I faced the same issue with a Pi 400. It looks that the issue is specific with the resolution and the second HDMI2 port. If I boot the system with the default resolution everything is fine. If i change the resolution to CEA 4 (1280x720 60hz) then a black screen appear instead of Emulationstation.

To be sure, I try to a second RPi4 and in a different TV and the same issue occured.

So if someone have the same issue, the HDMI 1 port for Rpi4 is near to power cable and in the Pi 400i is near to SD card slot or leave the default resolution if you want to use the HDMI2.

@kartillian said in No Audio but only in ES / Roms:

I now still get the error message.

This means the Audio Device is not set properly in the EmulationStation settings. Make sure you have chosen 'HDMI' as the output in the Audio settings dialog in the RetroPie menu, then configure again ES with Default/HDMI as Audio Card/Device.

EDIT: I've merged your new topic here. Please don't open separate topics for the same issue.

Well I finally found another image viewer that lets me specify something to display on the second hdmi port: vlc!

But although it worked fine on FKMS, nothing showed up when I ran it with KMS... not sure if I’m doing something wrong or if that is expected.

@VictimRLSH Hm, a quick test shows it's not working at runtime (i.e. without rebooting the device). Maybe fiddling with tvservice would allow this - I'll have a to check more.