S-VHS
From Wikipedia, the free encyclopedia
 |
This article does not cite any references or sources. (May 2008) Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. |
Introduced in Japan in 1987, S-VHS (Super VHS) is an improved version of the VHS standard for consumer video cassette recorders.
Contents |
[edit] Technical details
Like VHS, the S-VHS format uses a "color under" modulation scheme. S-VHS improves luminance resolution by boosting the luminance carrier from 3 MHz to 5.4 MHz. This produces a 60% improvement in (luminance) picture detail, or a horizontal resolution of 420 lines per picture height versus VHS's 240 lines. The often quoted horizontal resolution of "over 400" means S-VHS captures greater picture detail than even analog (NTSC) cable broadcast TV, which is limited to about 330 lines. In practice, when time shifting TV programs on S-VHS equipment, the improvement over VHS is quite noticeable. Yet, the trained eye can easily spot the difference between live broadcast TV and a S-VHS recording of it. This is explained by S-VHS's failure to improve other key aspects of the video signal, especially the chroma signal. In VHS, the chroma carrier is both severely bandlimited and rather noisy, a limitation that S-VHS does not address. To be fair, poor color resolution was a deficiency shared by S-VHS's contemporaries (Hi8, ED-Beta.), all of which were limited to 0.4 megahertz or 30 lines resolution.
In terms of audio recording, S-VHS retains VHS's conventional analog (linear) and Hi-Fi (AFM) soundtracks. As neither is changed from the VHS format, the linear audio track delivers sound quality scarcely better than AM radio. The Hi-Fi soundtrack is identical to that of VHS: an AFM (audio frequency-modulated) signal is sandwiched between the two carriers of the video signal, and recorded at a physically lower layer in the tape, literally underneath the video signals. This delivers excellent audio fidelity, approaching CD-quality. In addition, some professional S-VHS decks can record a PCM digital audio track (stereo 48 kHz), along with the normal video and Hi-Fi analog audio.
Nearly all S-VHS VCRs are backward compatible with VHS tapes, meaning S-VHS equipment is fully functional as a legacy VHS record/playback unit. Older VHS VCRs cannot view S-VHS recordings at all. Many newer VHS VCRs offer a feature called S-VHS quasi-playback (SQPB.) SQPB allows VHS players to view (but not record) S-VHS recordings, albeit at VHS quality levels. This feature is useful for viewing S-VHS-C camcorder tapes.
In recording mode, S-VHS VCRs require S-VHS videotape, which has a different oxide media formulation for higher magnetic coercitivity. (As a sidenote, most S-VHS VCRs can also make VHS recordings on S-VHS tape, and conversely, conventional VHS VCRs can record on S-VHS videotape. Both functions are useful for low volume, high-quality duplication.) Finally, recent model S-VHS VCRs offer a recording capability called S-VHS ET. S-VHS ET permits near S-VHS level recording on conventional, cheap VHS tapes, offering an economical way to get a better picture out of older VHS tapes. The S-VHS ET recordings can be viewed in most VHS SQPB VCRs and non-ET S-VHS VCRs.
[edit] Comparison to other media
Here is a list of modern-day, digital-type measurements (and traditional, analog horizontal resolutions) for various media. The list only includes popular formats, not rare formats, and all values are approximate (rounded to the nearest 10), since the actual quality can vary machine-to-machine or tape-to-tape. For ease-of-comparison all values are for the NTSC system, and listed in ascending order from lowest quality to highest quality.
- 350×240 (250 lines): Video CD
- 330×480 (250 lines): Umatic, Betamax, VHS, Video8
- 400×480 (300 lines): Super Betamax, Betacam (professional)
- 440×480 (330 lines): analog broadcast
- 560×480 (420 lines): LaserDisc, Super VHS, Hi8
- 670×480 (500 lines): Enhanced Definition Betamax
- 720×480 (520 lines): DVD, miniDV, Digital8, Digital Betacam (professional)
- 720×480 (400 lines): Widescreen DVD (anamorphic)
- 1280×720 (720 lines): D-VHS, HD DVD, Blu-ray, HDV (miniDV)
- 1920×1080 (1080 lines): D-VHS, HD DVD, Blu-ray, HDCAM SR (professional)
[edit] Shadow of VHS
Despite its designation as the logical successor to VHS, S-VHS did not come close to replacing VHS. In the home market, S-VHS failed to gain significant market share; for various reasons, consumers were not interested in paying more for an improved picture. Likewise, S-VHS rentals and movie sales did very poorly. A few prerecorded movies were released to S-VHS, but poor market acceptance prompted studios to transition their high-end product from S-VHS to Laserdisc.
