Television Recording, Tape

The development of video tape recording is closely associated with the development of television. The rapid expansion of television broadcasting in the post-World War II period led to a demand for video recording to facilitate production of programming. Initially, this demand was satisfied by the use of motion picture camera to photograph images produced by a high-brightness cathode-ray tube called a kinescope tube.

Such kinescope recordings (the word came to describe a filmed recording although the word actually refers to the cathode-ray tube) were less than ideal, as the process introduces a variety of image defects due to poor resolution, compressed brightness range, nonlinearity, and film grain and video processing artifacts. Given that the resulting signal to noise ratio was often less than 40 decibels (dB), it is not surprising that television producers sought an alternative recording method to make a permanent document for rebroadcast or archiving.

Initial experiments with video recording in the early 1950s were based on magnetic tape technology developed for audio tape recording, a technology that had reached maturity in the late 1940s. However, video recording proved to be a much more difficult technical challenge than audio recording, due to the higher bandwidth required. In contrast to audio signals, which range from about 20 hertz to 20 kilohertz, or roughly 10 octaves, video signals require a recording range from about 30 hertz up to 5 megahertz, more than 17 octaves.

With contemporary technology, this required very high tape speeds, which consumed enormous amounts tape. Moreover, these high speeds led to unacceptable wear on tape recording and reproducing heads.

Early experiments, which used a fixed recording head, attempted to solve the problem by using multiple tracks on a single piece of tape, either by running the tape past the head back and forth, or electronically splitting the incoming signal into several frequency bands and recording on separate parallel tracks on the tape. Attempts to solve the mechanical and electronic issues associated with these systems were unsuccessful, and no such machine was ever commercialized.

Led by Charles Ginsburg, the Ampex Corporation solved the problem of video recording by adopting a new type of recording head. The VRX-1000, introduced in 1956, was the first practical videotape recorder. At $50,000, it was used by television networks for videotape delayed broadcast, rather than home recording. Referred to as the quadraplex system, the Ampex machine moved tape past a thin wheel on which were mounted four recording heads that rotated at right angles to the tape motion.

This system allowed writing on thin parallel tracks on the tape at very high effective speeds, thereby allowing the capture of television pictures. Initial quadraplex machines were capable of monochrome recording and subsequent improvements allowed the recording of color video. Quadraplex machines were used until the mid-1970s, when they were supplanted by helical scan recorders.

Quadraplex video recorders were in widespread use in television production by the late 1950s. However, these machines were expensive and required constant adjustment to perform well, and manufacturers sought to develop less expensive machines based on emerging transistor technology. In 1958 Ampex developed the helical scan recorder, which wrapped the recording tape in a spiral path around a rotating cylindrical recording head.

This allowed the recording of a complete TV field on a single track, and considerably simplified the electronics needed to process the image. However, due to problems with timebase correction, helical scan systems did not match the performance of quadraplex recorders until the early 1970s. After that time, advances in large- scale integration of silicon devices improved the quality and lowered the cost of helical scan recorders so that they replaced quadraplex machines for studio use by the late 1970s.

Helical scan machines were marketed and used in a number of other applications during the 1960s. Television stations in smaller markets or that were not affiliated with the large networks were willing to use helical scan machines with lower levels of performance due to their lower cost. Portable helical scan machines were also developed during the 1960s allowing taping of news and sports recording, though these units were rather heavy and required carts to move them.

Continued development led to the first successful video cassette recorder, the U-Matic system, jointly developed by the Japanese firms Sony, Matsushita, and JVC, and introduced in 1969. The tape cassettes were expensive (almost $100 for one hour), but the machines were widely adopted by institutional users to make training films, replacing 16-millimeter film. In 1974 Sony developed a portable camera system for CBS, which was very successful, but still heavy—one person was needed to carry the recorder, the other the camera. Subsequent competition led to the introduction of smaller recording camera units.

The first home video recorders were introduced by Sony and Matsushita in the mid-1960s, but these reel-to-reel machines were very expensive, had poor picture quality and could only record for a short period of time (less than one hour). With the introduction of chromium dioxide tape in the late 1960s, higher recording densities became possible, and home machines based on the U- Matic format were introduced.

Their high cost largely limited their use to institutional settings, and it was not until the introduction of the VHS and Beta cassette formats in the mid-1970s that prices declined to a level that led to widespread consumer acceptance. The key technical innovation used in both VHS and Beta was azimuth recording, which allowed tracks to be recorded much closer together, reducing the amount of tape needed for a given recording time.

VHS and Beta machines offered similar levels of performance, but the earlier introduction of longer recording times by VHS machine makers led to their eventual domination of the market by the late 1980s. Subsequently, smaller size cassettes, such as the 8 mm and VHS-C formats, were developed for use in portable video cameras for consumer use.

Although digital recording is an idea that dates to the late 1930s, the digital recording of video signals was delayed for many years by the difficulty of developing adequate analog to digital converters. The rise of large-scale integrated circuits in the 1970s solved this problem, and the first digital video recorders were operating in laboratories by the mid-1970s.

Negotiations over a common digital recording format extended into the early 1980s, and it was not until 1986 that the first generation of digital video recorders were marketed by Sony of Japan and Bosch-Fernseh of Germany. By the end of the twentieth century, digital video recording dominated broadcast recording.