On Mon, 13 Feb 2012, Charlie wrote:
On 2/13/2012 7:37 AM, Vladimir Ivanov wrote:
On Sun, 12 Feb 2012, Charlie wrote:
I have yet to see an algorithm that correctly produces a DHR picture.
The exception being those who used very large look-up tables to cover
every case of color changes. That's something I don't have the luxury
of in the Carte Blanche card.
How much memory you have available for lookup?
The Carte Blanche card has 250Kbytes of SRAM but that isn't practical
to use for a lookup table since we're using it to read/write some of
the video buffer. The internal FPGA BRAM is only about 24KBytes and
that's virtually all used.
Too bad. My experiments showed that 9-bit lookup vector is quite nice
looking for NTSC emulation. This needs 4 tables of 512 entries, each
entry being your DAC triplet output (12-bit or less, I assume).
Check sample 6, 9, 12 and 24-bit lookup vectors here:
http://www.softjunk.org/sw/apple2/ra2/files/screenshot/ntsc/bpp/
The IIgs simple yet effective mode you can already implement in few
hours. :-)
If you are talking about the SHR mode it's already done. :-)
No, about the IIgs DHGR mode - the non-linear 4-bit sliding window from
that US patent. It's very simple and effective.