MAMEWorld Forums - EmuChat

Regarding dithering:

The Megadrive (Genesis) made use of dithering specifically because being displayed through a composite connection would tend to blur colors together horizontally.

Making MAME "dither" the output is exactly what you don't want.

Instead, what you want is to use one of the post-processing shaders that MAME supports, with a few tweaks to handle the resolution difference between the Megadrive and the NES (which is what the NTSC simulation was designed for).

So yeah, first things first.

Create a file in the following path, with the following name, relative to the MAME executable: ini/presets/source/megadriv.ini

Next, copy/paste the following data into it:

Code:


#
# NTSC POST-PROCESSING OPTIONS
#
yiq_enable                1
yiq_jitter                0.0
yiq_cc                    3.57954545
yiq_a                     0.0
yiq_b                     0.5
yiq_o                     0.0
yiq_p                     1.0
yiq_n                     2.0
yiq_y                     6.0
yiq_i                     1.2
yiq_q                     0.6
yiq_scan_time             45.1
yiq_phase_count           2

Finally, when you run MAME, be sure to:

A) Run the 'genesis' driver, not the 'megadriv' driver, and
B) Run with the "-hlsl" parameter, to enable HLSL post-processing.

This all assumes that you are running on a Windows-based machine with a halfway-decent graphics card. If one or both of these things aren't the case, all bets are off.

But the end result is that this choppy-looking, obviously-dithered picture:

Will be smoothed out into something more akin to what you'd get on a real CRT, including various adjustments to color balance:

Share and enjoy!