Posted By
Rybags
on 2013-09-16
10:00:53
|  Re: Two Tech Demos
Nice being able to change the colour phase at the scanline level.
AFAIK no other popular 8-bitter from Atari or C= can do this.
I was able a few years ago with experimenting and exploitation of an Antic hardware bug to create a "near enough" interlaced video signal on the Atari 8-bit computer. The actual signal produced isn't a "proper" VSync to generate interlace but is close enough to fool most analog TVs.
Analog TVs are usually generous re breaking the standards and will happily accept off-standard VSync and also generate stable displays with # of scanlines outside the normal expected range.
Many Atari 2600 games don't use the standard # of scanlines and work fine.
Most of the Atari 8-bit computers and consoles don't even generate a "standard" VSync pulse train. Normally, pulses are generated at half-scanline intervals but Atari only does them at full scanline intervals.
The phase modifying stuff - I was able to get Atari 8-bit computer to throw the phase out but it occurs for an entire field (not scanline).
The usefullness is questionable in their case - Atari has it's colours evenly spaced around the colour wheel so effectively all you end up with is different assignment to colours you can already access (so far as I could see).
I also had trouble from memory getting the phase shift to work on both fields, and due to the previous mentioned assignment issue didn't bother going further with it.
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