VHS

. See articles Stereoscopy and 3-D film. However, Tivos and DVRs are the main competitors with the VHS in home recording. The first commercially available HD players are expected to debut at the 2006 NAB Show in Las Vegas in April. It can also be more convenient to use VHS tapes because they can be rewritten easily, and VCRs can be easier than DVD recorders to use. New HD DVD and HD Blu-ray disks will greatly improve the 3D effect, in color coded stereo programs. Despite DVD's better quality, however, VHS is still widely used in home recording of television programs, due to the large installed base and the lower cost of VHS recorders. Simple Red/Cyan plastic glasses provide the means to view the images discreetly to form a stereoscopic view of the content.

Commentators predict that 2006 will be the final year of new releases on VHS, as major studios continue to phase out VHS. This left and right layer technique is occasionally used for network broadcast, or recent "anaglyph" releases of 3D movies on DVD. Moreover, most television programs released as box sets are for sale in DVD format only. Stereoscopic video requires either two channels — a right channel for the right eye and a left channel for the left eye or two overlayed color coded layers. Many films released to theaters from 2004 onwards have later been released only on DVD and not on VHS, and many other new feature films are being released solely on DVD. in videoconferencing delivered on channels of fixed bandwidth, a constant bit rate (CBR) must be used. retailers Circuit City and Best Buy stopped selling VHS tapes in 2002 and 2003, respectively. For real-time and non-buffered video streaming when the available bandwidth is fixed, e.g.

Major U.S. On fast motion scenes, a variable bit rate uses more bits than it does on slow motion scenes of similar duration yet achieves a consistent visual quality. The DVD format was introduced in 1997 and has since overtaken VHS in sales and rentals. Variable bit rate (VBR) is a strategy to maximize the visual video quality and minimize the bit rate. In addition, it offers superior audiovisual quality, and the storage of data in digital format on tape makes for improved transfer and editing. HDTV has a still higher quality, with a bit rate of 10 Mbit/s. MiniDV has largely replaced 8mm tapes as the de facto camcorder standard in more recent years as it is smaller still (some MiniDV camcorders being no larger than one's hand). For example, VHS, with a bit rate of about 1 Mbit/s, is lower quality than DVD, with a bit rate of about 5 Mbit/s.

8mm tapes, introduced in the early 1980s, succeeded as a format for camcorders (both in the consumer, and to an extent, professional market), as VHS and Betamax camcorders were unsuitably large and heavy in comparison. A higher bit rate allows better video quality. As these cassettes are much more compact in design — which also means the hardware to play and record the tapes has to be more compact than VHS, and therefore more expensive — they are much more suited to portable applications such as camcorders. It is quantified using the bit per second (bit/s) unit or Megabits per second (Mbit/s). Other formats such as 8mm video cassettes and MiniDV have emerged since, but these formats are by no means in complete competition with VHS. Bit rate is a measure of the rate of information content in a video stream. Netscape. The most common modern standards are MPEG-2, used for DVD and satellite television, and MPEG-4, used for home video.

Windows and Microsoft vs. Likewise, temporal redundancy can be reduced by registering differences between frames; this task is known as interframe compression, including motion compensation and other techniques. IBM, Macintosh vs. Broadly speaking, spatial redundancy is reduced by registering differences between parts of a single frame; this task is known as intraframe compression and is closely related to image compression. The format war and the "marketing over technology" claims have taken on a life of their own, and have been used as analogies in the battles of the computer industry, including Apple vs. Video data contains spatial and temporal redundancy, making uncompressed video streams extremely inefficient. Sony ultimately conceded the fight in the late '80s, bringing out a line of VHS VCRs. A wide variety of methods are used to compress video streams.

Ultimately Betamax did manage to make up some of the difference on recording time, but this was too little, too late. The expert then rates the impaired video using a scale ranging from "impairments are imperceptible" to "impairments are very annoying". The longer tape time is sometimes cited as the defining factor in the format war, as the longer VHS tapes allowed consumers to record entire programs unattended, and arguably created the entire video rental industry by providing sufficient playing time for most feature films to be distributed on a single cassette. In DSIS, each expert views an unimpaired reference video followed by an impaired version of the same video. Betamax held an early lead in the format war, offering some technical advantages, but by 1980 VHS was gaining due to its longer tape time (3 hours maximum, compared to just 60 minutes for Betamax) and JVC's less strict licensing program. One of the standardized method is the Double Stimulus Impairment Scale (DSIS). In fact, however, the root causes of VHS' victory are somewhat more complex. Many subjective video quality methods are described in the ITU-T recommendation BT.500.

