Available options for core-provided aspect ratio are "auto", "NTSC PAR" and "PAL PAR".
- NTSC PAR forces pixel aspect ratio of NTSC tvs always, regardless of game or core region
- PAL PAR forces pixel aspect ratio of PAL tvs always, regardless of game or core region
- auto works as following
-- NTSC PAR is used when core region is set to auto and game region is NTSC, or core region is set to ntsc-u or ntsc-j.
-- PAL PAR is used when core region is set to auto and game region is PAL, or core region is set to pal.
-- 6:5 PAR is used for Game Gear games, if core options Borders and Game Gear extended screen are both disabled
