HD-DVD Vs. Blu-Ray: The Technical View

In this cross-blog feature, I'm taking a look at the optical media format war currently raging across the world.

Optical media is currently dominated by the ubiquitous Digital Versatile Disc, DVD. The DVD was in the right place at the right time, smashed VHS thanks to better pricing, better quality and more features.

It also schooled the older CD standard in the data optical disc market, thanks in large part to an increase of over 300% in per-layer capacity. Most households in the West now contain at least one DVD player, many have several. Additionally, most computers ship with one or 2 DVD drives.

But with the HD era approaching and the capacity of the DVD not really sufficient to hold enough content at HD to justify the effort - never mind the increasingly bloated size of video games - a new standard is needed. 2 competitors have emerged to take this role.

HD-DVD, Toshiba and NEC's direct successor to the DVD (In name only, it is technologically different) and the one endorsed by the DVD Forum and Sony's Blu-Ray Disc.

Both have upsides. In this part of my cross-blog feature I'll be looking at the discs from a technological and data perspective.

The primary concern on this front is the overall capacity. Blu-Ray wins out at 25GB per layer, supporting up to 2 layers for a total of 50GB. HD-DVD uses 15GB layes, so a single-layer HD-DVD has 10GB less than a Blu-Ray disc with the same number of layers. This gap increases to fully 20GB - the difference between the two formats capacity-per-layer.

That would seem to close the debate. But, alas, no.

For you see, the DVD Forum has an HD-DVD spec for a triple-layer, 51GB disc. I don't know where they found the 6GB from either, but the spec exists. This means that the higher capacity format is technically HD-DVD with the caveat of being only at the high-end. And it is a piddling advantage.

So the next consideration from a technical standpoint is read/write speed. Blu-Ray is an easy victor here over HD-DVD being 10-18Mbit/s faster. HD-DVD is roughly 3 times as fast as DVD.

Of course, these numbers being both significantly faster than DVD reduces the importance of the comparison, but that is beside the point. From a purely technical standpoint, Blu-Ray is - by and large - an easy winner.

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