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From: poynton@vector.Sun.COM (Charles A. Poynton)
Newsgroups: sci.electronics
Subject: Re: Converting PAL to NTSC on the fly
Summary: Flicker, twitter, judder indeed.
Message-ID: <120927@sun.Eng.Sun.COM>
Date: 11 Aug 89 07:18:36 GMT
References: <15315@pasteur.Berkeley.EDU> <10350003@otter.hpl.hp.com> <893@corpane.UUCP>
Sender: news@sun.Eng.Sun.COM
Reply-To: poynton@sun.com (Charles A. Poynton)
Organization: Sun Microsystems, Mountain View
Lines: 29

John Sparks  writes:

> Interlacing does not reduce flickering, it increases it. 

Television egineers have precise terminology for this otherwise confusing
topic.  Interlace improves wide-area FLICKER for a given frame rate, such
as 29.97 Hz, over a non-interlaced sytstem of the same frame rate.
However, this improvement comes at the expense of introducing inter-line
TWITTER.

Of course motion rendition is implicated in selection of a frame rate, and
depends on interlace as well.  Poor motion rendition can lead to JUDDER.

> The even lines are sent in one frame and the odd in the next. 

No, the even lines are sent in one FIELD and the odd in the next.  An odd
field and an even field comprise a FRAME.

> As far as we know, our computer has never had an undetected error.

As far as we know, As far as we know, As far as we know, As far as we know,

C.

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