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D-VHS is a digital recording format developed by JVC, in collaboration with Hitachi, Matsushita, and Philips. The "D" in D-VHS originally stood for Data VHS, but with the expansion of the format from standard definition to high definition capability, JVC renamed it Digital VHS and uses that designation on its website. It uses the same physical cassette format and recording mechanism as S-VHS (but needs higher quality and more expensive tapes), and is capable of recording and displaying both standard definition and high definition content. The content data format is in MPEG transport stream, the same data format used for most digital television applications. The format was introduced in 1998. As a final effort for VHS, the D-VHS system is seen by its fans as a highly versatile domestic recorder (the other tape-based formats are DV and Digital8, which never gained any traction except as camcorder media), but given the wholesale move to DVD and then hard disk drive (HDD) recording, the format has failed to make any headway into the video market. There has been no small-format version of D-VHS equivalent to VHS-C; JVC, the originator of the format, chose to use MiniDV for its digital camcorder lines, and since 2005 has also expanded into tapeless camcorder designs based on hard drive storage (the Everio line). JVC does market the Digital-S format for professional use; while the tapes and technology used are superficially similar to D-VHS tapes, the underlying data format is based on the DV codec and the media formulation is drastically different. ==Tape length and speeds== D-VHS VCRs come with multiple speeds. "HS" is "High Speed", "STD" is "Standard" and "LS" is "Low Speed"; where LS3 and LS5 represent 3 and 5 times the standard length of tape. High-definition content such as 1920x1080 or 1280x720 is typically stored at 28.2 Mbit/s (HS speed). Standard-definition content such as 720x576 (720x480) can be stored at bit rates from 14.1 Mbit/s down to 2.8 Mbit/s (STD, LS3, LS5 speeds). The quality of STD speed is actually superior to the average DVD, since this speed has a much higher bitrate (approximately 14 versus 5 Mbit/s average) and suffers few compression artifacts. The LS3 speed is roughly equal to an amateur DVD with some visible artifacts in high-action scenes (4.7 Mbit/s), and LS5 appears similar to a medium-quality video download (2.8 Mbit/s). JVC's HM-DH40000U and SR-VD400U were the only units to support LS5 recording. As a result of all these different speeds, the tape labels are a bit confusing for the consumer. D-VHS was originally a standard definition format that recorded at the STD speed. When High Definition recording and HS speed was later introduced, it required twice the amount of tape. For this reason, a DF-240 will record 240 minutes of standard definition, and 240/2 = 120 minutes of high definition. When reviewing the table, note that the digital speeds HS and STD are equivalent to the older analog speeds SP and LP. 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「D-VHS」の詳細全文を読む スポンサード リンク
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