JPS6026355B2 - Dubbing mechanism for magnetic recording and reproducing devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording/reproducing mechanism, and more particularly to a mechanism for dubbing a color video reproduction signal without deteriorating image quality.

According to the NTSC standard, a composite color video signal consists of a luminance (Y) signal and a signal modulated in phase corresponding to hue and amplitude corresponding to saturation. chrominance (C) signals in the form of subcarriers.

This amplitude and phase modulated color subcarrier combines two signals (1 and Q) representing color information in quadrature with 3. The MHz frequency is amplitude modulated, and then this 3.
It is formed by suppressing the carrier signal of the world. The composite color video signal can also be used as a synchronization signal.
3. at the start of each horizontal scan, along with horizontal and vertical synchronization signals.
Contains the color burst signal of Isomisaki Z. This color burst signal is used to control a demodulator that reproduces the 1 and Q signals in a receiver or the like. The color hue produced at the receiver depends on the phase of the color subcarrier with respect to the burst signal. The relative phase error between the burst signal and the color subcarrier appears as a hue shift in the reproduced color image. In a typical magnetic color video recording device, the carrier signal is F by a composite color video signal.
M modulation is performed, and this modulated signal is recorded on a magnetic recording medium such as a magnetic tape, drum, or sheet.

During reproduction, the reproduced recorded signal is demodulated through a limiter to form the original composite color video signal. A phase error occurs in the reproduced chrominance signal due to limiting factors such as relative speed fluctuations between the head and the tape. This cost is called a time base error. If it is a low frequency signal, it will be a wow, and if it is a high frequency signal, it will be a flutter. Compensate for such time axis errors,
In particular, various methods have been developed to reduce high frequency (flutter) fluctuations and obtain stable color images. In the figure, a composite color video playback signal reproduced by a playback head 12 is processed by separating luminance signals and chrominance signals by a luminance signal path 16 and a chrominance signal path 14, respectively, and then mixed by a mixer 18 to form a composite color video signal. A color video player 10 is shown having a color video output terminal 201.

During recording, only the luminance signal is modulated, and the chrominance signal is down-converted. Luminance signal path 16 thus includes a demodulator 24 and chrominance signal path 14 includes a frequency converter 26. Head 12 reproduces a composite color video signal from the magnetic recording medium, which is transmitted to reproduction amplifier 2.
8, and the reduction filter 30 transmits the chrominance signal reduced during recording to the chrominance signal path 14.
The Takagi filter 32 passes the FM-modulated luminance signal to the luminance signal path 16 during recording. Luminance signal path 16 includes an FM demodulator 2 including a limiter.
4 and a noise removal circuit 34. On the other hand, the chrominance signal path 14 has an ACC circuit 36 that compensates for fluctuations in the level.
, automatic phase compensation circuit 38, and frequency conversion circuit 26 described above.
and Obijo Philharmonic Festival 40. The signal from mixer 18 is provided to output terminal 201 via video amplifier 42. The conventional dubbing system connects the video signal from the video output terminal 20 to the video recording input of the recording recorder 12.

This method is 'i) Automatic phase compensation circuit (APC circuit) 38
Generation of humura by passing through.

(o} Deterioration of the phase characteristics of the chrominance signal by passing it through the bandpass filter 40.

1. Deterioration of the luminance signal by passing it through the noise removal circuit 34.

I learned that repeated dubbing, in particular, can have a major negative impact on the image.

The inventor of the present invention aims to eliminate such drawbacks during dubbing, and extracts the luminance signal from the demodulator 24 of the luminance signal path 16 of the playback recorder 10, and extracts the luminance signal from the chrominance signal path 14 as it is with low frequency conversion. It has been proposed to extract the chrominance signal, mix it, and process it in the recording recorder 12 as a signal to be dubbed.

More specifically, the recording recorder 12 has an input 100 for receiving the color video signal to be recorded, which receives the output of the luminance demodulator 24 of the playback recorder 10 into an amplifier 103 and other video signals. It can be selectively connected to Satoko 104 for receiving input.

