D-VHS
D-VHS is a digital video 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-2 Transport stream, the same data format used for most digital television applications. The format was introduced in 1998.
As a "last hurrah" 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.
Contents
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* 1 Tape Length and Speeds
* 2 Issues/Advantages
* 3 D-Theater
* 4 DTS
* 5 Rare D-Theater tapes
* 6 See also
* 7 External links
Tape Length and Speeds
D-VHS VCRs come with multiple speeds. "HS" is "High Speed", "STD" is "Standard Speed" 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 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 40000 VCR was the only unit 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.
There are technical issues with compatibility between recordings from Mitsubishi and JVC D-VHS decks. PAL and NTSC recordings are also incompatible. Very few models are available to the world market and sales of this format have been weak; correspondingly, prices have remained high for both VCRs and media, contributing to low demand. Also hurting demand, say D-VHS advocates, is poor marketing, resulting in low consumer knowledge of D-VHS's advantages and capabilities. Although cable companies are gradually switching to the H.264 codec, this should not be an issue for D-VHS units(Mitsubishi only, see JVC exception below) since they can act purely as data stores (like a hard drive but using tape instead), and thereby pass the previously-recorded H.264 data from the tape to the Set-top Box or TV (via i.Link/Firewire). Finally, since machines will soon no longer be manufactured, maintenance of current recorders may prove difficult.
D-VHS's primary advantage is that it is still the best way to archive encrypted high definition material from cable programming. Though a new device from Hauppauge (HD DVR) has enabled removal of encrypted content off many of the above proprietary boxes. Cable, satellite companies, TiVo, and PCs equipped with cable card tuners all offer high-definition digital video recorders, but archival has proven to be an obstacle because proprietary boxes have restrictions on moving encrypted content. The HD DVR's analog conversion is slightly degraded but still high definition grade, and much better than standard definition. Monthly rental fees to cable, tivo, and satellite are less with D-VHS. D-VHS format has proven itself to an ultimate HD recorder of encrypted content for many years, and will continue to be a workhorse for many informed high definition connoisseurs.
The JVC D-VHS deck released in the UK, was not a bitstream recorder, although it did have a FireWire input. Instead it is best thought of as a digital recorder for traditional analog inputs such as domestic analog TV and digiboxes for digital broadcasts. The deck was able to record D-VHS signals onto S-VHS tapes, which made it a cost-effective source of high quality domestic recordings. Pictures were noticeably superior to S-VHS and were essentially transparent when compared to an off-air source. Using the LS3 mode, approximately 17.25 hours of digital video could be stored on a S-VHS E-240. The deck's biggest shortcomings were the lack of a DV output and, perhaps more crucially, the lack of RGB input via the SCART connector (PAL territories only as the NTSC versions had component outputs). The industry switch to h.264 will gradually obsolete the JVC decks as a recorder of cable content. The unit will still be able to record but won't play on unit. A lengthy transfer to computer may allow another software player to allow viewing.