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Old 10 March 2014, 20:45   #1
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Join Date: Aug 2004
Posts: 2,480
Reducing motion blur by forcing interlacing

Over in this posting I attached an ADF containing two versions of the "Demons Are Forever" demo by D.O.C.. One is the original which uses non-interlaced mode. The other is a modified version which uses interlaced mode (I just set bit 2 in each BPLCON0 write in the copperlist).

That was a proof-of-concept to show that it can be fairly simple to patch a demo/game to force interlace mode. Many modern TVs and video capture devices don't work properly with non-interlaced component video. While the best video quality from a real Amiga could be achieved using an RGB to component video converter, unfortunately that might only work with interlaced modes. And most games and demos don't use interlaced mode.

Anyway. I noticed something about the forced-interlaced version which might be of interest for emulation. When using "double, fields+" line mode, the scrolltext at the bottom is much less blurry on my laptop screen than with the non-interlaced version.

Can anyone else see that effect? It should be more noticeable on LCD screens with a slower response time. The effect is probably similar to black frame insertion but doesn't require a 100Hz monitor. Might it be worth adding a "double, fields+"-like line mode for non-interlaced modes? It could make fast-moving scrollers easier to read.

[Does anyone know of any other demos with fast scrolling text that I could try patching to force interlace too?]

Edit to add: Here's a forced-interlaced patched version of the Jump Jet cracktro by Bamiga Sector One and The Kent Team. This is a good test for scrolling blur. You can independently change the scroll speed and direction of the foreground and background images by using joystick left/right (hold fire to change background speed).
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Last edited by mark_k; 10 March 2014 at 21:25.
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