JPH0630439A - Regenerative signal processor - Google Patents

Abstract

PURPOSE:To prevent the generation of achromatism and hue variation on a television(TV) screen by stopping the comparing operation of a hue comparator by using a drop-out signal in the case of reproducing a guard band part or a tape deteriorated in its recording state. CONSTITUTION:When an output signal from an amplifier 2 is extremely small, an envelope detector 14 judges the signal as a drop-out state and controls a switch circuit 12, which switches the current signal to a signal obtained before 1H to prevent the influence of the extremetely small signal. A synchronizing separator circuit 15 separates a synchronizing signal from a reproduced luminance signal and an HHK circuit 16 removes a vertical synchronizing signal and an equalizing pulse and outputs a signal synchronized with a horizontal synchronizing signal. A phase comparator 17 compares a signal outputted from a frequency divider 20 with the signal outputted from the HHK 16. When the detector 14 detects a drop-out state, the comparing operation is stopped. A phase error signal is smoothed by an LPF 18 to control a VCO 19. Consequently the oscillation frequency of a VCO 21 is locked to a prescribed value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a reproduction signal processing device which can be used in a video tape recorder (hereinafter abbreviated as VTR).

[0002]

2. Description of the Related Art In recent years, in a consumer VTR, a luminance signal is frequency-modulated (hereinafter abbreviated as FM modulation), a chrominance signal is frequency-converted to a low frequency range, a luminance signal is FM-demodulated at the time of reproduction, and a chrominance signal is Signal processing is used that translates to the original frequency.

An example of a conventional reproduction signal processing device will be described below with reference to the drawings.

FIG. 2 is a block diagram of an example of a conventional VHS / pseudo-SECAM system reproduction signal processing apparatus. In FIG. 2, 1 is an input terminal, 2 is an amplifier, 3 is a low-pass filter (hereinafter abbreviated as LPF), 4 is an automatic gain control circuit (hereinafter abbreviated as ACC), 5 is a balanced modulator,
6 is a band pass filter (hereinafter abbreviated as BPF), 7 is an adder, 8 is an output terminal, 9 is a high pass filter (hereinafter abbreviated as HPF), 10 is an FM demodulator, 11 is an LPF, 12 Is a switch circuit, 12 is a horizontal scanning period (hereinafter abbreviated as 1H) delay circuit, 14 is an envelope detector, 15 is a synchronous separation circuit, 16 is a half-etch killer (hereinafter abbreviated as HHK) circuit, Reference numeral 17 is a phase comparator, 18 is an LPF, and 19 is a center frequency of 32.
A voltage-controlled oscillator (hereinafter, abbreviated as VCO) having a horizontal scanning frequency (hereinafter, abbreviated as f _H ) of 1 times, 20 is 3
1/21 divider, 21/8 divider, 22 balanced modulator, 23 crystal oscillator (XO
Is abbreviated. ) And 24 are BPFs.

The operation of the conventional reproduction signal processing apparatus configured as described above will be described below.

The reproduction signal input from the input terminal 1 is amplified and the LPF 3 extracts the low-frequency conversion color signal. The low-pass conversion color signal has its amplitude adjusted by the ACC 4, and then frequency-converted by the balanced modulator 5. The output signal of the balanced modulator 5 is removed by the unnecessary component BPF 6 generated at the time of frequency conversion to become the original SECAM system color signal, which is supplied to the adder 7. On the other hand, the output signal of the amplifier 2 is supplied to the HPF 9,
The FM modulated luminance signal is extracted. This FM-modulated luminance signal is FM-demodulated by the FM demodulator 10, passes through the LPF 11, and becomes a luminance signal. This luminance signal passes through the switch circuit 12 and is supplied to the adder 7. The adder 7 adds the color signal and the luminance signal and outputs the result as a composite video signal from the output terminal 8. Also, the envelope detector 14 judges that the output signal of the amplifier 2 is in the dropout state when the output signal is extremely small, controls the switch circuit 12, and controls the 1H delay circuit 13.
The influence is prevented by switching to the signal 1H before. The sync separation circuit 15 separates the sync signal from the reproduced luminance signal, the HHK circuit 16 removes the vertical sync signal and the equalization pulse, and outputs a signal synchronized with the horizontal sync signal. The phase comparator 17 compares the phase of the signal from the frequency divider 20 with the signal from the HHK. This phase error signal is smoothed by the LPF 18 and controls the VCO 19. As a result, the oscillation frequency of the VCO 21 is locked at 321f _H. Control for locking the VCO at a predetermined frequency in this manner is automatic frequency control (hereinafter, abbreviated as AFC).
Say. The output signal frequency of the VCO 19 is 8 by the frequency divider 21.
It is divided by one. In the balanced modulator 22, the output signal of the frequency divider 21 and the output signal of the XO 23 are balanced-modulated and supplied to the BPF 24. The BPF 24 takes out a necessary frequency component as a carrier of the balanced modulator 5.

