HD DVD
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| Media type | High-density optical disc |
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| Encoding | VC-1, H.264, and MPEG-2 |
| Capacity | 15 GB (single layer) 30 GB (dual layer) |
| Read mechanism | 405 nm laser: 1× @ 36 Mbit/s & 2× @ 72 Mbit/s |
| Developed by | DVD Forum |
| Usage | Data storage, 1080p high-definition video |
| Extended from | DVD-Video |
HD DVD (short for High Definition/Density Digital Versatile/Video Disc) is a discontinued high-density optical disc format for storing data and playback of high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format.
On 19 February 2008, after a protracted format war with rival Blu-ray, Toshiba abandoned the format, announcing it would no longer develop or manufacture HD DVD players and drives. The HD DVD Promotion Group was dissolved on March 28, 2008.
The HD DVD physical disc specifications (but not the codecs) were still in use as the basis for the China Blue High-definition Disc (CBHD) formerly called CH-DVD.
Because all variants except 3× DVD and HD REC employed a blue laser with a shorter wavelength, HD DVD stored about 3.2 times as much data per layer as its predecessor (maximum capacity: 15 GB per layer compared to 4.7 GB per layer).
In the late 1990s, commercial HDTV sets started to enter a larger market, but there was no inexpensive way to record or play back HD content. JVC's D-VHS and Sony's HDCAM formats could store that amount of data, but were neither popular nor well-known. It was well known that using lasers with shorter wavelengths would yield optical storage with higher density. Shuji Nakamura invented practical blue laser diodes, but a lengthy patent lawsuit delayed commercial introduction.
Sony started two projects applying the new diodes: UDO (Ultra Density Optical) and DVR Blue together with Philips, a format of rewritable discs which would eventually become Blu-ray Disc (more specifically, BD-RE) and later on with Pioneer a format of read only discs (BD-ROM). The two formats share several technologies (such as the AV codecs and the laser diode). In February 2002, the project was officially announced as Blu-ray Disc, and the Blu-ray Disc Association was founded by the nine initial members.
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