25G vs 50G

[GOAT]

Alright so I have noticed that many of the titles that are on 25G discs seem to have weaker audio/video... (EG Terminator 2, Robocop)... is this just by chance or is a 50G disc that much better? THANKS

[Anthony P]

a bit of both. 50GB has twice as much space as 25GB, if the content is short enough then 25GB can be enough but the more you compress content thge more information is lost, so if, because the studio wants to use a 25GB disk, it way over compresses then you will see it in the content.

On the other hand those titles you mentined are older titles both in when they where produced and when they where mastered for BD, so there can be other factors as well.

[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.

[Anthony P]

no, it is because of older vs newer. For example BD50 disks started months after the launch of BD25. So early on there where no BD50, when they launched they where harder to get (i.e. limited supply to the studio). As for MPEG2 every studio/authoring house had/has mpeg2 encoders for DVD, so some used what they had while deciding what to get next while at other times they might have bought new encoders but needed to get acquainted with them. So it makes perfect sense that movies went from 25GB mpeg2 to 50GB AVC (or VC-1). It is a matter of progression.

[digitalfilmlover]

Originally Posted by 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.

I wouldn't say that. The key here is bitrate. The higher the bitrate the more detail and less compression you will have. You can fit a 1080p video with DD audio on a regular DVD. But, the bitrate will be just around 4 or 5. So, technically more space is better because you have less compression.