JPS63141492A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To apply time base compensation with simple constitution by using an output of a control oscillator whose oscillated frequency is controlled in response to the time base fluctuation of a color burst so as to eliminate the time base fluctuation of a chrominance signal and a luminance signal. CONSTITUTION:A BPF 3 and an LPF 4 separate respectively a frequency modulation luminance signal and a low frequency conversion chrominance carrier signal from a video signal reproduced from a recording medium. After the luminance signal subject to frequency modulation is demodulate by a demodulator 16 and given to an adder 17 and the low frequency conversion chrominance carrier signal is given to the adder 17 via a frequency converter 5 and a BPF 15. A variable delay line 21 is provided to a pre-stage where the reproduced video signal is separated into the luminance signal subject to frequency modulation and a low frequency conversion chrominance signal. The carrier frequency of the chrominance carrier signal is converted by using an output of a VCO 12 whose oscillating frequency is controlled in response to the time base fluctuation of the color burst of the chrominance signal whose carrier frequency is converted and the variable delay line 21 is controlled.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention provides a method for separating a frequency-modulated luminance signal and a low-frequency conversion carrier chrominance signal from a video signal reproduced from a recording medium.
The present invention relates to a video signal reproducing device that performs demodulation and carrier frequency conversion, and then adds the respective signals to form a composite video signal.

(Prior Art) Time axis error correction in video signals has been performed for a long time. So-called automatic phase compensation using automatic phase control (APC) and automatic frequency compensation using automatic frequency control (AFC) have been used.

In other words, APC corrects the frequency of the time axis error included in the color subcarrier frequency during reproduction by detecting the phase difference between the frequency of this time axis error and the reference color subcarrier frequency. Furthermore, in AFC, a time axis error signal included in the frequency of a horizontal synchronizing signal during reproduction is detected as a frequency difference and corrected.

FIG. 2 is a block diagram of a conventional VTR playback system including a circuit for correcting this type of time axis error.

In Figure 2, 1 is a playback head, 2 is an amplifier, and 3
, 15 is a band pass filter (BPF), 4 is a low pass filter (LPF), 5.7 is a frequency converter (FC),
6 is a phase converter, 8 is a crystal oscillator, and 9.10 is 1/1, respectively.
n, a frequency divider with a frequency division ratio of 1/m, 11.13 a phase comparator (PC), 12 a voltage controlled oscillator (VCO), 1
4 is a burst gate, 16 is a demodulator (DEM), 17 is an adder, and 18 and 19 are terminals.

Now, the carrier color signal which has been low frequency converted is separated from the head 1 via the amplifier 2 by the LPF 4 during reproduction, and is further inputted to the frequency converter 5. The frequency of this input signal is expressed as f SCL±Δf including the time axis error (however, f
SCL is the low gamut color subcarrier frequency, and Δf is f (the time axis error of SCL). The frequency converter 5 calculates the frequency of the difference between the frequency of the signal from the phase converter 6 (where f'sc is the color subcarrier frequency) and the frequency of the difference between the frequency of the input signal (f
sc+ f SCL±Δf ) (f SCL±Δ
f)-fsc. This conversion completely corrects the time axis error component. The frequency fsc+fSCL±Δf of the signal from the phase converter 6 is created as follows.

First, the frequency of the horizontal synchronizing signal in the reproduced signal input from terminal 19 is ±Δf-n/m (where m and n are natural numbers).
This includes a considerable time error, and by multiplying this by n/m using a PLL circuit composed of frequency dividers 9 and 10, phase comparator 11, and VCO 12, f! Obtain iCL±Δf. Human signal frequency f ScL±Δf and crystal oscillator 8
The frequencies f'sc from are added by the frequency converter 7 to obtain a signal frequency of fsc+fSCL±Δf. In addition, in order to synchronize the phase of the color subcarrier of frequency f'sc with the reference crystal oscillator 8, a burst signal is extracted from the reproduced signal obtained from the BPF 15 by the burst gate 14, and a correction signal is obtained by the phase comparator 13. The phase is adjusted using the

As described above, the frequency fsc obtained from the frequency converter 5
After passing through the BPF 15, the carrier color signal based on the color subcarrier is added to the brightness signal demodulated by the BPF 3 and the demodulator 16 by the adder 17, and is sent to the terminal 18 as a composite video signal.
is output from.

[Problem that the invention seeks to solve]

The time axis compensation performed by the conventional video signal reproducing apparatus as described above is limited to compensation of only the color signal, as described above. Furthermore, if an attempt is made to compensate for the time axis of the luminance signal, there is a problem in that a large-scale circuit is required.

