JP3427271B2 - 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-4τ) added signal 1/4 · Y (t) + 1/2 · Y (t-2τ) + 1/4 · Y (t-4τ) output terminal 8 Output from.

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 [kHz] or 2 × 1.3 [MHz] -1.7 [MHz] =
It is 900 [kHz]. The color signals are two color difference signals R
It is a low-frequency conversion carrier color signal obtained by low-frequency converting the carrier color signal obtained by quadrature-phase modulating -Y and BY with a carrier wave of 3.58 [MHz] to 629 [kHz]. From this, 400 [kH
The spurious components of z] and 900 [kHz] appear as a component of 629-400 = 229 [kHz] 900-629 = 271 [kHz] in the color difference signal. 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) output terminal 8 Output from. The color difference signal output from the output terminal 8 is most attenuated at about 247 [kHz], and the beat interference is attenuated.

[0009]

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 to solve the above-mentioned problems, and removes interference and noise components, and minimizes attenuation of high-frequency components of an image or high-frequency components of color signals. It is an object to obtain a video signal processing circuit that can perform.

[0011]

Means for Solving the Problems A video signal processing circuit according to claim 1, contained in the luminance signal in the composite video signal
Low-pass fill <br/> and capacitor circuit, a luminance signal and a low-pass filter circuit of the output signal to remove interfering components or noise components Ru have
A switching circuit for selecting and outputting one of the luminance
When the signal level of the signal is higher than a predetermined value and the luminance signal
If it is lower than around the black level of
The same output, and the signal level of the luminance signal is a specified value.
If it is lower and higher than near the black level of the luminance signal,
And a control circuit for controlling the switching circuit so that the output signal is the same as the output signal of the low-pass filter circuit .

A video signal processing circuit according to a second aspect is a predetermined
The value can correspond to a signal level where vertical stripe interference is not noticeable.
It is said that .

The video signal processing circuit according to claim 3 is a composite
Interfering components Ru Tei included in the luminance signal in the video signal also
Is a low-pass filter circuit that removes noise components, a switching circuit that selects and outputs either the luminance signal or the output signal of the low-pass filter circuit, and the signal level of the luminance signal.
Is higher than a predetermined value and includes the sync signal of the luminance signal
The period is the same as the output of the brightness signal, and the brightness
The signal level of the signal is lower than the specified value and the composite video signal
The output signal of the low-pass filter is included in the period that does not include the sync signal of
Control circuit for controlling the switching circuit so that the same output as the signal is output .

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

A video signal processing circuit according to claim 1, wherein the control circuit compares the signal potential of the luminance signal with a predetermined potential and a potential in the vicinity of the black level when the signal potential of the luminance signal is higher than the predetermined potential. , I.e., in the bright image part where the disturbing component or noise component included in the luminance signal is not noticeable , or near the black level
When it is lower than the potential, that is, it is included in the dark image area,
Includes a sync signal whose waveform characteristics are degraded by filtering
Moiety as a luminance signal, also the signal potential of the luminance signal higher than the potential of the low Ku Moreover black level near the predetermined potential
When, i.e. other <br/> dark image portion interfering components or noise components are conspicuous controls the circuit switching so as to select and output the output signal of the filter circuit for removing interfering components or noise components included in the luminance signal .

According to a second aspect of the present invention, the video signal processing circuit has a predetermined potential.
For example, in the case of a PAL system TV image, about 3.5 [MH
z] Longitudinal band interference around the frequency disappears,
The circuit is controlled by setting the potential such that the region component does not deteriorate so much .

According to another aspect of the video signal processing circuit of the present invention, the control circuit compares the signal potential of the luminance signal with a predetermined potential, and when the signal potential of the luminance signal is higher than the predetermined potential, that is, an interference component included in the luminance signal or The brightness signal remains as it is during the bright image part where the noise component is inconspicuous or the synchronization signal whose waveform characteristic deteriorates due to filtering, or when the signal potential of the brightness signal is lower than the predetermined potential except the period including the synchronization signal. That is, in the dark image portion where the disturbing component or the noise component is conspicuous, the switching circuit is controlled to selectively output the output signal of the filter circuit that removes the disturbing component or the noise component included in the luminance signal.

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[Embodiment] For example, a program etc. produced by the NTSC system
Approximately 3.5 [MH] generated in the image when converted to the AL system
z] A video signal processing circuit for eliminating vertical stripe interference of frequencies around z will be described as Embodiments 1 to 6.

Example 1. FIG. 1 is a block circuit diagram of a first embodiment of a video signal processing circuit of the present invention. In FIG. 1, 9 is a low-pass filter circuit that attenuates the high-frequency component of the luminance signal applied to the input terminal 1, and 10 is the input luminance signal Y that is delayed by the same time as the delay time of the low-pass filter circuit 9. A delay circuit 11 for switching the output luminance signal YD of the delay circuit 10 and an output luminance signal YL of the low-pass filter circuit 9 for output, and a potential generation circuit 12 for generating a potential E1 of a predetermined level, 13 Is the luminance signal YD output from the delay circuit 10 and the potential generation circuit 1
2 is a comparison circuit that compares the potential E1 output from the output 2 and outputs the 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. .

