41MB for 15 seconds sounds like it's writing full uncompressed frames, which is probably what I'd want for a direct recording of such a short period of time. As for the poor quality, that's because it's USB and USB doesn't have enough bandwidth for hi-res video that USB2 or Firewire could handle. You could reencode the video to something like XviD, bu that'd only make the filesize smaller and more sensible for the video length, it won't increase the quality of the video though.