I think someone said Comcast is supposed to provide local stations.
More precisely, the Communications Act of 1934 requires that all cable service providers include stations/programming that you could otherwise receive with an antenna.
AFAIK, not one single local television station in the US broadcasts OTA with an analog signal anymore...as a result, Comcast must provide digital delivery for those local stations. In other words: plug your bare cable into any ATSC tuner, and you will receive HD programming for local stations that broadcast in HD (example: KOMO/ABC 4.1). You will also receive local digital stations that broadcast in SD (example: KOMO/ThisTV 4.2).
All cable service providers also broadcast local stations in analog. This is so the cable provider can still rake in the dough for the millions of analog televisions still in use that subscribe to the Basic package. How many analog channels you receive depends on your location and service provider, but I believe that at a bare minimum, channels 2 thru 13 are broadcasted in analog via cable.
This means you can use an analog TV tuner in your computer, regardless of which cable provider you have. This doesn't mean that you
should use an analog card, just that you can...this is primarily because PCI's days are numbered, and that the analog picture quality really sorta sucks. And the quality sucks a lot worse on an HDTV than on a computer monitor.
Now, here's the deal with you being able to receive TV with cable: even though you only subscribe to broadband, everything still comes thru a single cable. The cable company is required by law NOT to scramble the lowest-tier package they provide (usually known as "Basic"), whereas they would otherwise force their customers to pay additional fees for a descrambler. As a result, they can't block Basic channels. It makes sense...if you bundle broadband and basic TV for a "price break", you'll find there is only a $5 difference per month over broadband-only. They know they can't stop the TV signal, they just hope you don't find out about it and pay the extra few bucks for it. They also hope you don't find out that getting Basic channels in HD does not require their box, which they would use to "upsell" you to much more expensive packages. And if you get the box, you can't record on your computer...that's how they "upsell" you even further to rent their own (crappy) DVR box.
Two of my HTPCs have the Hauppauge 1250 tuner. It will do either OTA or cable. It's PCI-E, so it won't become obsolete in the near future. It delivers a fantastic HD picture on MCE. And it's relatively cheap.
Griffinhart said:
OTA HD tends to be higher quality than Cable TV as well.
This part is essentially true. OTA for most markets today broadcast at about 12Mbps (720P) or 16Mbps (1080i), and I believe it's CBR. On the other hand, cable bitrate is usually much lower, and usually depends on the programming: some programs or channels get more compression than others. I tried this one night with the David Letterman Show: antenna jacked into my HTPC, and cable jacked directly to my P54G25, and then jogged between inputs a few times...the quality difference was more than noticeable, it was striking.