D-VHS
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|
Television production | |
Extended from | S-VHS |
---|---|
Released | December 1997 |
D-VHS is a
Design
As a final effort for VHS, the D-VHS system had significant advantages 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 failed to make any headway into the video market.
Existing tape media is bulky and more expensive than hard drives. Although cable companies are gradually switching to the
D-VHS's primary advantage is that it is still the best way to archive encrypted high definition material from cable programming in the US. Cable, satellite companies, TiVo, and PCs equipped with cable card tuners all offered high-definition digital video recorders, but archival has proven to be an obstacle, as proprietary boxes have restrictions on moving encrypted content. Outside of D-VHS, only HD capture devices that use an analog conversion process, such as the Hauppauge HD PVR, have enabled removal of encrypted content off many of the above proprietary boxes. This uses an analog conversion process, producing slightly degraded but still high definition grade recordings. D-VHS, on the other hand, does not need to take advantage of this so-called "analog hole", since D-VHS makes a pure bit-for-bit recording with no conversion necessary. This is made possible by compliance with CCI flag values carried by the digital streams, wherein only D-VHS is allowed to digitally move recordings of content originally flagged as Copy Once off of a DVR device and onto a D-VHS tape. This programming that complies with the CCI flags then marks such material on the tape such that no second generation copies can be made from the tape itself, though additional copies can still be made directly from the original DVR unit to additional tapes.
Monthly rental fees to cable, TiVo, and satellite were also less with D-VHS.[clarification needed]
The only PAL D-VHS model sold in Europe was the JVC HM-DR10000, also sold as the Philips VR-20D, and was standard definition only. This model was not a
Tape length and speeds
D-VHS VCRs can record at 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, respectively.
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. LS2 speed has a bitrate of 7 Mbits/s. The LS3 speed is roughly equal to an amateur DVD with some visible artifacts in high-action scenes (4.7 Mbit/s),[6] and LS5 appears similar to a medium-quality video download (2.8 Mbit/s).[7] 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.
Label | Data storage | Length | Recording time | |||
---|---|---|---|---|---|---|
HS or VHS-SP | STD or VHS-LP | LS3 | LS5 | |||
DF-240 | 25 GB | 248 m (813 ft) | 120 min (2 h) | 240 min (4 h) | 720 min (12 h) | 1,200 min (20 h) |
DF-300[6] | 31.7 GB | 314.5 m (1,048 ft) | 150 min (2:30 h) | 300 min (5 h) | 900 min (15 h) | 1,500 min (25 h) |
DF-420 | 44 GB | 433 m (1,420 ft) | 210 min (3:30 h) | 420 min (7 h) | 1,260 min (21 h) | 2,100 min (35 h) |
DF-480[6] | 50 GB | 500 m (1,640 ft) | 240 min (4 h) | 480 min (8 h) | 1,440 min (24 h) | 2,400 min (40 h) |
Pre-recorded tapes
In 2002, prerecorded D-VHS cassettes were sold under the brand name D-Theater in the US. While D-Theater is a D-VHS tape, it is incompatible with D-VHS decks not bearing the D-Theater logo. They provide content in both
Most tapes have built-in copy protection mechanism (DTCP, also known as "5c") (copy never) that disables copying via FireWire. HDNet productions and 2929 Entertainment via Magnolia Entertainment did provide some of their original content on D-VHS but without copy protection. Many of the tapes have an introduction by owner Mark Cuban encouraging the viewer to make copies of the program in order to help distribute them.
Additional tracks may be included on D-Theater in other sound formats such as DTS. However, only the newest D-VHS players, like the JVC HM-DH40000, HM-DH5U, HM-DT100U, and Marantz MV-8300, include alternate audio track capabilities.
Compatibility
There are technical issues with compatibility between recordings from Mitsubishi and JVC D-VHS decks.[9] PAL and NTSC recordings are also incompatible.[citation needed]
Adoption
Very few models were available to the world market and sales of this format have been weak; correspondingly, prices remained high for both VCRs and media, contributing to low demand. Additionally, low consumer knowledge of D-VHS's advantages and capabilities as well as input limitations led to its eventual demise. The introduction in 2006 of Blu-ray and HD-DVD rendered the format abandoned.[10]
Similar formats
There has been no small-format version of D-VHS equivalent to
See also
References
- ^ "All Specifications of D-VHS Digital Recording Format Finalized". JVC. July 3, 1998. Archived from the original on 2005-01-09.
- ^ Corporation, Bonnier (September 23, 1997). "Popular Science". Bonnier Corporation – via Google Books.
- ISBN 9780080550664.
- ^ "IEC 60774-5:2004 Helical-scan video tape cassette system using 12.65 mm (0.5 in) magnetic tape on type VHS – Part 5: D-VHS" (PDF). International Electrotechnical Commission. 7 April 2004.
- ^ "JVC Pro Technical Description". pro.jvc.com. Retrieved 2022-09-02.
- ^ a b c "究極のD-VHSまるごと大全 (1/3)". ASCII.jp.
- ^ "JVC Pro Technical Description". pro.jvc.com.
- ^ Pennington, Adrian. "D-VHS: This is how your HD film collection might have been". www.redsharknews.com.
- ^ "A Look Back at The D-VHS Video Format". Lifewife. April 26, 2021. Archived from the original on 2021-04-26.
- ^ Pennington, Adrian. "D-VHS: This is how your HD film collection might have been". www.redsharknews.com. Retrieved 2022-09-02.