JPH0671338B2 - Signal processing circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video signal processing circuit used in a VTR or the like.

2. Description of the Related Art In recent years, a lot of comb filters have been used in signal processing circuits that handle video signals.

For example, in the case of an NTSC signal, the color signal (abbreviated as C signal) is set to a frequency that interleaves every 1 horizontal cycle (abbreviated as 1H), so a Y-shaped signal that adds the input signal and the input signal delayed by 1H is added. The luminance signal (abbreviated as Y signal) is separated by the comb filter, and the chrominance signal is separated by the C-shaped comb filter that subtracts the signal delayed by 1H from the input signal. In other words, comb filters are often used in Y / C separation circuits. Also, in the color S / N improvement circuit of the VTR, the C-shaped comb filter is used.

However, these comb filters assume that the vertical correlation of the color signals is strong, and Y / C
Separation was not performed normally, and adverse effects such as color sag and dot interference occurred. Therefore, various methods have been proposed as means for detecting the presence or absence of the vertical correlation of the conventional colors. First
The above method uses the strong correlation between the Y signal and the C signal to detect and use the vertical correlation of the Y signal, but this will malfunction in a signal in which there is no correlation between the Y signal and the C signal.

As a second method, set the signal level of the color signal frequency component to 1H.
A method for detecting the correlation by comparing with the previous signal level has been proposed by the present inventor in Japanese Patent Application No. 59-168251.
According to this method, the presence or absence of vertical correlation is detected by the change in saturation of the color vertical method.

A simple block diagram of this conventional example is shown in FIG. In order to compare the amplitude direction of the color signal with that before 1H, the delay circuit 21,
It is composed of detectors 22 and 23 and a comparison circuit 24. According to this configuration, when a color signal as shown in FIG. 6a is input, a period in which the color signal has no vertical correlation is detected and a signal as shown in d is output. Here, b and c indicate the waveforms of the respective parts.

However, when signals having different phases as shown in c are input, the output signal becomes d, and the presence or absence of vertical color correlation cannot be detected.

Problems to be Solved by the Invention In the above configuration, there is no correlation between the C signal and the Y signal,
Moreover, it is not possible to detect that there is no vertical correlation of the color signal for a signal that has no change in the vertical amplitude of the color signal and only a change in hue, that is, the signal causes color sag and dot interference due to the comb filter. I could not avoid doing it.

In view of the above problems, the present invention is a signal processing circuit that surely detects the presence or absence of color vertical correlation by comparing the amplitude level and phase vertical correlation of color signals.

Means for Solving the Problems In order to solve the above problems, the signal processing circuit of the present invention is a conversion that converts both the vertical and vertical changes in the amplitude and phase of an input color signal into changes in the amplitude direction and outputs the changes. Delay circuit, a first delay circuit that delays the output of the converter for a predetermined time, a comparison circuit that compares the amplitude level of the output of the converter with the amplitude level of the output of the first delay circuit, and the comparison circuit. A second delay circuit for delaying the output of the above-mentioned output for a predetermined time, and an arithmetic circuit for computing the output of the first comparison circuit and the output of the second delay circuit, and the vertical correlation of the amplitude and phase of the input color signal. Is configured to detect.

Operation According to the present invention, it is possible to detect the change in the amplitude level and the phase of the color signal in the vertical direction by the above-described configuration, and it is possible to reliably detect the presence or absence of the vertical correlation of the color signal.

Embodiment A signal processing circuit according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the first embodiment of the present invention. The signal input from the input terminal 1 passes through the bandpass filter 2, and the phase change in the vertical direction of the color signal is converted into an amplitude change by the converter 3 including the 1H delay circuit 4 and the combiner 5. The color signal is sent to the delay circuit 6 and the comparison circuit 7, and the output of the delay circuit 6 is sent to the comparison circuit 7. In the comparison circuit 7, the input signals are detected by the detectors 8 and 9, and the detected outputs are compared by the comparator 10. When the level difference becomes large, for example, a high level signal is output to the arithmetic circuit 12 and at the same time. Send to the delay circuit 11. The output of the delay circuit 11 is sent to the arithmetic circuit 12. The arithmetic circuit 12 is composed of, for example, an inverter circuit 13 and an AND circuit 14, and performs arithmetic so as to output 1 only when the output of the comparison circuit 7 is 1 and the output of the delay circuit 11 is 0. . This polarity may of course be reversed depending on the circuit configuration of the subsequent stage.

Here, an example of the comparator 10 is shown in FIG.

The output of the detector 8 is connected to the-input of the comparator 16 and the + input of the comparator 17, and the output of the detector 9 is connected to the + input of the comparator 16 and the-input of the comparator 17,
The output of the comparator is set to high level with diodes 18 and 19.
ORed and output. With respect to the present invention having such a configuration, the operation of each unit will be described with reference to the waveform chart of FIG.

