In the early 1980s, a battle was being waged for every video-watching household in America. On one side was Sony's Betamax, which was technologically adept but expensive. On the other side was VHS, a cheaper but lower-quality format. Ultimately, because of its larger video storage capacity, VHS won the battle. For years it reigned supreme in the home-video market, while Betamax essentially vanished from American homes.


Courtesy Blu-ray Disc Association (left) and DVD FLLC
Digital video is in the midst of a next-generation format war.

Now another technology battle is on the horizon, this time for the digital home market. The two contenders are Blu-ray, a high-capacity disc that can hold and play back tons of high-definition video and audio; and HD-DVD, a cheaper but less technologically able disc. They're not compatible with one another, so one format must eventually come out on top.

In this article, we'll compare the pros and cons of Blu-ray and HD-DVD and see how they stack up in the digital home-entertainment war.

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Why do we Need New Formats?
A current, single-sided, standard DVD can hold 4.7 GB (gigabytes) of information. That's about the size of an average two-hour, standard-definition movie with a few extra features. But a high-definition movie, which has a much clearer image (see How Digital Television Works), takes up about five times more bandwidth and therefore requires a disc with about five times more storage. As TV sets and movie studios make the move to high definition, consumers are going to need playback systems with a lot more storage capacity. That's where Blu-ray and HD-DVD come in.

What is the Blu-ray Disc?
Blu-ray can record, store and play back high-definition video and digital audio, as well as computer data. The advantage to Blu-ray is the sheer amount of information it can hold:

  • A single-layer, rewritable Blu-ray disc, which is roughly the same size as a DVD, can hold up to 27 GB of data -- that's more than two hours of high-definition video or about 13 hours of standard video.
  • A double-layer, rewritable Blu-ray disc can store about 54 GB, enough to hold about 4.5 hours of high-definition video or more than 20 hours of standard video.
  • A version of the Blu-ray disc that can hold up to 200 GB of data is in development.
  • Blu-ray can record high-definition programming without any quality loss, record one program while watching another, edit or reorder programs on the disc and access the Web to download subtitles and special features.


What is HD-DVD?
HD-DVD, also called AOD (Advanced Optical Disc), was actually in the works before regular DVD, but it didn't begin real development until 2003. It uses the same basic structure as a DVD but with enhanced storage capacity.

  • A single-layer, rewritable HD-DVD disc can hold 20 GB - that's just over an hour of high-definition video or about six hours of standard video.
  • A double-layer, rewritable HD-DVD can hold 32 GB - that's about 2.5 hours of high-definition video and more than 13 hours of standard video.

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How do the Formats Work?
Discs store digitally encoded video and audio information in pits -- spiral grooves that run from the center of the disc to its edges. A laser reads the other side of these pits -- the bumps -- to play the movie or program that is stored on the DVD. The more data that is contained on a disc, the smaller and more closely packed the pits must be. The smaller the pits (and therefore the bumps), the more precise the reading laser must be.


Photo courtesy Toshiba, Japan (left) and TDK, Japan
HD-DVD (left) and Blu-ray

Unlike current DVDs, which use a red laser to read and write data, both Blu-ray and HD-DVD use a blue laser. A blue laser has a shorter wavelength (405 nanometers) than a red laser (650 nanometers). The smaller beam focuses more precisely, enabling it to read information recorded in smaller pits. Blu-ray discs and HD-DVDs can both read pits that are much smaller than the pits on a DVD. That's pretty much where the similarity ends.

The recording layer on Blu-ray and HD-DVD differs. Whereas the HD-DVD recording layer is sandwiched between two 0.6 mm layers of polycarbonate plastic -- much like the recording layer on today's DVD -- Blu-ray places the data on top of a 1.1-mm-thick polycarbonate layer. The smaller pits, smaller beam and closer recording layer together enable a single-layer Blu-ray disc to hold more than 25 GB of information -- about five times the amount of information that can be stored on today's DVD and about twice that of an HD-DVD. To learn more about the structure of a Blu-ray disc, check out How Blu-ray Discs Work.

