I believe these are the aspect_ratio_index settings
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
http://smartretro.co.uk/forums/viewtopic.php?t=52
