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Nine years later, we're about to get our first taste of DVD's even higher-quality successors, HD DVD and Blu-ray Disc. There are plenty of fine points separating the two formats, but both can deliver an unparalleled home theater experience — one that combines high-def pictures with high-rez 7.1-channel audio formats developed especially for these discs. And the advanced interactive features that both Blu-ray and HD DVD bring to the table will make the extras we currently enjoy on DVD look like kid stuff. With so much going for each format, it'll be hard to choose which machine to take home — but most folks will make that decision based on how many movie titles become available for each over the next few years. After all, a player is just a player, but content is king.
Getting Physical: The Discs
The new high-def discs are decidedly different creatures from DVD. Most important, they won't work in a DVD player (both HD DVD and Blu-ray players, on the other hand, can handle regular DVDs and CDs). But both types of disc are 12 centimeters in diameter — the same as DVD. And an HD DVD has the same physical construction as a DVD, with two 0.6-mm substrate layers (only the top one contains data) bonded to make a single disc. Blu-ray discs, in contrast, have a single substrate with the data layer residing close (a mere tenth of a millimeter away) to the bottom surface. Since this proximity makes the data layer susceptible to nicks and scratches, the initial Blu-ray design called for a protective caddy — an idea that was eventually scrapped when a scratchproof coating was developed.
A newly developed blue laser, with a shorter wavelength than DVD's red laser, allows both formats to store a lot more data on a disc. (See the diagrams above and below.) An HD DVD can hold three times as much as a DVD, while the even smaller beam spot size in Blu-ray players enables those discs to hold five times as much. As with DVD, multiple data layers allow even more information. For example, a dual-layer HD DVD can contain 30 gigabytes of data, enough to hold up to 8 hours of high-def video — plenty of room for the entire Terminator trilogy. And depending on what type of encoding is used, a 50-GB dual-layer Blu-ray disc could handle all three installments of Peter Jackson's Lord of the Rings cycle!
Of course, this massive storage capacity will matter most when Blu-ray and HD DVD recorders begin to appear over the next year or so. By then, you can expect to see even higher-capacity discs. The HD DVD camp is working on triple-layer discs that can hold 45 GB of data, and a dual-sided disc that doubles that amount. Meanwhile, Blu-ray has already demonstrated a 100-GB multilayer disc.
Both HD DVD and Blu-ray use Advanced Access Content System (AACS) copy protection. This bit of digital number-crunching works behind the scenes to prevent anyone from distributing pristine high-def copies of movies over the Internet. But AACS's Mandatory Managed Copy feature will let you copy discs to a Media Center PC or a home server for distribution over a local area network. You should also be able to copy movies to a portable video player like an iPod or an Archos mobile DVR.
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Image is Everything
Most people would agree that DVDs look great. So why do we need a new disc format? Here's one excellent reason: both Blu-ray and HD DVD discs have enough capacity to contain high-def video versions of movies. To put this in perspective, the picture from a DVD is made up of around 345,000 discrete picture elements, or pixels. But the images in the HD DVD or Blu-ray high-def versions of that same movie can have more than 2 million pixels — a fivefold increase in resolution!
High data-transfer rates don't only deliver remarkably crisp images. They also give both formats the potential to deliver more solid, stable-looking high-def pictures than those on cable, satellite, and broadcast TV. While broadcast HDTV channels send data at 19 megabits per second (Mbps) and DVD maxes out at 10 Mbps, the maximum data-transfer rate for HD DVD is 36 Mbps, while Blu-ray can go up to 48 Mbps.
Also, along with standard MPEG-2 compression (the format currently used for DVD authoring and HDTV broadcasting), both HD DVD and Blu-ray support MPEG-4 AVC and Microsoft's VC1 compression. These advanced codecs were designed with high-def in mind and are much more efficient than MPEG-2.
It will be up to individual studios to decide what combination of compression scheme and data-transfer rate ultimately works best for its releases. Sony Pictures, for example, has committed to sticking with MPEG-2 in its initial Blu-ray titles, claiming better image quality at the 18 Mbps data rate they've settled on for those discs. (See "Tech Talk: MPEG-2 vs. MPEG-4?," for more on this.)
Beyond mere specs, another reason why it's time for high-rez discs is that more and more regular people — not just early adopters and gearheads — are upgrading their old tubes to swanky new HDTVs. According to the Consumer Electronics Association, U.S. sales of digital TVs and related products in 2005 increased 60% over 2004. It might be easy to get high-def programming via broadcast, cable, and satellite TV, but the number of high-def movies in circulation has been pretty limited. HD DVD and Blu-ray are about to change all that.
Audio Advancements
Both Blu-ray and HD DVD players will put out signals in the standard Dolby Digital and DTS formats. But there's new audio excitement brewing, with Dolby Digital Plus debuting on both formats. DD Plus is an enhanced version of Dolby Digital, able to deliver up to 7.1 discrete audio channels as well as higher audio data rates (3 Mbps on HD DVD and up to 4.7 Mbps on Blu-ray).
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Two more audio formats we'll be hearing on both HD DVD and Blu-ray are Dolby True HD and DTS HD Master Audio. While both can provide up to eight discrete channels, like DD Plus, they use 24-bit encoding and a 192-kHz sampling rate to allow wider dynamic range and frequency response. And both use lossless digital coding that enables bit-for-bit reconstruction of the original audio signal. These new high-resolution lossless formats require much higher data rates, however — up to 18 Mbps for Dolby True HD and 24 Mbps for DTS HD Master Audio.
