Re: RGB output from C64

On Sun, Mar 10, 2019 at 08:15:16PM +0100, Mia Magnusson wrote:
> Den Sun, 10 Mar 2019 12:32:28 -0500 skrev Segher Boessenkool
> <segher@kernel.crashing.org>:
> > On Sun, Mar 10, 2019 at 05:57:09PM +0100, groepaz@gmx.net wrote:
> > > Would be interesting to see some details on how it works (i am
> > > hoping for something else than plain VICII emulation... it could be
> > > a nice way to make pixel perfect screenshots from a real VICII
> > > eventually)
> > 
> > It has to be emulation, a lot of state is needed to create the picture
> > that cannot be seen from anything happening on the pins (like ECM/MCM
> > modes, sprite X coordinate, sprite/data priority), so all that has to
> > be emulated, and you are looking at pretty much all of a VIC-II by
> > then. (Well, you don't need anything for accessing memory of course,
> > all that is done by the real chip and you can sniff it).
> 
> On the other hand, the S-video signal out from the VIC-II is really
> enough to "know" what's going on, and it could most likely be sampled
> and cleaned, and PAL/NTSC demodulated, to generate a perfect signal.
> 
> With some automatic level detection, the hardware could learn how the
> signals from the VIC-II particular actually look re unwanted stripes
> and similar problems. I.e. a kind of auto-lumafix.

But that won't use 22 signals (the VIC-II has 12 address and 12 data pins;
you only need 8 of the address pins, but apparently they sample at least
some of these, there are only 40 pins total :-)


Segher