Digital broadcasters are not restricted to just sending a high-definition
picture. They can still broadcast a standard-definition picture,
but why would they want to do that? There's a very good reason. In the
same amount of signal they can "multi-cast" four standard-definition
pictures instead of only one high-definition picture.
Some broadcasters, including many
PBS stations, are already planning to multi-cast four choices of programming
during the day, and then switch to high-definition for prime-time. When
you tune to your local Public Broadcasting station during the day, you
may have a choice between children's programming, do-it-yourself shows,
adult education, popular documentaries, or other programming. All from
the same broadcaster.
Digital TV is going to offer us more choice, and it's going to make
our viewing experience more interactive.