On Wednesday 01 June 2005 01:12, Timothy Miller wrote: > On 5/31/05, Lourens Veen <[EMAIL PROTECTED]> wrote: > > > 8 bit is a palette lookup, which with a block ram (in 512x36 mode so we > > can get the RGB values in one lookup) is trivial as well. The problem may > > be loading the palette with the RAM in 512x36 mode, since that is done > > bytewise IIRC. Maybe we could fetch the 36-bit line when the address > > register is written, and then write back the line with the new value in > > it when the data register is written after that. I don't think that that > > should be a performance problem. > > It just occurred to me that we might be able to use the palette in the > main video controller. I'm going to design it with various modes that > allow for lookup of the RGB going out. So all we need to do is give > the VGA palette some way to get at that. When the video is > translated, we can convert paletted to paletted, just arranged > differently and let the video controller to the lookup.
Ah, yes, gamma correction. Which doesn't exist in the VGA standard, so if we have a lookup table there anyway, we could abuse it for palettes. It would have to be a somewhat beefier lookup table than usually used for gamma correction on video cards though. OTOH, it will probabl be in block ram anyway; on the 3S4000 we'll have plenty of those. All that's needed then is that instead of doing a lookup for red, green and blue using the R, G and B parts of the pixel, all of them have the same input (e.g. R). Then we just write the palette indexes into that one channel, and let the video controller do the lookup. Lourens
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