JPH0822087B2 - Video recorder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video recording apparatus in which a time axis error correction function is selectable.

[Conventional technology and its problems]

In a magnetic recording / reproducing device, the output of the magnetic head includes a time axis error due to uneven rotation of the magnetic head and fluctuations of the tape running speed. Therefore, there is provided a time axis error correction circuit for correcting a video signal with a correct time axis. However, when considering the image display, it is not necessary to forcibly correct the time axis error for the luminance signal, but for the color signal, the time axis error causes color unevenness and the like, so it is essential to correct the time axis error. Specifically, the time axis error is corrected at the same time as the frequency conversion for restoring the color signal that has been low-pass converted for recording.

A video signal reproduced and output from such a reproducing apparatus is
Although the chrominance signal component does not include a time axis error, the luminance signal component does include a time axis error. Therefore, for example, when performing dubbing, the luminance signal originally including the time axis error is recorded on the copy destination magnetic tape. become. When the dubbed magnetic tape is reproduced, a time axis error occurs again, so that the time axis error is accumulated, which causes a remarkable deterioration in image quality. Further, when the time base error of the luminance signal is accumulated in this way, finally, the time base error correction of the color signal at the time of frequency conversion becomes impossible.

However, the time base correction circuit, so-called time base collector, basically corrects the time base error by changing the delay time of the variable delay line according to the time base error amount. The variable delay line has frequency characteristics and S /
Deteriorate N. This signal deterioration is not a problematic level when a reproduced video signal from a magnetic tape is input, but when a very stable signal such as a broadcast signal that does not include a time axis error is input, However, it causes relatively large signal deterioration.

Therefore, an object of the present invention is to provide a video recording device that overcomes these problems.

[Means for solving problems]

The video recording apparatus according to the present invention is an apparatus for recording a video signal on a recording medium, and corrects the time axis of the composite signal so as to cancel the time axis error of the brightness signal in the composite state of the brightness signal and the color signal. A time axis correcting means, a detouring means for bypassing the time axis correcting means when the input video signal does not include a time axis error, a signal output by the time axis correcting means or a signal bypassed by the detouring means and a luminance signal Frequency conversion means for converting the frequency of the color signal after being separated into signals based on a reference signal that does not include a time axis error.

[Action]

When a video signal that images the time base error is input,
The time-axis correction means operates to correct the time-axis error of the luminance signal, and gives the time-axis error of the same magnitude and in the opposite direction to the color signal. In this case, the frequency conversion means corrects the time axis error added to the color signal by the time axis correction means and converts the frequency to a low frequency. On the other hand, when a video signal that does not include a time axis error is input, the detouring unit detours the time axis correcting unit to prevent deterioration of frequency characteristics and S / N. The frequency conversion means simply performs frequency conversion. As a result, the signal recorded on the recording medium is as high in quality as possible with substantially no time axis error.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. still,
Y is a luminance signal, C is a chrominance signal, f _SC is a carrier chrominance signal or its frequency, f _LSC is a low frequency carrier chrominance signal or its frequency, and f _H is a horizontal synchronizing signal or its frequency. Those marked with "*" indicate that a time axis error is included.

In FIG. 1, an input terminal 10 is provided with a video signal output from a conventional reproducing apparatus, that is, a luminance signal including a time axis error.
A composite video signal composed of Y ^* and a carrier color signal f _SC that does not include a time axis error, or a composite video signal that does not include a time axis error such as a broadcast signal is input. Reference numeral 40 is a time axis correction circuit, and 60 and 62 are switches for bypassing the time axis correction circuit 40. That is, when a video signal having no time axis error is input to the input terminal 10, the switches 60 and 62 are connected to the a contact side, and when a video signal including a time axis error is input to the input terminal 12. Connects the switches 60 and 62 to the contact B side.

First, the case where the luminance signal includes a time base error will be described.
Since the switches 60 and 62 are connected to the b contact side, the input terminal 10
The video signal (Y ^* + f _SC) is inputted to the time base correction circuit through a switch 60 40, details will be described later, is CCD42 by correcting the time base error of Y ^* as the variable delay element. At the same time, the same time axis error is added to the carrier color signal C in the opposite direction. The output of the time axis correction circuit 40 is input to the Y / C separation circuit 12 via the switch 62, where it is separated into a luminance signal Y and a carrier color signal C ^* (or _fSC ^* ),
The Y signal is FM-modulated by the FM modulation circuit 14 and applied to the adder 16. The carrier color signal f _SC ^* is applied to the multiplier 18, and the carrier (f _SC ^* + f _LSC ) that reflects the time base error of the input Y ^* signal is applied to the multiplier 18, as described below. Therefore, the multiplier 18 is a low-frequency carrier color signal that does not include time base error.
Output f _LSC . The adder 16 is an FM-modulated luminance signal Y from the FM modulation circuit 14 and a low-frequency carrier color signal f _LSC from the multiplier 18.
Are added and superposed, and the output of the adder 16 is applied to the recording head 22 via the recording amplifier 20 and recorded on the magnetic tape 24. That is, the video signal whose time axis error is corrected is recorded on the magnetic tape 24.

