What is HD-DVD (high-definition DVD)?
HD-DVD (high-definition DVD) is a defunct high-capacity optical storage medium that was once seen as the successor to the DVD. A standard single-sided, one-layer DVD can hold 4.7 gigabytes of data and 8.5 GB if it's a double-layer disc. A single-layer HD-DVD stores up to 15 GB of storage capacity, and a dual-layer disk provides up to 30 GB.
A double-layer HD-DVD can store up to eight hours of 1,125-line high-definition television (HDTV) programming or up to 48 hours of standard-definition television programming. The data transfer rate of an HD-DVD drive is approximately 36 megabits per second (Mbps). That is more than enough to accommodate digital TV signals, which are transmitted at 24 Mbps.
How does an HD-DVD work?
HD-DVD is based on the Advanced Optical Disc technology that Toshiba and NEC developed in the early 2000s. The disks store data using a series of microscopic pits. HD-DVD technology uses a blue laser to read the opposite side of the pits and reflect the laser's light to a sensor. The player reads data from the sensor as digital signals.
HD-DVD disks are able to store more data than a conventional DVD because of the following features:
- Lasers with a shorter wavelength. HD-DVDs use 405 nanometers in the visible blue range compared with 650 nm in the visible red range for a conventional DVD. Blue lasers have a larger storage capacity and enable higher resolution than red lasers.
- More sophisticated data compression. DVD players reproduce data from disks that use the MPEG-2 data compression standard. An HD-DVD player can use either MPEG-2 or the more extensive MPEG-4 Advanced Video Coding and VC-1 video compression standards. These more advanced standards enable higher-quality video and smaller file sizes.
- More closely spaced tracks. The pits on an HD-DVD are smaller than those of a conventional DVD. This enabled the tracks to be closer together. The track pitch or spacing on a DVD is 0.75 micrometers, while the track pitch on an HD-DVD is 0.40 μm.
- The speed advantage. HD-DVDs players read and play back data from a disk three times faster than a DVD player. They also use High-Definition Multimedia Interface, or HDMI, technology to send digital signals to an HDTV with no need for analog conversion and the quality issues that causes.
The great Blu-ray vs. HD-DVD format war
When HD-DVD technology was first introduced, it offered several advantages over Blu-ray, an optical disk format for high-definition video that stores large amounts of data. The HD-DVD format was more in line with the standard DVD than the early Blu-ray disks, making disks cheaper and easier to produce.
In November 2003, the DVD Forum selected HD-DVD as the successor to DVD by a vote of eight to six. In March 2006, Toshiba released the first consumer HD-DVD player. Many industry experts believed the Toshiba player would lock in HD-DVD as the industry standard.
Despite these advantages, Blu-ray remained a dominant force, in part because the disks could handle more capacity than HD-DVD. In most other respects, the two formats were comparable, including in the following three ways:
- They both supported 405 nm blue laser technology.
- They both could work with the same video and audio compression technology.
- Both were the same size as a standard DVD, and either type of player could run standard DVDs.
At this point, the momentum was behind HD-DVD, especially after Intel and Microsoft endorsed the format in 2005. However, both formats gained the support of big-name movie studios:
- Paramount Pictures and Universal Pictures backed HD-DVD.
- Sony and Disney joined the Blu-ray camp.
- A few studios supported both formats, most notably Warner Brothers, but they were the exception.
The balance of power started to change as more studios aligned with Blu-ray, putting the future of HD-DVD in doubt.
The final blow came in January 2008 when Warner Brothers announced its exclusive support for Blu-ray. That ended the debate about which technology would emerge as the victor. A month later, on Feb. 19, 2008, Toshiba announced it would stop developing, manufacturing and marketing HD-DVD players and recorders.
Since then, Blu-ray players and disks have emerged as the industry standard for optical storage and are now the fastest optical media on the market. Blu-ray disks store as much as 128 GB of data.
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