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Atari demoscene BBS
| Re: More or less Zero Overscan |
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Posted by: evil
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Oct,29.2008-18:51
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Cool demo. Only watched it on video (no ste) but your overscan code's pretty impressive. Is the mountain calculated in synchronized code? Or do you just render it there, and calculate it in the non-overscan part:
Hi and thanks :)
The mountain stuff is rendered over the entire frame, non-overscan as well as overscan parts. There is quite little free time there in fact (about one scanline).
FWIW, overscan without stabilizer is a really old technique... My first overscan routines didn't have it and were unstable to my disappointment. Stabilizers were the missing puzzle piece to make overscan work on vanilla ST's. It's like fashions... the old thing is now the new new thing :-) Interesting that STE's don't need it.
As far as I know it's the first demo to use non-stabilizer overscan, as it simply doesn't work on ST and people seems to have taken that for granted on STe as well. But of course people have been experimenting :) We might be wrong though.
I remember than DOM's "official" Atari ST demo (paid for by Atari IIRC) had overscan (and Krazy Rex's picture) -- do you know if he used a stabilizer?
I can't even remember this demo, do you have a download link?
Also I take it that there are no DMA conflicts for memory access between fetching the digital sound and overscan? On the ST, if you read from the floppy while in overscan, your code fetches would be delayed by the floppy DMA -- causing the overscan to flake out?
There are conflicts with the sound dma and shifter which makes the overscan hardsync to fail, at least using the method with timer-a to trigger just before the top border.
When writing to the dma soundchip hardware registers for start, stop and change replay quality the overscan fucks up.
After a few days of pulling my hair we got a solution: play samples in looped mode, and update only the start/end registers of the dma hardware one vbl ahead of the actual change. That fixed it (and my hair finally grew back as well).
--
Anders Eriksson
ae@dhs.nu
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[All messages in this thread] [Start new thread]
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Topic
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Posted by
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Date
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More or less Zero Overscan
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Alien / ST-CNX
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Oct,29.2008-17:46
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Re: More or less Zero Overscan
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evil
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Oct,29.2008-18:51
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Re: More or less Zero Overscan
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mikro
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Oct,29.2008-21:59
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Re: More or less Zero Overscan
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JUL
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Oct,30.2008-08:00
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Re: More or less Zero Overscan
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gizmo
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Oct,30.2008-10:59
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Re: More or less Zero Overscan
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ray
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Oct,30.2008-13:58
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Re: More or less Zero Overscan
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gloky
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Nov,01.2008-15:13
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Re: More or less Zero Overscan
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Chuck
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Nov,01.2008-20:12
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Re: More or less Zero Overscan
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s_t_s
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Nov,04.2008-14:31
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Re: More or less Zero Overscan
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s_t_s
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Nov,06.2008-15:22
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Re: More or less Zero Overscan
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evil
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Nov,06.2008-16:19
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Re: More or less Zero Overscan
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s_t_s
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Nov,06.2008-18:42
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Re: More or less Zero Overscan
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alien / ST-CNX
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Nov,06.2008-22:14
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What's the anti-troll code?
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Don't have a code or forgot it? Fix it here.
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