Larger sensors and more megapixels not needed
For video, even for Blue Ray quality, the best you can do is 1080p, which is 1920 x 1080 pixels or about 2 megapixels. So those large sensors in DSLR cameras with 10, 12, 15 or more megapixels won't get you any better video. DSLR Camera video mode will cut it down to 1920 x 1080 or 2 megapixels as it writes each frame. DSLR electronics simply can not process those huge megapixel images running at 60 or even 30 frames per second. DSLR burst mode speeds in photo mode recording can at best do somewhere between 3 and 10 frames per second processing all those pixels. And besides, the video output quality will be at best 1080p.
My only point is, DLSR large sensors and megapixels have very little to do with video quality.