JP3507987B2 - Video signal processing circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit for removing interference and noise components mixed in a video signal.

[0002]

2. Description of the Related Art As interference and noise components mixed in a video signal, for example, a program produced by the NTSC system is PAL.
When converted into a system, vertical stripe interference of a frequency of about 3.5 [MHz] that occurs in an image can be mentioned.

FIG. 17 is a block diagram showing a conventional video signal processing circuit for removing the vertical stripe interference. In the figure, 1 is an input terminal to which a luminance signal is applied, 2 and 3 are first and second delay circuits for delaying the signal by a predetermined time, 4,
Reference numerals 5 and 6 denote first, second, and third coefficient circuits that multiply input signals by predetermined coefficients, and reference numeral 7 adds the input signals of three systems from the first to third coefficient circuits 4 to 6. Adder circuit, 8
Is an output terminal for transmitting the output signal from the adder circuit 7, and the video signal processing circuit of this conventional example is constituted by a 3-tap low-pass filter circuit.

Next, the operation will be described by taking as an example the case of digital signal processing for a quantized signal sequence sampled at a sampling frequency four times the color subcarrier frequency of a PAL system TV signal. For example, a composite video signal YC is input to the input terminal 1.
The luminance signal Y (t) obtained by separation is input and supplied to the first delay circuit 2 and the first coefficient circuit 4. The first delay circuit 2 supplies the output signal Y (t−2τ) obtained by delaying the luminance signal Y (t) by two sampling periods (2τ) to the second delay circuit 3 and the second coefficient circuit 5. . The second delay circuit 3 delays the output signal Y (t-2τ) of the first delay circuit 2 by the same time as the delay time of the first delay circuit 2 to output the output signal Y (t-4τ). 3 to the coefficient circuit 6.
The first coefficient circuit 4 supplies to the adder circuit 7 an output signal 1/4 · Y (t) obtained by multiplying the luminance signal Y (t) by a coefficient 1/4, for example. The second coefficient circuit 5 adds the output signal Y (t−2τ) of the first delay circuit 2 to an output signal 1/2 · Y (t−2τ), for example, by multiplying the output signal Y (t−2τ) by a coefficient 1/2. Supply to. The third coefficient circuit 6 adds an output signal 1/4 · Y (t-4τ) obtained by multiplying the output signal Y (t-4τ) of the second delay circuit 3 by a coefficient 1/4, for example, to an adder circuit 7 Supply to. The adder circuit 7 outputs the output signal 1/4 · Y (t) of the first coefficient circuit 4, the output signal 1/2 · Y (t−2τ) of the second coefficient circuit 5, and the third coefficient circuit. 6 output signal 1 / 4.Y (t-4.tau.) Added signal 1 / 4.Y (t) + 1 / 2.Y (t-2.tau.) + 1/4.
Y (t-4τ) is output from the output terminal 8.

FIG. 18 shows the gain vs. frequency characteristic of the 3-tap low pass filter circuit. Vertical axis shows gain 0 to 1
Is shown in increments of 0.1. Horizontal axis is frequency 0
.About.7.0 [MHz] is shown in increments of 0.7 [MHz]. As is clear from the figure, 3.5 [MHz]
The gain at is less than 0.1. Therefore, about 3.5
Vertical stripe interference of frequencies around [MHz] is attenuated to 1/10 or less.

As the interference and noise components mixed in the video signal, for example, several hundreds [kHz] generated in a VHS (S-VHS) type VTR image in which a 2-channel audio signal is recorded in a deep layer of a magnetic tape. Frequency beat interference can be mentioned. FIG. 19 shows a recording format of an S-VHS system Hi-Fi standard VTR for converting a 2-channel audio signal into a frequency-modulated signal of 2 frequencies and recording the signal. Main (L) channel audio has a center carrier frequency of 1.3 [M
Hz], the sub (R) channel sound is modulated at the center carrier frequency of 1.7 [MHz] and is deeply recorded in a magnetic layer deeper than the surface layer of the magnetic tape on which the video signal is recorded.
Since the frequency-modulated signal of two frequencies is recorded and reproduced through the electromagnetic conversion system, non-linear distortion is generated and spurious is generated. Of these, the component mixed in the color signal band is 1.7 [MHz] -1.3 [MHz] = 400 [kH
z] or 2 × 1.3 [MHz] -1.7 [MHz] = 900 [k
Hz]. The color signals are two color difference signals R-Y and B-
It is a low-frequency conversion carrier color signal obtained by low-frequency converting the carrier color signal in which Y is quadrature-phase-modulated with a carrier wave of 3.58 [MHz] to 629 [kHz]. From this, 400 [kHz] and 900
The [kHz] spurious component appears in the color difference signal as a component of 629-400 = 229 [kHz] 900-629 = 271 [kHz]. This 229 [kHz] and 27
The 1 [kHz] component has a high degree of saturation on the screen and is a large area where there is not much color change, and is noticeable as a beat disturbance in which the amplitude or hue component fluctuates in an oblique line.

FIG. 20 is a block diagram of a conventional video signal processing circuit for removing this beat interference. In the figure, 1
Is an input terminal to which a color difference signal is applied, 2 and 3 are first and second delay circuits for delaying the signal by a predetermined time, 4, 5 and 6
Is a first, second, and third coefficient circuit that multiplies the input signal by a predetermined coefficient, and 7 is an addition that adds the input signals of three systems from the first to third coefficient circuits 4 to 6. Circuit, 8
Is an output terminal for transmitting the output signal from the adder circuit 7, and the video signal processing circuit of this conventional example is constituted by a 3-tap low-pass filter circuit.

Next, the operation will be described by taking as an example the case of digital signal processing of a quantized signal sequence sampled at a sampling frequency four times the color subcarrier frequency of an NTSC TV signal. To the input terminal 1, for example, a composite video signal Y
The color difference signal C (t) obtained by color demodulating the carrier color signal obtained by C separation is input, and the first delay circuit 2 and the first delay circuit 2 are provided.
Is supplied to the coefficient circuit 4. The first delay circuit 2 supplies the output signal C (t−29τ) obtained by delaying the color difference signal C (t) by 29 sampling periods (29τ) to the second delay circuit 3 and the second coefficient circuit 5. . The second delay circuit 3 has a first delay
Output signal C (t−29τ) of the first delay circuit 2 is delayed by the same time as the delay time of the first delay circuit 2.
(T−58τ) is supplied to the third coefficient circuit 6. The first coefficient circuit 4 adds, for example, a coefficient ¼ to the color difference signal C (t).
Output signal 1/4 · C (t) multiplied by
Supply to. The second coefficient circuit 5 adds the output signal C (t−29τ) of the first delay circuit 2 to an output signal ½ · C (t−29τ) obtained by multiplying the output signal C (t−29τ) by a coefficient ½, for example. Supply to. The third coefficient circuit 6 includes the second delay circuit 3
Of the output signal C (t-58τ) is multiplied by, for example, a coefficient ¼, and is supplied to the adder circuit 1/4 · C (t-58τ). The adder circuit 7 outputs the output signal 1/4 · C (t) of the first coefficient circuit 4, the output signal 1/2 · C (t−29τ) of the second coefficient circuit 5, and the third coefficient circuit. 6 output signal 1/4 · C (t−58τ) added signal 1/4 · C (t) + 1/2 · C (t−29τ) +1/4
・ C (t-58τ) is output from the output terminal 8. The color difference signal output from the output terminal 8 is most attenuated at about 247 [kHz], and the beat interference is attenuated.

[0009]

[Patent Document 1] Japanese Patent Publication No. 62-4907

[0010]

Since the conventional video signal processing circuit is constructed as described above, the interference and noise components can be removed, but the high frequency component of the luminance signal or the high frequency component of the color signal is attenuated. As a result, there is a problem that an image is deteriorated in resolution or color resolution.

