Written by jdgleaver
Two new core options have been added:
Color Depth (Restart): This allows the user to select between RGB565 and XRGB8888 pixel formats. At present, the core forces XRGB8888, which is very slow on some platforms. Selecting 16-bit colour can significantly improve performance.
Interframe Blending: This enables the (crude) simulation of CRT phosphor ghosting effects. Simple performs a 50:50 mix of the current and previous frames. The Ghosting options accumulate pixels over successive frames, with persistence from 65% to 95%.
The main purpose of Interframe Blending is to alleviate the flickering that is common in many Atari 2600 games, caused when developers used the workaround of toggling sprites on alternate frames to show more simultaneous on-screen objects than the hardware strictly allowed. For example:
- Setting Interframe Blending to Simple will remove the flashing in Asteroids
- Setting Interframe Blending to Ghosting (95%) will almost completely remove the flashing in Pac Man
Ghosting can also produce nice effects in games that don’t flash – e.g. Beamrider looks rather special with Ghosting (85%).
Care has been taken to implement these options in a performant manner. With 16-bit colour depth, all Interframe Blending methods run full speed even on an RG350M (OpenDingux) with 2x video filters.