In the camcorder role, the smaller form (S-VHS-C) camcorder did enjoy limited success among home video users. It was more popular for the amateur video industry, as it allowed for at least second generation copies (necessary for editing) to be made at reasonable quality. JVC, Panasonic and Sony have sold industrial S-VHS decks for amateur and semi-professional production use. Community access television, local cable stations and other low-budget venues have made extensive use of the S-VHS format, both for acquisition and subsequent studio editing, but the network studios largely avoided S-VHS, as descendants of the more expensive Betacam format had already become a de facto industry standard. S-VHS-C competed directly with Hi8, the latter offering smaller cassettes and longer running time and ultimately selling much better.
As of 2007, consumer S-VHS VCRs are still available, but difficult to find in retail outlets. The largest VCR manufacturers, such as Matsushita (Panasonic) and Mitsubishi, are gradually moving toward DVD recorders and hard-disk based DVRs. DVD/VCR combo units rarely offer S-VHS, only VHS. In the mainstream consumer camcorder market, DV and DVD camcorders have largely eliminated S-VHS-C camcorders from the mainstream, confining the format to a small niche on the very low end of the market. The digital camcorder generally outperforms S-VHS-C units in most technical aspects: audio/video quality, recording time, lossless duplication, and form-factor. The videotapes themselves are available, mostly by mail order or online, but are vanishingly rare in retail channels, and substantially more expensive than high-quality standard VHS media.
[edit] S-VHS vs ED-Beta
Shortly after the announcement of S-VHS, Sony responded with an announcement of Extended Definition Betamax (ED-Beta). S-VHS was JVC's next generation video format designed to dominate the competing SuperBeta format (which already offered better-than-VHS quality). Not to be outdone, Sony developed ED-Beta as their next generation competitor to S-VHS.
In terms of video performance, ED-Beta offered even greater luminance bandwidth than S-VHS: 500 lines of horizontal resolution per picture height versus S-VHS's or Laserdisc's 420 lines, putting ED-Beta nearly on par with professional digital video formats (520 lines). However, chroma performance was far less spectacular, as neither S-VHS nor ED-Beta exceeded 0.4 megahertz or ~30 lines maximum, whereas NTSC broadcast has a chroma resolution of ~120 lines, and DVD has a chroma resolution of ~240 lines. S-VHS was used in some TV stations for inexpensive "on the spot" camcorder capture of breaking news, however it was not suitable for multi-generational (studio) use.
In terms of audio performance, both VHS and Beta had offered analog Hi-Fi stereo of outstanding quality. Rather than re-invent the wheel, both S-VHS and ED-Beta re-used the AFM schemes of their predecessors without change. Professional S-VHS decks did offer digital PCM audio, a feature not matched by ED-Beta decks.
In the U.S. market, the mainstream consumer market had largely ignored the release of S-VHS. With the Betamax market already in sharp decline, a "format war" for the next generation of video simply did not materialize. Sony discontinued the ED-Beta product line in the U.S. market after less than two years, handing S-VHS a victory by default, if it can even be called that. (VHS decks continued to outsell S-VHS decks until the end of the VCR product life cycle.)
There is anecdotal evidence that some TV stations purchased ED-Beta equipment as a low-cost alternative to professional Betacam equipment, prompting speculation that Sony's management took steps to prevent its consumer (ED-Beta) division from cannibalizing the sales of its more lucrative professional video division. Nevertheless, it is clear to all that by the time of ED-Beta's introduction, VHS had already won a decisive victory, and no amount of fair competition on behalf of ED-Beta could possibly have regained the home video market.
[edit] Home Use
To get the most benefit from S-VHS, a direct video connection to the monitor is required, ideally via an S-Video or component video connection. However, consumer S-VHS equipment was usually limited to S-Video and composite input jacks, with older television sets tending to also lack S-Video inputs. Nevertheless, viewing an S-VHS recording through a VCR's built-in RF modulator yields a discernible perceived quality improvement over VHS. Since the late 1990s, the increased popularity of S-VHS and other formats, such as DVD, has made S-Video and component video hookups commonplace on many TV sets.
It is not unusual to see the term S-VHS incorrectly used to refer to S-Video connectors (also called "Y/C connectors"), even in printed material. This may be due to S-VHS being one of the first consumer video products equipped with the Y/C connector; however, Y/C connectors are now common on many American and Japanese video devices other than video tape recorders: DVD players and recorders, MiniDV camcorders, cable/satellite set-top boxes, graphics cards, video game consoles, and TV sets themselves. Where the "S-" in "S-VHS" means "super", the "S-" in "S-Video" refers to the "separated" luminance and chrominance signals.
[edit] Use for digital audio
In 1991 Alesis introduced Adat, an 8 track digital audio recording system using S-VHS as media. An A-dat machine would record 8 tracks of uncompressed audio material in 16-bit (later 20-bit) resolution. The recording time is one-third of the cassette's nominal playing time. That is a 120 min S-VHS cassette would hold 40 minutes of Adat recording
[edit] See also
|
|||||||||||||||||||||||||||||||||
