High-Definition DVD as next-generation optical disc format
Nothing lasts forever and now that the world is enjoying the magic of the DVD, there are new technologies that will make today’s DVDs look like the old VHS tapes; and that is the high-definition, next generation DVDs.
Like the CD started the era of digital audio and the DVD made it possible to save a two hour movie on a disc, the successors to the DVD will be able to offer up to eight hours of HDTV-quality content. Finally, we’ll be able to enjoy the same high resolution image and multi-channel sound of movie theatres, in the comfort of home.
The need of a medium that can store high resolution movies comes at the advent of HDTV; offering up to six times the resolution of standard TVs. The DVD made it possible to save up to two hours of video, but in standard definition (SD). For higher resolution, high-definition playback, it is necessary to have a much larger storage capacity.
There are two contenders for the DVD successor crown: the Blu-ray Disc format created by Sony and the HD-DVD invented by Toshiba. Both formats use shorter wavelength lasers, but where one is more advanced in its hardware specs (Blu-Ray), the other (HD-DVD) has been backed by the DVD forum and has a better software technology.
HD DVD
The High-Definition DVD is a next-generation optical disc format conceived by Toshiba, and has the endorsement of the DVD Forum - the official international DVD standard development body for all technologies bearing the authorized DVD logo. It is worth noting that the HD DVD standard was initially called Advanced Optical Disc (AOD) and it wasn’t until the DVD Forum gave it the rank of “HDTV successor of DVD” that the format changed its name to HD DVD. From now on, when we refer to HD DVD it means we are talking about AOD and we will reserve the expression “high-definition DVD” as the generic term for both Blu-ray Disc and HD DVD.
The High-Definition DVD is a next-generation optical disc format conceived by Toshiba, and has the endorsement of the DVD Forum - the official international DVD standard development body for all technologies bearing the authorized DVD logo. It is worth noting that the HD DVD standard was initially called Advanced Optical Disc (AOD) and it wasn’t until the DVD Forum gave it the rank of “HDTV successor of DVD” that the format changed its name to HD DVD. From now on, when we refer to HD DVD it means we are talking about AOD and we will reserve the expression “high-definition DVD” as the generic term for both Blu-ray Disc and HD DVD.
Just like the DVD used the Compact Disc technology principles and reduced the laser’s wavelength (from 780 to 650 nm) to increase the amount of data that can be read or written within the same area, the HD-DVD format reduces even more wavelength of the laser; now from the 650 nm of the red laser used in DVDs to 405 nm.
Reducing the laser’s wavelength to 405 nm, results in a blue-violet laser that has a smaller spot size and therefore can read data at a higher density within the same space.
This is why HD DVD discs have the same size as CD and DVD discs, but can store larger amounts of data in the same 12 mm area. In the same way the DVD format kept the same area of its predecessor, the Compact Disc, to assure backward compatibility, HD DVD also uses 12cm diameter discs that have the same 1.2mm thickness of DVDs and Compact Discs.
This is one of the aspects that the DVD Forum and the supporters of the HD DVD format highlight the most as a way to emphasize the little changes that hardware and media manufacturers need to perform in order to switch to the new format. By sharing the basic structure of DVD, media makers will be able to utilize their current disc manufacturing lines with only needing minimal upgrades, while hardware manufacturers can develop players and computer drives that play previous optical disc formats.
As proof of the compatibility that HD-DVD offers with the previous format, Toshiba has announced the development of different types of discs that sandwich different formats.
Initially, the HD-DVD spec included a single-side, single-layer disc with a capacity of 15 GB and a dual-layer variant capable of holding 30GB of data. But in December 2004, Toshiba and Memory-Tech (Japan's largest independent disc replicator) announced the development of a single-sided, dual-layer HD-DVD-ROM/DVD-ROM hybrid disc. The DVD layer had the standard 4.7GB capacity, while the HD-DVD layer had a 15GB capacity.
Then in May 2005, Toshiba took things a step further by announcing two new types of discs; a double-sided, dual-layer hybrid ROM disc comprised of a dual-layer HD-DVD-ROM side and a dual-layer DVD-ROM side. This hybrid disc can store 30GB of high-definition content on the HD-DVD-ROM side and 8.5GB of standard-definition content on the DVD-ROM dual layer side.
The second disc announced was a triple-layer HD-DVD-ROM (read-only) disc with a data capacity of 45 gigabytes, 50% more than the original 30-gigabyte dual-layer HD-DVD-ROM, which offers enough capacity to record twelve hours of high-definition video on a single disc.
These announcements were not casual and the different developments came as result of Blu-ray Disc's superiority in regards to storage space. While a single-side, single-layer HD DVD disc is able to store a maximum of 15 GB, a single-side, single-layer Blu-ray Disc offers a maximum of 25GB. As a result a two layer HD DVD will offer up to 30 GB of storage, while a two-layer Blu-ray Disc will offer a maximum capacity of 50 GB. This superior storage capability offered by Blu-ray forced Toshiba to develop new configurations to match its competitor.
