Why don't I get 5.1 sound on HD channels from my cable company?

First - only recent shows shot for HD include 5.1 sound and many sitcoms and dramas do not make much use of the various channels. Some shows like last years "Terminator : The Sara Connor.." show had a rather aggressive 5.1 mix. Second - If you feed your TV with HDMI from the set top box - how do you expect the sound to get to your AV Receiver? Most televisions only have stereo speakers (and often crappy ones at that) You need to feed the Optical output of the TV to a 5.1 receiver. Not a crap-tastic DVD/Receiver with plastic speakers you bought for $299. A real 5.1 receiver. Then you will get 5.1 sound on some shows.

The tv program must have the Dolby Digital in it to have the surround sound of 5.1. You also need a receiver or a home theater in a box to decode the information into 5.1. Your tv does not provide you a surround sound, only stereo. Hope this will help you out.

Un compressed audio (full quality 5.1, 7.1 or 7.2 etc,) take up a HUGE amount of bandwith. The audio is the main reason why Blu-Ray, or HD uses soo much space. Imagine if you were the cable company. Would you devote 40% of your bandwidth to sound? Considering more people use internet than quality audio components, they tone down the sound to give you faster internet. I would invest in a good receiver, if you don't already have one. I love Yahmaha, and they do a reasonably good job of making the sound better. Also, are you trying to listen to your cable programming through LCD or plasma speakers? But to really answer your question, without dedicated fiberoptic lines from the cable company to your house, there is no way the standard infastructure of a typical cable company can do high speed internet And 5.1. Digital is usually they best they can do. It's why I don't have cable (c: