Solved Force emulationstation in 4/3 from a 16/9 screen

[mYSt]

I need to make some 4/3 testing with my theme but i have no such screen and i can't figure out how to force 4/3. So far i tried to modify system.es.videomode=DMT 16 from conf and i tried to use tvservice command tvservice -m "DMT 16" but i got Invalid group. Anything else i can try?
ps : i don't want to run cores in 4/3, i want emulationstation to run in 4/3
Thx!

[voljega]

@myst recalbox.conf is for emulators, for ES you have to modify config.txt (if you use pi, otherwise I don't know)

[mYSt]

@voljega Ok thx you lead me to the solution i modify config.txt with the following

hdmi_drive=2
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=16

and it works!