Path: utzoo!mnetor!uunet!cbmvax!hedley
From: hedley@cbmvax.UUCP (Hedley Davis)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Fixing flicker, & future frame rate issues
Message-ID: <3626@cbmvax.UUCP>
Date: 13 Apr 88 14:58:26 GMT
References: <11157@ut-sally.UUCP> <8528@agate.BERKELEY.EDU> <11182@ut-sally.UUCP> <8577@agate.BERKELEY.EDU> <1367@hubcap.UUCP>
Reply-To: hedley@cbmvax.UUCP (Hedley Davis)
Organization: Commodore Technology, West Chester, PA
Lines: 50

In article <1367@hubcap.UUCP> rchampe@hubcap.UUCP (Richard Champeaux) writes:
>In article <8577@agate.BERKELEY.EDU>, doug@eris (Doug Merritt) writes:

	....Lots of deleted text about Fixing Flicker and the
FlickerFixer.......

I just thought I'd throw some idle thoughts into the fray.


FlickerFixer design flaw:

The FlickerFixer design is not flawed given the boundary values of the
problem.  As was previously stated, ( by someone else whose .sig I've
lost ), the information which comes from the amiga for adjacent lines is
separated in time by 1/60 th of a second. In this time, animated objects
have moved and therefore you have the 'split image' artifact that is
being complained about.  True this artifact is not desirable, but the
only solution is to change the in which the data is emitted from the
amiga, IE software change.  The flickerfixer is totally software
compatible, indeed from the perspective of the board, it has no ability
to change the system software, and hence, fetch ordering of bitplane or
sprite data. Given this constraint, its about the highest degree of
functionality you can get.

A minor point:
	You do not need to buffer 400 lines of information for a 60hz
flicker fixer. You only need half the full screen and a couple of lines.
The reason for this is that you only need to hold onto data for 1/60th
of a second ( displaying it twice ) before it becomes obsolete. The
minimum-ram implementation of this type of device requires a large
circular buffer where only 200+ lines are stored.

About film and 24 Hz and double shuttering.
	Film is indeed 24 frames per second. But the image is shown
three times, not two. The purpose here is to ( in my mind anyway ) to
eliminate flicker. If you really wanted to emulate film quality, you
would probably update the display at only 24 Hz, but refresh the image 
much faster ( like maybe 72 Hz ).

About 120 Hz displays.
	Yow ! This would look great, ok. Indeed, you could scroll one
pixel per frame twice as fast IF you had the CPU/blitter bandwidth to
do it. ( Arguements about clever bitplane manipulations not withstanding
due to generality of windowing enviroment ). The point is that you
really don't have the horsepower to use at this time.

	Further, this display type is indeed much more expensive for a
marginal improvement in perceived display quality.

Hedley