Since Betamax was widely perceived at the time as the better format, it is often stated that VHS' eventual victory was a victory of marketing over technical excellence. The subjective video quality of a video processing system may be evaluated as follows:. As mentioned, VHS was the winner of a protracted and somewhat bitter format war during the early 1980s against Sony's Betamax format. Video quality can be measured with formal metrics like PSNR or with subjective video quality using expert observation. Conversely, an E-300 tape runs for 300 minutes in PAL-SP, but 200 minutes in NTSC-SP. 4:4:4, 4:2:2, 4:2:0). For example, a T-120 tape runs for 120 minutes in NTSC-SP, but 180 minutes in PAL-SP. A common way to reduce the number of bits per pixel in digital video is by chroma subsampling (e.g.

It can easily be derived by multiplying with 3/2 or 2/3, respectively. The number of distinct colours that can be represented by a pixel depends on the number of bits per pixel (bpp). It is perfectly possible to record and play back a blank T-XXX tape in a PAL machine or a blank E-XXX tape in an NTSC machine, but the resulting playing time will be different than indicated. It corresponds closely to the YUV scheme used in PAL television and the YDbDr scheme used by SÉCAM television. In order to avoid confusion, manufacturers indicate the playing time in minutes that can be expected for the market the tape is sold in:. YIQ is used in NTSC television. Both NTSC and PAL/SECAM VHS cassettes are physically identical (although the signals recorded on the tape are incompatible.) However, as tape speeds differ between NTSC and PAL/SECAM, the playing time for any given cassette will vary accordingly between the systems. Color model name describes the video color representation.

Likewise, S-VHS machines for the Brazilian market record in NTSC and convert to/from PAL-M. Pixels on computer monitors are usually square, but pixels used in digital video have non-square aspect ratios, such as those used in the PAL and NTSC variants of the CCIR 601 digital video standard, and the corresponding anamorphic widescreen formats. S-VHS machines sold in SECAM markets record internally in PAL, and convert to/from SECAM during record/playback, respectively. The aspect ratio of a full 35 mm film frame with soundtrack (also known as "Academy standard") is around 1.37:1. S-VHS only exists in PAL/625/25 and NTSC/525/30. High definition televisions use an aspect ratio of 16:9, or about 1.78:1. Dedicated multistandard machines can usually handle all standards listed, some high end model can even convert a tape from one standard to another by using a built-in standards converter. The screen aspect ratio of a traditional television screen is 4:3, or 1.33:1.

regular VHS machines sold in Europe nowadays can typically handle PAL, MESECAM for record and playback, plus NTSC for playback only. Aspect ratio describes the dimensions of video screens and video picture elements. E.g. For example 512×512×512 voxels resolution, now used for simple 3D-video, can be displayed even on some PDAs. These can handle VHS tapes of more than one standards. Video resolution for 3D-video is measured in voxels (volume picture element, representing a value in three dimensional space). Since the 1990s dual- and multistandard VHS machines have become more and more common. 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second.

The following signal varieties exist in conventional VHS:. New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080p60, i.e. Typically, a VHS machine can only handle signals of the country it was sold in. Standard-definition television (SDTV) is specified as 640×480i60 for NTSC and 720×576i50 for PAL or SÉCAM resolution. However, a machine must be designed to record a given standard. The size of a video image is measured in pixels for digital video or horizontal scan lines for analog video. VHS can record and play back all varieties of analogue television signals in existence at the time VHS was devised. Deinterlacing inevitably decreases video quality.

This format is most notably used by Fox for some of its cable networks. A procedure known as deinterlacing can be used for converting an interlaced stream, such as analog, DVD, or satellite, to be processed by progressive scan devices, such as TFT TV-sets, projectors, and plasma panels. This format is the least expensive format to support a pre-read edit. The result is a much higher perceived resolution. There is also a JVC-designed component digital professional production format known as Digital-S or (officially) D9 that uses a VHS form factor tape and essentially the same mechanical tape handling techniques as an S-VHS recorder. In progressive scan systems, each frame includes all of the scan lines. This development hampered the sales of the Betamax system somewhat, because the Betamax cassette geometry prevented a similar development. For example, PAL video format is often specified as 576i50, where 576 indicates the horizontal resolution, i indicates interlacing, and 50 indicates 50 (single-field) frames per second.

The magnetic tape on VHS-C cassettes is wound on one main spool and uses a gear wheel to advance the tape; the wheel and spool can also be moved by hand. Abbreviated video resolution specifications often include an i to indicate interlacing. Since VHS-C tapes are based on the same magnetic tape as full size tapes, they can be played back in standard VHS players using a mechanical adapter, without the need of any kind of signal conversion. NTSC, PAL and SECAM are interlaced formats. Another variant is VHS-C (C for compact), used in some camcorders. The horizontal scan lines of each interlaced frame are numbered consecutively and partitioned into two fields: the odd field consisting of the odd-numbered lines and the even field consisting of the even-numbered lines. W-VHS caters for high definition video. Interlacing was invented as a way to achieve good visual quality within the limitations of a narrow bandwidth.

