Posted By
Charles
on 2022-02-16
16:58:24
|  Re: Is there such a thing as an interlaced picture for the +4?
Maybe @gerliczer can help with fixing the routine  Saturday at 4 am I was glad to be able to extract something which makes sense to bring the discussion forward. But you are right, it is ways more appropriate to use $0f9 vs $02 $f9 :) I think raster line $100 = 313. PAL line (for second frame), can we agree on that?
I am not afraid of admitting what I don't understand or not experienced with. As I wrote I suspect this is indeed "bringing those 5 long syncs forward" but I don't fully understand what a short sync and a long sync truly mean, how these are generated by TED, and how these can be altered by writing to horizontal scanning. I'm quite experienced w vert sync tricks, but not yet with the horizontal counterpart.
I would appreciate if you explained what writing $6d @ pos $1c and then later $ad @ pos $c4 is ($ff1e) supposed to do. "Shifting" is into the same direction. My _guess_ is the first (6 lines before the new frame) brings the long sync fwd and the second (first line of new frame) does the same w a short sync, but timing wise these are hieroglyphs to me.
And most of all do you have any idea how to improve to make it more PAL std compliant?
@litwr, I wish I could help with an oscilloscope, but I can help with testing. Next week if I can again find some time I will do some changes to the timing to see what happens. But again would be nice if someone also tested the effect on a CRT monitor. Most hdmi converters today use line doubling (“bob de-interlacing”) so the output would lack the additional vertical resolution anyway. 
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