JPH01268295A - Chrominance signal processing unit - Google Patents

Abstract

PURPOSE:To prevent color from being faded by selecting a comb line filter output, which is constituted with a component before 1H, or a comb line filter output, which is constituted with the component after 1H, according to correlative condition. CONSTITUTION:Difference, for which a chrominance signal to be inputted to a first delay circuit 6 is subtracted from a chrominance signal to be outputted from a second delay circuit 7, is calculated by a first subtracting circuit 8. The output of the first subtracting circuit 8 is inputted to a converting circuit 11 which converts the output to the constant type of correlative values. The output of the converting circuit 11 is delayed by a third delay circuit 12. Then, according to the output of the converting circuit 11 and the contents of the correlative value to be outputted from the third delay circuit 12, whether the comb line filter to use the first delay circuit 6 is outputted or the comb line filter to use the second delay circuit 7 is outputted is selected in a selecting circuit 13 and a switching circuit 14 is controlled by the output of the selecting circuit 13. Thus, cross-talk to be received from an adjacent track is removed and the color can be prevented from being faded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color signal processing device used in a video tape recorder.

2. Description of the Related Art In recent years, there has been an increasing demand for higher image quality in consumer video tape recorders, and deterioration in image quality due to dubbing during editing has become a particular problem.

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

FIG. 2 shows a part of conventional color signal reproduction processing. In FIG. 2, 1 is a head, 2 is an amplifier, 17 is a low-pass filter, 18 is a frequency conversion circuit, 19 is a delay circuit, 20 is a subtraction circuit, and 21 is a band-pass filter. The operation of the color signal processing device configured as described above will be described below with reference to FIG. 2.

A reproduced signal output from the head 1 is amplified by an amplifier 2, and a color signal portion is extracted by a low-pass filter 17.

The color signal outputted from the low-pass filter 17 is subjected to frequency conversion by a frequency conversion circuit 18. At the same time, the phase for each horizontal period is restored. The frequency-converted color signal is input to the delay circuit 19. Subtraction circuit 20
Then, a signal output is obtained by subtracting the color signal output from the delay circuit 19 from the frequency-converted color signal, and
The signal passes through a bandpass filter 21 and becomes a reproduced color signal output.

Problems to be Solved by the Invention However, in the above configuration, the comb filter for removing crosstalk consisting of the delay circuit 19 and the subtraction circuit 20 is always operating, so that the signal input to the delay circuit 19 and When there is no correlation between the output signals, there is a problem that color distortion occurs. By repeating dubbing, this color discoloration will spread by the number of times of dubbing.

In view of the above-mentioned problems, the present invention does not cause color fading and has a 6-h.

Further, the present invention provides a color signal processing device that does not significantly increase the circuit scale.

Means for Solving the Problems In order to solve the above-mentioned problems, the color signal processing device of the present invention is a helical scan type device having a plurality of heads that frequency modulates the luminance signal and converts the color signal into a low frequency range for recording. In a video tape recorder, the playback signal output from the head passes through a low-pass filter, the color signal is separated from the playback signal, the phase of which is restored for each horizontal period, and then crosstalk received from adjacent tracks is eliminated. As a removing means, a first delay circuit that delays the color signal by n horizontal periods (n is an integer); a second delay circuit that delays the color signal output from the first delay circuit by n horizontal periods; a first subtraction circuit that takes the difference between the color signal output from the second delay circuit and the color signal input to the first delay circuit;
a second subtraction circuit that subtracts the color signal input to the first delay circuit from the color signal output from the delay circuit; and a second subtraction circuit that subtracts the color signal input from the first delay circuit to the second delay circuit. or 6
A third subtraction circuit that subtracts the color signal output from the page, and a second subtraction circuit.
a switching circuit that outputs either the output of the subtraction circuit or the output of the third subtraction circuit; a conversion circuit that converts the output of the first subtraction circuit into a certain type of correlation value; a third delay circuit that delays the correlation value output from the conversion circuit by m (m is an integer) horizontal period; and a correlation value output from the conversion circuit and the correlation value output from the third delay circuit. and a selection circuit that determines which output of the switching circuit should be made based on the correlation value.

Effects of the present invention The first subtraction circuit calculates the difference between the color signal inputted to the first delay circuit and the color signal outputted from the second delay circuit, and The output of the calculator 5 is input to a conversion circuit that converts it into a certain type of correlation value. Further, the output of the conversion circuit is delayed by a third delay circuit, and based on the content of the correlation value output from the output of the conversion circuit and the third delay circuit, the selection circuit uses the first delay circuit. It selects whether to output a comb filter using the second delay circuit or to output a comb filter using the second delay circuit, and controls the switching circuit based on the output of the selection circuit. Therefore, crosstalk caused by adjacent tracks can be removed.

Example Below, regarding a color signal processing device which is an example of the present invention,
This will be explained with reference to the drawings. FIG. 1 shows a color signal processing device according to an embodiment of the present invention.

In Figure 1, 1 is a head, 2 is an amplifier, and 3 is an A/D
Converter, 4 is a low-pass filter, 6 is a demodulation circuit, 6 is a first delay circuit, 7 is a second delay circuit, 8 is a first subtraction circuit, 9 is a second subtraction circuit, 10 is the third subtraction circuit, 11
is a conversion circuit, 12 is a third delay circuit, 13 is a selection circuit,
14 is a switching circuit, 16 is a modulation circuit, and 16 is a D/A converter.

