Using Windows 10 64bit with 4:3 crt monitor, retroarch 1.18 genesisplusgx core, the default aspect ratio is correct 4:3 for genesis/game gear (with borders off), but for master system/sg-1000 it gets stretched widescreen. I know master system/sg-1000 had 4:3 aspect ratios, so why is the default incorrectly stretching them? I also saw a reddit post where someone said to add borders top/bottom, which did somewhat fix the master system/game gear aspect ratios (still uneven black bars on the sides) but messed up the proper 4:3 ratio for genesis games (they got a little squished vertically). Also, if I set window scale x3 for master system/sg-1000 they still have too much widescreen, and a black bar on only the left side, uneven. So what is going on with the master system/sg-1000 default aspect ratios not being proper 4:3 in genesisplusgx?
if you are using a 4/3 monitor then: Settings -> Video -> Aspect Ratio -> Full
The Master System and SG-1000 are are not supposed to be 4:3 with borders off. They only output 192 active lines, but stretch the screen like a NES. Border emulation is somewhat trickier, so I won’t comment too much on that without seeing screens of the supposed problems and knowing the host display in question, but on eg. the Master System there is the issue that games often leave the 8 pixels on the left blank because of scrolling etc.
I play in a window, so this don’t work, it stretches it widescreen.
If you inspect the log output you will see the following when running a master system game with Genesis Plus GX:
[INFO] [Core]: Geometry: 256x192, Aspect: 1.524, FPS: 59.92, Sample rate: 44100.00 Hz.
The aspect is 1.524 which is indeed wider that 4:3. That aspect ratio is derived from the dot clock rate of the digital picture generator which results in a non-square pixel aspect ratio, which in the case of SMS is 8:7 (link)
So the display aspect ratio is the result of:
256/192 x 8/7 = 32/21 = 1.52380952380952380952
So, no error in the calculation of the proper aspect ratio. It is up to the user to use another one if desired.