The present invention has been made to solve these conventional problems, and provides a video signal reproducing device that can perform time axis compensation not only for color signals but also for luminance signals with a simple configuration. The purpose is to

[Means for solving problems]

For this purpose, the present invention separates a frequency-modulated luminance signal and a low-pass conversion carrier color signal from a video signal reproduced from a recording medium, demodulates the frequency-modulated luminance signal, and In a video signal reproducing device that converts the carrier frequency of a low-pass conversion carrier chrominance signal and then adds the luminance signal and chrominance signal to form a composite video signal, the reproduced video signal is combined with a frequency-modulated luminance signal and A variable delay circuit is provided before separating the color signal into the gamut-converted color signal, and the output of the control oscillator whose oscillation frequency is controlled according to the time-axis fluctuation of the color burst of the color signal whose carrier frequency has been converted is used to convert the carrier color into the color signal. The configuration is such that the carrier frequency of the signal is converted and the delay circuit is controlled.

[Effect]

By configuring as described above, it becomes possible to remove time axis fluctuations in both the color signal and the luminance signal using the output of the controlled oscillator, which was conventionally used only for converting the carrier frequency of the carrier color signal. Ta.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the video signal reproducing device of the present invention, in which 21 is a variable delay line (VDL), 22
The VCO 123 is a frequency-voltage (FV) converter, and 24 is a BPF. Further, in FIG. 1, the same reference numerals as in FIG. 2 indicate the same or equivalent parts.

Now, during playback, the low frequency converted carrier color signal is transmitted from the head 1 to the amplifier 2 and to the LP via the variable delay line 21 consisting of a CCD.
After being separated at F4 and converted into the original carrier frequency by the frequency converter 5, it is outputted via the BPF 15 and the adder 17, or the frequency converter 5 converts the frequency from the phase converter 6 (f sc + f The difference (fsc +
fscL) (fscL±Δf)=f,. +Δf. The signal of the same frequency as the color subcarrier of frequency fBc for this conversion is the reference signal from the water crystal oscillator 8, and the signal of the same frequency as the low range color subcarrier of frequency fSCL is the reproduction level synchronization signal. 9.10, phase comparator 1
1. This is a signal generated by supplying a PLL circuit composed of VCO12. Also, the converted frequency f
The signal of the SC king Δf is input to the phase comparator 13 via the burst gate 14 for phase comparison with the signal from the reference crystal oscillator 8, and an error signal corresponding to the time axis error frequency Δf is obtained. The VCO 12 is controlled by this error signal and the above-mentioned phase matching is performed.

This VCO 12 output signal has a frequency f S
While the signal is converted to CL and supplied to the frequency converter 7 as in the conventional case, it is FV converted by the FV converter 23 and becomes the control input of the VCO 22 via the BPF 24. Since the output signal of the VCO 22 is used as a driving pulse for the variable delay line 21, the delay time of the variable delay line 21 is determined according to the output of the FV converter 23. Therefore, the signal output from the variable delay line 21 is a signal with time axis fluctuations removed, and both the frequency modulated luminance signal and the low frequency converted carrier chrominance signal separated at the subsequent stage are signals with time axis fluctuations removed.

In the above embodiment, the output signal of the frequency divider 9 is
Although the signal is supplied to the converter 23, the same effect can be obtained by subjecting the output signal of the frequency converter 7 to FV conversion and using it as a control input to the VCO 22.

However, in this case, an FV converter having different conversion characteristics from the FV converter 23 is used.

[Effects of the Invention] As explained above, the present invention provides a variable delay circuit at a stage before separating a video signal reproduced from a recording medium into a frequency modulated luminance signal and a low frequency converted carrier color signal, and uses this variable delay circuit. , the frequency band is controlled using an output signal of a control oscillator whose oscillation frequency is controlled according to time-axis fluctuations of the color burst of the converted color signal,
It has become possible to perform time axis compensation of luminance signals and color signals by using circuits that have been conventionally used and without requiring large-scale circuits.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the video signal reproducing device of the present invention, and FIG. 2 is a circuit block diagram of a conventional video signal reproducing device. In the figure, 1: Het 2: Amplifier 3.15.24: BPF 4: LPF5.7 = Frequency converter 6: Phase converter 8: Crystal oscillator,
9.10: Frequency divider 11.13: Phase comparator 12, 22
:VC○14: Burst gate 16: Demodulator 17:
Adder 21: Variable delay line 18.19: Terminal 23: FV converter.

Claims (1)

[Claims] After separating the frequency-modulated luminance signal and the low-frequency conversion carrier color signal from the video signal reproduced from the recording medium, demodulating the frequency-modulated luminance signal, and converting the carrier frequency of the low-frequency conversion carrier color signal, In the video signal reproducing device that adds the luminance signal and the chrominance signal to form a composite video signal, a variable delay circuit is provided at a stage before separating the reproduced video signal into a frequency modulated luminance signal and a low frequency converted chrominance signal. , converting the carrier frequency of the carrier color signal and controlling the delay circuit using an output of a control oscillator whose oscillation frequency is controlled according to a time axis variation of the color burst of the color signal whose carrier frequency has been converted. A video signal reproducing device characterized by: