onkyo receiver owners how do you know what sound format is being output or select the proper 1?

I am wondering , how do i set or know i am outputting the proper sound format through my receiver , does it auto detect , do i have to select it myself? example - i put a blu ray movie into my player and choose in the bluray menu dts hd master audio 5.1 , does the reciever pick this up and detect what i had selected and output that format ? and does it stil apply if i change to different sound modes on the receiver like selecting thx cinema dolby digital2x and so fourth? , i am new to this and confused , i just want audio to come through the proper way . I have a onkyo 616 receiver