D-VHS
D-VHS is a digital video format developed by JVC, in collaboration with Hitachi, Matsushita and Philips. The "D" in D-VHS is for Data not Digital. It uses the same physical cassette format and recording mechanism as VHS, 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 format was introduced in 1998.
The JVC D-VHS deck, released in the UK, was not a bitstream recorder, although it did have a DV input. Instead it is best thought of as a digital recorder for traditional analogue inputs such as domestic analogue 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 noticably 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 out (although this is perhaps an understandable anti-piracy precaution) and perhaps more crucially the lack of RGB input via the scart. This is a feature made popular on domestic DVD Recorders, and picture quality is noticably better when recording this way than via s-video or of course composite.
As a last "hurrah" for VHS, the D-VHS system was terrific as a domestic recorder, the only comparison at the time being the DV format, but given the wholesale move to DVD and then HDD recording, it was perhaps too little too late.
Tape Length
HD content is stored at 28.2 Mbit/s, while SD content can be stored at bit rates from 14.2 Mbit/s down to 2.0 Mbit/s. The tape labels are a bit confusing for HD as D-VHS was originally a standard definition format that recorded at the "STD" speed. When HD was introduced it required double the amount of tape. So that's why a DF-300 will only record 150min and not 300min. High Definition can only be recorded at the "HS" speed.
| Tape Label | Data storage | Tape Length | Rec. Time | |||
|---|---|---|---|---|---|---|
| HS | STD | LS3 | LS5 | |||
| DF-240 | ?? | 240m | 120min (2 hrs) | 240min (4hrs) | 720min (12hrs) | 1,200min (20hrs) |
| DF-300 | 31.7 gig | 300m | 150min (2 1/2 hrs) | 300min (5hrs) | 900min (15hrs) | 1,500min (25hrs) |
| DF-420 | 44 gig | 420m | 210min (3 1/2 hrs) | 420min (7hrs) | 1,260min (21hrs) | 2,100min (35hrs) |
| DF-480 | ?? | 480m | 240min (4hrs) | 480min (8hrs) | 1,440min (24hrs) | 2,400min (40hrs) |
Issues
There are technical issues with compatibility with recordings from Mitsubishi and JVC D-VHS decks. PAL and NTSC recordings are incompatible too. Very few models are available to the UK market and sales of this format have been weak. It is by no means certain that it has a long-term future.
D-Theater
In 2002, prerecorded D-VHS cassettes are sold under the brand name D-Theater in the US. They provide content in both 720p and 1080i as well as at least one Dolby Digital audio track. Optionally, additional tracks may be included in other sound formats such as DTS. However, only the newest D-VHS players like JVC HM-DH40000, HM-DH5U, HM-DT1000, and Marantz MV-8300 include alternate audio track capabilities. Supported movies studios include 20th Century Fox, Artisan Entertainment, DreamWorks and Universal Pictures. D-VHS provides much more video quality than previous formats, but may be displaced by newer format such as Blu-ray Disc or HD-DVD.
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 do provide some of their original content on D-VHS but without copy protection. Many of the tapes have an introduction by the owner Mark Cuban encouraging you to make copies of the program.
Here is a link to a list of all the D-Theater movies that were released: http://www.avsforum.com/avs-vb/showthread.php?t=313242
See also
External links
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