The present invention has been made in order to solve the above problems, and removes interference and noise components, and minimizes attenuation of high frequency components of an image or high frequency components of a color signal. It is an object to obtain a video signal processing circuit that can perform.

[0012]

A video signal processing circuit according to the present invention includes a band pass filter circuit for extracting only a band including an interference component or a noise component of a luminance signal in a composite video signal, and a signal level of the luminance signal When it is higher than a predetermined value and when it is lower than around the black level of the luminance signal,
A control circuit that cuts off the output signal of the band pass filter circuit and outputs the output signal of the band pass filter circuit when the signal level of the luminance signal is lower than a predetermined value and higher than near the black level of the luminance signal. And a subtraction circuit for subtracting the output signal of the control circuit from the luminance signal.

The video signal processing circuit according to the present invention is
A bandpass filter circuit for extracting only a band including an interference component or a noise component of a luminance signal in a composite video signal,
During the period when the signal level of the luminance signal is higher than the predetermined value and the period including the synchronization signal of the luminance signal, the output signal from the band pass filter circuit is blocked, the signal level of the luminance signal is lower than the predetermined value, and the luminance A control circuit that outputs the output signal of the bandpass filter circuit and a subtraction circuit that subtracts the output signal of the control circuit from the luminance signal are included in the period in which the synchronization signal of the signal is not included.

In the video signal processing circuit according to the present invention, the control circuit outputs the output from the band-pass filter circuit when the signal level of the luminance signal is higher than a predetermined value and lower than near the black level of the luminance signal. When the signal level is cut off and the signal level of the luminance signal is lower than a predetermined value and higher than near the black level of the luminance signal, control is performed to output the output signal from the bandpass filter circuit. In other words, the part containing the sync signal whose waveform characteristics are deteriorated by filtering is included in the bright image part and the dark image part in which the disturbing component or the noise component included in the luminance signal is inconspicuous. The other dark image portion where the disturbing component or the noise component is conspicuous is the output obtained by subtracting the output signal of the bandpass filter circuit.

The video signal processing circuit according to the present invention is
The control circuit cuts off the output signal from the band pass filter circuit during the period when the signal level of the luminance signal is higher than the predetermined value and the period including the synchronization signal of the luminance signal, and the signal level of the luminance signal is higher than the predetermined value. It is controlled so that the output signal from the band pass filter circuit is output during a period in which the brightness signal is low and the synchronization signal of the luminance signal is not included. In other words, the same output as the luminance signal is set so that the bright signal portion in which the interference component or the noise component included in the luminance signal is inconspicuous and the period including the synchronization signal in which the waveform characteristics are deteriorated by filtering have the same output as the luminance signal. The dark image portion in the period other than the period including the sync signal, which is conspicuous, has an output obtained by subtracting the output signal of the bandpass filter circuit.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION For example, when a program or the like produced by the NTSC system is converted into the PAL system, about 3.
A video signal processing circuit for removing vertical stripe interference of a frequency around 5 [MHz] will be described as the first to sixth embodiments.

Embodiment 1. FIG. 1 is a block circuit diagram of a first embodiment of a video signal processing circuit of the present invention. Figure 1
9 is a low-pass filter circuit for attenuating the high-frequency component of the luminance signal applied to the input terminal 1, and 10 is a delay for delaying the input luminance signal Y by the same time as the delay time of the low-pass filter circuit 9. Circuit, 11 is a delay circuit 10
A switching circuit for switching and outputting the output luminance signal YD of the low pass filter circuit 9 and the output luminance signal YL of the low pass filter circuit 12;
Is a potential generating circuit for generating a predetermined level of potential E1, 13
Is a comparison circuit which compares the luminance signal YD output from the delay circuit 10 with the potential E1 output from the potential generation circuit 12 and outputs a comparison result.

Next, the operation will be described. The input terminal 1 has, for example, a luminance signal Y obtained by YC separating the composite video signal.
Is input and supplied to the delay circuit 10 and the low-pass filter circuit 9. The low-pass filter circuit 9 supplies the luminance signal YL obtained by attenuating the high-frequency component of the input luminance signal Y to one input terminal of the switching circuit 11. The low-pass filter circuit 9 may be a circuit configured similarly to the conventional video signal processing circuit shown in FIG. 17, for example.
The delay circuit 10 delays the input luminance signal Y by a time necessary for the input luminance signal Y to pass through the low-pass filter circuit 9, and compares the luminance signal YD with the comparison circuit 13 and the switching circuit 1.
1 to the other input terminal. The potential generation circuit 12 is
A potential E1 is generated and supplied to the comparison circuit 13. The comparison circuit 13 compares the luminance signal YD with the potential E1 to determine the luminance signal YD.
When D is higher than the potential E1, the switching circuit 11 controls so as to select the output luminance signal YD of the delay circuit 10, and when the luminance signal YD is lower than the potential E1, the switching circuit 11 outputs the output of the low-pass filter circuit 9. The luminance signal YL is controlled to be selected. The luminance signal selected by the switching circuit 11 is output from the output terminal 8.

The state of this processing will be described based on the video signal waveform of the staircase wave shown in FIG. The vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL system TV image is noticeable in a dark image portion, but is not so noticeable in a bright image portion. Therefore, it is not necessary to remove the vertical stripe interference with respect to the bright image portion, that is, the luminance signal having a potential higher than the potential E1 output from the potential generation circuit 12, and therefore, the delay circuit 10 that is not subjected to the filter processing is used.
The output luminance signal YD is controlled by the switching circuit 11 to be selected. On the other hand, for a dark image portion, that is, a luminance signal having a potential lower than the potential E1 output from the potential generation circuit 12, it is necessary to remove the vertical stripe interference. Therefore, a high-frequency elimination filter for removing the vertical stripe interference is required. The output luminance signal YL of the processed low-pass filter circuit 9 is controlled so that the switching circuit 11 selects it. The potential E1 output from the potential generation circuit 12 is set to a potential at which vertical stripe interference of a frequency of about 3.5 [MHz] that occurs in a PAL system TV image is invisible and the high frequency component is not significantly deteriorated. .

Embodiment 2. FIG. 3 is a block circuit diagram of a video signal processing circuit according to a second embodiment of the present invention, and the same reference numerals as those in FIG. In FIG. 3, 14 is a second potential generating circuit for generating a second potential E2 near the black level, which is the second potential E2.
Is input to the comparison circuit 13 together with the first potential E1 output from the first potential generation circuit 12.

Next, the operation will be described. The luminance signal Y input to the input terminal 1 is switched by the switching circuit 11 via the delay circuit 10 or the low-pass filter circuit 9 and output from the output terminal 8 according to the embodiment shown in FIG. Since the operation is the same as the operation No. 1, the description of the operation is omitted here.

Next, the operation until the control signal for controlling the switching circuit 11 is supplied to the switching circuit 11 will be described. The first potential generation circuit 12 supplies the first potential E1 to the second potential E1.
The potential generation circuit 14 generates the second potential E2 and supplies it to the comparison circuit 13 together with the output luminance signal YD of the delay circuit 10. The comparison circuit 13 has a luminance signal YD and a first potential E.
At the same time as comparing 1 with the luminance signal YD and the second potential E2
When the potential of the luminance signal YD is higher than the first potential E1 or lower than the second potential E2, the switching circuit 11 controls so as to select the output luminance signal YD of the delay circuit 10. , When the potential of the luminance signal YD is lower than the first potential E1 and higher than the second potential E2, the output luminance signal YL of the low pass filter circuit 9 is controlled to be selected.

