could be wrong, but if i am trust me someone will correct me. Even with Digital Sat. Your home theater system to get digital sound needs to have at least dolby 5.1 running on the channel your watching. this might be more of a question for the home theater section though.
in a nutshell. many channels are starting to offer DOLBY 5.1 sound thru the channels (more and more movie channels are observing that customers wish to have the better sound quality) but as far as that. rest is analog.