HDMI output with kodi plugin

Hello all,
Last weekend I switched from Max2Play to Volumio for my livingroom media player, based on an RPi4.
I´m very happy with the interface and sound, so far so good.
But now I also wanted to add the media player-part. So I installed the Kodi-plugin and configured it.
Now Kodi seems to work, but only on the little 7"RPI screen which is on my player. NOT on the attached TV over HDMI.
However, the sound IS coming through the TV, so this can be sent over the cable. I tested the cable with my laptop, and it is working OK.

I tried enabling and disabling hotplug, increasing GPU memory, tried different scenarios like first TV, then RPi, and the other way round, but nothing works so far.

In the ideal situation, I want to my media player as a music player with Volumio when the TV is off, and as a media player with Kodi when the TV is on.

Am I asking something which is impossible? Or am I missing a setting?

Thanks for your help.

Best regards,

I am not a specialist. But I can say that for the sound to travel via HDMI, it has to be interlaced with a video signal. The TV must be completely synced with the Raspi, otherwise you would not hear anything. Can you display what kind of video the TV receives, like 640 lines 60 hz or else?
You can google hdmi setting for Raspi in the configuration file, and you could see if there is something worth trying.

Thank you for your reply. Something is definitely happening over HDMI, because the TV always starts when the mediaplayer starts. I could not manage to see what the TV receives or how to manipulate that though. Where is the config.txt file which people point to?

Try this