First, FIG. 3 shows a case where the color signal amplitude changes in the vertical direction. Here, a to i indicate waveforms corresponding to the respective parts of a to i in FIGS.

The input signal a becomes a color signal b obtained by the comb filter 3 which is a converter, becomes c and d by being detected by the detectors 8 and 9, and the comparator 10 ORs the signals e and f. As a result, a signal g is output and sent to the arithmetic circuit 12. The signal g is delayed by 1H by the delay circuit 11 and then sent to the arithmetic circuit 12 as a signal h. And the signals g, h
Is calculated by the calculation circuit 12, a signal i is output. Here, it can be seen that the signal i represents the period z in which there is no vertical color correlation.

Next, FIG. 4 shows the case where the hue changes in the vertical direction.

The input signal a becomes a color signal b by the comb filter 3 which is a converter, and c and d are detected by the detectors 8 and 9.
Then, the comparator 10 obtains the signals e and f, and the signal g is output and sent to the arithmetic circuit 12. Further, the signal g is delayed by 1H by the delay circuit 11 and then sent to the arithmetic circuit 12 as the signal h. Then, the signals g and h are calculated by the calculation circuit 12 to output a signal i. Here, it can be seen that the signal i indicates a period z in which there is no vertical correlation of hue, which cannot be detected in the conventional example. That is, as shown in FIG. 1, the converter composed of the 1H delay circuit converts the change in the vertical direction of the hue into the change in the amplitude direction of the color. It made it possible to detect.

Here, the bandpass filter BPF2 may be located at the latter stage of the combiner 5, may be located before and after the detectors 8 and 9, or may be omitted.

When the present invention is applied to a recording / reproducing system such as a VTR, the BPF2 and the converter 3 shown in FIG. 1 of the embodiment are inserted into the recording system, and the subsequent blocks are inserted into the reproducing system and passed through the recording / reproducing system. Therefore, the present invention can be realized. This has the advantage that only two delay circuits are required.

Further, when the present invention is applied to the PAL system, some modification such as setting the delay time of the delay circuit to 2H is necessary.

Although the present invention can be realized by a digital circuit by replacing the delay circuit with a memory or the like, it does not fall outside the scope of the present invention.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, a change in the amplitude and phase of an input color signal in the vertical direction is once converted into a change in the amplitude direction by a converter, and then the amplitude levels are compared by the comparison circuit. Since the output of the comparison circuit is calculated by the calculation circuit, the presence or absence of the vertical correlation of the color signals is surely detected, and the effect is great for the signal processing circuit using the comb filter.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal processing circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a main portion thereof, FIGS. 3 and 4.
FIG. 5 is a waveform diagram showing the signal waveform of each part of FIG. 1 and FIG. 2, FIG. 5 is a block diagram of a conventional signal processing circuit, and FIG. 6 is its waveform diagram. 3 ... converter, 7 ... comparison circuit, 12 ... arithmetic circuit, 4,
6, 11 ... 1H delay circuit, 8, 9 ... Detection circuit, 10 ... Comparator, 16, 17 ... Operational amplifier, 18, 19 ... Diode,
5: Synthesizer.

Claims (7)

[Claims] 1. A converter for converting both a change in the amplitude and phase of an input color signal in the vertical direction into a change in the amplitude direction and outputting the change.
A first delay circuit that delays the output of the converter for a predetermined time; a comparison circuit that compares the amplitude level of the output of the converter with the amplitude level of the output of the first delay circuit; and the output of the comparison circuit. A second delay circuit that delays for a predetermined time, and an arithmetic circuit that calculates the output of the first comparison circuit and the output of the second delay circuit are provided, and the vertical correlation between the amplitude and the phase of the input color signal is detected. A signal processing circuit characterized by the above. 2. The converter comprises a third delay circuit for delaying an input signal for a predetermined period, and a combiner for combining the output of the third delay circuit and the input signal. The signal processing circuit according to claim 1. 3. The comparison circuit is composed of first and second detectors for detecting an input signal and a comparator for comparing output levels of the first and second detectors. The signal processing circuit according to claim 1. 4. The arithmetic circuit outputs 1 only when the output of the first comparison circuit is 1 and the output of the second comparison circuit is 0.
The signal processing circuit according to claim 1, wherein the signal processing circuit is configured to output 5. The arithmetic circuit outputs 0 only when the output of the first comparison circuit is 0 and the output of the second comparison circuit is 1.
The signal processing circuit according to claim 1, wherein the signal processing circuit is configured to output 6. The signal processing circuit according to claim 1, wherein the predetermined period is one horizontal cycle period. 7. A band pass filter for passing a color signal component is provided at an input stage or a post stage of a converter, or at a stage before a comparison circuit.
The signal processing circuit according to the item.