Typically, the recording recorder 12 includes a low-pass filter 05 and a filter filter 106 that separate the color video signal into luminance and chrominance components. The luminance signal is led to the modulator 110 via the AGC circuit 108, where it is FM modulated, and further provided to the mixer 116 via the Takagi filter 112 and the recording amplifier 114. On the other hand, the chrominance signal is passed through the ACC circuit 118 and subjected to low-pass conversion in a circuit consisting of a converter 120 and an oscillator 122, and is then applied to the mixer 116 via a low-pass filter 124 and a recording amplifier 126. The signal from mixer 116 is transmitted to recording head 128. According to the dubbing method of this prior invention, the recording amplifier 126 receives the low-pass converted chrominance component via the low-pass filter 124.
The input of the amplifier 125 is separated and receives the output of the ACC circuit of the playback recorder via the amplifier 125.

Further, the demodulated luminance signal at the terminal 100 is directly applied to the AGC circuit 108 without passing through the low-pass filter 105. It has been known that if a dubbing signal is left in the low-pass filter 105 of a recording recorder, the phase and frequency characteristics of the luminance signal deteriorate. A switch 130 for connecting the recording recorder 12 to the output of the luminance demodulation circuit 24 of the reproduction coder 10, a switch 132 for connecting the recording recorder 12 to the output of the chrominance ACC circuit 36 of the reproduction recorder 10, a recording Switches 134 for bypassing the low-pass filter 105 for extracting the luminance component of the recorder 12 are shown connected to the dubbing side. With the above configuration, desirable dubbing can be achieved simply by selecting the input position without changing the configuration of the conventional playback and recording recorders.

However, in the dubbing method invented by Sensame, the luminance signal when dubbing to the recording recorder 12 passes through the modulator 110 and then the Takagi filter 112, so this filter 112 changes the frequency characteristics. I also learned that the phase characteristics are degraded.

This filter is used to limit the low frequency sideband that occurs during FM modulation in a recording recorder so that it does not enter the chroma band and cause a blackout, but at the same time it prevents the low frequency sideband that occurs when FM modulation is performed from entering the luminance component. A chrominance component exists near the low range of the sideband during FM modulation, and the purpose is to remove the low range of the sideband so that this leaked chrominance component does not give a shadow to the luminance component. In the above-described dubbing method, the reproduction luminance signal obtained from the reproduction recorder 10 has sideband low-frequency components already removed by the high-pass filter at the time of recording. No harmful sideband low-frequency components are generated by the modulator 1 10, and even without passing through the Takashiro filter 12, the above-mentioned interference with the low-frequency converted chrominance signal and interference with the luminance component caused by leaked chrominance components can be avoided. will not occur. According to the present invention, a switch 136 is provided to bypass the Takagi filter 12 during dubbing.

Therefore, during dubbing, the output of the modulator 110 is directly given to the mixer 116 via the recording amplifier 114, and the frequency characteristics and phase characteristics during dubbing are further improved by passing through the high frequency filter 112. .

[Brief explanation of the drawing]

The figure is a circuit diagram of an embodiment of the present invention, and 136 is a switch for bypassing the high frequency filter 112 during dubbing.

Claims (1)

[Claims] 1. A composite color video signal is separated into a luminance signal and a chrominance signal by a separating means, the chrominance signal is low-frequency converted by a low-frequency converting means, and the luminance signal is FM-modulated by a modulating means, and then generated at the time of modulation. passing through a filter means for removing low-frequency sideband components, mixing the low-frequency converted chrominance signal and the FM luminance signal by a mixing means, and recording the mixed signal on a magnetic recording medium;
During reproduction, the reproduced signal is separated into a reproduced low-frequency converted chrominance signal and a reproduced FM luminance signal, the reproduced low-frequency converted chrominance signal is converted to the original chrominance signal by a frequency conversion means, and the demodulated luminance signal is converted to a demodulated luminance signal by a demodulation means. When the reproduced signal reproduced by the first magnetic recording and reproducing apparatus is re-recorded by a second magnetic recording and reproducing apparatus having the same configuration, the first magnetic recording and reproducing apparatus means for supplying the reproduced low frequency converted chrominance signal of the recording and reproducing device to the mixing means of the second magnetic recording and reproducing device; and means for supplying the demodulated luminance signal of the first magnetic recording and reproducing device to the second magnetic recording and reproducing device. A dubbing mechanism for a magnetic recording and reproducing apparatus having a means for supplying a signal to the modulation means, comprising a bypass means provided in parallel with the filter means, and a switch means for selecting the filter means or the bypass means, A dubbing mechanism for a magnetic recording/reproducing device, characterized in that the above-mentioned bypass means is selected by the switch means.