The HD DVD route to hi-res entertainment

The DVD Forum, which has regulated DVD standards since the birth of the format, listened to its members – studios, disc replicators, authoring companies, consumer electronics manufacturers – and concluded that the ideal next-generation format is HD DVD, an evolution from current DVD standards. Industry analyst MEGUMI KOMIYA explains why.

In September 1995, the competing developers of the new generation of optical discs were persuaded to listen to the entertainment industry executives, who were desperate to avoid a so-called ‘format war’. The MultiMedia Compact Disc from Sony and Philips came together with the Super Density disc from Toshiba and together they spawned the DVD.

With the union blessed by the global media and entertainment company Time Warner and by several other CE manufacturers, the two groups joined together to form the DVD Consortium, with the desire of the two technologies never to do battle again.

The DVD Forum, as the organisation was to become, has presided over ten years of outstanding success for the format. The wisdom of having a non-commercial arbiter of technical standards and format verification that represented all interested parties has been confirmed time and again in the past decade.

DVD players and discs could be produced to a fixed specification and the consumer benefited from knowing that, in most cases, any DVD disc would play in any DVD player. Over the past decade, industry pundits have frequently questioned why the DVD specification was set in stone, with apparently restrictive technical limitations.

The logic of keeping component, manufacturing and replication costs low has been reflected in the availability of affordable players and inexpensive discs for most of the life of format so far. Seen from the perspective of 2006, it is easy to ask why so little on-board memory was specified, why there are just four colours available to create sub-pictures and why there was no web connectivity.

The HD DVD advantage

In 2006 we are confronted with a similar problem to the one that existed when DVD was born. Two formats are competing to deliver High Definition sound and pictures to the home: the DVD Forum approved HD DVD, which is an evolutionary development from existing technology, and a completely new disc called Blu-ray, which has been proposed by Sony and Philips.

Both HD DVD and Blu-ray are able to deliver feature films and other content in beautiful High Definition quality, which is not surprising as the methods used for digitising sound and vision are technically identical. Both formats use blue-violet lasers to scan the disc, offer Internet connectivity, provide AACS content protection and promise DVD compatible playback. So how is the consumer to choose between two almost identical systems? The DVD Forum received only one proposal for the next-generation of blue laser discs, the one that eventually became HD DVD.

Instead of adopting a completely new format, HD DVD shares the 12cm diameter and 1.2mm thickness of the current generation of DVD discs, yet is able to deliver eight hours of High Definition video on a dual-layer, single-sided disc. Enhanced interactivity, multi-media functions, secure AACS content protection and the capacity to store ten thousand average MP3 tracks on one disc means that the HD DVD format matches the real-world needs of today’s consumer market.

For the IT industry, a dual-layer HD DVD-R disc can hold up to 30GBytes of data. For replicators, there is the reassurance that today’s DVDs can be produced on tomorrow’s HD DVD lines, a commercial consideration that takes into account the anticipated take-up curve of High Definition discs.

Of course, HD DVD systems can play the current generation of red laser DVD discs without problems, but part of the secret of their increased data capacity lies in the use of new blue-violet lasers, operating at the other extreme of the visible light spectrum from the red lasers of today. The blue laser can read (and, in HD DVD recorders, write) a much smaller spot on each disc layer, which means that a dual-layer HD DVD can store over three times the data of today’s DVD-9.

Since 1996, when MPEG-2 video compression at around 8 Mbps was specified for DVD, codec efficiencies have improved considerably. Some broadcasters still believe that satisfactory reception of High Definition MPEG-2 pictures in the home requires up to 19.3 Mbps and there are videophiles that consider data rates of 25 Mbps are needed to view HD at the ultimate quality. However, alternative codecs, such as AVC (MPEG-4) and VC-1(Windows Media) are now available that can reduce HD data rates to 8 Mbps or even below. The capacity of a dual-layer HD DVD disc allows authors and content owners to optimise their bit-budgets for both quality and running time, whiles still leaving space for value-added extras.

Whatever bit rates are chosen and even allowing for multiple 7.1 audio tracks, HD DVD discs will offer higher quality (less compression) than satellite, cable or IPTV services. The new compression strategies would allow an hour or more of value-added material to accompany the longest movie: HD DVD is designed from the start for real-world titles.

Audiophiles will love HD DVD. Both Dolby and DTS enthusiasts are catered for and the discs are designed to include audio-only operation. You can play audio from an HD DVD disc without the need for a TV monitor - a simple CD-like remote will give access to all the audio playback functions.

Dolby Digital Plus delivers the full audio potential of the HD DVD experience. Derived from Dolby Digital, which is familiar to today’s DVD enthusiasts, it is fully compatible with current A/V systems, ensuring that consumers do not have to rush out and buy new audio systems before they can enjoy the High definition video content.

Up to 7.1support for Dolby Digital Plus audio is mandatory in the new generation of HD DVD players. Both ‘lossy’ and ‘lossless’ options are specified by Dolby, giving maximum flexibility to authors when preparing the bit-budget.

In the past, DTS support on DVD has been limited, as support was an option for player manufacturers. With HD DVD, the DVD Forum has made DTS 5.1 Digital Surround a mandatory feature, allowing producers to use DTS without fear of ‘silent’ playback. DTS also features a ‘lossless’ mode, for the closest approach to the original sound.

