Mavericks said:
Wait, how 1080p can be upscaled to 4K? First of all if the signal is Full HD then - when transmitted - regardless of what def a receiver is it will still be 1080p.
Correct.
Mavericks said:
When Blu-ray is played on so called "4K" display the image is downscaled to High Definition.
With all due respect, this reads as nonsense.
Displaying an AxB image on a fixed-pixel NxM display where A<N and B<M requires an upsampling algorithm. This is what danny_boy means by "upscaling".
JEDIT: I think what you're trying to say is that an HD image on a UHD display is still HD. If this is true, then the word "downgrade" would be more appropriate for what I quoted above.