Video Cassette Recording
Video Cassette Recording is an early domestic analog recording format designed by Philips. It was the first successful consumer-level home videocassette recorder system. Variants included the VCR-LP and Super Video formats; the VCR format was introduced in 1972, just after the Sony U-matic format in 1971. Although at first glance the two might appear to have been competing formats, they were aimed at different markets. After failing as a consumer format, U-matic was marketed as a professional television production format, whilst VCR was targeted at educational but domestic users. Unlike some other early formats such as Cartrivision, the VCR format does record a high-quality video signal without resorting to Skip field. Home video systems had been available, but they were open-reel systems and were expensive to both buy and operate, they were unreliable and only recorded in black and white such as the EIAJ-1. The VCR system was easy to use and recorded in colour but was still expensive: when it was introduced in 1972 the N1500 recorder cost nearly £600.
By comparison, a small car could be purchased for just over £600. The VCR format used large square cassettes with 2 co-axial reels, one on top of the other, containing half inch wide chrome dioxide magnetic tape. Three playing times were available: 30, 45 and 60 minutes; the 60-minute videocassettes proved unreliable, suffering numerous snags and breakages due to the thin 17μm video tape. Tapes of 45 minutes or less contained 20 μm thickness tape; the mechanically complicated recorders themselves proved somewhat unreliable. One common failing occurred should tape slack develop within the cassette; the cassette would completely jam and require dismantling to clear the problem, the tape would be creased and damaged. The system predated the development of the slant azimuth technique to prevent crosstalk between adjacent video tracks, so it had to use an unrecorded guard band between tracks; this required the system to run at a high tape speed of 11.26 inches per second. The Philips VCR system was groundbreaking and brought together many advances in video recording technology to produce the first practical home video cassette system.
The first Philips N1500 model included all the essential elements of a domestic video cassette recorder: Simple loading of cassette and simple operation by "Piano Key" controls, with full auto-stop at tape ends. A tuner for recording off-air television programmes. A clock with timer for unattended recordings. A modulator to allow connection to a normal television receiver without audio and video input connectors; the Philips VCR system was only marketed in the U. K. mainland Europe and South Africa. In mid-1977, Philips announced they were considering distribution of the format in North America, it was test marketed for several months; because the format was designed only for use with the 625-line 50 Hz PAL system, VCR units had to be modified in order to work with the 60 Hz NTSC system. For mechanical and electronic reasons, the tape speed had to be increased by 20%, which resulted in a 60-minute PAL tape running for 50 minutes in a NTSC machine. DuPont announced a thinner videotape formulation that would allow a 60-minute NTSC VCR tape, but the tape was less reliable than previous formulations.
Philips abandoned any hope of trying to sell their VCR format in North America because of the reliability issues, because of the introduction of VHS that same year. VCR evolved into a related format known as VCR-LP; this exploited slant azimuth to increase the recording time. Although both formats used identical VCR cassettes, the recordings were incompatible between the two systems, few if any dual-format recorders existed. Philips N1700, released in 1977, supported the VCR-LP format. A even longer-playing variant, Super Video was manufactured by Grundig exclusively. SVR was designed to use BASF- and Agfa-manufactured chrome-dioxide tape in cassettes that were identical to the earlier Philips ones, with the exception of a small actuator added to the bottom of the cassette; this meant that only the BASF/Agfa tapes would work in SVR machines, but that such tapes could be used in the older VCR and VCR-LP machines. Just as VCR-LP recordings are incompatible with VCR, so SVR recordings are incompatible with both VCR and VCR-LP.
