JPH01174091A - Color signal processor - Google Patents

Abstract

PURPOSE:To prevent missing of color while crosstalk component is eliminated by comparing the correlation between a present color signal and a signal in 2H preceding and the correlation between the present color signal and in 2H succeeding period and applying a comb-line filter at the signal having a higher correlation. CONSTITUTION:A produced signal outputted from a head 1 is converted into a digital signal by an A/D converter 3, the color signal component is separated by a low pass filter 4. The separated color signal is demodulated into two color difference signals by a demodulation circuit 5 and the phase for each horizontal period is decoded simultaneously. The color difference signal passes through delay circuits 6, 7, 8 and 9 in this order. The correlation between the output signal of the delay circuit 7 and the input signal of the delay circuit 6 (referred to as 1st correlation) is calculated by a subtraction circuit 10. Moreover, the correlation between the output signal of the delay circuit 7 and the output signal of the delay circuit 9 (referred to as 2nd correlation) is calculated by a subtraction circuit 11. Further, a selection circuit 15 compares a 1st correlation with a 2nd correlation to control a switching circuit 14, and when the 1st correlation has a higher correlation, the output of the subtraction circuit 12 is selected and when the 2nd correlation is higher, the output of the subtraction circuit 13 is selected.

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 without 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, 18
1 is a low-pass filter, 19 is a frequency conversion circuit, 20 is a delay circuit, 21 is a subtraction circuit, and 22 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 18.

The color signal output from the low-pass filter 18 is subjected to frequency conversion by a frequency conversion 19. Here, the phase for each horizontal period is simultaneously restored. The frequency-converted color signal is input to the delay circuit 20. A signal output obtained by subtracting the color signal output from the delay circuit 20 from the frequency-converted color signal in the subtraction circuit 21 is passed through the band-pass filter 22.
It passes through and becomes the playback signal output. In the above description of the color signal reproduction processing, parts such as ACC and APC that are not directly related to the present invention are omitted.

Problems to be Solved by the Invention However, in the above configuration, since the crosstalk eliminating filter consisting of the delay circuit 20 and the subtraction circuit 21 is always operating, the input signal to the delay circuit 20 is When there is no correlation between the output signal and the output signal, there is a problem in that color distortion occurs.As dubbing is repeated, this color distortion increases by the number of times of dubbing.

In view of the above problems, the present invention provides a color signal processing device that does not cause color fading.

Means for Solving the Problems In order to solve the above problems, the color signal processing device of the present invention frequency-modulates the luminance signal, low-frequency converts the color signal, and uses a helical scan type device having a plurality of heads for recording. In the video tape recorder, the playback signal output from the head passes through a low-pass filter, and the color signal separated from the playback signal is received from an adjacent track after its phase is restored for each horizontal period. A first delay circuit that delays the color signal by n horizontal periods (n is an integer) as a means for removing crosstalk; and a second delay circuit that delays the color signal output from the first delay circuit by n horizontal periods. and,
a third delay circuit that delays the frequency-modulated color signal from the second delay circuit by n horizontal periods; a fourth delay circuit that delays the color signal output from the third 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 calculates the difference between the color signal output from the delay circuit and a subtraction circuit that subtracts the color signal output from the first delay circuit from the color signal output from the second delay circuit. a fourth subtraction circuit that subtracts the color signal output from the third delay circuit from the color signal output from the second delay circuit; A switching circuit that outputs either the output or the output of the fourth subtraction circuit, and comparing the absolute value of the output of the first subtraction circuit with the absolute value of the output of the second subtraction circuit,
If the absolute value of the first subtraction circuit output is smaller, the third
A control signal such that the output of the subtraction circuit becomes the output of the switching circuit is input to the control input of the switching circuit, and conversely, if the absolute value of the output of the second subtraction circuit is smaller, the output of the fourth subtraction circuit becomes the output of the switching circuit. and a selection circuit that operates to input a control signal such that the output of the subtraction circuit becomes the output of the switching circuit to the control input of the switching circuit.

Operation The present invention uses the above-described configuration to eliminate crosstalk from adjacent tracks by the operation described below. By subtracting the color signal input to the first delay circuit from the color signal output from the second delay circuit by a first subtraction circuit, a color signal input to the first delay circuit; Correlation with the color signal output from the second delay circuit (first
), and by subtracting the color signal output from the fourth delay circuit from the color signal output from the second delay circuit using the second subtraction circuit, A correlation (referred to as a second correlation) between the color signal output from the fourth delay circuit and the color signal output from the fourth delay circuit is calculated. Comparing the first correlation and the second correlation in a selection circuit,
Select the one with the smaller value, that is, the one with higher correlation. 1st
If the correlation is higher, then as the output of the switching circuit,
A comb filter output based on the second delay circuit output and the first delay circuit output is selected, and if the second correlation is higher, the second delay circuit output is selected as the output of the switching circuit. and the third delay circuit output.

Embodiment Hereinafter, regarding a color signal processing device which is an embodiment 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, 5 is a demodulation circuit, 6 is a first delay circuit, 7 is a second delay circuit, 8 is a third delay circuit, 9 is a fourth delay circuit, 10.11 , 12 and 13 are subtraction circuits, 14 is a switching circuit, 15 is a selection circuit, 16 is a modulation circuit, and 17 is a D/A converter.

