Whether or not the display is interlaced is controlled by the CRTC (CRT controller). It is initialized by the running program. It's possible to patch the program so it will make the CRTC to run in deinterlaced mode. This is what I've done.
I was hoping the deinterlaced display would at least fix the weirdness you get when scrolling horizontally (in tate mode - moving along the screen's short axis) - scrolling left and scrolling right feel very different. Unfortunately, it didn't work. The deinterlacing seems to cause it to alternate between the even and odd lines of the image, so the image distorts somewhat as it scrolls. It's only really noticable in the background in either video mode. It fixed that particular problem, but introduced another equally bad one.
Anyway, the patch:
Change:
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01 00 24 32 ff 00 45 32
Code: Select all
00 00 04 20 ff 00 45 32
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01 00 24 32 04 00 06 a6
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00 00 04 20 04 00 06 a6
(The code is MIPS machine code, if you're interested. If you want to see how it actually works read Dreamtime's PS2 programming tutorials and mess around with the code. Knowing MIPS assembly will help immensely.)
[EDIT]
The same strings work on Ibara. The results are somewhat better. The lack of interlacing seems to make the filtering more apparent.