The only model to be built was the Grundig SVR4004, with a few detail variations such as optional audio/video connectors, plus a rebadged ITT 240. This chart provides an overview of playing times for the most common cassettes released for standard VCR, VCR-LP and SVR. VC cassettes were developed for standard VCR. LVC cassettes are physically identical to VC cassettes. SVC cassettes were developed for SVR. *) LVC 180 was not recommended for use in a standard VCR machine due to a thin tape base.**) VC and LVC cassettes do not work in a SVR machine. However, SVC cassettes may be used in VCR-LP machines; the First Philips machine was model number N1500, after which the format is known. This had "first generation" mechanics including magnetic braking servo systems applied to large mains voltage induction motors; the outer edge of the cabinet was wooden. The power cable was detachable, but used an obscure connector for which replacements are not available; the N1520 was a N1500 without TV tune
Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light and water waves; the law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection. In acoustics, reflection is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types besides visible light. Reflection of VHF and higher frequencies is important for radar. Hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors. Reflection of light is either diffuse depending on the nature of the interface. In specular reflection the phase of the reflected waves depends on the choice of the origin of coordinates, but the relative phase between s and p polarizations is fixed by the properties of the media and of the interface between them.
A mirror provides the most common model for specular light reflection, consists of a glass sheet with a metallic coating where the significant reflection occurs. Reflection is enhanced in metals by suppression of wave propagation beyond their skin depths. Reflection occurs at the surface of transparent media, such as water or glass. In the diagram, a light ray PO strikes a vertical mirror at point O, the reflected ray is OQ. By projecting an imaginary line through point O perpendicular to the mirror, known as the normal, we can measure the angle of incidence, θi and the angle of reflection, θr; the law of reflection states that θi = θr, or in other words, the angle of incidence equals the angle of reflection. In fact, reflection of light may occur whenever light travels from a medium of a given refractive index into a medium with a different refractive index. In the most general case, a certain fraction of the light is reflected from the interface, the remainder is refracted. Solving Maxwell's equations for a light ray striking a boundary allows the derivation of the Fresnel equations, which can be used to predict how much of the light is reflected, how much is refracted in a given situation.
This is analogous to the way impedance mismatch in an electric circuit causes reflection of signals. Total internal reflection of light from a denser medium occurs if the angle of incidence is greater than the critical angle. Total internal reflection is used as a means of focusing waves that cannot be reflected by common means. X-ray telescopes are constructed by creating a converging "tunnel" for the waves; as the waves interact at low angle with the surface of this tunnel they are reflected toward the focus point. A conventional reflector would be useless as the X-rays would pass through the intended reflector; when light reflects off a material denser than the external medium, it undergoes a phase inversion. In contrast, a less dense, lower refractive index material will reflect light in phase; this is an important principle in the field of thin-film optics. Specular reflection forms images. Reflection from a flat surface forms a mirror image, which appears to be reversed from left to right because we compare the image we see to what we would see if we were rotated into the position of the image.
Specular reflection at a curved surface forms an image which may be demagnified. Such mirrors may have surfaces that are parabolic. If the reflecting surface is smooth, the reflection of light that occurs is called specular or regular reflection; the laws of reflection are as follows: The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane. The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal; the reflected ray and the incident ray are on the opposite sides of the normal. These three laws can all be derived from the Fresnel equations. In classical electrodynamics, light is considered as an electromagnetic wave, described by Maxwell's equations. Light waves incident on a material induce small oscillations of polarisation in the individual atoms, causing each particle to radiate a small secondary wave in all directions, like a dipole antenna. All these waves add up to give specular reflection and refraction, according to the Huygens–Fresnel principle.