The operation of the color signal processing device configured as described above will be described below with reference to FIG.

A reproduced signal output from the head 1 is input to an amplifier 2. The output of the amplifier 2 is input to an A/D converter 3 and converted into a digital signal. The reproduced signal converted into a digital 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 5 is sent to a first delay circuit 6. Second delay circuit 7.
Third delay circuit 8. It passes through the fourth delay circuit 9 in order. By subtracting the input signal of the first delay circuit from the output signal of the second delay circuit by the subtraction circuit 10, the correlation between the output signal of the second delay circuit and the input signal of the first delay circuit ( (the first correlation) is calculated. Further, by subtracting the output signal of the fourth delay circuit from the output signal of the second delay circuit by the subtraction circuit 11, the output signal of the second delay circuit and the output signal of the fourth delay circuit are Calculate the correlation (referred to as the second correlation). The subtraction circuit 12 subtracts the output signal of the first delay circuit from the output signal of the second delay circuit. The subtraction circuit 13 subtracts the output signal of the third delay circuit from the output signal of the second delay circuit. The selection circuit 15 compares the first correlation and the second correlation and selects the one with the smaller value, that is, the one with the higher correlation. If the first correlation is higher, a control signal that selects the output of the subtraction circuit 12 as the output of the switching circuit 14 is output from the selection circuit 15 and inputted to the switching circuit 14 . Conversely, if the second correlation is higher, the selection circuit 1 outputs a control signal that selects the output of the subtraction circuit 13 as the output of the switching circuit 14.
5 and input to the switching circuit 14. Switching circuit 1
The output of D/A converter 1 is modulated by modulation circuit 16 and
7 and becomes the reproduced color signal output.

As described above, according to this embodiment, in the case of an NTSC signal, the correlation between the current color signal to be output and a signal 2H earlier than that is checked, and the correlation between the current color signal to be output and a signal 2H earlier than that is
Look at the correlation with that after H, compare the correlations between the two, and apply a rectangular filter to the signal side with the higher correlation to prevent color fading.For PAL signals, check the length of the delay circuit. The processing content is the same, only that it is doubled.

Effects of the Invention As described above, according to the present invention, in the case of reproducing an NTSC signal, by having a memory for 4H, it is possible to simultaneously view the correlation between the actual signal component and the crosstalk component received from adjacent tracks. Signal before 2H and 2H
By using the later signal, the correlation between the current signal and the signal before 2H and the correlation between the current signal and the signal after 2H are calculated, and the two are compared and the one with higher correlation is selected,
If the correlation with the previous signal is higher, the current signal and the signal before IH will form a skewer filter, and if the correlation with the signal after 2H is higher, the current signal and the signal after IH will be configured. By configuring a comb filter with the signal, it is possible to obtain an excellent effect of realizing a color signal processing device that can remove crosstalk components without causing a single color drop.

In the case of PAL signals, the same effect can be obtained by doubling the respective delay amounts.

[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, 5...
... Demodulation circuit, 6 ... First delay circuit, 7
...Second delay circuit, 8...Third delay circuit, 9...Fourth delay circuit, 10,11゜12.13...・Subtraction circuit, 14...Switching circuit, 15...Selection circuit, 16...
Modulation circuit, 17...A/D converter, 18...
...LPF, 19... Frequency conversion circuit, 20
...Delay circuit, 21 ...Subtraction circuit, 2
2...BPF. Name of agent: Patent attorney Toshio Nakao and one other person Procedural amendment (A)

Claims (3)

[Claims] (1) The color signal separated from the reproduced signal output from the head through a low-pass filter is
a first delay circuit that delays the color signal by n horizontal periods (n is an integer) as a means for removing crosstalk from adjacent tracks after the phase is restored for each horizontal period; a second delay circuit that delays the color signal output from the delay circuit for n horizontal periods; a third delay circuit that delays the color signal output from the second delay circuit for n horizontal periods; and a third delay circuit. a fourth delay circuit that delays the color signal output from the second delay circuit for 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 takes the difference between the color signal output from the second delay circuit and the color signal output from the fourth delay circuit; A third subtraction circuit subtracts the color signal output from the first delay circuit from the color signal output from the second delay circuit, and subtracts the color signal output from the third delay circuit from the color signal output from the second delay circuit. A fourth subtraction circuit that subtracts the color signal, a switching circuit that outputs either the output of the third subtraction circuit or the output of the fourth subtraction circuit, and the output of the first subtraction circuit. The absolute value is compared with the absolute value of the output of the second subtraction circuit, and if the absolute value of the output of the first subtraction circuit is smaller, the output of the third subtraction circuit is the output of the switching circuit. If a control signal such that and a selection circuit that operates to input a control signal such that the switching circuit has a control signal to a control input of a switching circuit. (2) Claim 1, characterized in that the delay amount of the first delay circuit, second delay circuit, third delay circuit, and fourth delay circuit is one soot period. The color signal processing device described above. (3) The color according to claim 1, wherein the delay amount of the first delay circuit, second delay circuit, third delay circuit, and fourth delay circuit is two horizontal periods. Signal processing device.