The state of this processing will be described based on the video signal waveform of the staircase wave shown in FIG. The vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL system TV image is noticeable in a dark image portion, but is not so noticeable in a bright image portion. Further, although the synchronizing signal portion is included in the dark image portion, when the synchronizing signal is passed through the low-pass filter circuit 9, the waveform characteristic of the synchronizing signal is deteriorated and the synchronizing processing system of the TV receiver malfunctions. The image may be unstable on the time axis. Therefore, it is not necessary to remove the vertical stripe interference with respect to a bright image portion, that is, a luminance signal having a potential higher than the first potential E1. Therefore, the output luminance signal YD of the delay circuit 10 that has not been filtered is set. The switching circuit 11 controls so as to select. Dark image part,
That is, for the luminance signal having a potential lower than the first potential E1 and higher than the second potential E2 other than the synchronization signal portion, it is necessary to remove the vertical stripe interference, so the vertical stripe interference is removed. The switching luminance is controlled so that the switching circuit 11 selects the output luminance signal YL of the low-pass filter circuit 9 that has been subjected to the high-pass removal filtering process.

However, it is better not to filter the synchronizing signal portion of the dark image portion, that is, the luminance signal having a potential lower than the second potential E2. Output luminance signal Y
The switching circuit 11 is controlled to select D. First
The potential E1 of the PAL system TV image is about 3.5.
Vertical stripe interference of frequencies around [MHz] becomes inconspicuous, and a high frequency component is set to a potential that does not deteriorate much. The second electric potential E2 is lower than the first electric potential E1 and is near the black level higher than the potential of the sync signal so that the sync signal portion is not affected even if the luminance signal has a slight sag. Is set to the potential of.

Embodiment 3. FIG. 5 is a block circuit diagram of a video signal processing circuit according to a third embodiment of the present invention. The same reference numerals as those in FIG. In FIG. 5, reference numeral 15 is a sync signal separation circuit for separating the sync signal S from the luminance signal YD output from the delay circuit 10, and 16 is a pulse signal P in which the phase of the sync signal S output from the sync signal separation circuit 15 is adjusted. A phase adjusting circuit for outputting, 17 is an output signal of the comparing circuit 13 and the phase adjusting circuit 1
6 is a control circuit for generating a control signal for controlling the switching circuit 11 from the output pulse signal P of FIG.

Next, the operation will be described. The luminance signal Y input to the input terminal 1 is switched by the switching circuit 11 via the delay circuit 10 or the low-pass filter circuit 9 and output from the output terminal 8 according to the embodiment shown in FIG. Since the operation is the same as the operation No. 1, the description of the operation is omitted here.

Next, the operation until the control signal for controlling the switching circuit 11 is supplied to the switching circuit 11 will be described. The potential generation circuit 12 generates the potential E1 and supplies it to the comparison circuit 13 at the same time as the output luminance signal YD of the delay circuit 10. The comparison circuit 13 compares the luminance signal YD with the potential E1 and supplies the comparison result to the control circuit 17. The sync signal separation circuit 15 separates the sync signal S from the luminance signal YD output from the delay circuit 10 and supplies it to the phase adjustment circuit 16. The phase adjustment circuit 16 adjusts the phase and pulse width of the synchronization signal S output from the synchronization signal separation circuit 15, and the delay circuit 1
A pulse signal P indicating a period including a sync signal portion in the luminance signal YD output from 0 is supplied to the control circuit 17. The phase adjusting circuit 16 may be composed of any circuit such as a monostable multivibrator, a frequency counter, a delay circuit, or an automatic frequency control circuit as long as the same operation can be obtained. Control circuit 17
Is the switching circuit 1 when the potential of the luminance signal YD is higher than the potential E1 or during the period around the synchronizing signal S.
1 controls so as to select the output luminance signal YD of the delay circuit 10, and when the luminance signal YD has a potential lower than the potential E1 and is not included in the period centered on the synchronizing signal S, The switching circuit 11 is a low-pass filter circuit 9
The output luminance signal YL is controlled to be selected.

The state of this processing will be described based on the video signal waveform of the staircase wave shown in FIG. The vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL system TV image is noticeable in a dark image portion, but is not so noticeable in a bright image portion. Further, although the sync signal part is included in the dark image part, when the sync signal is passed through the low-pass filter circuit 9, the waveform characteristics of the sync signal are deteriorated, and the sync processing system of the TV receiver malfunctions. The image may be unstable on the axis. Therefore, it is not necessary to remove the vertical stripe interference with respect to a bright image portion, that is, a luminance signal having a potential higher than the potential E1. Therefore, the output luminance signal YD of the delay circuit 10 not subjected to the filter processing is switched to the switching circuit 1
A control signal selected by 1 is supplied to the control circuit 17. It is necessary to remove the vertical stripe interference for a dark image portion, that is, for a luminance signal having a potential lower than the potential E1 and not included in the period including the synchronization signal. The control circuit 17 is supplied with a control signal such that the switching circuit 11 selects the output luminance signal YL of the low-pass filter circuit 9 which has been subjected to the filtering process of FIG.

However, it is better not to perform the filtering process in the synchronizing signal portion of the dark image portion, that is, in the period including the synchronizing signal, which is indicated by the pulse signal P output from the phase adjusting circuit 16, so that it is preferable to perform the filtering. Switching circuit 1 for switching the output luminance signal YD of the delay circuit 10 that has not been processed
A control signal selected by 1 is supplied to the control circuit 17. The potential E1 output from the potential generation circuit 12 is PA
A vertical stripe interference of a frequency of about 3.5 [MHz] that occurs in an L-type TV image becomes inconspicuous, and a high frequency component is set to a potential that does not deteriorate so much.

Fourth Embodiment FIG. 7 is a block circuit diagram of a video processing circuit according to a fourth embodiment of the present invention. The same reference numerals as those in FIG. In FIG. 7, reference numeral 18 denotes a bandpass filter circuit that passes only the band in which interference and noise components exist in the luminance signal Y applied to the input terminal 1, and 19 denotes the same delay time as that of the bandpass filter circuit 18. A delay circuit for delaying the luminance signal Y, 20 is a band pass filter circuit 18
A switching circuit for switching between the output luminance signal YB and no signal, 13 is a comparison circuit for comparing the luminance signal YD output from the delay circuit 19 with the potential E1 output from the potential generation circuit 12, and outputting a comparison result, Reference numeral 21 is a subtraction circuit for subtracting the output signal of the switching circuit 20 from the luminance signal YD output by the delay circuit 19.

Next, the operation will be described. The input terminal 1 has, for example, a luminance signal Y obtained by YC separating the composite video signal.
Is input to the delay circuit 19 and the band pass filter circuit 18.
Is supplied to. The bandpass filter circuit 18 passes only the band in which the interference and noise components are present in the luminance signal Y applied to the input terminal 1 and supplies it to one input terminal of the switching circuit 20. For example, the bandpass filter circuit 18
Is a first coefficient circuit 4 of the 3-tap filter circuit that constitutes the conventional video signal processing circuit shown in FIG.
The circuit configuration may be such that the multiplication coefficient of -1 is changed to -1/4 and the multiplication coefficient of the third coefficient circuit 6 is changed to -1/4. In this case, when the input luminance signal is Y (t), the output luminance signal YB is -1 / 4.Y (t) + 1 / 2.Y (t-2?)-1/4.
-Y (t-4?).

The delay circuit 19 delays the input luminance signal by the time required for the luminance signal Y applied to the input terminal 1 to pass through the band pass filter circuit 18, and subtracts it from the subtraction circuit 2.
1, supplied to the comparison circuit 13. The potential generation circuit 12 generates the potential E1 and supplies it to the comparison circuit 13 at the same time as the luminance signal YD output from the delay circuit 19. Comparison circuit 13
Compares the luminance signal YD with the potential E1 and controls the switching circuit 20 to select no signal when the potential of the luminance signal YD is higher than the potential E1, and when the luminance signal YD is lower than the potential E1. The switching circuit 20 controls so as to select the output luminance signal YB of the band pass filter circuit 18.
The switching circuit 20 switches between no signal and the output luminance signal YB of the band pass filter circuit 18 in accordance with the output signal of the comparison circuit 13 and supplies it to the subtraction circuit 21. Subtraction circuit 21
Outputs to the output terminal 8 a signal obtained by subtracting the output signal of the switching circuit 20 from the luminance signal YD output by the delay circuit 19.

Here, the switching circuit 20 has the subtraction circuit 21.
When no signal is supplied to the input terminal 1, assuming that the luminance signal applied to the input terminal 1 is Y (t), the output of the delay circuit 19 obtained by delaying the input luminance signal Y (t) by the same delay time as that of the bandpass filter circuit 18. The luminance signal Y (t−2τ) is directly output from the output terminal 8.

When the output luminance signal YB of the bandpass filter circuit 18 is directly supplied to the subtraction circuit 21, the output of the delay circuit 19 which delays the input luminance signal Y (t) by the same delay time as that of the bandpass filter circuit 18. Luminance signal Y
From (t-2τ), the output signal of the bandpass filter circuit -1 / 4 · Y (t) + 1/2 · Y (t-2τ) -1/4
Since Y (t-4τ) is subtracted, the output signal from the output terminal 8 is Y (t-2τ)-{-1/4 · Y (t) + 1/2 · Y
(T-2τ) -1 / 4 · Y (t-4τ)} = 1/4 · Y
(T) + 1 / 2.Y (t-2.tau.) + 1 / 4.Y (t-4
τ), and the same output signal as the output signal of the video signal processing circuit of the conventional example is output from the output terminal 8.

The state of this processing will be described based on the video signal waveform of the staircase wave shown in FIG. The vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL system TV image is noticeable in a dark image portion, but is not so noticeable in a bright image portion. Therefore, it is not necessary to remove vertical stripe interference for a bright image portion, that is, for a luminance signal having a potential higher than the potential E1. Therefore, the band pass filter circuit 18 and the subtraction circuit 21 form a low pass filter. Therefore, the switching circuit 20 controls so as to select no signal. For a dark image portion, that is, for a luminance signal having a potential lower than the potential E1, it is necessary to remove the vertical stripe interference, so the band pass filter circuit 1
8 and the subtraction circuit 21 control the switching circuit 20 to select the output luminance signal YB of the band pass filter circuit 18 so as to form a low pass filter for removing vertical interference. Potential E output from the potential generation circuit 12
1 is about 3.5 [MHz] that occurs in PAL TV images
The vertical stripe interference of the front and rear frequencies becomes invisible, and the high frequency component is set to a potential that does not deteriorate much.

Embodiment 5. FIG. 8 is a block circuit diagram of a video signal processing circuit according to a fifth embodiment of the present invention. The same reference numerals as those in FIG. 7 denote the same parts, and a description thereof will be omitted. In FIG. 8, 14 is a second potential generating circuit for generating a second potential E2 near the black level, which is the first potential E1.
It is also input to the comparison circuit 13.

Next, the operation will be described. The luminance signal Y input to the input terminal 1 is subtracted by the subtraction circuit 21 via the delay circuit 19, the band pass filter circuit 18, and the switching circuit 20, and output from the output terminal 8.
Since the operation is the same as that of the fourth embodiment shown in FIG. 7, the description of the operation is omitted here.

Next, the operation until the control signal for controlling the switching circuit 20 is supplied to the switching circuit 20 will be described. The first potential generating circuit 12 generates the potential E1 and the second potential generating circuit 14 generates the potential E2, and supplies them to the comparison circuit 13 at the same time as the output luminance signal YD of the delay circuit 19. The comparator circuit 13 compares the luminance signal YD with the first potential E1 and simultaneously compares the luminance signal YD with the second potential E2. When the luminance signal YD is higher than the first potential E1, or with the second potential E1. When the potential is lower than the potential E2 of the switching circuit 20, the switching circuit 20
Control so that no signal is selected, and the luminance signal YD is the first
Of the second electric potential E1 which is lower than the electric potential E1 of
When the potential is higher than 2, the switching circuit 20 controls so as to select the output luminance signal YB of the band pass filter circuit 18.

The state of this processing will be described based on the video signal waveform of the staircase wave shown in FIG. The vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL system TV image is noticeable in a dark image portion, but is not so noticeable in a bright image portion. Further, although the sync signal portion is included in the dark image portion, when the sync signal is passed through the low pass filter including the band pass filter circuit 18 and the subtraction circuit 21, the waveform characteristic of the sync signal deteriorates, There is a possibility that the synchronous processing system of the TV receiver malfunctions and the image becomes unstable on the time axis. Therefore, it is not necessary to remove the vertical stripe interference for a bright image portion, that is, for a luminance signal having a potential higher than the first potential E1, so that the band pass filter circuit 18 and the subtraction circuit 21 form a low pass filter. The switching circuit 20 controls so as to select no signal so as not to be caused. Since it is necessary to remove the vertical stripe interference for a dark image portion, that is, a luminance signal having a potential lower than the first potential E1 and higher than the second potential E2 other than the synchronization signal portion, it is necessary to remove the vertical stripe interference. The switching circuit 20 is configured so that the pass filter circuit 18 and the subtraction circuit 21 form a low pass filter for removing vertical stripe interference.
Controls to select the output luminance signal YB of the bandpass filter circuit 18.

However, it is better not to filter the sync signal portion in the dark image portion, that is, the luminance signal output from the second potential generating circuit 14 and having a potential lower than the potential in the vicinity of the black level. The switching circuit 20 controls to select no signal so that the band pass filter circuit 18 and the subtraction circuit 21 do not constitute a low pass filter. The first potential E1 is set to a potential at which a vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL TV image becomes invisible and a high frequency component is not deteriorated so much. The second electric potential E2 is lower than the first electric potential E1, and even if the luminance signal has a slight sag, the second electric potential E2 is a potential near the black level which is higher than the electric potential of the synchronizing signal and does not affect the synchronizing signal portion. Is set.

Sixth Embodiment FIG. 9 is a block circuit diagram of a video signal processing circuit according to a sixth embodiment of the present invention, and the same reference numerals as those in FIG. In FIG. 9, reference numeral 15 is a sync signal separation circuit for separating the sync signal S from the luminance signal YD output from the delay circuit 19, and 16 is a pulse signal P in which the phase of the sync signal S output from the sync signal separation circuit 15 is adjusted. A phase adjusting circuit for outputting, 17 is an output signal of the comparing circuit 13 and the phase adjusting circuit 1
6 is a control circuit for generating a control signal for controlling the switching circuit 20 from the output pulse signal P of FIG.

Next, the operation will be described. The luminance signal Y input to the input terminal 1 is subtracted by the subtraction circuit 21 via the delay circuit 19, the band pass filter circuit 18, and the switching circuit 20, and output from the output terminal 8.
Since the operation is the same as that of the fourth embodiment shown in FIG. 7, the description of the operation is omitted here.

Next, the operation until the control signal for controlling the switching circuit 20 is supplied to the switching circuit 20 will be described. The potential generation circuit 12 generates the potential E1 and supplies it to the comparison circuit 17 at the same time as the output luminance signal YD of the delay circuit 19. The comparison circuit 13 compares the luminance signal YD with the potential E1 and supplies the comparison result to the control circuit 17. The sync signal separation circuit 15 separates the sync signal S from the luminance signal YD output from the delay circuit 19 and supplies it to the phase adjustment circuit 16. The phase adjustment circuit 16 adjusts the phase and pulse width of the synchronization signal S output from the synchronization signal separation circuit 15 to adjust the delay circuit 1.
The pulse signal P indicating the period including the synchronizing signal portion of the luminance signal output from the reference numeral 9 is supplied to the control circuit 17. The phase adjusting circuit 16 may be composed of any circuit such as a monostable multivibrator, a frequency counter, a delay circuit, or an automatic frequency control circuit as long as the same operation can be obtained. The control circuit 17 controls so that the switching circuit 20 selects no signal when the potential of the luminance signal YD is higher than the potential E1 or during the period centered on the synchronizing signal S, and the luminance signal YD is higher than the potential E1. When the potential is low and is not included in the period centered on the synchronization signal S, the switching circuit 20 controls so as to select the output luminance signal YB of the band pass filter circuit 18.

The state of this processing will be described based on the video signal waveform of the staircase wave shown in FIG. The vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL system TV image is noticeable in a dark image portion, but is not so noticeable in a bright image portion. Further, although the sync signal portion is included in the dark image portion, when the sync signal is passed through the low pass filter including the band pass filter circuit 18 and the subtraction circuit 21, the waveform characteristic of the sync signal is deteriorated and the TV The synchronous processing system of the receiver may malfunction, resulting in an unstable image on the time axis. Therefore, the bright image portion, that is, the potential E1
Since it is not necessary to remove vertical stripe interference with respect to a luminance signal having a higher potential, a switching circuit 20 is provided so that the band pass filter circuit 18 and the subtraction circuit 21 do not form a low pass filter. A control signal for selecting no signal is supplied to the control circuit 17. Since it is necessary to remove the vertical stripe interference for a dark image portion, that is, a luminance signal having a potential lower than the potential E1 and other than the period including the synchronization signal, the bandpass filter circuit 18 and the subtraction circuit 21 are required. The switching circuit 20 supplies the control circuit 17 with a control signal for selecting the output luminance signal YB of the band-pass filter circuit 18 so as to form a low-pass filter for eliminating vertical stripe interference.

However, since it is better not to perform the filtering process in the synchronizing signal portion of the dark image portion, that is, in the period including the synchronizing signal indicated by the pulse signal P output from the phase adjusting circuit 16, it is preferable to perform the band pass. Filter circuit 18
The switching circuit 20 supplies the control circuit 17 with a control signal for selecting no signal so that the subtraction circuit 21 does not constitute a low-pass filter. The potential E1 output from the potential generation circuit 12 is set to a potential at which a vertical stripe interference of a frequency of about 3.5 [MHz] generated in a PAL system TV image becomes invisible and a high frequency component is not deteriorated so much.

Next, a video signal circuit for removing beat interference of a frequency of several hundreds [kHz] which occurs in an image in a VHS system VTR for recording, for example, a 2-channel audio signal in a deep layer of a magnetic tape is used. It will be described as 10.

Embodiment 7. FIG. 10 is a block circuit diagram of the seventh embodiment of the video signal processing circuit of the present invention. In FIG. 10, 9 is a low-pass filter circuit that attenuates the high-frequency component of the color-difference signal applied to the input terminal 1, and 10 is the color-difference signal C that is delayed by the same time as the delay time of the low-pass filter circuit 9. Delay circuit, 11 is delay circuit 10
Output color difference signal CD and output color difference signal CL of the low-pass filter circuit 9 are switched and output.
Is a potential generating circuit for generating a predetermined level of potential E1, 13
Is a comparison circuit for comparing the color saturation of the color difference signal CD output from the delay circuit 10 with the potential E1 output from the potential generation circuit 12 and outputting the comparison result.

Next, the operation will be described. A color difference signal C obtained by color demodulating a carrier color signal, for example, is input to the input terminal 1 and supplied to the delay circuit 10 and the low pass filter circuit 9. The low-pass filter circuit 9 supplies the color difference signal CL obtained by attenuating the high-frequency component of the input color difference signal C to one input terminal of the switching circuit 11. The low-pass filter circuit 9 may be, for example, a circuit configured similarly to the conventional video signal processing circuit shown in FIG. 20, or a filter having a steeper characteristic that attenuates only interference and noise components. It may be a circuit. The delay circuit 10 delays the color difference signal C by the time required for the color difference signal C to pass through the low-pass filter circuit 9, and compares the color difference signal CD with the comparison circuit 1
3 and the other input terminal of the switching circuit 11. The potential generation circuit 12 generates the potential E1 and supplies it to the comparison circuit 13. The comparison circuit 13 compares the potential of the signal obtained by full-wave rectifying the color difference signal CD with the potential E1, and when the potential of the signal obtained by full-wave rectification of the color difference signal CD is lower than the potential E1, the switching circuit 11 outputs the output of the delay circuit 10. The color difference signal CD is controlled to be selected, and when the potential of the signal obtained by full-wave rectifying the color difference signal CD is higher than the potential E1, the switching circuit 11 is controlled to select the output color difference signal CL of the low pass filter circuit 9. To do. The switching circuit 11 outputs the selected color difference signal to the output terminal 8
Output to.

The state of this processing will be described based on the color difference signal waveform shown in FIG. In FIG. 11, the RY signal is shown as the color difference signal. In a VHS system VTR that records a two-channel audio signal in a deep layer of a magnetic tape, beat interference at a frequency of several hundreds [kHz] that occurs in an image is noticeable in an image portion with high color saturation, but color saturation It is not very noticeable in low-frequency image areas. Therefore, an image portion with low color saturation, that is, the potential generation circuit 1
Since it is not necessary to remove beat interference with respect to the color difference signal C in which the potential of the color difference signal subjected to full-wave rectification becomes lower than the potential E1 output from 2, the delay circuit 10 that has not been filtered The output color difference signal CD is controlled by the switching circuit 11 to be selected. On the other hand, with respect to the image portion having a high color saturation, that is, the color difference signal C in which the full-wave rectified color difference signal has a higher potential than the potential E1 output from the potential generation circuit 12, the beat interference is removed. Since it is necessary to perform this, the switching circuit 11 controls the output color difference signal CL of the low-pass filter circuit 9 that has been subjected to the high-pass removal filter processing for removing beat interference. The electric potential E1 output from the electric potential generating circuit 12 is VH for recording a two-channel audio signal in the deep layer of the magnetic tape.
In the S type VTR, several hundreds [kHz] generated in the image
z] frequency beat interference is invisible, and
The potential is set so that the high frequency components do not deteriorate much.

Here, the color difference signals are the RY signal and the BY signal.
Signal refers to two signals. Therefore, although the input signals have been described simply as color difference signals based on the block circuit diagram of one system, the input signals are RY signals and B- signals, respectively.
It is also possible to have a two-system circuit configuration for the Y signal, or RY
The signal and the BY signal may be time-division-multiplexed to form one input signal, and the circuit configuration may be one system. This also applies to the following embodiments.

Further, the input signals are simply RY signals and B signals, respectively.
Not only a two-system circuit configuration for -Y signal, but R
If the potential of either the signal obtained by full-wave rectifying the -Y signal or the signal obtained by full-wave rectifying the BY signal is higher than the potential E1, the other signal processing system performs the same processing.
The processing systems of the -Y signal and the BY signal may be configured to perform processing related to each other. A block circuit diagram of such a video signal processing circuit is shown in FIG. In FIG.
Input terminal 1, low-pass filter circuit 9, delay circuit 10,
The switching circuit 11 and the output terminal 8 constitute, for example, an RY signal processing system, and the input terminal 201, the low-pass filter circuit 209, the delay circuit 210, the switching circuit 211, and the output terminal 208 process, for example, BY signal. The system is configured, and the potential generation circuit 12, the comparison circuit 13, the comparison circuit 213, and the control circuit 217 include the switching circuit 11 and the switching circuit 211.
A control signal generating portion for controlling the signal selected by is configured.