There is a downside, though. While the new discs will remain compatible with current gear by defaulting to standard DD and DTS bitstreams through the regular digital audio output on your player, you'll need to upgrade your digital surround receiver to one with an HDMI connection and enhanced decoding to experience the new audio formats in their full 7.1-channel, high-rez glory.
Interactive Extras
Everybody seems to like DVD extras, whether they're behind-the-scenes features on special effects or Easter eggs unlocking previously unknown treasures. (Although some of these "treasures" might even be unwanted, like the deleted scene on the Boogie Nights Special Edition disc revealing actor John C. Reilly's butt.) Happily, both HD DVD and Blu-ray are poised to take extras to interesting new heights. One reason is the sheer storage capacity of both formats. Along with a high-def movie, a single-layer Blu-ray or HD DVD can hold many hours of standard-def video features. But a bigger reason is the new interactive systems designed to exploit the players' data connections.
Most people won't care what flavor of interactivity a player uses because they'll get to experience the same cool stuff regardless. For instance, multiple video and audio streams will let you watch the director commentary via an onscreen overlay while the movie runs in the background. You'll also be able to navigate onscreen menus and perform chapter searches without stopping the movie. And if your player is hooked up to a home network, you'll have access to related Web links, games, and online shopping features.
HD DVD's interactivity specification is called iHD, while Blu-ray uses Blu-ray Disc Java, or BD-J. The main difference is that iHD, which was developed by Microsoft and Disney, is based on XML (Extensible Markup Language), a text-based format that allows a wide range of data to be easily exchanged over the Web. BD-J, meanwhile, is based on Sun Microsystems' Java, an environment that, interestingly, was originally created for use in home-entertainment devices.
Microsoft — an exclusive backer of HD DVD — holds a secret weapon in the format war, since it plans to make its forthcoming Windows Vista operating system iHD-compatible. This no doubt sweetens the deal for computer companies, who will have to pay royalties to incorporate third-party software support for Blu-ray disc drives. (Not surprisingly, computer maker HP, which had previously thrown its weight behind Blu-ray, recently decided to support both formats.) Toshiba has announced that its first two HD DVD players —the HD-AX1 and HD-A1 — won't handle the full suite of iHD interactivity when they go on sale. But the company has said it will eventually make a firmware upgrade available so first-gen players can take advantage of all the interactive features on HD DVD releases.
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The Hookup
You'll be happy to know that you won't have to use new types of connectors with an HD DVD or Blu-ray player: they'll be compatible with your current equipment. Both players will feature digital HDMI connections for newer HDTVs and analog component-video connections for older ones. They'll also have standard composite- and S-video jacks, although the best video resolution you'll get from these is a standard 480i (interlaced) signal. On the audio side, there'll be HDMI and coaxial or optical digital connections along with analog 6-channel and downmixed stereo outputs.
But other connection options — including USB, Ethernet, and RS-232C — reveal the players' networking capabilities. The USB and Ethernet jacks will let you connect a Blu-ray or HD DVD player to your home network to go online or retrieve music, pictures, and video files from a desktop PC. But you won't have to make a networking connection to use the players, since they'll continue to perform basic disc-playing duties even in an "unwired" state.
What Works, and What Doesn't
Since both HD DVD and Blu-ray players are backward-compatible with current TVs and audio gear, you shouldn't have any trouble making one work with your system. But there are a few caveats. First, AACS copy protection gives movie studios the option to "down-rez" high-def video passing through a player's analog component-video output. This feature, called Image Constraint Token, is triggered by a digital flag embedded on the disc and reduces picture resolution to 960 x 540 pixels — a 75% decrease in detail. How aggressively studios decide to use the Image Constraint option remains to be seen, but, if implemented, it would disenfranchise early HDTV adopters whose sets don't have HDMI or HDCP-compliant DVI inputs — the very same group who will be first in line to buy Blu-ray and HD DVD players! Of the studios planning high-def discs, Blu-ray backers Sony, Disney, Fox, MGM, and Paramount have all stated that they don't plan to use Image Constraint on their discs unless piracy becomes a problem.
A second issue is that most current HDTVs — including the new breed of 1080p projection and flat-panel sets — can't accept 1080p-resolution video via an HDMI connection. That means most people will have to rely on the deinterlacers in their TVs to restore the super-high-rez pictures on many of the discs to their original progressive format. This isn't an immediate problem with HD DVD, since first-gen players can deliver only1080i- and 720p-format signals. But it is somewhat of a limitation for Blu-ray, since most of its titles will be mastered in 1080p, and virtually all of the players are capable of native 1080p output. Fortunately, Blu-ray players also provide a 1080i output for compatibility with almost all current HDTVs.
A third issue involves the version of HDMI on most first-gen HD DVD and Blu-ray players and current A/V receivers. To fully experience Dolby True HD and DTS HD Master Audio, you need HDMI version 1.3 — but that specification hadn't been completed as of early 2006. So, even though these formats were designed specifically for Blu-ray and HD DVD, the HDMI jacks on early players can't pass their signals on without some form of downsampling or transcoding. With some discs, however, including Sony's first round of Blu-ray releases, you'll be able to use a multichannel analog connection to hear an uncompressed PCM version of a movie's soundtrack.
We could all do without another format war. But given the huge number of corporate interests involved — which include videogame and computer hardware and software companies along with consumer-electronics manufacturers and movie studios — war was all but inevitable. Both sides are bound to do a lot of hyping and swiping, but when you enter your local electronics emporium to check things out, just remember: Both formats are spec'd to deliver a remarkable home theater experience, surpassing that of both DVDs and much of the HDTV programming on cable and satellite TV. With those credentials, they've both got to be good.
HD DVD/Blu-ray Info Center
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