What is the difference between a blu-ray player that has 1080p output vs. 1080p upconversion?

I thought that all blu-ray players output in 1080p. Is this not the case?What is the difference between a blu-ray player that has 1080p output vs. 1080p upconversion?
You can tell the player to output in 480, 720 or 1080 resolution.



Sony players will output 1080i out the component cable jacks, but not 1080p. For copy protection reasons you only get 1080p from the HDMI jack with Sony BluRay players.



Also - BluRay players will up-convert standard DVD's to what ever resolution you say - but this only works using a HDMI cable. If you use analog cables - you only get 480 resolution. (This is not bad as most televisions also up-convert from 480 to their internal resolution).What is the difference between a blu-ray player that has 1080p output vs. 1080p upconversion?
They do playback at 1080p. But a standard dvd is 480p %26amp; gets the resolution upconverted to 1080p. Either the dvd player can upconvert the video or the receiver can do it. But the TV can only playback the max resolution that it's given.