Cable and satellite companies are aware of the tiny number of HD channels contrasted with the increasing demand for HD. At CES 2007, DIRECTV proudly announced that it would have 100 HD channels available by year end. Now, Comcast is reportedly trying to trump its competitor by saying that it will have over 800 HD channels by the end of 2008. Comcast hopes to have half of those 800 channels in place by year end, but the majority of those will be channels that show a single movie in an endless loop or a channel devoted to episodes of a popular cable show. Categorizing channels in that manner is an easy way to score a quick PR victory by claiming you have more channels than your competitor. The reality is many cable networks have yet to commit to launching HD versions of their programming.
HD content needs a lot more bandwidth than standard programming: satellite providers need to make the expensive move of adding more satellites while cable companies, which have a finite amount of bandwidth available in their infrastructure, have to use compression methods or specific technologies to get around the problem. For example, Switched Digital Video sends video to neighbourhood nodes from the cable company, and individual subscribers grab specific content as it is requested. Other companies use IPTV, which means only transmitting a handful of channels to a subscriber at any given time.
News source: Ars Technica