The phase comparator 26, the VCO 28, and the frequency divider 30 form a PLL circuit, and the phase comparison circuit 26 includes a horizontal synchronization signal f that does not include a time axis error extracted from the luminance signal separated by the Y / C separation circuit 12. _H is applied. The phase comparison circuit 26 compares the phase of the horizontal synchronizing signal f _H with the output of the frequency divider 30, and outputs the phase difference signal as VC.
Apply to O28. VCO28 has a frequency depending on the phase difference signal.
It oscillates at 378f _H , and the frequency divider 30 divides the output of the VCO 28 into 1/378 and feeds it back to the phase comparator circuit 26. After all, VC
The output of O28 does not include the time base error.
It is _divided to form a carrier of frequency f _LSC .

The phase comparison circuit 34 and the VXO 36 also form a PLL circuit, and the phase comparison circuit 34 supplies the carrier color signals f _SC ^* and VXO from the Y / C separation circuit 12.
Phase compare with 36 outputs. The VXO 36 outputs a signal (referred to as f _SC ^* for convenience of explanation) in synchronization with the carrier color signal f _SC ^* .
The multiplier 38 multiplies the carrier f _SC ^* from the VXO 36 and the carrier f _LSC from the frequency divider 32 to output a carrier (f _SC ^* + f _LSC ), which is applied to the multiplier 18. As a result, as described above,
The multiplier 18 outputs the low-frequency carrier color signal f _LSC that does not include the time axis error.

Next, the operation of the time axis correction circuit 40 will be described. PLL circuit 41
Is a circuit similar to the PLL circuit comprising a phase comparator 26, VCO 28 and frequency divider 30 extracts a horizontal synchronization signal f _H ^* from the luminance signal including a time base error from the switch 60, the frequency at 378F _H The carrier including the time base error is output. The frequency divider 44 divides the output of the PLL circuit 43 by 1 / N. Phase comparison circuit 4
6, LPF 48, VCO 50 and 1 / N frequency divider 52 constitute a PLL circuit. That is, the phase comparison circuit 46 compares the phase of the carrier (including the time axis error) output from the frequency divider 44 with the carrier from the frequency divider 52, and outputs the phase error signal to V through the LPF 48.
Applied to the control input of CO50. VCO50 oscillates at a frequency 378f _H, and applies the output to the frequency divider 52. The output of the phase comparison circuit 46 contains the time base error of the input luminance signal and is applied to the control input of the VCO 56 via the BPF 54. Therefore, the frequency of the clock output from the VCO 56 also includes a time axis error. Under the control of the clock, the CCD 42 acts on the input multiplex signal (Y ^* + f _SC ) in the direction of canceling the time axis error of Y ^* . That is, the time axis correction circuit 40 corrects the time axis error in the luminance signal, while the carrier color signal includes the time axis error in the opposite direction.

A case where a video signal including no time axis error is input to the input terminal 10 will be briefly described. In this case, switch 6
0 and 62 are connected to the a-contact side, and the video signal input to the input terminal 10 is directly applied to the Y / C separation circuit 12. The luminance signal and the chrominance signal separated by the Y / C separation circuit 12 do not include a time axis error, and the output of the multiplier 38, and thus the output of the multiplier 8 does not include a time axis error. Therefore, the signal recorded on the magnetic tape 24 does not include the time axis error.

In the above description, the switches 60 and 62 are described as if they are manually switched, but the switching of the switches 60 and 62 is automatic, for example, the presence or absence of a time axis error is inspected at an appropriate processing stage, and based on the inspection result. You may do it automatically. Of course, in the case of automatic switching, it is necessary to prevent the switches 60 and 62 from being unnecessarily switched even if the time axis error changes for a short time.

〔The invention's effect〕

As can be easily understood from the above description, according to the present invention, when the input video signal includes a time axis error, the time axis error is corrected and recorded on the recording medium. No axis error is accumulated. Further, when the input video signal does not include a time axis error, the time axis correcting means is bypassed, so that it is possible to prevent the time axis correcting means from unnecessarily deteriorating the frequency characteristic and the S / N.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. 12 ... Y / C separation circuit, 14 ... FM modulation circuit, 26,34,46 ... Phase comparison circuit, 28,50,56 ... VCO, 40 ... Time axis correction circuit, 42 ... CCD
(Variable delay line)

Claims (1)

[Claims] 1. A device for recording a video signal on a recording medium, wherein a time axis correction is performed to correct the time axis of the composite signal so as to cancel the time axis error of the brightness signal in the composite state of the brightness signal and the color signal. Means, a detouring means for bypassing the time axis correcting means when the input video signal does not include a time axis error, and a signal output by the time axis correcting means or a signal bypassed by the detouring means is separated into a luminance signal and a color signal. A video recording device, comprising: a frequency conversion unit that frequency-converts the subsequent color signal based on a reference signal that does not include a time axis error.