The operation of the color signal processing device constructed as described above will be described below with reference to FIG. 1. A reproduced signal output from the 0 head 1 is input to the amplifier 2. The output of the amplifier 2 is input to the A/D converter 3 and converted into a digital signal. The playback signal converted to a digital signal is
The signal is input to a low-pass filter 4, and color signal components are separated.

The separated color signals are input to the demodulation circuit 5 and demodulated into two color difference signals. At the same time, the phase for each horizontal period is restored. The color difference signal output from the demodulation circuit 6 is input to the first delay circuit 6 and delayed by one horizontal period. The output of the first delay circuit 6 is input to the second delay circuit 7 and delayed by one horizontal period. By subtracting the input of the first delay circuit 6 from the output of the second delay circuit 7 by the subtraction circuit 8, the output signal of the second delay circuit 7 and the input signal of the first delay circuit 6 are Calculate correlation.

The subtraction circuit 9 extracts the first signal from the output signal of the first delay circuit 6.
The input signal of the delay circuit 6 is passed through. The output of the subtraction circuit 9 becomes a first comb filter output using the first delay circuit 6. The subtraction circuit 10 subtracts the output signal of the first delay circuit 6 from the output signal of the second delay circuit. The output 9 of the subtraction circuit 10 becomes the second comb filter output using the second delay circuit A. The output of the subtraction circuit 8 is converted by a conversion circuit 11 into two types of correlation information (correlated and non-correlated). The output of the conversion circuit 11 is input to the third delay circuit 12 and delayed by one horizontal period. The output of the conversion circuit 11,
The output of the third delay circuit 12 is input to a selection circuit 13, which selects either the first comb filter output or the second comb filter output as the color signal output. When the output of the 0 conversion circuit 11 is correlated, it is considered that the output of the second delay circuit 7 and the input of the first delay circuit 6 are correlated. No matter which comb filter output is selected, no color fading occurs. In the embodiment, the second comb filter is output. Next, when the output of the conversion circuit 11 has no correlation and the output of the third delay circuit 12 has a correlation, it is determined that the output of the second delay circuit 7 and the output of the first delay circuit 6 have a correlation. Therefore, when the output of the Hage correction circuit 11 is uncorrelated and the output of the third delay circuit 12 is uncorrelated, the output of the first delay circuit 6 is selected. It is considered that there is a correlation between the input of the first delay circuit 6 and the input of the first delay circuit 6.
Select the comb filter output. Such a control signal is output from the selection circuit 13 and input to the switching circuit 14. In the switching circuit 14, the first
Either the comb filter output or the second comb filter output is output. The output of the switching circuit 14 is modulated by the modulation circuit 16, passed through the D/A converter 16, and outputs the reproduced color signal.As described above, according to this embodiment, the current color signal to be output is By looking at the correlation between the signal before one horizontal period and the signal after one horizontal period, color fading can be prevented by switching the comb filter for removing p5 crosstalk.

Effects of the Invention As described above, according to the present invention, by having a memory for 2H, it is possible to calculate the correlation between the actual signal component and the crosstalk component received from the adjacent track at the same time, and to obtain the correlation information. By storing this information and using that information later, it is possible to accurately detect the presence or absence of correlation without increasing the amount of memory. Color fading can be prevented by selecting the output or the output of the comb filter configured with the component after 1H.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a color signal processing device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional color signal processing device. 1...Head, 2...Amplifier, 3...
...A/D converter, 4...LPF, 6...
... Demodulation circuit, 6 ... First delay circuit, 7
...Second delay circuit, 8th... 1 subtraction circuit, 9...second subtraction circuit, 10.
...Third subtraction circuit, 11...Conversion circuit, 12...Third delay circuit, 13...
Selection circuit, 14...Switching circuit, 15...
- Modulation circuit, 16...D/MU converter.

Claims (2)

[Claims] (1) After passing the reproduced signal output from the head through a low-pass filter to restore the phase of the color signal separated from the reproduced signal for each horizontal period, crosstalk received from adjacent tracks is removed. A color signal processing device comprising crosstalk removal means, the crosstalk removal means including a first delay circuit that delays the color signal by n (n is an integer) horizontal period; a second delay circuit that delays the output color signal by n horizontal periods, and a first delay circuit that takes the difference between the color signal output from the second delay circuit and the color signal input to the first delay circuit. a second subtraction circuit that subtracts the color signal input to the first delay circuit from the color signal output from the first delay circuit; a third subtraction circuit that subtracts the color signal output from the second delay circuit from the output color signal; and a third subtraction circuit that subtracts the color signal output from the second delay circuit; a conversion circuit that converts the output of the first subtraction circuit into a certain type of correlation value; and a conversion circuit that converts the output of the first subtraction circuit into a correlation value of a certain type; ) A third delay circuit that delays the horizontal period; and a selection that determines which output of the switching circuit should be made from the correlation value output from the conversion circuit and the correlation value output from the third delay circuit. A color signal processing device comprising a circuit. (2) The delay amount of the first delay circuit, the second delay circuit, and the third delay circuit is one horizontal period, and the correlation value output from the conversion circuit is a binary value of correlation and no correlation, When the content of the selection circuit is that the output of the conversion circuit is correlated, and when the output of the conversion circuit is uncorrelated and the output of the third delay circuit is correlated, the output of the third subtraction circuit is selected; Claim 1, characterized in that when the output of the conversion circuit has no correlation and the output of the third delay circuit has no correlation, the output of the second subtraction circuit is selected. The color signal processing device described above.