Devices have also been invented which directly connect a personal computer to VHS tape recorders for use as a data backup device. Video can be interlaced or progressive. Several improved versions of VHS exist, most notably S-VHS, an improved analog standard, and D-VHS, which records digital video onto a VHS form factor tape. To achieve the illusion of a moving image, the minimum frame rate is about ten frames per second. There was a time when higher-end VCRs provided functions for manually removing and adding these index marks — so that, for example, they coincide with the actual start of the program — but this feature has become hard to find in recent models. PAL (Europe, Asia, Australia, etc.) and SECAM (France, Russia, parts of Africa etc.) standards specify 25 fps, while NTSC (USA, Canada, Japan, etc.) specifies 30 fps. These are normally written at the beginning of each recording session, and can be found using the VCR's index search function: this will fast-wind forward or backward to the nth specified index mark, and resume playback from there. Frame rate, the number of still pictures per unit of time of video, ranges from six or eight frames per second (fps) for old mechanical cameras to 120 or more frames per second for new professional cameras.

The control track can additionally hold index marks. In the UK, the term video is often used informally to refer to both video recorders and video cassettes; the meaning is normally clear from the context. Since good tracking depends on the exact distance between the rotating drum and the fixed control/audio head reading the linear tracks, which usually varies by a couple of micrometers between machines due to manufacturing tolerances, most VCRs offer tracking adjustment, either manual or automatic, to correct such mismatches. The format of 3D-video is fixed in MPEG-4 Part 16 Animation Framework eXtension (AFX). Another linear control track, at the tape's lower edge, holds pulses that mark the beginning of every frame of video; these are used to fine-tune the tape speed during playback and to get the rotating heads exactly on their helical tracks rather than having them end up somewhere between two adjacent tracks (a feature called tracking). Six or eight cameras with realtime depth measurement are typically used to capture 3D-video streams. These advanced features are impossible to find on later-model VCRs due to the rise of digital video formats. 3D-video, digital video in three dimensions, premiered at the end of 20th century.

Another high-end feature was manual audio level control, which made the VHS HiFi format much more useful for high-quality audio-only recording purposes as discussed above. (See List of digital television deployments by country.). (Due to the different ways in which linear and HiFi audio are recorded, these kinds of dubbing were not possible with the HiFi tracks). Digital television (DTV) is a relatively recent format with higher quality than earlier television formats and has become a standard for television video. Without the dubbing features, this task would've required the tape to be copied to another tape which would cause generational loss. Quality of video essentially depends on the capturing method and storage used. This was useful, for example, for laying a song over a previously edited-together montage of short video clips that were the same total duration as that song. Video can be recorded and transmitted in various physical media: in celluloid film when recorded by mechanical cameras, in PAL or NTSC electric signals when recorded by video cameras, or in MPEG-4 or DV digital media when recorded by digital cameras.

These would move the tape past the heads and keep the video unchanged while recording new linear audio or keep the linear audio unchanged while recording new video, respectively. The term video (from the Latin for "I see") commonly refers to several storage formats for moving pictures: digital video formats, including DVD, QuickTime, and MPEG-4; and analog videotapes, including VHS and Betamax. Some higher-end VHS and S-VHS VCRs once offered "audio dubbing" and "video dubbing" functions. . Of course, for backward compatibility, hi-fi VCRs still write the linear audio track during recording, and can automatically read it during playback if the hi-fi audio is not present. Video is the technology of capturing, recording, processing, transmitting, and reconstructing moving pictures, typically using celluloid film, electronic signals, or digital media. The excellent sound quality of hi-fi VHS has gained it some popularity as an audio format in certain applications; in particular, ordinary home hi-fi VCRs are sometimes used by home recording enthusiasts as a handy and inexpensive medium for making high-quality stereo mixdowns and master recordings from multitrack audio tape. Calculate the average marks for each HRC based on the experts' ratings.

When the video signal is written by the following video head, it erases and overwrites the audio signal at the surface of the tape, but leaves the deeper portion of the signal undisturbed. Carry out testing. These audio tracks take advantage of depth multiplexing: since they use lower frequencies than the video, their magnetization signals penetrate deeper into the tape. Invite a sufficient number of experts, preferably not fewer than 15. More recent hi-fi VCRs add higher-quality stereo audio tracks which are read and written by heads located on the same spinning drum that carries the video heads, frequency modulated to the unused frequency range in between the chroma and luma signals. Choose a test method for how to present video sequences to experts and to collect their ratings. In the original VHS format, audio was recorded unmodulated in a single (monaural) linear track at the upper edge of the tape, which was limited in frequency response by the tape speed. Choose the settings of the system to evaluate (the HRC).

