Blu-ray with picture "noise"... Confused..

[Killer Cop]

I got two Blu-ray movies, Die Hard 4 and Casino Royale for now, and a rather cheap HD-DVD with 720p & 1080i. While watching the movies which I find very very good, I still can't stop noticing some noise in my Blu-ray movies. It's not only on my TV also in my friend's much more expensive 50" 1080p TV, also the same with his Blu-ray movie (Pirates 3).

The noise I can't stop noticing once in a while, I can't figure out what makes that noise? I have knowledge in picture quality an so on, but I question this..

When you have bright clear scenes like pictures of sky, you easily see this noise. I can try post a picture if you need.

I conclude it's one of three things which cause this; compression noise, camera noise or cable noise.

I would say it's the camera noise. But I don't have a clue. It doesn't look like compression noise, unless it's anoter kind of compression.

Anyone who can explain it furher please?