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This article compares the technical specifications of multiple high definition formats, including HD DVD and Blu-ray Disc; two mutually incompatible, high definition optical disc formats that, beginning in 2006, attempted to improve upon and eventually replace the DVD standard. The two formats remained in a format war until February 19, 2008 when Toshiba, HD DVD's creator, announced plans to cease development, manufacturing and marketing of HD DVD players and recorders. Other high-definition optical disc formats were attempted, including the multi-layered red-laser Versatile Multilayer Disc and a Chinese made format called EVD. Both appear to have been abandoned by their respective developers. ==Technical details== a These maximum storage capacities apply to currently released media as of January 2012. First two layers of Blu-ray have a 25 GB capacity, but the triple layer disc adds a further 50 GB making 100 GB total. The fourth layer adds a further 28 GB. b All HD DVD players are required to decode the two primary channels (left and right) of any Dolby TrueHD track;〔(HD DVD Promotion Group )〕〔(DVD Forum.org HD DVD Technology )〕 however, every Toshiba made stand-alone HD DVD player released thus far decodes 5.1 channels of TrueHD. c On November 1, 2007 Secondary video and audio decoder became mandatory for new Blu-ray Disc players when the Bonus View requirement came into effect. However, players introduced to the market before this date can continue to be sold without Bonus View. d There are some differences in the implementation of Dolby Digital Plus (DD+) on the two formats. On Blu-ray Disc, DD+ can only be used to extend a primary Dolby Digital (DD) 5.1 audiotrack. In this method 640 kbit/s is allocated to the primary DD 5.1 audiotrack (which is independently playable on players that do not support DD+), and up to 1 Mbit/s is allocated for the DD+ extension. The DD+ extension is used to replace the rear channels of the DD track with higher fidelity versions, along with adding additional channels for 6.1/7.1 audiotracks. On HD DVD, DD+ is used to encode all channels (up to 7.1), and no legacy DD track is required since all HD DVD players are required to decode DD+. e On PAL DVDs, 24 frame per second content is stored as 50 interlaced frames per second and gets replayed 4% faster. This process can be reversed to retrieve the original 24 frame per second content. On NTSC DVDs, 24 frame per second content is stored as 60 interlaced frames per second using a process called 3:2 pulldown, which if done properly can also be reversed. f As of July 2008, about 66.7% of Blu-ray discs are region free and 33.3% use region codes. g DVD supports any valid MPEG-2 refresh rate as long as it is packaged with metadata converting it to 576i50 or 480i60, This metadata takes the form of REPEAT_FIRST_FIELD instructions embedded in the MPEG-2 stream itself, and is a part of the MPEG-2 standard. HD DVD is the only high-def disc format that can decode 1080p25 while Blu-ray and HD DVD can both decode 1080p24 and 1080p30. 1080p25 content can only be presented on Blu-ray as 1080i50. h Linear PCM is the only lossless audio codec that is mandatory for both HD DVD and Blu-ray disc players, only HD DVD players are required to decode two lossless sound formats and those are Linear PCM and Dolby TrueHD. Dolby TrueHD and DTS-HD Master Audio have become sound format of choice for many studios on their Blu-ray titles but ever since Blu-ray won the format war, it has not become clear if they are now Mandatory for all new Blu-ray disc players since the end of the format war. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Comparison of high definition optical disc formats」の詳細全文を読む スポンサード リンク
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