Since the operation of the RY signal processing system and the BY signal processing system is the same as the operation of the circuit shown in FIG. 10, the description thereof is omitted and the operation of the control signal generating portion is omitted. Will be described. The comparator circuit 13 compares the potential of the signal obtained by full-wave rectifying the RY signal output from the delay circuit 10 with the potential E1 output from the potential generation circuit 12, and outputs RY
A pulse signal indicating the portion where the potential of the signal obtained by full-wave rectifying the signal is higher than the potential E1 is output. The comparison circuit 213 compares the potential of the signal obtained by full-wave rectifying the BY signal output from the delay circuit 210 and the potential E1 outputted from the potential generation circuit 12 to obtain the signal obtained by full-wave rectifying the BY signal. Potential is potential E
Output a pulse signal that indicates the part higher than 1. The control circuit 217 outputs a pulse signal indicating a portion in which the potential of the signal obtained by full-wave rectifying the input RY signal is higher than the potential E1 and BY.
The signal of full-wave rectified signal is ORed with the pulse signal indicating the portion where the potential of the signal is higher than the potential E1.
When the potential of either or both of the signals obtained by full-wave rectifying the Y signal is higher than the potential E1, the switching circuit 11 and the switching circuit 211 respectively output the color difference signal of the low-pass filter circuit 9 and the output of the low-pass filter circuit 209. The color difference signal is controlled to be selected and output. Further, when the potentials of the signals obtained by full-wave rectifying the RY signal and the BY signal are both lower than the potential E1, the switching circuit 11 and the switching circuit 211
Control so that the output color difference signal of the delay circuit 10 and the output color difference signal of the delay circuit 210 are selected and output. As described above, the configuration in which the two systems of the R-Y signal and the B-Y signal are not related to each other but the processes of the two systems are mutually related is limited to the seventh embodiment. Instead, the same configuration can be adopted in the following embodiments, and the operation is the same.

Embodiment 8. 13 is a block circuit diagram of an eighth embodiment of the video signal processing circuit of the present invention.
The same reference numerals as those used in FIG. In FIG. 13, 15 is a luminance signal input terminal 2
A sync signal separation circuit that separates the sync signal S from the luminance signal Y applied to 2; a phase adjustment circuit 16 that outputs a pulse signal P that adjusts the phase of the sync signal S output from the sync signal separation circuit 15; Is a control circuit that generates a control signal for controlling the switching circuit 11 from the output signal of the comparison circuit 13 and the output pulse signal P of the phase adjustment circuit 16.

Next, the operation will be described. The operation in which the color difference signal C input to the input terminal 1 is switched by the switching circuit 11 via the delay circuit 10 or the low pass filter circuit 9 and output from the output terminal 8 is the same as in the embodiment shown in FIG. Since it is the same as the operation of No. 7, the explanation of the operation is omitted here.

Next, the operation until the control signal for controlling the switching circuit 11 is supplied to the switching circuit 11 will be described. The potential generation circuit 12 generates the potential E1 to generate the delay circuit 1
The output color difference signal CD of 0 is supplied to the comparison circuit 13 at the same time. The comparison circuit 13 compares the potential of the signal obtained by full-wave rectifying the color difference signal CD with the potential E1 and supplies the comparison result to the control circuit 17. The sync signal separation circuit 15 separates the sync signal S from the brightness signal Y applied to the brightness signal input terminal 22 and supplies it to the phase adjustment circuit 16. The phase adjusting circuit 16 adjusts the phase and the pulse width of the synchronizing signal S output from the synchronizing signal separating circuit 15 so that a portion of the color difference signal CD output from the delay circuit 10 corresponding to a color burst in the composite video signal. The control circuit 1 outputs a pulse signal P indicating a period S2 including (hereinafter, simply referred to as a color burst portion).
Supply to 7. The phase adjusting circuit 16 may be composed of any circuit such as a monostable multivibrator, a frequency counter, a delay circuit, or an automatic frequency control circuit as long as the same operation can be obtained. The control circuit 17 causes the switching circuit 11 to output the output color difference signal CD of the delay circuit 10 when the signal obtained by full-wave rectifying the color difference signal CD is lower than the potential E1 or during the period S2 centered on the color burst portion. The switching circuit 11 controls the selection so that the full-wave rectified signal of the color difference signal CD is higher than the potential E1 and is not included in the period S2 centered on the color burst portion. The output color difference signal CL of the low pass filter circuit 9 is controlled to be selected.

The state of this processing will be described based on the color difference signal waveform shown in FIG. In FIG. 14, B is used as the color difference signal.
-Y signal is shown. In a VHS system VTR that records a two-channel audio signal in a deep layer of a magnetic tape, beat interference of a frequency of several 100 [kHz] generated in an image is
It is quite noticeable in the image part with high color saturation, but not so noticeable in the image part with low color saturation. Further, if the color burst portion is passed through the low-pass filter circuit 9, the modulated signal forming the color burst is deteriorated, the color signal processing system of the TV receiver malfunctions, and an image with unstable hue may occur. There is. Therefore, beat interference is removed from the image portion having a low color saturation, that is, the color difference signal C in which the potential of the color difference signal subjected to full-wave rectification becomes lower than the potential E1 output from the potential generation circuit 12. Since there is no need, the switching circuit 11 supplies the control circuit 17 with a control signal for selecting the output color difference signal CD of the delay circuit 10 which is not subjected to the filter processing. On the other hand, the full-wave rectified color difference signal has a higher potential than the image portion having a high color saturation, that is, the potential E1 output from the potential generation circuit 12, and the portion other than the color burst portion, that is, the phase adjustment circuit 16 outputs. For the color difference signal C in the period other than the period S2 including the color burst indicated by the pulse signal P, it is necessary to remove the beat interference. Therefore, the switching circuit 11 performs the high-frequency removal filtering process for removing the beat interference. The control circuit 17 is supplied with a control signal for selecting the output color difference signal CL of the low-pass filter circuit 9 which is the color difference signal obtained by performing the above.

However, the color difference signal C such that the potential of the full-wave rectified color difference signal is higher than the potential E1 output from the potential generation circuit 12 in the image portion having high color saturation.
Of the color burst portion, that is, the phase adjustment circuit 16
Since it is better not to filter the period S2 including the color burst indicated by the pulse signal P output from the switch circuit 11, the switching circuit 11 selects the output color difference signal CD of the delay circuit 10 which is not filtered. A control signal that causes the control signal to be supplied to the control circuit 17. The electric potential E1 output from the electric potential generating circuit 12 is a VHS system VTR which records a two-channel audio signal in a deep layer of a magnetic tape, and beat interference of a frequency of several hundred kHz which is generated in an image becomes invisible, and , The high frequency component is set to a potential that does not deteriorate so much.

Here, the two color difference signals of the R-Y signal and the B-Y signal are quadrature two-phase modulated by the color subcarrier of 3.58 [MHz] to become a carrier color signal, but in the color burst portion. The BY signal has a potential of 2.03 × (−0.2) [V] superimposed with 100 [IRE] = 1 [V], and the RY signal has a 0 [V] potential. Therefore,
Filter processing is not performed on the color burst portion only in the BY signal processing system, and for the RY signal processing system, the luminance signal input terminal 22, the sync signal separation circuit 15, the phase. The circuit for generating the pulse signal P indicating the color burst portion formed of the adjusting circuit 16 is not necessary, and the switching circuit 11 may be controlled only based on the result of the comparison circuit 13.

Ninth Embodiment FIG. 15 is a block circuit diagram showing a ninth embodiment of the video signal processing circuit of the present invention. The same reference numerals as those in FIG. 10 denote the same parts, and the description thereof will be omitted. In FIG. 15, reference numeral 18 denotes a band-pass filter circuit that passes only the band in which interference or color components of the color-difference signal C applied to the input terminal 1 pass, and 19 denotes the color difference for the same time as the delay time of the band-pass filter circuit 18. A delay circuit for delaying the signal C, a switching circuit 20 for switching between the output color difference signal CB of the band pass filter circuit 18 and no signal, and a reference numeral 13 for a color saturation degree of the color difference signal CD output from the delay circuit 19 and a potential generation circuit 12 A comparator circuit for comparing the potential E1 output from the
Is a subtraction circuit for subtracting the output signal of the switching circuit 20 from the color difference signal CD output by the delay circuit 19.