The video bandwidth is achieved with a relatively low tape speed by the use of helical scan recording of a frequency modulated luminance (black and white) signal, to which a frequency-reduced "color under" chroma (hue and saturation) signal is added. Choose the video sequences (the SRC) to use for testing. The vertical resolution of VHS (and all other analog recording methods) is determined by the TV standard — a maximum of 486 lines are visible in NTSC and a maximum of 576 lines in PAL. The frequency modulation of the luminance signal makes higher resolutions impossible within the VHS standard, no matter how advanced the recorder's technology. VHS tapes have approximately 3 MHz of video bandwidth, and a horizontal resolution of about 240 discernible lines per scanline [1].

An unofficial LP mode with half the standard speed exists on some NTSC machines, but is not part of the VHS standard. Because of this, commercial prerecorded tapes were almost always recorded in SP mode. Of course, these speed reductions cause corresponding reductions in video quality; also, tapes recorded at the lower speed often exhibit poor playback performance on recorders other than the one they were produced on. More recent machines usually allow the selection of longer recording times by lowering the tape speed: LP mode (for PAL and some NTSC machines) halves the tape speed and doubles the recording time, while EP mode (for NTSC and some newer PAL machines, aka SLP mode) drops the tape speed to one-third, for triple the recording time.

Most cassettes have lower recording times because they use thicker tape, which helps avoid jams; careful users generally avoid the thinnest tapes. A cassette holds a maximum of about 430 m of tape at the lowest acceptable tape thickness, giving a maximum playing time of about 3.5 hours for NTSC and 5 hours for PAL at "standard" (SP) quality. The tape speed is 3.335 cm/s for NTSC, 2.339 cm/s for PAL. A VHS cassette contains a ½ inch (12.7 mm) wide magnetic tape wound between two spools, allowing it to be slowly passed over the various playback and recording heads of the video cassette recorder.

. Most newer VHS machines do not perform this unthreading step, as due to improved engineering, head-tape contact is no longer an impediment to fast winding. Early VHS machines could rewind and fast forward the tape considerably faster than a Betamax VCR since they unthreaded the tape from the playback heads before commencing any high-speed winding. VHS initially offered a longer playing time than the Betamax system, and it also had the advantage of a far less complex tape transport mechanism.

VHS became a standard format for consumer recording and viewing in the 1980s and 1990s after competing in a fierce format war with Sony's Betamax and, to a lesser extent, Philips' Video 2000. Some early reports claim the name originally stood for Victor Helical Scan System. VHS officially stands for Video Home System, but it initially stood for Vertical Helical Scan, after the relative head/tape scan technique. The Video Home System, first released in September 1976, better known by its abbreviation VHS, is a recording and playing standard for video cassette recorders (VCRs), developed by JVC (with some of its critical technology under lucrative licensing agreements with Sony) and launched in 1976.

Viz Video (1993-). Buena Vista Home Entertainment (1989-). Miramax Home Entertainment, a unit of Buena Vista Home Entertainment (1989-). New Line Home Entertainment, a TimeWarner Company (1989-).

Carolco Home Video, a division of Artisan Entertainment, a Lions Gate Company (1988-1995). Orion Home Video, a Sony Pictures Entertainment Company (1988-1997). Anchor Bay Entertainment (1980s-). Hi-Tops Video, a Heron Communications Company (1985-1992).

Simitar Entertainment (1980s-1990s). Touchstone Home Entertainment, a unit of the Walt Disney Company (1984-). Artisan Entertainment, a Lions Gate Company (1984-). Family Home Entertainment, a division of Artisan Entertainment, a Lions Gate Company (1982-).

NBC Home Video, an NBC/Universal Company (1981-). Universal Studios Home Video, an NBC/Universal Company (1980-). Magnetic Video, the first duplicator/distributor of movies on video cassette for home use (1977-1981). Vestron Video, a division of Artisan Entertainment, a Lions Gate Company (1979-).

MGM Home Entertainment, a Sony Pictures Entertainment Company (1979-). Media Home Entertainment, a Heron Communications Company (1978-1992). Warner Home Video, a TimeWarner Company (1978-). HBO Video, a TimeWarner Company (1978-).

Sony Pictures Home Entertainment (1978-). Walt Disney Home Entertainment (1978-). Twentieth (20th) Century-Fox Home Entertainment, a News Corporation Company (1977-). Paramount Home Video, a Viacom Company (1976-).

E-XXX indicates playing time for PAL or SECAM in SP speed. T-XXX indicates playing time for NTSC or PAL-M in SP speed. PAL-M, Brazil). PAL/525/30 (i.e.

NTSC/525/30 (Most parts of North and South America, Japan, South Korea). MESECAM/625/25 (most other SECAM countries, notably Eastern Europe and Middle East). SECAM/625/25 (SECAM, French variety). PAL/625/25 (most of Western Europe, many parts of Asia and Africa).