector.Sun.COM (Charles A. Poynton)
Newsgroups: comp.graphics,rec.video
Subject: Re: HDTV and ATV Glossary (TN32)
Summary: 24 Hz is sufficient for motion rendition.  With modern framestore
   technology, the issues of motion rendition and flicker can be separated.
Keywords: 525/59.94, 625/50, NTSC, PAL, SECAM, Component, Composite,
Message-ID: <121076@sun.Eng.Sun.COM>
Date: 11 Aug 89 22:48:48 GMT
References: <120919@sun.Eng.Sun.COM>
Sender: news@sun.Eng.Sun.COM
Lines: 53

A correspondent writes:

>> p.s. 1250/24, 2048-by-1152, 74.25 MHz.  Dare to be square!

> Why frame rate of 24? Given there is movement in the film industry to 
> move to 30, ...

A few people in Hollywood proposed 30 Hz film, and SMPTE had a study group
on it, but there was never any popular support behind the idea.  Among
other things,

- 24 Hz is quite sufficient for motion rendition,

- 30 Hz consumes more film stock (tied to the price of silver!),

- international program exchange would suffer (3 G$ U.S. trade surplus
  in exported movies),

- few commercial projectors are capable of 30 Hz without modification.

All in all, just no good reason to do it.

> ... why burden TV with a slower rate.

Ah, wait a minute here, we want to burden TVs with a slower rate because
we can't afford the bandwidth to raise it!  Keep in mind that in the olden
days one had to choose a frame rate which simultaneously satisfied motion
rendition AND flicker constraints.  The fact of living rooms being (on
average) brighter than movie theatres forced television in 1941 to adopt a
30 Hz frame rate.  With framestore technology, these issues can be
separated.

> Look to the future, not the past.

The future is now.  Sony and Hitachi are recording digital HDTV on
one-inch magtape at 1.188 Gb/s, a full order of magnitude higher than the
best available U.S. technology (the Ampex D-2 machine at 114 Mb/s).  Sony
are shipping 2k-by-2k Trinitrons when the best Zenith can do is
640-by-480.  That's a factor of eight.  Sure we could glibly standardize
double the horizontal and vertical resolution of HDTV but that would be a
pointless theoretical exercise unless we can build the stuff.  The best
way for us to get back into building the stuff is to exploit the
commercially-available Japanese technology -- now.

C.

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Charles A. Poynton			Sun Microsystems Inc.
			2550 Garcia Avenue, MS 8-04
415-336-7846				Mountain View, CA 94043

"There's no offense where none is taken."  -- Ancient Chinese proverb
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