Next, the operation will be described. A color difference signal C obtained by color demodulating a carrier color signal, for example, is input to the input terminal 1 and supplied to the delay circuit 19 and the band pass filter circuit 18. The bandpass filter circuit 18 passes only the band in which the interference and noise components of the color difference signal C applied to the input terminal 1 exist and supplies it to one input terminal of the switching circuit 20. For example, the bandpass filter circuit 18 is shown in FIG.
Of the 3-tap filter circuit that constitutes the conventional video signal processing circuit shown in 0, the multiplication coefficient of the first coefficient circuit 4 is -1/4 and the multiplication coefficient of the third coefficient circuit 6 is-. 1 /
A circuit configuration changed to 4 may be used. In this case, the color difference signal is C
The output color difference signal CB of the band pass filter circuit 18 when (t) is -1 / 4.C (t) + 1 / 2.C (t-29.tau.)-1 /
4 · C (t−58τ).

The delay circuit 19 delays the color-difference signal C applied to the input terminal 1 by a time required for passing the color-difference signal C through the band-pass filter circuit 18, and supplies it to the subtraction circuit 21 and the comparison circuit 13. The potential generation circuit 12 generates the potential E1 and supplies it to the comparison circuit 13 at the same time as the color difference signal CD output from the delay circuit 19. The comparator circuit 13 compares the potential of the full-wave rectified signal of the color difference signal CD with the potential E1, and the potential of the full-wave rectified signal of the color difference signal CD is the potential E1.
When it is lower, the switching circuit 20 controls so as to select no signal, and when the potential of the signal obtained by full-wave rectifying the color difference signal CD is higher than the potential E1, the switching circuit 20 outputs the color difference signal CB of the band pass filter circuit 18. Control to select. The switching circuit 20 outputs no signal and the output color difference signal C of the band pass filter circuit 18 according to the output signal of the comparison circuit 13.
B is switched and supplied to the subtraction circuit 21. Subtraction circuit 2
1 outputs a signal obtained by subtracting the output color difference signal CB of the switching circuit 20 from the color difference signal CD output from the delay circuit 19 to the output terminal 8.

Here, when the switching circuit 20 supplies no signal to the subtraction circuit 21, the color difference signal C (t) is represented by the band difference filter circuit 18 when the color difference signal applied to the input terminal 1 is C (t). The output color difference signal C (t−29τ) of the delay circuit 19 delayed by the same delay time as is output from the output terminal 8 as it is.

When the output color difference signal CB of the band pass filter circuit 18 is directly supplied to the subtraction circuit 21, the output color difference of the delay circuit 19 obtained by delaying the color difference signal C (t) by the same delay time as that of the band pass filter circuit 18. Signal C (t-
29τ), the output signal of the bandpass filter circuit −1 / 4 · C (t) + ½ · C (t−29τ) −1 /
Since 4 · C (t−58τ) will be subtracted, C (t−29τ) − {− 1/4 · C (t) + 1/2 · C
(T-29τ) -1 / 4 · C (t-58τ)} = 1/4
・ C (t) +1/2 ・ C (t-29τ) +1/4 ・ C
(T−58τ), and the output signal output from the output terminal 8 has the same result as the output signal of the conventional video signal processing circuit.

The state of this processing will be described based on the color difference signal waveform shown in FIG. In FIG. 11, RY is used as the color difference signal.
Signaled. In a VHS system VTR that records a two-channel audio signal in a deep layer of a magnetic tape, beat interference at a frequency of several hundreds [kHz] that occurs in an image is noticeable in an image portion with high color saturation, but color saturation It is not very noticeable in low-frequency image areas. Therefore, beat interference is removed from the image portion having a low color saturation, that is, the color difference signal C in which the potential of the color difference signal subjected to full-wave rectification becomes lower than the potential E1 output from the potential generation circuit 12. Since it is not necessary, the switching circuit 20 controls to select no signal so that the band pass filter circuit 18 and the subtraction circuit 21 do not constitute a low pass filter. On the other hand, beat interference is removed for the color difference signal C in which the potential of the full-wave rectified color difference signal C is higher than the potential E1 output from the potential generation circuit 12 in the image portion having high color saturation. So you have to do
The band pass filter circuit 18 and the subtraction circuit 21 form a low pass filter for removing beat interference,
The switching circuit 20 controls so as to select the output color difference signal CB of the band pass filter circuit 18. Potential generation circuit 1
The electric potential E1 output from 2 is a high frequency band where a beat interference of a frequency of several 100 [kHz] generated in an image is invisible in a VHS system VTR which records a two-channel audio signal in a deep layer of a magnetic tape. The potential is set so that the components do not deteriorate much.

Embodiment 10. FIG. 16 is a block circuit diagram showing a video signal processing circuit according to a tenth embodiment of the present invention. The same reference numerals as those in FIG. 15 denote the same parts, and the description thereof will be omitted. In FIG. 16, reference numeral 15 is a sync signal separation circuit for separating the sync signal S from the brightness signal Y applied to the brightness signal input terminal 22, and 16 is the sync signal separation circuit 1.
5, a phase adjustment circuit that outputs a pulse signal P in which the phase of the synchronization signal S output from 5 is output, and 17 is a control that controls the switching circuit 20 from the output signal of the comparison circuit 13 and the output pulse signal P of the phase adjustment circuit 16. It is a control circuit that generates a signal.

Next, the operation will be described. The operation in which the color difference signal C input to the input terminal 1 is subtracted by the subtraction circuit 21 via the delay circuit 19, the band pass filter circuit 18, and the switching circuit 20 and output from the output terminal 8 is shown in FIG. The operation is the same as that of the ninth embodiment, and the description of the operation is omitted here.

Next, the operation until the control signal for controlling the switching circuit 20 is supplied to the switching circuit 20 will be described. The potential generation circuit 12 generates the potential E1 and supplies it to the comparison circuit 13 at the same time as the output color difference signal CD of the delay circuit 19. The comparison circuit 13 compares the color difference signal CD and the potential E1 and supplies the comparison result to the control circuit 17. The sync signal separation circuit 15 separates the sync signal S from the brightness signal Y applied to the brightness signal input terminal 22 and supplies it to the phase adjustment circuit 16. The phase adjusting circuit 16 adjusts the phase and pulse width of the synchronizing signal S output from the synchronizing signal separating circuit 15, and the pulse signal indicating the period S2 including the color burst portion of the color difference signal CD output from the delay circuit 19. P is supplied to the control circuit 17. The phase adjusting circuit 16 may be composed of any circuit such as a monostable multivibrator, a frequency counter, a delay circuit, or an automatic frequency control circuit as long as the same operation can be obtained.
The control circuit 17 controls the switching circuit 20 when the potential of the signal obtained by full-wave rectifying the color difference signal CD is lower than the potential E1 or during the period S2 centered on the color burst portion.
Control so that no signal is selected, and the potential of the signal obtained by full-wave rectifying the color difference signal CD is higher than the potential E1.
In addition, during the period not included in the period S2 centering on the color burst portion, the switching circuit 20 controls so as to select the output color difference signal CB of the band pass filter circuit 18.

The state of this processing will be described based on the color difference signal waveform shown in FIG. In FIG. 14, B is used as the color difference signal.
-Y signal is shown. In a VHS system VTR that records a two-channel audio signal in a deep layer of a magnetic tape, beat interference of a frequency of several 100 [kHz] generated in an image is
It is quite noticeable in the image part with high color saturation, but not so noticeable in the image part with low color saturation. Further, when the color burst portion is passed through a low pass filter composed of the band pass filter circuit 18 and the subtraction circuit 21, the modulated signal forming the color burst is deteriorated and the color signal processing system of the TV receiver malfunctions. However, the image may have an unstable hue. Therefore, an image portion having a low color saturation, that is, a potential E1 output from the potential generation circuit 12,
Since it is not necessary to remove the beat interference for the color difference signal C in which the potential of the full-wave rectified color difference signal becomes low,
The switching circuit 20 supplies a control signal for selecting no signal to the control circuit 17 so that the band pass filter circuit 18 and the subtraction circuit 21 do not constitute a low pass filter. On the other hand, the image portion having a high color saturation, that is, the potential E1 output from the potential generation circuit 12,
The full-wave rectified color difference signal has a high potential, and beats with respect to the color difference signal C other than the color burst portion, that is, in the period other than the period S2 including the color burst indicated by the pulse signal P output from the phase adjusting circuit 16. Since it is necessary to remove the interference, the switching circuit 20 outputs the output color difference signal CB of the bandpass filter circuit 18 so that the bandpass filter circuit 18 and the subtraction circuit 21 form a low-pass filter for removing the beat interference. A control signal for selection is supplied to the control circuit 17.