In the case of dielectrics such as glass, the electric field of the light acts on the electrons in the material, the moving electrons generate fields and become new radiators. The refracted light in the glass is the combination of the forward radiation of the electrons and the incident light; the reflected light is the combination of the backward radiation of all of the electrons. In metals, electrons with no binding energy are called free electrons; when these electrons oscillate with the incident light, the phase difference between their radiation field and the incident field is π, so the forward radiation cancels the incident light, backward radiation is just the reflected light. Light–matter interaction in terms of photons is a topic of quantum electrodynamics, is described in detail by Richard Feynman in his popular book QED: The Strange Theory of Light and Matter; when light strikes the surface of a mate
D-1 or 4:2:2 Component Digital is a SMPTE digital recording video standard, introduced in 1986 through efforts by SMPTE engineering committees. It started as a Sony and Bosch - BTS product and was the first major professional digital video format. SMPTE standardized the format within ITU-R 601 known as Rec. 601, derived from SMPTE 125M and EBU 3246-E standards. D-1 or 4:2:2 D-1 was a major feat in broadcast quality digital video recording, it stores uncompressed digitized component video, encoded at Y'CbCr 4:2:2 using the CCIR 601 raster format with 8 bits, along with PCM audio tracks as well as timecode on a 3/4 inch videocassette tape. The uncompressed component video used 173 Mbit/sec, for its time; the maximum record time on a D-1 tape is 94 minutes. Because of the uncompromising picture quality - component processing and uncompressed recording, D-1 was most popular in high-end graphic and animation production - where multiple layering had been done in short run times via hard drives or via multiple analog machines running at once.
Hard drives in the 1980s that stored broadcast-quality video would only hold 30 seconds to a few minutes of space, yet the systems that made them work could cost $500,000. By contrast, the D-1 machine allowed 94 minutes of recording on a $200 cassette. D-1 resolution is 720 × 486 for 720 × 576 for PAL systems. 601. A small variation removing the top 6 lines to save space was introduced and made popular in the 1/4-inch DV/DVCAM/DVCPro formats and for digital broadcasting, which have 720 x 480 pixels for NTSC; the D1 units are switchable between NTSC and PAL. Luma is sampled at 13.5 Chroma at 6.75 MHz with an overall data rate of 27 MHz. Sampling at 13.5 MHz was used as it is a common multiple of NTSC/PAL line rate. The first input/output interface was a 25 pin parallel cable and updated to serial digital interface on coaxial cable. Ancillary data can be put in H/V blanking intervals. Color space for Y’ B’-Y’ R’-Y’ is defined in ITU Rec. 601 or Rec. 709 color space. Panasonic's D-5 format has similar specifications, but sampled at 10-bits as opposed to D-1's 8-bits.
It had the advantage of development time as it was introduced much than Sony's D-1 and two years after Sony's Digital Betacam format was unveiled. The D-2 format system from Sony and Ampex soon followed two years using composite video in order to lower the bandwidth needed; this reduced D-2's price tag to half that of D-1. Since D-2 was composite digital as opposed to component, it could be dropped into the space and infrastructure of composite analog machines presently used at the time. Since less information was recorded on D-2 than on D-1, tape speed could be reduced and hold a maximum of 208 minutes compared to D-1's 94 minutes. However, D-2 was still a compromise; as broadcasters would convert from analog to digital wiring, component digital infrastructure became feasible. Sony's popular component Digital Betacam would usher the transition of keeping the colors separated in component digital space rather than combined together in composite space. Digital Betacam could play previous analog Betacam/Betacam SP tapes – which by now – had built a library archive for broadcasters using its 1/2-inch tape format.
1/2-inch Digital Betacam thus became the de facto standard-definition broadcast editing and archive standard. As HD broadcasting and delivery became more commonplace in the U. S. after 2008-2010, networks would require standard definition copies on Digital Betacam. Television shows such as CBS' The Rachael Ray Show were still recorded and archived on Digital Betacam as late as 2012. In the early 2000s, 2-inch Quadruplex and 1-inch Type C reel-to-reel TV programs from 1956 through 1996 were being copied onto Digital Betacam for library vault and re-archiving purposes since spare parts and engineers with the expertise to maintain 2-inch and 1-inch VTRs were diminishing with each passing year. D-1 was notoriously expensive and the equipment required large infrastructure changes in facilities which upgraded to this digital recording format, because the machines being uncompromising in quality reverted to component processing and its primary colors red and blue were kept separate in a sampling algorithm known as 4:2:2, why many machines have a badge of "4:2:2" instead of "D-1."
