Hey, Thank you for Batocera.
I share my searches in this post for community :thumbup:
I searched around for how to change internal emulator resolution for PS2 and I found that it can be done by changing the upscale_multiplier value in the /userdata/system/configs/PCSX2/inis/GSdx.ini file. By default this value is 1. I set it to 3 or 4 to have somehow a 720p or 1080p rendering.
this can be done easily with the following command
sed s/upscale_multiplier\ =\ [0-9]*/upscale_multiplier\ =\ 4/ /userdata/system/configs/PCSX2/inis/GSdx.ini -i
that will change the value in the file. (the scale factor here is 4, but it is possible to set it to 1, 2, 3, 4 or 5.
I made it using x86_64 (standard PC) but I think this also works for other devices (pi / odroid ...) but PS2 may not work well on such devices...