Great debate has been made over HD-DVD vs Blu-Ray and the issue always comes up that Blu-Ray can store 50GB of data wheras HD-DVD tops out (currently) at 30GB. A 45GB disc is in the works. Regardless, it begs the question, how much data is actually in a high-definition movie to begin with? I took out all the interactive content and menus etc and made some back-of-the-napkin calculations just focusing on the movie and audio to see where I’d end up…

Assume average movie length is 105 minutes and a screen resolution of 1080 x 1920.
That gives…
For video:
2073600 pixels in a frame
  1.25 bytes per pixel (assume 10-bit color)
2,592,000 bytes per frame
  24 frames per second
62,208,000 bytes per second
3,732,480,000 bytes per minute
3,560 MB per minute
3.476 GB per minute

365 GB per Movie for basic movie content

DTS-HD High Resolution Audio:
3018 kbps (kilobits per second) according to www.dts.com
368.41 kB/s (kilobytes per second)
0.37 MB per second
22.2 MB per minute
2,331 MB per movie
2.28 GB per movie for basic audio content

367 GB Total

That’s a RAW, theoretical worst-case number with no compression. Amazingly with MPEG compression this can typically be squeezed down into 25GB (14:1) or less with no quality loss leaving plenty of room for those menus or even an extra audio track.