[0007]

However, in the conventional configuration as described above, when the noise level of the luminance signal supplied to the sync separation circuit 15 is high, the sync signal separation is incomplete and the output sync signal is It will be lost or noise will be output. As a result, the output signal of the HHK circuit 16 also becomes a missing state or a noise state. In the phase comparator 17, the output signal of the HHK circuit 16 is used as a reference for V
In order to control the oscillation frequency of the CO 19, the 1H period may become longer or shorter than the normal in the case of a missing state or a noise state. Therefore, even if the VCO 19 oscillates at the regular oscillation frequency, Will be in a malfunctioning state in which control is performed to shift a large amount. Therefore, as a result of this, the malfunction control of the phase comparator 17 frequently occurs when the reproducing head is reproducing the guard band portion during the special reproduction of the VTR or when reproducing the tape in the poor recording state, There is a problem that the oscillation frequency of the VCO 19 largely shifts from the normal state, causing color fading and hue variation.

The present invention solves the above-mentioned problems, and the color disappears on the television screen after the reproducing head reproduces the guard band portion during special reproduction or when reproducing a tape in a poor recording state. It is an object of the present invention to provide a reproduction signal processing device that prevents hue variation.

[0009]

In order to achieve this object, a reproduction signal processing apparatus of the present invention includes an envelope detector for detecting a dropout state by an amplitude level of a frequency-modulated luminance signal during reproduction, A sync signal separation circuit that separates and outputs a sync signal from the demodulated luminance signal, a half-etch killer circuit that removes the vertical sync signal and the equalization pulse from the sync signal, and extracts a signal that is synchronized with the horizontal sync signal, A voltage-controlled oscillator having a horizontal scanning frequency of several times as the center frequency, a frequency divider for making the output signal frequency of the voltage-controlled oscillator a fraction of the predetermined number, an output signal of the half-etch killer circuit and the frequency divider. And a low-pass filter for smoothing the phase error signal from the phase comparator and controlling the voltage controlled oscillator. , In a case where the Embedded detector is detecting the dropout condition, in which to perform the control to stop the phase comparison operation of the phase comparator.

[0010]

With this configuration, the phase comparison operation of the phase comparator at the time of the dropout signal is generated by utilizing the characteristic that the dropout signal is generated during the reproduction of the guard band or the tape reproduction in the bad recording state. By stopping the, the malfunction control of the phase comparator is reduced,
It is possible to prevent disappearance of color and fluctuation of hue.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reproduction signal processing device used in a VTR of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. Since FIG. 1 is almost the same as the block diagram of FIG. 2 shown in the conventional example, only the differences will be described and the others will be omitted. The only difference is that the phase detector 17 stops the phase comparison operation when the envelope detector 14 detects the dropout state.

As a result, when a guard band is reproduced or a tape in a poor recording state is reproduced,
It is possible to reduce malfunctions of the phase comparator.

Although the reproducing circuit of the VTR of the pseudo SECAM system is shown in this embodiment, this patent uses not only the case shown in the embodiment but also the AFC with the horizontal synchronizing signal as a reference when reproducing the VTR. Effective for circuits.

[0015]

As is apparent from the above description, according to the present invention, the dropout signal is used when the guard band portion is being reproduced or the tape in a poor recording state is being reproduced. By stopping the phase comparison operation of the low level comparator, the malfunction control of the phase comparator is reduced,
It has an excellent effect that it is possible to prevent color disappearance and hue variation that appear on the screen.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a reproduction signal processing device of the present invention.

FIG. 2 is a block diagram showing a conventional reproduction signal processing device.

[Explanation of symbols]

 1 Input Terminal 2 Amplifier 3,11,18 LPF 4 ACC 5,22 Balanced Modulator 6,24 BPF 7 Adder 8 Output Terminal 9 HPF 10 FM Demodulator 12 Switch Circuit 13 1H Delay Circuit 14 Embe Detector 15 Sync Separation Circuit 16 HHK circuit 17 Phase comparator 19 VCO 20, 21 Frequency divider 23 XO

Claims (1)

[Claims] 1. A signal recorded by frequency division multiplexing a frequency-modulated luminance signal obtained by frequency-modulating a luminance signal and a low-frequency conversion color signal obtained by frequency-converting a carrier signal into a low frequency band. Is a reproduction signal processing device that demodulates the frequency-modulated luminance signal into a luminance signal during reproduction and reverse-converts the low-frequency converted color signal into a carrier color signal, and drops out depending on the amplitude level of the frequency-modulated luminance signal during reproduction. An envelope detector for detecting a state, a sync signal separating circuit for separating and outputting a sync signal from a demodulated luminance signal, a vertical sync signal and a horizontal sync signal for removing a vertical sync signal and an equalization pulse from the sync signal, and A half-etch killer circuit that extracts synchronized signals,
A voltage-controlled oscillator having a horizontal scanning frequency of a predetermined number of times as a center frequency, a frequency divider that divides the output signal frequency of the voltage-controlled oscillator by a predetermined number, an output signal of the half-etch killer circuit, and the A phase comparator that compares the phases of the output signals of the frequency dividers and a low-pass filter that smoothes the phase error signal from the phase comparator and controls the voltage controlled oscillator are provided, and the envelope detector is in a dropout state. A reproduction signal processing device, characterized in that control is performed to stop the phase comparison operation of the phase comparator when it is detected.