Blu-Ray and HD-DVD FAQ

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As optical technology advances, it brings with it the necessity to understand new devices and how they function. At Cd-writer.com it is our intent to help you understand how these new technologies work and to help you make an informed decision about which is best for you.

At first glance the new array of optical storage devices can be rather daunting to even the most literate of computer users. Each have their own unique properties, burn speeds, storage capacity & software. Blu-Ray, Dual Layer, ± Media & HD-DVD are all terms we will need to familiarise ourselves with in the coming months.

What exactly is the difference between Blu-Ray and HD DVD? Which of those formats are better? Why the sudden surge of new technology?

The basic principles for both Blu-ray and HD DVD are the same. An optical laser embeds code onto a disc as it spins, altering its surface, storing data from the centre of the disc outwards. Information is extracted off the disc by a laser of the same frequency that interprets the reflections of the laser off the discs surface.

The amount of data a disc can store is down to the frequency of the laser used when making the disc, and only drives using the same frequency laser can extract that same information. The newer technologies essentially use a laser that emits towards the blue (higher frequency) end of the spectrum. This allows a lot more data to be stored on the disc, greatly increasing capacity and launching us into a new optical age.

Many will be aware of the “format-wars” between Betamax and VHS in the early 1980’s. General consensus would seem to imply there is currently a newer technological war brewing between Blu-Ray and HD-DVD that could rival it. Does this mean one format will never be used? Chances of that happening are very unlikely, it is important to remember that both HD-DVD and Blu-ray have been released for different markets.

Blu-ray launched with the intention of dominating the Information Technology sector, where as HD-DVD aims to be dominant in the consumer products sector, essentially with audio-visual devices. Although neither of the formats have been released in the UK as yet, the early part of 2006 will see a flurry of activity, with many computer components being developed to cater for both Blu-ray and HD-DVD.

A closer look at Blu-ray and HD DVD:

Frequency 650nm 405nm 405nm
Capacity(SL) 4.7GB 20GB 25GB
Transfer rate 11.08Mbps 36Mbps 36Mbps
(SL) = Single Layer


Single layer Blu-ray discs will have a capacity of 25Gb (equating to approximately 2 hours of High Definition video, or 13 hours of standard definition video).

Blu-ray discs will also have multiple layers, allowing up to 50Gbs of storage on a dual layer disc, increasing to 100-200Gb on a multi-layered disc. The technologies are likely to support backward compatibility with both CD and DVD formats.

To burn a full 25GB Blu-ray disc at 1x speed would take approximately 90 minutes. It is expected that as the format matures, the overall speed of the drive will be 8x or more writing a full 25Gb in just under 12 minutes.


When comparing HD DVD to Blu-ray there is only one obvious difference, the storage capacity of the disc. As a single layer medium HD DVD will hold approximately 20Gb, with a maximum of around 45Gb on a dual layered disc. Higher capacity discs currently can not be produced, this is because the distance between the discs surface and the recording layer is too great.

The HD DVD products are also expected to be backwards compatible, and writable media (including HD DVD-R, HD DVD-RW & HD DVD-Rom) will be available.

So which is better, Blu-ray or HD DVD?

At the moment that is simply a matter of opinion. Each technology (although similar) is varied enough to argue its purpose to the industries for which they were intended. We hope our informative guide to both these mediums will help you understand the technologies, and make an informed decision about which is best for you.

How much can I expect to pay for a Blu-ray recorder?
As with all new technologies, you can expect to pay a high price for these first generation products. Currently Blu-ray is only on sale in Japan but is being released in the UK & US towards the beginning of 2006. The prices of Blu-ray and HD DVD are expected to drop dramatically as the year progresses.