As well as the above audio formats, consumer players are likely to support the conventional audio codecs that are found on the Internet, including MP3, which will permit the synchronous mixing of disc soundtracks with streamed audio.

Tried and tested technology

Today’s DVD is a familiar and very reliable data storage and delivery system, which has achieved widespread consumer acceptance and which is manufactured in its millions in plants around the world. The 1.2mm thick disc has the data placed in the middle of a protective outer layer of transparent plastic and HD DVD has built on this tried and trusted format by adopting the same physical disc parameters. The format even offers a ‘3xDVD-9’ option, which brings many of the HD DVD advantages to standard DVDs on a computer.

As a result of this informed choice of disc structure, no dedicated line is required and, in tests, an HD DVD production line has been changed over to conventional DVD replication in less than five minutes. According to one estimate, from organic dye manufacturer Clairiant in Switzerland, there are over 800 DVD-R mass production lines in the world and the majority of these can be easily converted to be HD DVD compliant. No other disc structure could offer such evolutionary compatibility, underscoring the advisability of this approach. The transition is a relatively simple matter for equipment manufacturers and disc replicators alike.

The data density is much greater in HD DVD and discs may be single or dual-layer, offering a data storage potential of some 30GB per side. Alternative architectures include the ‘Hybrid’ disc, in which one side is a conventional DVD-9 and the other side a dual-layer HD DVD, which offers a single inventory product for retailers and a future-proof purchase for consumers.

There is also a technology proposal, approved by the DVD Forum as a format option in version 1.2, for a ‘Twin format’ disc, in which the layer closest to the pick-up head is reflective to red and transparent to blue-violet light. With this structure, a conventional DVD video player ‘sees’ the disc as a normal DVD-5, while the blue laser penetrates the first layer to read the HD DVD data behind.

In summary, the family of HD DVD discs includes HD DVD-ROM, replicated as either single or dual layer, with a storage capacity of 15GB for a single layer and 30GB for a dual layer disc. Double sided versions may also be produced, for example with DVD data on one side and HD DVD data on the other.

HD DVD-R write-once discs will hold 15 GB per layer, and dual layer and double-sided discs are in development. An 8-cm mini HD DVD, offering 4.7GB capacity in single layer form and 9.4GB as dual layer is also specified and a double-sided disc is part of the standard.

Copy protection

The original CSS copy protection strategy was, as most people are aware, compromised from the start by the fact that 128-bit encryption could not be used as it was deemed to be a prohibited military export by the US government. Norwegian schoolboys notwithstanding, it was only a matter of time before it was cracked, which led some content owners to call for extreme levels of security in next-generation systems.

An agreement between the major studios and the consumer electronics and IT industries led to the Advanced Access Content System (AACS) which is applied in both HD DVD and Blu-ray discs. Founders of the venture include Toshiba, Microsoft, IBM and Warner Bros.

As well as inhibiting illegal copying, AACS enables the management of content transfer to other devices where permitted, for example on a Home Media Server. It is applicable equally to stand-alone, networked and portable consumer devices and also incorporates strategies to protect content from non-digital copying – the so-called ‘analogue gap’.

The mode of operation is relatively simple. Content owners provide the authored HD DVD data to a licensed replicator as today, together with the rules for content usage (copying is/is not permitted and in what circumstances). The AACS Licensing Authority provides the replicator with secret keys and a Content Certificate, cryptographically signed, together with data that allows compromised devices and content to be blocked. The replicator then manufactures the HD DVD discs, which carry the encrypted content and the AACS data.

AACS LA also supplies Device Keys and the Public Key to licensed player manufacturers, which will allow legally produced discs to play without problems. At the discretion of the Content owner, additional business streams can be created, with Service Providers offering secure Premium content, synchronized language and subtitle options, and offer other transactional and business links over the Internet.

AACS is format-neutral and has wide support from industry leaders. It takes over where previous content protection leaves off, providing protection for both HD and SD content on HD DVD discs. Furthermore, according to AACS LA the implementation costs are low. Other copy protection technologies can be applied, for example audio and video watermarking, but the DVD Forum has approved AACS as the basis for HD DVD security.

Interactive features

Many interactive features are available to the HD DVD author, and the user experience will be much richer than the previous generation of DVDs. The iHD (Interactivity for High Definition) programming for HD DVD is similar to the proven XML and is the most appropriate solution for the next generation discs. Unlike the Java-based alternative, iHD has an inexpensive licensing model, which will integrate well with Internet applications and to Microsoft’s new Vista operating system and which lends itself to the broadest range of applications.

The use of iHD will open an exciting new interface for the user, with pop-up menus that overlay the running video, picture-in-picture commentaries and game options within film entertainment titles. Connected players also gain e-commerce and downloadable content capabilities that far exceed the dreams of Web DVD pioneers.

HD DVD authoring tools are available today, with both professional and prosumer applications to choose from and, by opting for an evolutionary strategy, volume production of discs will ramp up over the next twelve months. While others may argue for larger disc capacities and extra layers of copy protection, for the home entertainment enthusiast, the HD DVD disc is the right product, at the right time and the right price....

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