Special Features
There’s more than higher capacity in HD-DVD over its predecessor and one of the coolest features found in HD-DVD is a new technology called Advanced Content; a set of advanced interactive capabilities that allows the creation of titles that include movie-synchronized bonus features, pop-up interactive menus, and Internet connectivity.
The big improvement that Advanced Content offers over the current generation is interactivity. In a DVD Video there are single video and audio streams and the user is forced to toggle between different tracks. For example, when selecting the commentary track, the user can’t enjoy the original dialogue and music. With the HD DVD spec forcing the inclusion of three video decoders and several audio components, HD DVD can offer interactive scenarios impossible on DVD.
Imagine you are watching a movie recorded on HD DVD, and an icon appears telling you there’s a director commentary available. Unlike DVD where a menu screen must first be selected by the user before the movie starts playing, on HD DVD you’ll be able to play a commentary in the middle of the film, without stopping or requiring to switch to another menu.
Even more, the director could appear on screen, walks across the scene as the movie continues playing and you could select the volume level of either track without ever having to stop the movie or switch to another menu screen.
But there’s even more than prerecorded interactivity. HD DVD content can be linked to the Internet so companies can create a catalog on HD DVD that automatically show a product’s availability and price in real time using the players capabilities to connect to the Internet.
HD DVD movies could interact with the Internet by incorporating content after the release of the movie, so you could stream new commentary that synchronized with the movie while playing.
Another scenario are see-through menus that pop up in a movie where you can click on a item on a screen: let’s say a watch that James Bond is using, and you can buy the item online while you are watching the movie.
Content Protection
The technology used to protect the content on a HD DVD is called AACS, Advanced Access Content System. It is worth mentioning since this has been one of the reasons why HD DVD and Blu-ray Disc have been delayed.
There’s more than higher capacity in HD-DVD over its predecessor and one of the coolest features found in HD-DVD is a new technology called Advanced Content; a set of advanced interactive capabilities that allows the creation of titles that include movie-synchronized bonus features, pop-up interactive menus, and Internet connectivity.
The big improvement that Advanced Content offers over the current generation is interactivity. In a DVD Video there are single video and audio streams and the user is forced to toggle between different tracks. For example, when selecting the commentary track, the user can’t enjoy the original dialogue and music. With the HD DVD spec forcing the inclusion of three video decoders and several audio components, HD DVD can offer interactive scenarios impossible on DVD.
Imagine you are watching a movie recorded on HD DVD, and an icon appears telling you there’s a director commentary available. Unlike DVD where a menu screen must first be selected by the user before the movie starts playing, on HD DVD you’ll be able to play a commentary in the middle of the film, without stopping or requiring to switch to another menu.
Even more, the director could appear on screen, walks across the scene as the movie continues playing and you could select the volume level of either track without ever having to stop the movie or switch to another menu screen.
But there’s even more than prerecorded interactivity. HD DVD content can be linked to the Internet so companies can create a catalog on HD DVD that automatically show a product’s availability and price in real time using the players capabilities to connect to the Internet.
HD DVD movies could interact with the Internet by incorporating content after the release of the movie, so you could stream new commentary that synchronized with the movie while playing.
Another scenario are see-through menus that pop up in a movie where you can click on a item on a screen: let’s say a watch that James Bond is using, and you can buy the item online while you are watching the movie.
Content Protection
The technology used to protect the content on a HD DVD is called AACS, Advanced Access Content System. It is worth mentioning since this has been one of the reasons why HD DVD and Blu-ray Disc have been delayed.
AACS is a mandatory cryptography technology in HD DVD (and also in Blu-ray Disc) specifications developed as copy protection and digital rights management designed in part as a moving target for hackers. After Jon Lech Johansen, aka DVD Jon, cracked the code of the technology used to protect DVD movies and released the hack on the Internet, movie studios have been working on designing a new technology that can not be decrypted. That technology is AACS, which features among others, a Media Key Block that enable HD DVD compliant players to play a disc. Embedded on a disc are a theatrical mark and a consumer mark, either of which can prevent playback of an unauthorized copy, and the developers of AACS claim that bit for bit copies can’t be made with this technology. Should the hardware’s Media Key be compromised by a hacker, the Advanced Access Content System Licensing Administrator (AACS LA) can provide a new Media Key Block to the replicator and render the player unusable for future discs.
The AACS LA has approved a temporary spec allowing manufacturers and disc replicators the access to an interim license for the copy protection system so they can start manufacturing players and media but the committee has yet to finalize the spec. A final standard will be released this summer.
So far, the AACS LA has decided that there will be restrictions imposed on high definition television (HDTV) signal output to analog terminals, at least for players sold in the US and EU markets. There will be no restrictions on HD signal output to analog terminals for discs sold in Japan and other specific regions, at least until 2011.
Manufacturers will have to incorporate an analog restrict function that uses a combination of software (Intel's HDCP and Microsoft’s COPP) and hardware (HDMI) technologies to impend the playback of HD content over analog connections such as component and VGA . If these technologies are not present, the player will only output a video signal with a 960x540 resolution and won’t allow 720p and 1080i images to be displayed on the screen.
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