Before I go on with the rest of the analysis, itís important to take a moment to talk about the perceived strengths and weakness of the Blu-ray and HD-DVD formats from a technical standpoint. The short summary? HD-DVD was designed to be a pragmatic real-world solution. Blu-ray was designed as a legacy-free clean-slate solution.
One of the misconceptions is that the actual data contained on a HD-DVD and Blu-ray is the same Ė after all, they both support MPEG-2, VC-1, and MPEG-4 AVC technologies. Things are a little different. The difference between HD-DVD and Blu-ray is bandwidth. A Blu-ray disc can support bitrates of 48Mb/sec (40Mb/sec dedicated to video) while a HD-DVD disc can only support bitrates of 30.24 Mb/sec (29.4 Mb/sec dedicated to video). For any given CODEC, Blu-ray theoretically offers higher potential performance. Current Blu-ray discs are either 25GB or 50GB whereas the majority of HD-DVD discs are dual-layer 30GB discs. The theoretical limit of HD-DVD is 60GB whereas Blu-ray can theoretically reach 200GB. In the lab, Blu-ray discs supporting 200GB of data have been manufactured whereas lab-sample HD-DVDs have only reached 51GB.
But there is always a trade-off. HD-DVD uses a format very similar to DVD. There is a 0.6mm surface layer and a 0.6mm base layer. This is identical to DVDís design which means that DVD factories can easily be converted to HD-DVD production. In contrast, Blu-ray has a 1.2mm base layer and a 0.1mm hardcoat. This is what makes Blu-rayís increased capacity possible Ė but it also means that you need to spend more money dedicated Blu-ray manufacturing plants. In the long-run, itís all the same but in the short term, Blu-ray discs are more expensive to manufacture and itís the studio that is taking the bulk of the financial hit.
The other difference is mandatory features. Blu-ray players manufactured later this Fall and Blu-ray players manufactured earlier have a different set of ďminimum specifications.Ē This hasnít been an issue with HD-DVD. HD-DVD players guarantee network connectivity and picture-in-picture support Ė this is optional for Blu-ray. On the other hand, many Blu-ray players feature 1080p/24 support Ė owners of HD-DVDs are still awaiting the firmware upgrade that will bring this feature to the table.
BD-J vs Advanced Navigation
BD-Java is Java, or specifically the Global Executable Media Home Protocol (GEM). This offers developers more flexibility to work with interactive tools. Importantly, since GEM-based standards are also in play for global digital TV standards (DVB, ACAP/ATSC, and OpenCable), special features on a Blu-ray disc programmed in BD-J could theoretically be ported over to broadcast digital TV with relative ease (for the day that we actually transition to downloadable content).
BD-J is more flexible but itís general purpose nature means that itíll result in higher development costs. Likewise, it also requires more powerful computational resources to be featured in each machine.