Floob
Member
Post count: 1629

Lots of good (and heated!) discussion on custom ratios here:
http://libretro.com/forums/showthread.php?t=1471

As they mention, sticking to an arbitrary 4:3 for the sake of it isnt really that relevant, with the goal really being to get close to each systems native output resolution.

For reference the “aspect_ratio_index” settings are:

0: 4:3
1: 16:9
2: 16:10
3: 16:15
4: 1:1
5: 2:1
6: 3:2
7: 3:4
8: 4:1
9: 4:4
10: 5:4
11: 6:5
12: 7:9
13: 8:3
14: 8:7
15: 19:12
16: 19:14
17: 30:17
18: 32:9
19: config (video_aspect_ratio setting)
20: 10:9 (1:1 PAR)
21: Core Provided
22: Custom

As an example, my Game Gear settings are (on a 720p TV):

aspect_ratio_index = "22"
custom_viewport_width = "432"
custom_viewport_height = "389"
custom_viewport_x = "423"
custom_viewport_y = "165"

As you can see the viewport width/height are a multiple of the native 160×144 to keep the ratio the same.

Although the more I read the thread below, the more I think I should check out the affect of using Core Provided instead.
The OP there has said:

If you want the native core AR then use “core provided” whether they got it wrong or right.
If you want the nostalgia look whether it’s right or wrong, don’t crop overscan and use 4:3 (display) aspect ratio.
If you want accurate ratio, check my thread here.
http://libretro.com/forums/showthread.php?t=1471