25G vs 50G

[greenray]

Strange that nearly all the 25G discs I have looked at have the video encoded with mpeg2, and all the 50G discs have used either VC-1 or Mpeg4 AVC. This is the exact opposite of what you would expect. Mpeg2 is not as efficient a codec as the more recent ones (VC-1 and AVC) and produces bigger files, so you would imagine would need the bigger 50G discs rather than the 25G ones. Similarly, the more efficient codec produce smaller files, yet apparently need bigger discs. This is either an amazing coincidence or there is some other factor at work here.