However, the color difference signal C such that the potential of the full-wave rectified color difference signal becomes higher than the potential E1 output from the potential generation circuit 12 in the image portion having high color saturation.
Also, in the period S2 including the color burst portion, that is, the color burst portion indicated by the pulse signal P output from the phase adjusting circuit 16, it is better not to perform the filtering process. The switching circuit 20 supplies a control signal for selecting no signal to the control circuit 17 so that the subtraction circuit 21 does not constitute a low-pass filter. Potential generation circuit 1
The electric potential E1 output from 2 is a high frequency band where a beat interference of a frequency of several 100 [kHz] generated in an image is invisible in a VHS system VTR which records a two-channel audio signal in a deep layer of a magnetic tape. The potential is set so that the components do not deteriorate much.

Here, the two color difference signals of the RY signal and the BY signal are quadrature two-phase modulated with a color subcarrier of 3.58 [MHz] to be a carrier color signal, but in the color burst portion. The BY signal has a potential of 2.03 × (−0.2) [V] superimposed with 100 [IRE] = 1 [V], and the RY signal has a 0 [V] potential. Therefore,
Filter processing is not performed on the color burst portion only in the BY signal processing system, and for the RY signal processing system, the luminance signal input terminal 22, the sync signal separation circuit 15, the phase. The circuit for generating the pulse signal P indicating the color burst portion formed of the adjusting circuit 16 is not necessary, and the switching circuit 20 may be controlled only based on the result of the comparison circuit 13.

[0071]

According to the video signal processing circuit of the present invention, the control circuit causes the bandpass filter circuit to operate when the signal level of the luminance signal is higher than a predetermined value and lower than near the black level of the luminance signal. When the signal level of the luminance signal is lower than a predetermined value and higher than near the black level of the luminance signal, the output signal from the band pass filter circuit is controlled to be output. In other words, the part containing the sync signal whose waveform characteristics are deteriorated by filtering is included in the bright image part and the dark image part in which the disturbing component or the noise component included in the luminance signal is inconspicuous. Since the output signal of the band-pass filter circuit is subtracted from the other dark image parts where the disturbing component or the noise component is conspicuous, the disturbing component of the video signal and the noise component are removed, and at the same time, the high range of the image is removed. This has the excellent effect of minimizing the component attenuation and preventing the instability of the image due to the deterioration of the synchronization signal.

Further, the video signal processing circuit according to the present invention is
The control circuit cuts off the output signal from the band pass filter circuit during the period when the signal level of the luminance signal is higher than the predetermined value and the period including the synchronization signal of the luminance signal, and the signal level of the luminance signal is higher than the predetermined value. It is controlled so that the output signal from the band pass filter circuit is output during a period in which the brightness signal is low and the synchronization signal of the luminance signal is not included. In other words, the same output as the luminance signal is set so that the bright signal portion in which the interference component or the noise component included in the luminance signal is inconspicuous and the period including the synchronization signal in which the waveform characteristics are deteriorated by filtering have the same output as the luminance signal. In the dark image part of the period other than the period including the noticeable sync signal, the output signal of the bandpass filter circuit is subtracted, so that the interference and noise components of the video signal are removed and the high frequency band of the image is removed. This has the excellent effect of minimizing the component attenuation and preventing the instability of the image due to the deterioration of the synchronization signal.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a first embodiment of a video signal processing circuit of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of the first and fourth embodiments of the video signal processing circuit of the present invention.

FIG. 3 is a block circuit diagram of a second embodiment of a video signal processing circuit of the present invention.

FIG. 4 is a signal waveform diagram for explaining the operations of the second and fifth embodiments of the video signal processing circuit of the present invention.

FIG. 5 is a block circuit diagram of a third embodiment of a video signal processing circuit of the present invention.

FIG. 6 is a signal waveform diagram for explaining the operations of the third and sixth embodiments of the video signal processing circuit of the present invention.

FIG. 7 is a block circuit diagram of a video signal processing circuit according to a fourth embodiment of the present invention.

FIG. 8 is a block circuit diagram of a fifth embodiment of a video signal processing circuit of the present invention.

FIG. 9 is a block circuit diagram of a video signal processing circuit according to a sixth embodiment of the present invention.

FIG. 10 is a block circuit diagram of a seventh embodiment of a video signal processing circuit of the present invention.

FIG. 11 is a seventh and a ninth video signal processing circuit of the present invention.
FIG. 7 is a signal waveform diagram for explaining the operation of the embodiment.

FIG. 12 is a block circuit diagram of a modified example of the seventh embodiment of the video signal processing circuit of the present invention.

FIG. 13 is a block circuit diagram of an eighth embodiment of a video signal processing circuit of the present invention.

FIG. 14 is an eighth and a first video signal processing circuit of the present invention.
FIG. 7 is a signal waveform diagram for explaining the operation of the 0th embodiment.

FIG. 15 is a block circuit diagram of a ninth embodiment of a video signal processing circuit of the present invention.

FIG. 16 is a block circuit diagram of a video signal processing circuit according to a tenth embodiment of the invention.

FIG. 17 is a block circuit diagram of a conventional video signal processing circuit.

FIG. 18 is a gain vs. frequency characteristic diagram of a low-pass filter circuit forming a conventional video signal processing circuit.

FIG. 19 is a frequency layout diagram showing a recording format of S-VHS system Hi-Fi standard VTR.

FIG. 20 is a block circuit diagram of another conventional video signal processing circuit.

[Explanation of symbols]

9 low-pass filter circuit, 10 delay circuit, 11 switching circuit, 12 potential generation circuit, 13 comparison circuit, 1
4 second potential generation circuit, 15 sync signal separation circuit, 1
6 phase adjustment circuit, 17 control circuit, 18 band pass filter circuit, 19 delay circuit, 21 subtraction circuit.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 5/21 H04N 9/64

Claims (3)

(57) [Claims] 1. A bandpass filter circuit for extracting only a band including an interference component or a noise component of a luminance signal in a composite video signal, when the signal level of the luminance signal is higher than a predetermined value, and a black level of the luminance signal. If lower than the vicinity, cut off the output signal of the band pass filter circuit, the signal level of the luminance signal is lower than a predetermined value, and
A control circuit that outputs an output signal of the band-pass filter circuit when the luminance signal is higher than the vicinity of the black level, and a subtraction circuit that subtracts the output signal of the control circuit from the luminance signal. Video signal processing circuit. 2. The video signal processing circuit according to claim 1, wherein the predetermined value corresponds to a signal level at which vertical stripe interference is inconspicuous. 3. A band pass filter circuit for extracting only a band including an interference component or a noise component of a luminance signal in a composite video signal, a period in which a signal level of the luminance signal is higher than a predetermined value, and a synchronization signal of the luminance signal. During the period including, the output signal from the band pass filter circuit is cut off, the signal level of the luminance signal is lower than a predetermined value, and
A control circuit that outputs the output signal of the band pass filter circuit during a period that does not include the synchronization signal of the luminance signal, and a subtraction circuit that subtracts the output signal of the control circuit from the luminance signal are provided. Video signal processing circuit.