Path: utzoo!mnetor!uunet!husc6!bbn!rochester!ritcv!cci632!ccicpg!leo!harald
From: harald@leo.UUCP ( Harald Milne)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Fixing flicker, & future frame rate issues
Message-ID: <2988@leo.UUCP>
Date: 21 Apr 88 10:56:02 GMT
References: <11157@ut-sally.UUCP> <8528@agate.BERKELEY.EDU> <11182@ut-sally.UUCP> <869@gethen.UUCP>
Organization: CCI CPD (Advanced Development), Irvine CA
Lines: 63

In article <869@gethen.UUCP>, farren@gethen.UUCP (Michael J. Farren) writes:
> In article <2972@leo.UUCP> harald@leo.UUCP ( Harald Milne) writes:
> >> 	Flicker:  A perceived INTERMITTENCE in an ENTIRE image, as in successive
> >> 	frames interleaved with intervals of 'darkness' (= absence of image).
> >
> >	For us normal Amiga types, this is called "Non interlaced"
> >Where alternate "half frames" are absent. That gives us the lines without
> >information in non interlaced modes.
> 
> This is not what happens at all.  Non-interlaced mode does NOT have
> "lines without information", and alternate half-frames are NOT absent.


	I was responding in the context of the original posting.

	If you don't believe me, record Amiga video in Interlace and
Non-Interlace.  Interlace will look fine, where Non-Interlace will look like
sh*t. There is information absent.

	In the mentality of FF users, Non-Interlaced video appears complete,
since FF fills this absence of non-existant information with duplicate data.

	You have to see FF in Non-Interlaced mode to see what I am talking
about. The display is solid and "Pseudo Filled".

> The difference is simply that in non-interlace, the lines are displayed
> in the same position on the screen each 60th of a second.

	Correct. But there is information missing. The lines that aren't 
there, obviously are missing. This is not a complete NTSC display.

> What you get
> are 60 screens per second, each 200 lines tall.  In interlace mode, every
> other half-frame is displayed on the screen such that it falls between
> the lines of the preceding half-frame.

	What falls in between is the missing information in Non-Interlaced
mode.

> Thus, you get a total of only
> 30 screens per second, each 400 lines tall.  There are no "lines without
> information" in either mode.

	To put it in better terminology, you get 30 video frames a second.
In Non-Interlace mode, you get 60 duplicate "even" fields. In Interlaced mode,
you get "odd and even" fields.

	The bottom line is you get more information in Interlaced mode.

	Did anything I said make sense? If it didn't, let me know. I'll try
again. Video displays can get terribly confusing.

> -- 
> Michael J. Farren             | "INVESTIGATE your point of view, don't just 
> {ucbvax, uunet, hoptoad}!     | dogmatize it!  Reflect on it and re-evaluate
>         unisoft!gethen!farren | it.  You may want to change your mind someday."
> gethen!farren@lll-winken.llnl.gov ----- Tom Reingold, from alt.flame 


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