Early D-1 operations were plagued with difficulties, though the format stabilized and is still renowned for its superb standard definition image quality. D-1 was the first real-time digital broadcast-quality tape format; the original Sony DVR-1000 unveiled in 1986 had a U. S. MSRP of $160,000. A few years Sony's engineers were able to drastically reduce the size of the machine by reducing the electronic processing to fit into the main cassette drive chassis, christened the DVR-2000, lowering the U. S. cost to $120,000. An external single-rack unit would enable the machine to record an additional key channel or double the horizontal resolution by combining two VTRs running simultaneously. "SP" and "OS" models ran Off-SPeed, making them technically friendly for 24-frame telecine fi
Sansui Electric Co. Ltd. is a Japanese manufacturer of audio and video equipment. Headquartered in Tokyo, Japan, it is part of Grande Holdings, a Chinese Hong Kong-based conglomerate, which owns Japanese brands Akai and Nakamichi. Founded in Tokyo in 1947, Sansui manufactured transformers, but by the 1960s had developed a reputation for making serious audio components, they were sold in foreign markets through the next decade. Sansui's amplifiers and tuners from the 1960s and 1970s remain in demand by audio enthusiasts. In 1971, Sansui introduced the Quadphonic Synthesizer QS-1, which could make simulated four channel stereo from two channel sources. Sansui developed the QS Regular Matrix system, which made it possible to transmit four channel Quadraphonic sound from a standard LP; the channel separation was only 3 dB, but because of the human way of hearing it sounded good. In 1973, Sansui introduced the more advanced QS Vario Matrix decoder with 20 dB separation; the SQ system developed by Columbia/CBS was the most popular so called matrix system.
But QS decoders could play SQ records. Some Sansui receivers could play the most advanced four channel system - CD-4/Quadradisc by Japanese JVC and American RCA. Most big record companies used either SQ or CD-4. During the late 1970s, the iconic matte-black-faced AU-series amplifiers were released; the first-generation'07' models included the dual-mono power supply AU-517 and AU-717, the second generation featured the updated AU-719, 819 and 919. The separate pre-amp/power-amp CA-F1/BA-F1 topped the model range along with the AU-X1 integrated amplifier. In the UK around 1982, the Sansui AU-D101 amplifier and its more powerful sibling the AU-D33, were acclaimed by audiophiles and were so well matched to a pair of KEF Coda III speakers that they could be bought as a set from some outlets; these amplifiers used a complex feed-forward servo system which resulted in low 2nd order harmonic distortion. Despite this success, Sansui failed to follow up with further mass market audiophile components; as the mid-1980s arrived, sales were lost to competitors.
Sansui began to lose visibility in the United States around 1988, focused on manufacturing high-end components in Japan. The company began to manufacture high-end television sets and other video equipment, but ceased exportation. In the late 1990s, the company's brand was used on video equipment manufactured by other companies; the current manufacturer of the rebranded sets is Orion Electric, based in Fukui, Japan. Its U. S. subsidiary markets products under the Sansui brand, among others. Sansui is thus a mere umbrella brand at present; this radical change in Sansui's corporate identity has resulted in a notable change in its product quality as consumers now tend to consider Sansui a mass-market brand rather than a maker of high-end electronics. Sansui had developed the patented a-x balanced circuit, that used in its high power amplifier along with the so-called double diamond differential, another patent for balanced driver stage, its latest amplifiers included the a-u alpha series like the 707 907, b-2105 mos vintage, au-x1111, b 2302, c 2302 and others.
