High Definition DVD: The Facts


What is Blu-ray?

Blu-ray (aka BD) is an alternate high definition technology that tries to compete with HD DVD. It was created by Sony originally as a recordable format using MPEG2 and a proprietory disc file system, but was later forced to include more advanced codecs (e.g. VC1) and use a standard disc file system (UDF). Blu-ray is governed by the BDA (and not the DVD Forum), and the majority of BDA members wanted to use HDi™ for the interactivity layer, but this was denied them. Instead they had to use a version of Java, now known as BD-J, for their interactivity, and this is now widely viewed as a huge mistake.

Theoretical advantages of Blu-ray

  • Larger disc capacity. BD discs can in theory hold up to 50G, but manufacturing problems limit usable capacity to 44G or so.
  • Greater bandwidth. Data can be read from the disc at a faster rate than HD DVD, but this has yet to be shown to provide any real value to the user. It does make the drives harder and more expensive to produce.

Problems with Blu-ray

  • BD-J is hard to get working the same way on different players, and very slow on some.
  • BD+ is an extra layer of copy protection which the DVD Forum rejected for HD DVD. Like BD-J it is very hard to get working reliably on all players.
  • Blu-ray is missing many of the features that are standard in HD DVD, such as
    • Secondary video decoder (e.g. for picture-in-picture Director's Commentary)
    • Support for lossless audio codecs (e.g. TrueHD)
    • Network support
    • Persistant storage (to store bookmarks, settings, downloads etc)
  • Multiple Profiles: today's players are Profile 1.0; Profiles 1.1 and 2.0 add some of the missing HD DVD features but currently there are no players that comply (and no discs that use it).
  • The cheapest BD players are around twice as expensive as the cheapest HD DVD players.
  • hybrid discs are not possible with Blu-ray.