If they are Blu Ray DVDs then you can only get 480P if your HDMI Video resolution is set to that.
You must set the Blu Ray player's VIDEO OUT resolution to 1080. HDMI can deliver any output signal you select, and 480P is one of 3 possible choices you have. 720P and 1080i are the others.
We could use your Blu Ray's model number...then I can check the unit.
Ok, use the HOME button on your Blu Ray remote, open the menu, arrow left to the toolbox icon.
Set the YELLOW HIGHLIGHTED settings to the yellow settings.
When you play a Blu Ray DVD on your player and you're connected using HDMI cables...you'll get 1080 on the TV screen.
The older DVDs that aren't Blu Ray....they'll only play back in their original 480 signal, no matter what setting you change.
But that will guarantee 1080 signal on Blu Ray .
It's late...I have got to go to bed.