S-VHS

Not to be confused with the video signal format S-Video.
S-VHS
Media type Magnetic tape
Encoding NTSC, PAL, ADAT
Capacity Nine Hours in SLP Mode
Usage Home movies, Time shifting

S-VHS (スーパー・ヴィエイチエス) (for Super VHS) is an improved version of the VHS standard for consumer-level analog recording videocassettes. JVC introduced the new standard in Japan in April 1987 with the HR-S7000 VCR, and in certain overseas markets soon afterward.

Technical information

Like VHS, the S-VHS format uses a "color under" modulation scheme. S-VHS improves luminance resolution by increasing luminance bandwidth. Increased bandwidth is possible because of increased luminance carrier from 3.4 MHz to 5.4 MHz.[1] Increased luminance bandwidth produces a 60% improvement in (luminance) picture detail, or a horizontal resolution of 420 vertical 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 NTSC analog cable and broadcast TV, which is limited to about 330 TV lines (TVL). 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 television and a S-VHS recording of it. This is because S-VHS does not improve other key aspects of the video signal, particularly the chroma signal. In VHS, the chroma carrier is both severely bandlimited and rather noisy, a limitation that S-VHS does not address. 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 TVL resolution.[2]

In terms of audio recording, S-VHS retains VHS's conventional linear (baseband) and Hi-Fi (AFM) soundtracks. 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.

As an added bonus, due to the increased bandwidth of S-VHS, Teletext (PAL) signals can be recorded along with the normal video signal. As a result these are also played back (though not on standard VHS machines). A suitably Teletext equipped receiver (TV, PC card, etc.) displays the recorded Teletext information as if the video were being viewed live.

Hardware

S-VHS VCRs and cassette tapes are nearly identical in appearance and operation and backward compatible with VHS. Older VHS VCRs cannot play back S-VHS recordings at all but can record to an S-VHS tape in the VHS format. Many newer VHS VCRs offered a feature called S-VHS quasi-playback or Super Quasi-Play Back (SQPB). SQPB lets VHS players view (but not record) S-VHS recordings, though reduced to VHS-quality. This feature is useful for viewing S-VHS-C camcorder tapes.

Later model S-VHS VCRs offered a recording option called S-VHS ET. S-VHS ET is a further modification of the VHS standards that permitted near S-VHS quality recordings on more common and less expensive VHS tapes. S-VHS ET recordings can be viewed in most VHS SQPB VCRs and S-VHS VCRs.

To get the most benefit from S-VHS, a direct video connection to the monitor or TV is required, ideally via an S-Video connection.

Media

For the best recordings and playback, an S-VHS VCR requires S-VHS videotape, which has a different oxide media formulation for higher magnetic coercivity. S-VHS video cassettes are sensed by the recorder via a hole in the underside of the cassette body.

Modifying VHS cassettes for S-VHS recordings

Videophiles were the first to theorize that since the only distinguishing feature of an S-VHS tape is a small 3mm hole in the cassette, it should be possible to use more common and inexpensive VHS tapes by duplicating that hole. However, S-VHS cassettes also contain a higher grade and coercivity of tape stock to effectively record the higher video bandwidth offered by S-VHS.

In attempts to record S-VHS content to a VHS tape, picture quality is somewhat better, however, after several months the quality drops dramatically to a point of severe graininess or video noise in dark areas in the images. This is due to the standard VHS tape's lack of coercivity that the S-VHS format requires, causing the stronger magnetization of the tape provided by a S-VHS deck's recording heads to not be fully retained by the magnetic oxide particles of the VHS tape over time, producing a weaker signal on playback.

Eventually, the recording becomes unwatchable (although it may be copied to another more suitable media while still in usable condition). The original tape itself can be reused for standard-format VHS format recordings without problems (as the oxide media itself remains physically undamaged).

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 (PAL analog broadcasts use the 625-line PAL system, and yield a resolution of 480 TVL), and are listed in ascending order from lowest quality to highest quality. (TVL means horizontal resolution in vertical lines per picture height.) It should be noted that this list makes no mention of the chroma resolution, only luma (brightness), nor is noise performance considered; while the luma resolution of SVHS may appear greater than BetacamSP, that doesn't mean that it's any meaningful way superior to professional BetacamSP in overall performance.

Digital:

  1. ↑ 1.0 1.1 For the horizontal resolution of 720 pixels, only 704 of them are actually used in most media due to the digital (horizontal) blanking. When all 720 lines are used, the TVL is 405 at 16:9 and 540 at 4:3.

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 enjoyed limited success among home video users. It was more popular for the amateur video industry, as it allowed for at least second generation copies at reasonable quality (necessary for editing). JVC, Panasonic, and Sony have sold industrial S-VHS decks for amateur and semi-professional production use. Some Public-access television stations and other low-budget cable TV venues used 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, longer running time, and ultimately selling much better.

As of 2007, consumer S-VHS VCRs were still available, but difficult to find in retail outlets. The largest VCR manufacturers, such as Matsushita (Panasonic) and Mitsubishi, gradually moved to DVD recorders, and hard-disk based DVRs. DVD/VCR combo units rarely offered S-VHS, only VHS. In the mainstream consumer camcorder market, DV, DVD, and—eventually—solid state memory-based camcorders replaced S-VHS-C camcorders. Digital camcorders generally outperform 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.

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 (TVL) of horizontal resolution per picture height versus S-VHS's or Laserdisc's 420 TVL, putting ED-Beta nearly on par with professional digital video formats (520 TVL). However, chroma performance was far less spectacular, as neither S-VHS nor ED-Beta exceeded 0.4 megahertz or ~30 TVL maximum, whereas NTSC broadcast has a chroma resolution of ~120 TVL, and DVD has a chroma resolution of ~240 TVL. 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 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 PAL markets, depth multiplexed audio was used for both formats.

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 competition on behalf of ED-Beta could regain the home video market.

Home use

Getting the most benefit from S-VHS required a direct video connection to the monitor, ideally via an S-Video connection. However, older television sets lacked S-Video or even any AV inputs. Nevertheless, viewing an S-VHS recording through a VCR's built-in RF modulator yields a discernible quality improvement over VHS.

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 having been one of the more common consumer video products equipped with the s-video connector. However, S-Video connectors became common on many video other devices: DVD players and recorders, MiniDV and Hi8 camcorders, cable/satellite set-top boxes, "TV Out" outputs on computers, 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.

Use for digital audio

An ADAT XT 8-channel digital audio recorder

In 1991, Alesis introduced ADAT, an eight-track digital audio recording system that used S-VHS cassettes. An ADAT machine recorded eight tracks of uncompressed audio material in 16-bit (later 20-bit) resolution. The recording time was one-third of the cassette's nominal playing time, e.g., a 120 min S-VHS cassette held 40 minutes of eight-track audio.

See also

References

  1. ↑ http://catalogs.infocommiq.com/AVCAT/images/documents/pdfs/TT189%20-%204611.pdf
  2. ↑ Damjanovski, Vlado (2005). CCTV. Butterworth-Heinemann. p. 238. ISBN 0-7506-7800-3.
  3. ↑ http://www.hdv-info.org/HDVSpecifications.pdf

External links