JPS62146097A - Video signal processor - Google Patents

Abstract

PURPOSE:To realize a complete correlation detecting circuit by a luminance signal without increasing the length of a delay circuit by delaying the output of 'the absence of correlation' obtained in the first detecting circuit by 1H. CONSTITUTION:When the output of 'the absence of correlation' is issued by the first detecting circuit 7 for detecting the correlation between the lines of the luminance signal, this signal passes through a logic circuit 22, is inputted to a limiter 14 to make the output of the limiter 14 zero and stop the function of a recursive filter 18. The first control signal is inputted to a memory control circuit 20, and data of a chrominance signal read in a memory before 1H in the second delay circuit 12 is recorded by using the memory in the second delay circuit 12 so as to obtain in formation of 'the absence of correlation' after the 1H. Then, the output of the second delay circuit 12 is inputted to the second detecting circuit 21 and the chrominance signal output of the second delay circuit, and thereby, the information of the presence and the absence of correlation is detected and outputted.

Description

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

Conventional technology In recent years, there has been an increasing demand for higher image quality in consumer video tape recorders, and noise reduction circuits that utilize the correlation between lines of video signals, such as comb filters and cursive filters, are being used. ing.

A circuit like the one described above is also used for color signals, but if there is no correlation between lines, color fading occurs, so it is necessary to prevent this circuit from functioning. For this correlation detection, there is a method that uses the correlation of luminance signals. PAL
In this method, color signals use correlation at 2H intervals, so
If the above circuit is used in areas with no correlation, color fading will be noticeable, so correlation detection becomes more important.

An example of the conventional PAL video signal processing apparatus described above will be described below with reference to the drawings.

FIG. 2 shows a part of reproduction signal processing including a conventional PAL system recursive filter. In FIG. 2, 1 is a head. 2 is an amplifier that amplifies the signal output from the head. 3 is an HPF that extracts the luminance signal portion. A demodulator 4 demodulates the FM-modulated luminance signal. 6 is a 1H delay circuit, which converts the demodulated luminance signal into 1H delay circuit.
H is delayed. 6 is an arithmetic circuit which calculates the difference between the signal output from the demodulator 4 and the signal output from the 1H delay circuit 6. A first detection circuit 7 detects the presence or absence of correlation from the signal output from the arithmetic circuit 6, and outputs a control signal accordingly.

8 is an LPF that extracts the color signal portion. 9 is a balanced modulator, which converts the color signal to its original frequency. 1o is a comb filter that removes adjacent cocoon stalk components. 1
It is an 8-beam cursive filter.

The recursive filter 18 includes an arithmetic circuit of 11, 13, 1A, a 2H delay circuit of 12, a limiter of 14, a 15, 1
It consists of 6 attenuators. The output of the first detection circuit 7 is input to the 14 IJ meter. When the control signal output from the first detection circuit 7 is correlated heat,
The output of limiter 14 becomes zero.

The arithmetic circuit 11 outputs a signal obtained by subtracting the signal output from the limiter 14 and passed through the attenuator 16 from the color signal output from the comb filter 10.

This output signal is input to the 2H delay circuit 12.

The arithmetic circuit 13 combines the color signal output from the comb filter 10 and the color signal output from the 2H delay circuit 12 and outputs the result. This output signal is the limiter 14
and passes through the attenuator 15. The arithmetic circuit 17 outputs a signal obtained by subtracting the signal output from the attenuator 15 from the color signal output from the comb filter 10.

With the above configuration, when the correlation detection circuit A determines that there is no correlation between the current luminance signal and the luminance signal 1H before, the function of the liquor 7 filter 18Ifi filter is lost, and the comb filter 1° The color signal output will be output as is.

Problems to be Solved by the Invention However, in the above configuration, since the luminance signal delay circuit is 1H and the color signal delay circuit is 2H,
The following problems occur. This will be explained using FIGS. 3 to 6. A, B, C, D, E, and F in FIG. 3 are continuous video signals, each having a length of 1H. The output obtained by subtracting the signals delayed by 1H from the above signals is shown in FIG. Also, from the above signal, 2H
The output after subtracting the delayed signal is shown in FIG. In FIG. 3, between C and D, there is a part where there is no correlation between lines. As can be seen from Figures 4 and 5, when there is a 1H delay, there is only one place, D-C, where there is no correlation, but 2H
If there is a delay, in addition to D-B, E-
Can be done in two places, C.

Since a 2H delay circuit is used for the color signal,
When there is no correlation between the signals during a certain 1H, as shown in Figure 5, 2
There will be uncorrelated parts in some places. On the other hand, since the luminance signal uses a 1H delay circuit, there is only one uncorrelated part as shown in FIG. Therefore, the correlation detection signal outputs "correlation heat"1
Even after H, if the output of "correlation heat" is not output, the correlation detection output is incomplete.

If the delay circuit for the luminance signal is also 2H, the above-mentioned problem will be solved, but an extra 1H of delay circuit will be required, resulting in an unnecessary increase in cost.

This problem also occurs when a video signal is digitized.

In view of the above problems, the present invention provides a video signal processing device that can perform complete correlation detection without increasing the number of delay circuits any further.

Means for Solving the Problems In order to solve the above-mentioned problems, the video signal processing device of the present invention includes: a first delay circuit that delays a luminance signal by one horizontal period; A first arithmetic circuit that outputs a difference component from a luminance signal delayed by one horizontal period by the circuit, the first arithmetic circuit, and the level of the luminance signal output from the first arithmetic circuit. a first detection circuit that detects the presence or absence of a correlation between the signal and the luminance signal delayed by one horizontal period and outputs a first control signal, and an A/D converter that converts the color signal into a digital signal; ,
a second delay circuit that delays the color signal data converted into a digital signal by the A/D converter by two horizontal periods using a memory; the color signal converted into the digital signal; and the second delay circuit; A second arithmetic circuit outputs the sum of the color signal delayed by two horizontal periods by the circuit, and a first control signal output from the first detection circuit is stored in a second delay circuit. A memory control circuit that rewrites the data of the color signal stored one horizontal period ago into the first data that the color signal cannot take among the data, and the second delay circuit that outputs the two horizontal a second detection circuit that compares the output of the color signal delayed by a period of time with the first signal, detects the presence or absence of a correlation, and outputs a second control signal; and the second arithmetic circuit. The apparatus includes a control circuit that controls the output level of the output color signal using the first ↓ control signal and the second control signal.

According to the present invention, with the above-described configuration, when an output indicating that there is no correlation is obtained from the first detection circuit, the second delay circuit converts the color signal data read into the memory 1H ago into a color signal. By rewriting the first data to the first data that cannot be taken by , 1H after the first detection circuit outputs that there is no correlation, the second detection circuit outputs that there is no correlation, and the first detection circuit or the second
When an uncorrelated output is obtained from either of the detection circuits,
By changing the level of the signal output from the second arithmetic circuit, it is possible to perform complete correlation detection.

Embodiment Hereinafter, a PAL video signal processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a part of reproduction signal processing including a PAL liquor filter in an embodiment of the present invention. In Figure 1, 1 is to.

It is de. 2 is an amplifier that amplifies the signal output from the head. 19 is an A/D converter, and the signal output from the amplifier 2 is digitized by this A/D converter. 3 is an HPF that extracts the luminance signal portion. A demodulator 4 demodulates the FM-modulated luminance signal. 5 is a 1H delay circuit using memory, which converts the demodulated luminance signal into 1H delay circuit.
delay.

6 is an arithmetic circuit that outputs the signal output from the demodulator 4 and 1H1.
8 and the signal output from the extension circuit 5.

A first detection circuit 7 detects the presence or absence of correlation from the signal output from the arithmetic circuit 6, and outputs a first control signal accordingly.

8 extracts the color signal portion using an LPF. 9 is a balanced modulator which converts the color signal to its original frequency.

A comb filter 10 removes adjacent crosstalk components. It is an 18 beam cursive filter. .

The recursive filter 18 includes arithmetic circuits 11, 13, and 17, a 2H extension circuit 12, and limiters 115 and 16 14.
It consists of attenuators.

From the color signal output from the arithmetic circuit 11U (j, type filter 1Q), the color signal is output from the IJ meter 14 and sent to the attenuator 16.
Outputs the signal obtained by subtracting the signal that passed through.

This output signal is input to a 2H delay circuit 12 using memory. The arithmetic circuit 13 adds the color signal output from the comb filter 10 and the color signal output from the 2H delay circuit 12 and outputs the result. This output signal passes through an IJ9 tube 14 and an attenuator 15. The arithmetic circuit 17 converts the color signal output from the comb filter 10 into an attenuator 16.
Outputs the signal obtained by subtracting the output signal from . Reference numeral 2o denotes a memory control circuit, into which a first control signal indicating the presence or absence of correlation between the luminance signals output from the first detection circuit 7 is input. The memory control circuit 2° is the first
When the control signal is "correlation heat", the second delay circuit 12
In this step, the color signal data that was read into the memory 1H ago is rewritten to the first data that the color signal cannot take. 21 is a second detection circuit, into which the color signal output from the second delay circuit 12 is input.

The M2 detection circuit compares this color signal with the first data and outputs a second control signal. If the color signal and the first data are equal, the second control signal is
It outputs a signal called "correlation heat," and if the two are not equal, it outputs a signal saying "there is a correlation."

22 is a logic circuit into which the first control signal output from the first detection circuit 7 and the second control signal output from the second detection circuit 21 are input. logic circuit 22
Then, from the first control signal input and the second control signal input to the third control signal input,
outputs a control signal. The third control signal is activated when the first control signal is “correlated heat” or when the second control signal is “correlation heat”.
When there is a correlated heat, a signal called "correlated heat" is output and the first
Both the control signal and the second control signal are "correlated"
When , a signal indicating "correlation exists" is output. The third control signal is input to limiter 14.

The limiter 14 performs normal limiter operation when the third control signal is "correlation enabled";
In the case of "correlated heat", the output of the limiter is configured to be zero.

With the above configuration, when the first detection circuit 7 that detects the correlation between lines of luminance signals outputs an output indicating that there is no correlation, this signal passes through the logic circuit 22 and is sent to the limiter. 14, the limiter output is set to zero, and the function of the recursive filter 18 is stopped.

At the same time, the first control signal is input to the memory control circuit 2o, and in the second delay circuit 12, the first control signal is input to the memory control circuit 2o. By rewriting the data to the data, the memory in the second delay circuit is used to record information such as "correlation heat" after 1H. Then, the output of the second delay circuit 12 is input to the second detection circuit 21, and the second detection circuit 21 compares the color signal output of the second delay circuit 12 with the first data. , detects and outputs information on the presence or absence of correlation. This output is input to the limiter 14 through the logic circuit 22, making the limiter output zero.

As described above, perfect correlation detection can be realized by delaying the output of "correlation heat" obtained by the first detection circuit by 1H.

Effects of the Invention As described above, according to the present invention, it is possible to obtain the excellent effect of realizing a complete correlation detection circuit using a luminance signal without increasing the length of the delay circuit using the PAL system.

[Brief explanation of drawings]

FIG. 1 shows a PAL system liquor 7 in an embodiment of the present invention.
Main part block diagram of the playback signal processing system including the filter,
Figure 2 is a block diagram of the main parts of a reproduction signal processing system including a conventional PAL type cursive filter, and Figures 3, 4, and 5 are signal diagrams for explaining the problems of the conventional example. be. 1...Head, 2...Amplifier, 3...
... HPF. 4...Demodulator, 5...1H delay circuit,
6,11. 13.17...Arithmetic circuit, 7...1st
detection circuit, 8...LPF, 9...balanced modulator, 10...comb filter, 12...
...2H delay circuit, 14...Limiter-1
15, 16... Attenuator, 18... Recursive filter, 19... A/D converter, 20
...Memory control circuit, 21...
...Second detection circuit, 22...Logic circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure B-. 1 Fig. 5 11 Heeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-0-loan- = 9-111 knee 11

Claims (1)

[Claims] a first delay circuit that delays a luminance signal by one horizontal period; a first arithmetic circuit that outputs a difference component between the luminance signal and a luminance signal delayed by one horizontal period by the first delay circuit; detecting the presence or absence of a correlation between the luminance signal and the luminance signal delayed by the one horizontal period from a first arithmetic circuit and the level of the luminance signal output from the first arithmetic circuit;
It includes a first detection circuit that outputs a first control signal, and also includes an A/D converter that converts a color signal into a digital signal, and data of the color signal converted into a digital signal by the A/D converter. The second delay of 2 horizontal periods using memory
a second arithmetic circuit that outputs the sum of the color signal converted into the digital signal and the color signal delayed by two horizontal periods by the second delay circuit; and the first detection circuit. Among the data stored in the second delay circuit, the first control signal output from the first control signal changes the first data whose color signal cannot take the data of the color signal stored one horizontal period ago. and the second delay circuit compare the output of the outputted color signal delayed by two horizontal periods with the first data to detect the presence or absence of a correlation. A second detection circuit that outputs a control signal and an output level of a color signal output from the second arithmetic circuit are connected to the first control signal and the second
A video signal processing device equipped with a control circuit that is controlled by a control signal.