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How do the Formats Compare?
Both formats have more overall storage capacity and interactivity than traditional DVD, but each has distinct advantages over the other.

The obvious advantage to Blu-ray is the sheer amount of information it can hold. A rewritable, double-layer HD-DVD can hold about 30 GB, compared to about 50 GB for Blu-ray. More storage means that Blu-ray can hold not only a movie, but several interactive features, as well.

But HD-DVD is not without its own perks. Because HD-DVD uses the same basic format as the traditional DVD, it can be manufactured with the same equipment, saving on costs. Its manufacturer says discs will initially cost 10 percent more than today's DVDs, but the production costs will eventually drop until HD-DVD is about the same price as a current DVD. Blu-ray, which requires a new technological infrastructure, will initially be more expensive, although its cost is expected to decrease as production increases.

Blu-ray vs. HD-DVD
 
Blu-ray
HD-DVD
Backers Sony, Philips, JVC, Pioneer, Panasonic, HP, Dell, Hitachi, Samsung, TDK Toshiba, NEC, Sanyo, Memory-Tech, the DVD Forum
Movie Studio Support Columbia TriStar, Disney, MGM New Line, Paramount, Universal, Warner Bros.
Storage Capacity Read-only:
Single layer - 25 GB
Double layer - 50 GB

Rewritable:
Single layer - 27 GB
Double layer - 54 GB

 Read-only:
Single layer - 15 GB
Double layer - 30 GB

Rewritable:
Single layer - 20 GB
Double layer - 32 GB
Cost About $10 more than today's DVDs Approximately 10 percent more than today's DVDs
Advantages Greater recording and playback capacity, more interactivity Same disc structure as today's DVDs means cheaper production costs
Disadvantages More expensive to produce; hasn't been able to support more advanced video compression codecs such as MPEG-2 and MPEG-4 AVC Lower storage capacity

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When Will Blu-ray and HD-DVD be Available?
Blu-ray recorders are already available in Japan, where more consumers have access to HDTV than in the United States.


Photo courtesy Blu-ray Disc Association
Blu-ray recorder/player

Outside of Japan, once more TV sets come equipped with a high-definition tuner, and more films and television shows are produced in high-definition (which is expected to happen by late 2005 or 2006), Blu-ray movies and TV shows on disc should become widely available; but the format is already available for home recording, professional recording and data storage. HD-DVD is expected to arrive in stores at the end of 2005.


Photo courtesy Toshiba, Japan
Toshiba HD-DVD player prototype

Even when the new video standard begins to replace current technologies, consumers won't have to throw away their DVDs; but they may need to invest in a new player, depending upon which format they choose. HD-DVD will work on today's standard DVD players, while a straight Blu-ray will not. JVC has developed a Blu-ray hybrid disc that pairs a Blu-ray disc with a standard DVD -- this type of hybrid disc will survive the format transition. In any event, the Blu-ray coalition is planning to market backward-compatible drives with both blue and red lasers, which will be able to play traditional DVDs and CDs as well as Blu-ray discs.

What will each format mean for consumers? Blu-ray is billing itself as more high-tech, offering greater storage and capabilities, while HD-DVD is boasting lower costs and a less radical departure from the DVDs we already know and love. Comparing it to the old VHS-Betamax battle, HD-DVD looks more like VHS, and Blu-ray like Betamax. But at this point, industry insiders say the format war could go either way.

Ultimately, which format prevails will have a lot to do with its backers. HD-DVD has the DVD Forum behind it: a consortium of 230 consumer-electronics and entertainment companies, as well as movie studios New Line, Paramount, Universal and Warner Bros. Plus, Microsoft plans to support HD-DVD with its next Windows operating system, code-named Longhorn. Blu-ray has more than 10 of the top electronics companies behind it, plus the support of Columbia TriStar, Disney and MGM studios. Also, it has been rumored that the new PlayStation 3 game system will support Blu-ray.

Industry analysts say that whichever format can release the most popular titles and keep costs low for consumers is likely to come out the winner.

For more information on Blu-ray discs, HD-DVD and related topics, check out the links on the next page.

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