Which audio format to use for 6.1 and 7.1

[bevo]

Whenever I watch blu rays, my ps3 automatically sends out a multi channel pcm 7.1 signal. My receiver can send sound to all 6 of my speakers.

But when I watch cable, and it's dolby digital, which type of audio signal should I use. My choices are
1.Dolby digital (only uses 5.1 channels)
2.dolby digital ex( with it my receiver uses all 6 speakers)
3.Dolby D PLIIx M(my receiver also uses 6 speakers)

So which is better EX, or PLIIx M?

[Keiko]

Whichever sounds best to you. ;)

As far as I know though, cable television only transmits Dolby Digital 5.1 and only if available.

[bevo]

Whichever sounds best to you. ;)

As far as I know though, cable television only transmits Dolby Digital 5.1 and only if available.

It's my receiver that converts it to dolby digital ex, or dolby d PLIIx M, that way I can use the back channel or channels for 6 or 7.1.
I'm really just wanting to know the differences in the 2.

[Keiko]

http://www.dolby.com/consumer/technology/prologic_IIx.html

http://www.dolby.com/consumer/technology/dolby_ex.html

Not sure about Dolby D PL IIx "M"

I'm guessing, but "M" could stand for music or movie. Might want to refer to your receiver's user guide and see if it specifies this.

Still, whichever sounds best on your ears is the one to use.