Re: [hatari-devel] How many colors when rendering in Hatari ?

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 16/04/2013 18:09, Eero Tamminen a écrit :
> There's no direct support for 24-bits, only 32-bits.
> Just look at the file names in src/convert/. :-)

24/32 are similar, just force the alpha byte to a constant value

> ST VDI and monochrome modes support only 8-bits, higher bitdepths
> are converted from 8-bit.

do you mean VDI mode is requesting a 8 bpp surface in SDL, whatever the 
screen real bpp is ?

> > Or we could add in Hatari an optionnal pass to convert the 24 bpp
> > surface to 8 or 16 bpp before. This would be a little slower (and that's
> > not even sure), but it would be much easier to maintain a 24->8 or
> > 24->16 conversion of the whole surface instead of doing a specific
> > conversion by blocks of 16 pixels as it is today.
>
> Most common screen formats nowadays are probably 16&  32-bit.
>
> Main reason for having direct convertors for different modes
> is speed, in ST emulation screen convertion is one of the
> largest CPU consumers (with full timer-D interrupts).

I'm not sure there's such a huge gap between working with a 8bbp surface 
and a 24 bpp surface. More bytes to move of course, but with today cpu 
architectures and caches I'm not sure it matters anymore (especially 
with the rather small window's size we're daealing with)
..
Still, could be interesting to benchmark 10 seconds of a demo doing lots 
of color change in 8 bpp, 16bpp and 24bpp to see what kind of numbers we 
get.

> But I think reducing&  simplifying that code would be good.
> You could consider changing the conversion routines to be
> line based, see todo.txt for more info.

The conversion routines could be line based / screen based (that's the 
same, just a loop for each line).

My aim for the video emulation is to have an adaptative mode that can 
draw pixels every 4 cycles when necessary or as a whole line when no 
video trick is detected (today, we always drw a whole line and that's 
also a pain to maintain when you consider all the border removal 
combinations that can happen)

Nicolas