Sansui ended its Japanese production of high end amplifiers some time between 2002 and 2005. Many Sansui devices vintage items, have a large following in the audio community to date, with online forums dedicated to the Sansui brand. List of phonograph manufacturers Audiokarma, a Popular Sansui Enthusiasts Forum Global website US website India website
8 mm video format
The 8mm video format refers informally to three related videocassette formats for the NTSC and PAL/SECAM television systems. These are the original Video8 format and its improved successor Hi8, as well as a more recent digital recording format known as Digital8, their user base consisted of amateur camcorder users, although they saw important use in the professional television production field. In January 1984, Eastman Kodak announced the new technology. In 1985, Sony of Japan introduced the Handycam, one of the first Video8 cameras with commercial success. Much smaller than the competition's VHS and Betamax video cameras, Video8 became popular in the consumer camcorder market; the three formats are physically similar, featuring both the same magnetic tape width and near-identical cassette shells, measuring 95 × 62.5 × 15 mm. This gives a measure of backward compatibility in some cases. One difference between them is in the quality of the tape itself, but the main differences lie in the encoding of the video when it is recorded onto the tape.
Video8 was the earliest of the three formats, is analog. The 8mm tape width was chosen as smaller successor to the 12mm Betamax format, using similar technology but in a smaller configuration in response to the small configuration VHS-C compact camcorders introduced by the competition, it was followed by a version with improved resolution. Although this was still analog, some professional Hi8 equipment could store additional digital stereo PCM sound on a special reserved track. Digital8 is the most recent 8mm video format, it retains the same physical cassette shell as its predecessors, can record onto Video8 or Hi8 cassettes. However, the format in which video is encoded and stored on the tape itself is the digital DV format; some Digital8 camcorders support Video8 and Hi8 with analog sound, but this is not required by the Digital8 specification. In all three cases, a length of 8mm-wide magnetic tape is wound between two spools and contained within a hard-shell cassette; these cassettes share similar size and appearance with the audio cassette, but their mechanical operation is far closer to that of VHS or Betamax videocassettes.
Standard recording time is up to 180 minutes for PAL and 120 minutes for NTSC. Like most other videocassette systems, Video8 uses a helical-scan head drum to read from and write to the magnetic tape; the drum rotates at high speed. Because the tape and drum are oriented at a slight angular offset, the recording tracks are laid down as parallel diagonal stripes on the tape. Unlike preceding systems, 8mm did not use a control track on the tape to facilitate the head following the diagonal tracks. Instead 8mm recorded a sequence of four sine waves on each video track such that adjacent tracks would produce one of two heterodyne frequencies if the head mistracked; the system automatically adjusted the tracking such that the two frequencies produced were of equal magnitude. This system was derived from the dynamic track following used by the Philips Video 2000 system. Sony rechristened the system as automatic track following as the 8mm system lacked the ability of the heads to physically move within the head drum.
The main disadvantage of the ATF system was that unlike in the case of a control track, an 8mm camera or player cannot keep track of where the tape is during fast forward and rewind. This made editing using a linear editing system problematic; some cameras and players attempted to derive the tape position from the differential rotation of the spools with limited success. Video8 was launched into a market dominated by the VHS-C and Betamax formats; the first model was the Sony Handycam CCD-V8, a record only model with no play back features, only three focus settings and a 6x zoom. Soon after, an Auto-focus model was introduced. In terms of video quality, Video8 and Beta-II offer similar performance in their standard-play modes. In terms of audio, Video8 outperforms its older rivals. Standard VHS and Beta audio is recorded along a narrow linear track at the edge of the tape, where it is vulnerable to damage. Coupled with the slow horizontal tape speed, the sound was comparable with that of a low-quality audio cassette.
