Digital over-the-air TV works similarly to analog over-the-air, but it's slower to change channels because the TV has to wait for a frame that isn't a delta from a previous frame to display a coherent image. That's just sort of par for the course with modern digital compression, you could increase the number of such frames but then the compression gets less effective and you'd still have more of a delay than with analog.
Oh I didn't know that over the air TV broadcasts use MPEG. I'm surprised that digital over the air even decodes at all considering how poor I remember the quality being in my childhood. I was referring more to cable.
