S-VHS

Like VHS, the S-VHS format uses a color under A modulation scheme. S-VHS improves luminance (luma) resolution by increasing luminance bandwidth. Increased luminance bandwidth produces a 60% improvement in luminance picture detail—a horizontal resolution of 420 vertical lines per picture height, versus VHS's 240 lines. The horizontal resolution of "over 400" means S-VHS captures greater picture detail than even NTSC In audio recording, S-VHS retains VHS's conventional linear (baseband) and high fidelity (Hi-Fi) – Audio Frequency Modulation (AFM) soundtracks. Some professional S-VHS decks, and high end domestic S-VHS VCRs such as the Victor HR-Z1 can additionally record a pulse-code modulation (PCM) digital audio track (stereo 48 kHz), onto S-VHS tape along with normal video and Hi-Fi stereo and mono analog audio. This is performed by using a high carrier frequency of 3 MHz for the digital audio with O-QDPSK (Offset Quadrature Differential Phase Shift Keying) modulation and PCM encoding which is then recorded onto the same helical tracks as the video. This frequency is above those used for VHS Hi-Fi (1.7 MHz for the left channel, 1.8 MHz for the right channel) but below the luminance signal frequency for regular VHS of 3.4 MHz. The digital audio stream has a bit rate of 2.6 Mbit/s. O-QDPSK is based on QDPSK (Quadrature Differential Phase Shift Keying), also known as DQPSK (Differential Quadrature Phase Shift Keying), and is very similar to it, except O-QDPSK signals are free from zero crossing; the signals never cross the 0 voltage point. Instead, they are above and below the 0 voltage point. This type of digital audio requires a bandwidth of 500 kHz. It is also possible for this audio channel to have a carrier frequency of 2 MHz. Newer VHS VCRs, depending upon their specification, offered a feature called S-VHS quasi-playback or Super Quasi-Play Back, abbreviated to SQPB. SQPB lets basic VHS players view (but not record) S-VHS recordings, though reduced to the lesser VHS quality. This feature is useful for viewing S-VHS camcorder recordings that use either the full-size S-VHS cassette or the smaller S-VHS-C cassette. Later model S-VHS VCRs offered a recording option called S-VHS ET, which allowed SVHS VCRs to record on VHS tape. S-VHS ET is a further modification of the VHS standards that permitted near S-VHS quality recordings on more common and less expensive basic VHS tapes. S-VHS ET recordings can be viewed on most SQPB-equipped VHS 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 connector and/or S-Video enabled SCART. Panasonic NV-S77 Media In order to take advantage of the enhanced capabilities of the S-VHS system an S-VHS VCR requires S-VHS video tape cassettes. ==Use for digital audio==

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-minute S-VHS cassette held 40 minutes of eight-track audio. Studer produced the V-Eight (manufactured and sold by Alesis as the M20) and the V-Twenty-Four digital multitrack recorders. These used S-VHS cassettes for 8-track and 24-track digital audio recording, at a significantly lower cost than their DASH reel-to-reel digital recorders. The videotape transports were made for Studer by Matsushita. ==See also==