The cable systems don't have to carry HD they just have to offer digital service cause the analog is going away and local TV stations will broadcast HD and/or digital signals. A 10 standard digital channels can fit in the bandwidth of an older analog channel (6.4mhz) and about 3 HD channels can fit into a 6.4mhz bandwidth channel where an analog carrier was. This issue with the cable companies is that most of there usable bandwidth for IPtv, Digital TV, HD, VoIP, and data is taking up by the analog spectrum. Once the FCC forces the broadcasters to remove the analog channels off the air the Cable companies (MSO's) can use the bandwidth. Another issue is that the FCC requires cable companies to offer basic service to additional TV's free and once the analog is gone you will have to have a rent free cable box (provided by the cable company) to receive the basic channels cause now they will all be digital. This cause the cable companies to have to give out alot more cable boxes (which will cost about 3 times what it takes them now to provide service) to fill the customers needs. Cable boxes can cost from $100-700 each and if each house now needs 3 boxes how will they keep there bottom line competitive with the dish providers....
Now to the Slingbox question... The traffic is encrypted (this is required by the broadcaster copyright issues) so only one client can watch the stream at a time. the stream only works with there encoder/decoder software. I also have a sling box and can so the low end one works great when your on the road and the hotel only has 20 channels to watch. You can make your own sling-like box with myth-TV and VLC. I have done this before and the video over IP is nice and can support as many users as your bandwidth can handle. With an IR blaster you can get myth TV to act like a sling box. Only issue with multi-casting video is copyright issues if anyone other than you is getting the feed.
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