New jargon alert: downconversion. You may have heard of upconversion; this refers to the process that some DVD players use to take standard definition DVD content and expand it to high definition resolution. This is a form of scaling that essentially fills in the “missing” data when the number of pixels is increased. Of course, it can’t know what’s missing — that only happens in the movies and TV crime shows — and your HDTV should be able to do this for itself, but the DVD player presumably has better scaling so maybe it will look better.
So what is downconversion? It’s the opposite of upconversion: taking a high definition image and throwing away pixels to make it standard resolution. Why would anyone want to do that? Cable operators want to do this to broadcast HD signals so that they can convert them to analog standard definition images that can be viewed by subscribers who don’t yet have a digital television. That’s fine with the broadcasters, but there’s another aspect of this. Current law allows cable operators to downconvert HD signals to digital standard definition signals. The only reason to do this is to save bandwidth on their systems. (There already is evidence the cable companies overcompress the digital HD signals to the point that the degradation is noticeable.) The broadcasters want the US Congress to require cable operators to deliver the HD content they receive as HD content to their subscribers.
This is a battle that is not likely to be resolved soon, but with the February 2009 deadline for ending analog broadcasts looming, it’s a topic you’re likely to hear more about in the future.