@alvin thanks kindly for your links, but unfortunately I don't get it to work. I've tried what has been suggested in the config guide and also found the right number for my 4K display but I don't get the right result.

I've found something out though:
IMG_7837.JPG

As you can see, the tv screen itself has a picture ratio of 16:9, the displayed part from Recalbox has a video ratio from 21:9 though. Makes sense to display the "21:9" image in the middle of the "16:9" screen - yes, but from Recalbox, the tv should get a 16:9 signal but it gets a 21:9 one (tried to change that in my Samsung menue but it always states, that the signal is 21:9 and not 16:9).

How can I force the output from Recalbox to be 16:9?

Best regards,
Dan

EDIT
I got it fixed somehow. Changing the HDMI port on my tv made it work... maybe this helps someone else as well 🙂

Bonjour @bigguerlame
quel est le rapport avec recalbox, le système d'exploitation de retrogaming ?

nous ne sommes pas un forum général sur un boitier pour raspberry pi.
tu dois aller poser ta question sur ce forum : https://www.raspberrypi.org/forums/viewforum.php?f=65

@vukilore Recalbox n'est pas une application mais un OS à part entière. Il n'est pas possible de l'installer sur smartphone, même jailbreacké.

Du coup wiki documentés:
https://github.com/recalbox/recalbox-os/wiki/Use-an-external-usb-storage-device-on-recalbox-(EN)#what-to-do-if-recalbox-still-doesnt-see-my-hard-drive-
https://github.com/recalbox/recalbox-os/wiki/Utiliser-un-périphérique-USB-de-stockage-sur-recalbox-(FR)#que-faire-si-après-le-redémarrage-recalbox-ne-voit-toujours-pas-le-disque-dur-

@dagda94 n'hésite pas à passer le sujet en résolu 😉

Well thanks to @paradadf it worked ... I completely forgot about it ... Thank you very much !

Now I have to set everything up ! 😄

Never mind it was an issue with the hdmi cable being dirty oops

@dayfluent to add a bit to @Substring 's answer... recalbox is free and should not be bought. What you can buy is the hardware to run recalboxOS.

Hello
No chance.

Thank you, this was exactly the problem. I forgot everything must be on FAT32 to work on the Pi. I used the Disk utility on my Mac to format and now everything works fine.

Mine was detected by windows as 64gb too, and i can used it, but when recalbox tried to format it on ext, there was on error. These fake SD are detected as 64gb but only 7 or 8 gb are available.