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In this article:
- What is HD DVD
- Features of the HD DVD standard
What is HD DVD?
HD DVD stands for High Density Digital Versatile Disc or High Definition Digital Video Disc. It is a optical media format which is capable of holding high definition video or other types of data. HD DVD is the closest competitor to the Blu-ray Disc standard. Both the formats have the same disc size with a diameter of 120 mm. HD DVD is supported by the certain companies, major ones in which include Toshiba, NEC, Sanyo, Microsoft, and Intel. Universal Studio is the only major studio backing this format exclusively.
The standard was actually announced on 19th of November 2003 at the DVD forum for being the successor to the DVD format. Originally called the Advanced Optical Disc or AOD, it was renamed to its current name, HD DVD. It is notable that Blu-ray was never given to the forum for consideration and so also that is was made out of the forum.
An HD DVD with a single-layer has a capacity of storing 15 GB of data. A dual-layer disc on the other hand can store 30 GB of data. Another offering is of a three-layer 45GB disc. The HD DVD format allows the storage of both, the DVD and the HD DVD formats on the same disc which allows the discs to be played on older and newer high definition players alike.
Toshiba released the first HD DVD players on April 18, 2006, called the Toshiba HD-A1 and Toshiba HD-XA1 in the United States.
Features of the HD DVD Standard
- Read-Write Methods
The HD DVD standard uses a blue-violet laser same as that used by the Blu-ray standard with a wavelength of 405 nm. However, the HD DVD standard uses an optical pick-up with a numerical aperture of 0.65 as against 0.85 in the Blu-ray standard. This allows for proper focus on the data layer and allows more data to be written in the same amount of space. On the reading side, this configuration enables reading of higher density data from the disc.
- Video and Audio Formats
Both, Blu-ray and HD DVD are to use the same video codecs, namely, MPEG-2, VC1 and H.264/MPEG-4 AVC.
HD DVD, like Blu-ray, supports up to 7.1 channel surround sound and supports the PCM, Dolby Digital, DTS, Dolby Digital Plus, Dolby TrueHD and DTS HD formats for audio.
- Backward Compatibility
All HD DVD players are to provide backward compatibility so that a single drive can play HD DVDs and the usual DVDs as well. There is also a provision for a hybrid variety of the format where one disc can store both the formatsof a movie (HD DVD and DVD). As against Blu-ray drives, the HD DVD drives are more compact in size.
- Access Restriction Technology
The HD DVD standard is to integrate the content protection scheme specified by the Advanced Access Content System License Administrator. Audio Watermark Protection is one of the standards that are planned to be integrated, though this is not decided upon. also being considered by AACS for use on HD DVD. The watermark would be an inaudible audio part of the movie soundtrack which will be identified by the sensors on the HD DVD player and will be used to identify an HD DVD as being original or an authentic copy.
- Interactive Content
For making interactive content for the HD DVDs such as menus, the iHD Interactive Format is used. This is different from the Blu-ray standard which uses Java for this purpose. At the moment however, the BD-J, the Java version on the Blu-ray players, seems to be more promising, given the fact that Java os well-known language all over the world. However, it is possible that inclusion of Java will increase costs of the players, which should work in favor of HD DVDs.
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