Or can you broadcast a show in HD that was NOT filmed in HD? Would a digital DVD be in HD?
Because I'm answering this after reading it, and not waiting till I'm caught up ('cause I'll surely forget to go back and respond by that time):
One can watch anything in a "digital" broadcast. I wasn't getting digital signals on my old set. I bought rabbit ears in order to pull in over-the-air digital and High-Def broadcast signals. One of the bonuses, of course, is seeing shows that air on digital transmissions and seeing them in a much LARGER format (37" versus my old 21" set). Interestingly, the channels that air digital broacasts, etc., also still air analog broadcasts.
For instance, I can watch ABC on Channel 7. Over-the-air, this station gives me an analog signal on Channel 7, and a high-def/digital signal on Channel 7.1. Some other stations, like channel 4 (independent) has analog on 4, standard definition on 4.1, high definition on 4.2. The signal off 4 is horrible on my new set....4.1 is digital, and 4.2 is sheer magic WHEN, but only when, a high def broadast is provided.
There are variations to be found at most stations, but primarily, my set by itself scanned to find digital/high def over-the-air/antenna signals and gave me what was locally available.
I want more, of course, but then I still have my cable broadcasts which come in rather well, if not nearly as nicely as the digital over-the-air stuff. There's nothing for me to do, really, but upgrade to a digital service.
Finding the right one is the time-consumer.
