Best of Techopedia weekly. News and Special Offers occasional. Techopedia Explains Video Cassette Recorder VCR The video cassette recorder evolved with the history of videotape recording in general, as it is not actually tied to a specific videotape format such as VHS and Betamax. Related Question How do machine learning professionals use structured prediction? Share this Term.
Tech moves fast! Stay ahead of the curve with Techopedia! However, the rental market has not been as large as I expected, but we will keep trying. Maybe it will catch on soon. Also renting video discs is Video Place. Its Monrovia W. Huntington Drive and Long Beach E.
However, the Video Place in Monterey Park does not provide this service. The first head writes one track, i. The second head writes a second track, i. This corresponds to the interlacing principle, as applied in television see Chapter 2: TV set.
One full revolution of both heads results in two diagonal tracks right next to each other, together forming one entire image scan a frame. This means that two apparently contradictory requirements can be realized simultaneously: low tape speed of only 2 cm per second and at the same time a high registration speed relative tape speed of no less than 5 meters per second.
These two requirements make it possible to record the high video frequencies up to 3. At the same time, the low tape speed gives a time capacity up to three hours. Compared with early video recorders, modern day video recorders have their video tracks lying right next to each other. To avoid interference, the two video heads are angled slightly away from each other.
As a result, the video head openings that transmit the magnetic tracks to the tape, create an angle between them. The heads are 15 degrees angled in opposite direction, making a total angle of 30 degrees. This diverted registration angle ensures no problems are caused if the heads slightly lose track when playing back and touch the next track.
The heads only register tape information at an angle that precisely corresponds to the position of the head opening. This system is called the azimuth recording system. If the video heads stray too far from the track, which could lead to distorted images, tracking control can correct this. Azimuth settings. The head openings are cut with different azimuth angles, so that the tracks can be written next to each other.
The revolutionary speed of the head drum and the video heads needs to maintain a constancy within strict parameters. Moreover, the tracks must be scanned during playback in precisely the same way as they were recorded. Each tape track is synchronized at the recording stage by means of field synchronization pulses. These pulses are generated in the video recorder by a separate head which are recorded on a separate narrow track at the side of the video tape.
This is called the synchronization, servo or control track. When the video recorders were first introduced, Philips also developed a system called V Despite the fact that is was a high quality system, it was not successful in the market.
Although Betamax was reasonably successful at first, its popularity waned and VHS was adopted as the world standard. When the cassette is inserted, the tape is guided around the head drum called threading. Threading the tape takes a few seconds, but once the tape is threaded, shifting from one tape function to another can be achieved rapidly and smoothly.
It is considered simpler and more compact than the U-system. Threading is faster and is done every time the tape guidance function is changed. It is therefore somewhat slower and noisier than the U-system.
This problem is being solved by "Quick-start" VHS video recorders, which allow fast and silent changes in tape guidance functions. To avoid excessive wear, M-tape guidance system recorders are provided with an automatic switch-off feature, activated some minutes after the recorder is put on hold, which automatically unthreads the tape. In the VHS system different starting points were used than in Betamax, such as track size and relative speed.
VHS has rather wide video tracks, but a slightly lower relative tape speed, and that also counts for the audio track. In general, the advantages of one aspect are tempered by the disadvantages of the other. The end result is that there is not too much difference between the sound and image qualities of both systems. The sound recording takes place digitally, making its sound quality very good. The Video-Hi8-recorder can also be used to make audio recordings digital stereo only.
Using a 90 minute cassette, one can record 6 x 90 minutes, making a total of 18 hours of continuous music. The video Hi8-system also allows manipulating digital images, such as picture-in-picture and editing. Video Hi8 uses a combination of the M- and U-tape guidance system. In case of a mono video recorder, the audio signal which corresponds with the image is transferred to a separate, fixed audio head. As in an audio cassette deck, this head writes an audio track in longitudinal direction of the tape.
This is called linear or longitudinal track recording. The video recorder has two erase heads. One is a wide erase head covering the whole tape width which automatically erases all existing image, synchronization and sound information when a new recording is made. The other erase head is smaller and positioned at the position of the audio track.
With this erase head, the soundtrack can be erased separately, without affecting the video information. In this way, separate audio can be added to a video recording. This is called audio dubbing, and can be particularly useful when making your own camera recordings. The linear audio track does have some restrictions. Due to its low tape speed, it is not suitable for hi-fi recordings.
Moreover, the audio track is so narrow 0. The frequency range is limited as is the dynamic range which relates to the amount of decibels , and the signal-to-noise ratio is not very high.
The signal-to-noise ratio relates to amount of noise compared to the total signal. The higher this ratio, the less noise and the better the signal will be. The sound quality of the mono track can be improved by a noise reduction system.
There is a way to get superior hi-fi stereo sound quality on a videotape used in hi-fi video recorders, which will be discussed later. Hi-fi video recorders were developed for improved sound quality. The most common quality of video images is HQ.
Conventional mono video recorders use linear audio registration, which does not allow hi-fi recordings. A special method was therefore devised to record stereo sound with hi-fi quality. In the case of hi-fi, the audio signal is also put on tape via revolving heads similar to the video signal, not on the linear track. As there is no space between the video tracks, as the video tracks lie right next to each other with no space in between, the audio tracks need to be recorded in the same place as the video tracks.
The way this is realized is by recording the audio signal under deeper than the video signal. Hi-fi video recording, where the audio signal is recorded at a deeper level, after which the video signal is recorded on top. In hi-fi video recorders, the audio signal is modulated to a high carrier frequency. Video recording technology itself dates to the early s, but the company Ampex is credited with developing the first commercially viable videotape recorder in The machine was bulky, expensive and designed primarily for professional broadcasters.
A variety of home video recorders from Phillips, Telcan and Sony, among others, came to market over the next two decades, but widespread consumer adoption remained elusive. In fact, VCRs found their earliest customers in hotel chains during the s, said Mark Schubin, a technology consultant and member of the Emmy Engineering Committee.
The number of households with VCRs climbed from 14 percent in to 66 percent in , according to Nielsen data. VCR penetration peaked at about 90 percent of households in If the knob was not doing its job, then a cleaning tape was required. Dust and other grime collecting in a VCR could distort playback, requiring users to purchase a special tape that wiped clean the play heads -- the components that read the tape. There was also the complaint of bad placement of stickers on the cover of cassettes.
Misaligned cover art could drive some people absolutely crazy.
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