When I'm playing a video or audio file, I sometimes want to jump backwards and forwards by small amounts, and sometimes skip around very quickly. Doing this with a VCR-style interface is clumsy because it's hard to indicate how fast to move with just a button press; using a single timeline is very quick for a single scale but not so good for fine control. One possibility would be to use multiple timelines, each with a different scale (so one which shows the whole file being played, and one which zooms in on the current play position at a higher resolution for jumping shorter distances), but a nicer way might be to have a two-dimension scale with the entire file across the top and a zoomed-in section across the bottom (and diagonal lines joining them); the top scale would be fixed and the bottom scale animated.