JPS62230287A - Color signal processor - Google Patents

Abstract

PURPOSE:To prevent the fading of color and/or irregular coloring at the time of dubbing from occurring by generating a burst gate pulse to extract a color burst signal to be used in the time-base-correction of a carrier color signal by using the voltage level of the color burst signal for the basis. CONSTITUTION:From a carrier color signal coming through a comb line filter 8, a color burst signal is extracted in the 1st burst gate circuit 15 at the timing of the first burst gate pulse from the 1st pulse generating circuit 14. The 1st level detecting circuit 16 detects the voltage level during the extracted duration of the pulse and thereby output a detection signal in the period where a color burst signal actually exists. The resulting signal is waveform-shaped by a pulse generating circuit 17. And thus the second burst gate pulse which follows the time-shifting of a color burst signal is generated. This gate pulse undergoes a switch 19 and is supplied to the second burst gate circuit 20. A color burst signal extracted in the circuit 20 is used in correcting the time base variation of the carrier color signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color signal processing device in a video tape recorder for recording and reproducing color video signals. The processing method is that the luminance signal is FM modulated, the signal is frequency-converted to a low frequency band, and the luminance signal is converted to FM during playback.
Demodulation is a method in which the color signal is converted back to its original frequency by converting it to a frequency of 3/, -7.

FIG. 3 is a block diagram of a reproduction system for conventional VH8 color signal processing. In the figure, a reproduced signal inputted through an input terminal 1 is supplied to a low spring filter (hereinafter referred to as LPF) 3 through an amplifier 2, where a low frequency conversion carrier color signal is extracted, and an automatic gain control is performed. The amplitude is limited in a circuit (hereinafter referred to as ACC circuit) 4, the frequency is converted in a balanced modulator 5, and a bandpass filter (hereinafter referred to as
(referred to as BPF) 6 removes unnecessary components that occur during balanced modulation. Further, in the parsing) 6 dB down circuit 7, the color burst signal which has been increased by 6 dB during recording is reduced by edB to the original state, and the adjacent crosstalk is removed in the comb filter 8, and the signal is outputted from the output terminal 9.

On the other hand, the reproduced signal outputted from the amplifier 2 is supplied to an FM pass filter (hereinafter referred to as HPF) 1o.
The modulated luminance signal is extracted, amplitude limited by a limiter 11, and demodulated into a luminance signal by an FM demodulator 12. Only the horizontal synchronization signal is extracted from the demodulated luminance signal in the H separation circuit 13, and based on the extracted horizontal synchronization signal, a third burst gate pulse is generated which temporally almost coincides with the timing of the color burst signal. is generated in the third pulse generation circuit 32, and the first pulse generation circuit 14 generates a third burst gate pulse having a wider pulse width both before and after than the third burst gate pulse outputted from the third pulse generation circuit 32. Outputs one burst gate pulse. The first burst gate pulse is used at the timing to down the color burst signal in edB down circuit 7.

The third burst gate pulse is used by the burst gate circuit 20' to extract only the color burst signal from the output signal of the comb filter 8.

The color burst signal extracted from the burst gate circuit 20' is phase-compared with the output signal of the reference oscillator 21 in the phase comparator 22, and the error signal is sent to the LPF 23.
, and controls a voltage controlled oscillator (hereinafter referred to as VCO) 25 through an adder 24.

6. The oscillation frequency of VCO25 is 320 in the case of NTSC system.
It oscillates at fH (fH is the horizontal scanning frequency) K. VCO2
The output signal of No. 5 is outputted to the μ frequency divider 28, which outputs four output signals having phases different by 90 degrees, one of which is selected in the selection circuit 29, and supplied to the balanced modulator 30. The output signal of the reference oscillator 21 is also supplied to the balanced modulator 30 and output to the BPF 31, where unnecessary components are removed, and the signal is supplied as a carrier to the balanced modulator 6. In the frequency detector 26, the VCO 25 is 32 Of
In order not to enter the block state at anything other than H, VCO25 (
7) Detect the oscillation frequency, LPF27.

The VCO 25 is controlled through the adder 24.

The above table structure is described in, for example, Japanese Patent Laid-Open No. 13484/1984.

Problems to be Solved by the Invention However, in the above configuration, when the color video signal reproduced on the video tape recorder is repeatedly recorded on the video tape recorder and dubbing is performed repeatedly, the luminance signal and the color 6. ,−,.

The timing of the signal gradually deviates, and when a burst gate pulse is created based on the horizontal synchronization signal, the burst gate pulse deviates from the timing of the actual color burst signal, causing phenomena such as color fading and color unevenness. occurs,
This has the disadvantage of causing discomfort to the user.

Means for Solving the Problems In order to solve the above problems, the color signal processing device of the present invention includes a first burst gate pulse that generates a first burst gate pulse including a color burst signal period based on a horizontal synchronization signal. a pulse generation circuit; a first burst gate circuit that extracts a color burst signal from a carrier color signal using a first burst gate pulse; and a voltage value of the color burst signal extracted by the first burst gate circuit. The first step is to detect
6 level detection circuit, a second pulse generation circuit that generates a second burst gate pulse by shaping the output signal of the first level detection circuit, and reproduction using the second burst gate pulse. This configuration includes a second gate circuit for extracting a color burst signal for correcting time axis fluctuations of the carrier color signal at a time.

Effect of the Invention With the above-described configuration, the present invention creates a burst gate node for extracting a color burst signal for correcting time axis fluctuations of a carrier color signal during reproduction based on the voltage level of the color burst signal. Therefore, even if the timings of the luminance signal and the color signal are shifted during dubbing, the burst signal matches the position of the color burst signal, making it possible to resist color fading and color unevenness during dubbing.