By contrast, all Video8 machines used audio frequency modulation to record sound along the same helical tape path as that of the video signal. This meant that Video8's standard audio was of a far higher quality than that of its rivals, although linear audio did have the advantage that it could be re-recorded without disturbing the video. Video8 included true stereo, but the limitations of camcorder microphones at the time meant that there was little practical difference between the two AFM systems for camcorder usage. In general, Video8 comfortably outperforms non-HiFi VHS/Beta. Video8 has one major advantage over the full-size competition. Thanks to their compact size, Video8 camcorders are small enough to hold in the palm of the user's hand; such a feat was impossible with Betamax and full-sized VHS camcorders, which operate best on sturdy tripods or strong shoulders. Video8 has an advantage in terms of time, because although VHS-C offers the same "p
Video is an electronic medium for the recording, playback and display of moving visual media. Video was first developed for mechanical television systems, which were replaced by cathode ray tube systems which were replaced by flat panel displays of several types. Video systems vary in display resolution, aspect ratio, refresh rate, color capabilities and other qualities. Analog and digital variants exist and can be carried on a variety of media, including radio broadcast, magnetic tape, optical discs, computer files, network streaming. Video technology was first developed for mechanical television systems, which were replaced by cathode ray tube television systems, but several new technologies for video display devices have since been invented. Video was exclusively a live technology. Charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder. In 1951 the first video tape recorder captured live images from television cameras by converting the camera's electrical impulses and saving the information onto magnetic video tape.
Video recorders were sold for US $50,000 in 1956, videotapes cost US $300 per one-hour reel. However, prices dropped over the years; the use of digital techniques in video created digital video, which allows higher quality and much lower cost than earlier analog technology. After the invention of the DVD in 1997 and Blu-ray Disc in 2006, sales of videotape and recording equipment plummeted. Advances in computer technology allows inexpensive personal computers and smartphones to capture, store and transmit digital video, further reducing the cost of video production, allowing program-makers and broadcasters to move to tapeless production; the advent of digital broadcasting and the subsequent digital television transition is in the process of relegating analog video to the status of a legacy technology in most parts of the world. As of 2015, with the increasing use of high-resolution video cameras with improved dynamic range and color gamuts, high-dynamic-range digital intermediate data formats with improved color depth, modern digital video technology is converging with digital film technology.
Frame rate, the number of still pictures per unit of time of video, ranges from six or eight frames per second for old mechanical cameras to 120 or more frames per second for new professional cameras. PAL standards and SECAM specify 25 frame/s. Film is shot at the slower frame rate of 24 frames per second, which complicates the process of transferring a cinematic motion picture to video; the minimum frame rate to achieve a comfortable illusion of a moving image is about sixteen frames per second. Video can be progressive. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence; when displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. Interlacing was invented as a way to reduce flicker in early mechanical and CRT video displays without increasing the number of complete frames per second. Interlacing retains detail while requiring lower bandwidth compared to progressive scanning.
In interlaced video, the horizontal scan lines of each complete frame are treated as if numbered consecutively, captured as two fields: an odd field consisting of the odd-numbered lines and an field consisting of the even-numbered lines. Analog display devices reproduce each frame doubling the frame rate as far as perceptible overall flicker is concerned; when the image capture device acquires the fields one at a time, rather than dividing up a complete frame after it is captured, the frame rate for motion is doubled as well, resulting in smoother, more lifelike reproduction of moving parts of the image when viewed on an interlaced CRT display. NTSC, PAL and SECAM are interlaced formats. Abbreviated video resolution specifications include an i to indicate interlacing. For example, PAL video format is described as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing, 50 indicates 50 fields per second; when displaying a natively interlaced signal on a progressive scan device, overall spatial resolution is degraded by simple line doubling—artifacts such as flickering or "comb" effects in moving parts of the image which appear unless special signal processing eliminates them.
A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog, DVD or satellite source on a progressive scan device such as an LCD television, digital video projector or plasma panel. Deinterlacing cannot, produce video quality, equivalent to true progressive scan source material. Aspect ratio describes the proportional relationship between the width and height of video screens and video picture elements. All popular video formats are rectangular, so can be described by a ratio between width and height; the ratio width to height for a traditional television screen is 4:3, or about 1.33:1. High definition televisions use an aspect ratio of 16:9, or about 1.78:1. The aspect ratio of a full 35 mm film frame with soundtrack is 1.375:1. Pixels on computer monitors are 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