Very Nooby Question regarding Sound Formats

[PaniqL]

Hello,

I Know this is a very basic question but i am yet to find my answer.
With all the different sound formats going around

How do you select what format you want to use?
I know that not all Blu's have a 7.1 Mix and will be matrixed, but how do you select?

Is it on the Disc Menu?
Or is it when you run the Speaker setup? like adding 7 channels you can choose PLIIz or normal 7.1?
Or is it in the receiver's Menu?

Thanks
- Callum