Embodiments Hereinafter, color signal processing apparatuses according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a color signal processing device according to an embodiment of the present invention. What is different from the conventional example shown in FIG. 3 is that the third) pulse generation circuit 32 is eliminated, and the first ．． The second level detection circuit 18° switch 19 is newly added, and the burst pulse supplied to the second nozzle gate circuit 20 is different.Other functions are the same as the explanation in FIG. 3. Therefore, the explanation will be omitted here.Now, the carrier color signal that has passed through the comb-shaped filter 8 is converted into a color burst signal by the first pulse generating circuit 14 in the first burst gate circuit 15 at the timing of the first burst gate pulse. is extracted.The first level detection circuit 16 detects the voltage level of the extracted period and outputs a detection signal during the period in which the color burst signal actually exists.
A second pulse generation circuit 17 shapes the waveform to create a second burst gate pulse. Note that the first level detection circuit 16. A specific circuit configuration example of the second pulse generating circuit 17 is described in, for example, Japanese Patent Laid-Open No. 56-80979. Now, the second level detection circuit 18 detects the level of the color burst signal extracted by the first burst gate circuit 15, and outputs a detection signal when the level is below a predetermined level.

The specific configuration of the second level detection circuit is, for example,
A possible example is a level detection circuit for color burst signals used in a no-killer circuit. Now, the burst gate pulse supplied to the second burst gate circuit 2o is supplied through the switch 19. The switch 19 selects the second burst gate pulse that is output more often than the second pulse generation circuit 17 in the normal state, but when the second level detection circuit 18 detects that the color burst level is below a predetermined level. If detected, the first pulse generating circuit 14
The first burst gate pulse x outputted from the first burst gate pulse x is selected. The reason for switching between the first burst gate pulse and the second burst gate pulse is that the second burst gate pulse is created by the color burst signal itself, so if the color burst signal is smaller than a predetermined level,
This is to prevent the burst gate pulse from being output, cutting off the system for removing phase error fluctuations in the carrier color signal, and causing color fading.

Figure 2 shows the color burst signal (a), the first bar 10
The waveforms and timing of the first gate pulse (b) and the second gate pulse (c) are shown.
If the time position of the color burst signal in (a) shifts to the left or right, the second node in (c) also follows within the range of the first burst gate node in (b). and match the position of the color burst signal.

As described above, in a video tape recorder that converts the frequency of a carrier color signal to a low frequency band and records it, and converts it back to the carrier color signal during playback, the first node including the color burst signal period is based on the horizontal synchronization signal. a first pulse generation circuit 14 that generates a burst pulse; a first pulse gate circuit 15 that extracts a color burst signal from a carrier color signal using a first burst gate pulse; The first color (-) extracted by the first gate circuit 15
a first level detection circuit 16 that detects the voltage value of the strike signal;
A second pulse generating circuit 17 generates a second burst gate pulse by shaping the output signal of the first level detection circuit 16, and a second pulse generating circuit 17 generates a second burst gate pulse by shaping the output signal of the first level detection circuit 16, and The timing of the color burst signal from the horizontal synchronization signal can be adjusted by including the second burst gate circuit 20 that extracts the color burst signal for correcting the time axis fluctuation of the transport 11 vane color signal during reproduction. Even if there is a shift, the second burst gate pulse follows the shifted position, so it can be made resistant to color fading and color unevenness.

Effects of the Invention With the above-described configuration, the present invention prevents a timing shift between a color burst signal and a burst gate pulse due to a timing shift between a luminance signal and a color signal that occurs when dubbing is repeated, and prevents color fading during dubbing playback. An excellent effect can be obtained in that the user's discomfort caused by uneven color can be removed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a color signal processing device according to an embodiment of the present invention, FIG. 2 is a timing diagram of FIG. 1, and FIG. 3 is a block diagram of a conventional color signal processing device. ...Input terminal, 2...Amplifier, 3.
...LPF, 4...ACC circuit, 5...
...Balanced modulator, 6...BPF, 7...
・Parse) edB down circuit, 8...Comb filter, 9...Output terminal, 10...H
PF, 11...Limiter, 12...F
M demodulator, 13...H separation circuit, 14...
・First Noculus generation circuit, 15...First burst gate circuit, 16...First level detection circuit, 17...Second Noculus generation circuit, 18...
. . . second level detection circuit, 19 . . . switch, 20 . . . second burst gate circuit, 21.
...Reference oscillator, 22 ... Phase comparator,
23...LPF, 24...Adder, 2
5...■C○, 26...Frequency detector, 2
7...LP328...Interval frequency divider, 29.
... Selection circuit, 30 ... Balanced modulator, 3
1...BPF.

Claims (2)

[Claims] (1) In a video tape recorder that converts the frequency of a carrier color signal to a lower frequency range and records it, and converts it back to the carrier color signal during playback, the first burst gate pulse that includes a color burst signal period is based on the horizontal synchronization signal. a first pulse generating circuit that generates a color burst signal; a first burst gate circuit that extracts a color burst signal from a carrier color signal using a first burst gate pulse; and a color burst signal extracted by the first burst gate circuit. a first level detection circuit that detects the voltage value of the color burst signal; a second pulse generation circuit that generates a second burst gate pulse by shaping the output signal of the first level detection circuit; A color signal comprising a second burst gate circuit that uses a second burst gate pulse to extract a color burst signal for correcting time axis fluctuations of a carrier color signal during reproduction. Processing equipment. (2) The burst gate pulse used in the second burst gate circuit detects that the color burst signal is at a predetermined level according to the output signal of the second level detector that detects that the color burst signal is below a predetermined level. 2. The color signal processing device according to claim 1, wherein the color signal processing device is configured to switch from the second burst gate pulse to the first burst gate pulse in the following cases.