[mythtv-users] Is anyone running the latest NVIDIA drivers?

[Bruce Markey]

Joseph A. Caputo wrote:
> On Monday 03 May 2004 16:41, Bruce Markey wrote:
> 
>>Paul Hyui wrote:
>>
>>>1) There seems to be some major flickering going on. If I use the
>>>GANT theme, my eyes will kill me - not so bad with the Blue theme.
>>>I can live with this because there's no flicker when I am watching
>>>something....
>>
>>Flicker has to do with how TVs work and how eyes work. Several
>>environmental factors can effect how much you perceive flicker
>>but one general thing is to reduce the maximum brightness (by
>>lowering "contrast" for most sets, go figure ;-).
...
> with flicker-free refreshes and transparency for all built-in and 
> custom widgets. "
> 
> Be interesting to see just what they mean by 'flicker-free refreshes'.

Agreed. That is the question.

I think this will turn out to be a completely different topic.
Probably something to do with redrawing the whole image at once
rather than a series of changes when several objects change at
about the same time or something like that. 'flicker-free refreshes'
for Qt would have nothing to do with the well known problem for
Cathode Ray Tubes known as "flicker".

A TV has a beam that scans across the screen. If we had some kind
of super vision or if the process was done in super slow-motion,
we'd see a black screen with a small dot moving back and forth.
The reason that we see a solid image is that the light persists in
the eye for a fraction of a second. if it is redrawn soon enough,
it appears to be solid color. The brighter the beam is, the faster
and further the persistence in the eye will drop off.

Early CRTs couldn't draw enough lines fast enough so the work-
around was to draw in two passes so that it only has to draw
half the lines per pass (field) which means that all areas of
the screen are illuminated twice per frame.

The problem is, for example, a white horizontal line has a bottom
edge against a dark area. The overall image is being updated every
1/60sec but the bottom of the line is redrawn in only one field at
every 30th of a second. Therefore, this edge is bright then dims
then bright again. The eye perceives this as if the edge is moving.
The brighter the white, the more it appear to flicker. This is
also affected by how much light and what type of light is in the
room, size of the screen and distance from the screen, design of
the tube itself, and characteristics of each individuals eye and
brain.

This seems to be the flicker that Paul described.

http://www.research.philips.com/InformationCenter/Global/FArticleSummary.asp?lNodeId=794&channel=794&channelId=N794A2323

http://www.displaymate.com/flicker.htm

--  bjm