On 01-Feb-12 20:07, Thomas Harte wrote:
I thought this was worth discussing separately but in the JAM
Assembler conversation earlier today Andrew Gillan provided a link to
http://sam.speccy.cz/ , on which one of the documents is
http://sam.speccy.cz/coding/hardware_scroll.txt — which alleges that
changing the border rapidly between black and white can affect the
position of the pixel area within the television frame by a row. Sadly
it doesn't bother to explain what aspect of the hardware it thinks is
responsible or to provide any real timing information, preferring to
talk at great length about how a single pixel hardware scroll would
buy you two frames to update the display rather than one if you wanted
a scrolling area. It's also weirdly specific to a particular monitor
in one place, and I notice that whatever effect it thinks it is
relying on doesn't work in Sim Coupe.
Can anyone comment on whether the article documents a real Sam
hardware effect rather than merely a perceived effect specific to a
particular monitor?
I noticed this while I was experimenting with the so-called software
interlace mode (see Momentum). Turning the top border white seemed to
help the interlace effect. Unfortunately it didn't seem replicable
between different monitors/TVs, the better the monitor, the slimmer the
effect. And the worst part was, this effect is evident based on *any*
colour on the screen, so to take advantage of the effect, you had to
know the average brightness of the whole screen for each frame.
Weird, I'm suddenly all vocal after not posting for a year...
Howard
