MAMEWorld Forums - EmuChat - Re: Sony CXA2025AS US

> EDIT: Nevermind. Now that I'm not on my laptop out in the sun I see that this is
> pretty bad on a calibrated monitor. But I'm still surprised at how far off the
> YIQ->RGB formulas are from the standard ones you see everywherw (like wikipedia).
>
> It's interesting how far off these are from the formulas on the YIQ wikipedia page.
>
> If you want to try out this effect now (it might be wrong if we need to do some kind
> of gamma correction first) you can do the following:
>
> (1)Get the RGB->YIQ matrix from wikipedia.
> (2)Get the YIQ->RGB matrix from your post
>
> To get the full RGB->YIQ->RGB you multiply the matrices together in the correct order
> (YIQ->RGB)*(RGB->YIQ) and use the result in the color convolution section of the hlsl
> shader. Either the BGFX version or D3D will work. But you'll need to edit the
> hlsl.json to allow negative slider values.
>
> For example, if I type the matrices into wolframalpha mostly correctly and copy paste
> the result, the result is:
>
> (1.33737 | -0.025411 | -0.311956
> 0.17323 | 0.446306 | 0.380464
> -0.005481 | 0.031327 | 0.974154)
>
> So
>
> Red from Red = 1.34
> Red from Green = -0.025
> Red from Blue = -0.0312
> Green from Red = 0.173
> Green from Green = 0.45
> Green from Blue = 0.38
> Blue from Red = -0.005
> Blue from Green = 0.031
> Blue from Blue = 0.97
>
>
> This would correspond to correctly converted YIQ but then converted back to RGB with
> your coefficients (barring typos). It does seem to make, for example, the nes output
> closer to my old crt PVM. The sky is much closer in smb1 anyway. But you might need
> to play with the gamma settings. And lower saturation if you haven't already. It was
> set at 150% by default in the bgfx hlsl chain!

Thanks for all the above, including the effort, it is appreciated. The Sony CXA2025AS US decode matrix is definitely something many NTSC(/US) users experience(d).

Absolutely, off the bat, the sky in SMB1 is one of the first noteworthy items, appearing as a 'true blue', rather than the current default of a very 'purple' colored sky.

Having an option, perhaps a command line switch (I.E. -matrix ntscsony) or some other way to have a preset display default, with the correctly converted and assigned attributes, would go a long way in MAME emulating the hue/color output as witnesses under many systems for a considerable portion of the population.

Hopefully, somewhere down the road we'll see it implemented "officially". Thanks, again