Example 2. FIG. 3 is a block circuit diagram of a second embodiment of the video signal processing circuit of the present invention. 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. The second potential E2 is the first potential E2.
Is input to the comparison circuit 13 together with the first potential E1 output from the potential generation circuit 12 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 first embodiment shown in FIG. Since it is the same as the operation of the above, the explanation of the operation will be 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 sync signal portion of the dark image portion, that is, the luminance signal having a potential lower than the second potential E2. Therefore, the delay circuit 10 that has not been filtered is performed. 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.

Example 3. FIG. 5 is a block circuit diagram of a video signal processing circuit according to a third embodiment of the present invention, and the same reference numerals as those in FIG. In FIG. 5, reference numeral 15 is a luminance signal Y output from the delay circuit 10.
A sync signal separation circuit for separating the sync signal S from D, 16 is a phase adjustment circuit for outputting a pulse signal P in which the phase of the sync signal S output from the sync signal separation circuit 15 is adjusted, 17
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 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 first embodiment shown in FIG. Since it is the same as the operation of the above, the explanation of the operation will be 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 in 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.

Example 4. FIG. 7 is a block circuit diagram of a video processing circuit according to a fourth embodiment of the present invention, and the same reference numerals as those in FIG. Figure 7
18 is a band pass filter circuit for passing only a band in which interference and noise components exist in the luminance signal Y applied to the input terminal 1, and 19 is a band pass filter circuit 18.
A delay circuit for delaying the luminance signal Y by the same time as the delay time of the circuit, 20 a switching circuit for switching between the output luminance signal YB of the band pass filter circuit 18 and no signal, 13
Is a comparison circuit which compares the luminance signal YD output from the delay circuit 19 with the potential E1 output from the potential generation circuit 12 and outputs a comparison result. Reference numeral 21 is a switching circuit 20 from the luminance signal YD output from the delay circuit 19. Is a subtraction circuit for subtracting the output signal of the.

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-2τ) -1 / 4 · Y (t-4τ). Is.

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
The output signal of the bandpass filter circuit −1 / 4 · Y (t) + 1/2 · Y (t−2τ) −1 / 4 · Y (t−4τ) is subtracted from (t−2τ). Therefore, 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.tau.), And the same output signal as the output signal of the conventional video signal processing circuit is output terminal 8 Is output from.

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.

Example 5. FIG. 8 is a block circuit diagram of a fifth embodiment of the video signal processing circuit of the present invention, and the same reference numerals as those in FIG. 7 indicate the same parts, and the 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 input to the comparison circuit 13 together with the first potential E1.

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. Therefore, 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 of the dark image portion, that is, the luminance signal output from the second potential generation circuit 14 and having a potential lower than the potential near 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.

Example 6. 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, 15 is a luminance signal Y output from the delay circuit 19.
A sync signal separation circuit for separating the sync signal S from D, 16 is a phase adjustment circuit for outputting a pulse signal P in which the phase of the sync signal S output from the sync signal separation circuit 15 is adjusted, 17
Is a control circuit that generates a control signal for controlling 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.

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 for the synchronizing signal portion of the dark image portion, that is, for 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] generated in an image in a VHS system VTR for recording, for example, a two-channel audio signal in a deep layer of a magnetic tape is used in Examples 7 to 10. As described below.

Example 7. FIG. 10 is a block circuit diagram of a 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. A delay circuit 11 is an output color difference signal CD of the delay circuit 10 and an output color difference signal C of the low pass filter circuit 9.
A switching circuit for switching and outputting L, a potential generating circuit for generating a potential E1 of a predetermined level, a reference numeral 13 for a color saturation of the color difference signal CD output from the delay circuit 10 and a potential output from the potential generating circuit 12. A comparison circuit that compares E1 and outputs a 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 examples.

Further, simply input signals are RY signal and B signal, 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 BY signal are not related to each other but the processes of the two systems are related to each other is limited to the seventh embodiment. Without
A similar configuration can be used in the following examples,
The operation is similar.

Example 8. FIG. 13 is a block circuit diagram of an eighth embodiment of the video signal processing circuit of the present invention, and the same reference numerals as those in FIG. 10 indicate the same parts, and the description thereof will be omitted. In FIG. 13, 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 a pulse in which the phase of the sync signal S output from the sync signal separation circuit 15 is adjusted. A phase adjustment circuit for outputting the signal P, and a control circuit 17 for generating 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 that of the seventh embodiment shown in FIG. Since it is the same as the operation of the above, the explanation of the operation will be 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 in which the full-wave rectified color-difference signal has a higher potential 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 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 11 may be controlled only based on the result of the comparison circuit 13.

Example 9. FIG. 15 is a block circuit diagram showing a ninth embodiment of the video signal processing circuit of the present invention, and the same reference numerals as those in FIG. 10 indicate 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, 20 is a bandpass filter circuit 18
Of the color difference signal CD output from the delay circuit 19 and the potential E1 output from the potential generation circuit 12 are compared, and a comparison result is output. Reference numeral 21 denotes 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−29τ) −1 / 4 · C (t−58τ). is there.

The delay circuit 19 delays the color difference signal C applied to the input terminal 1 by a time necessary for the color difference signal C to pass 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 a 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 bandpass 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 bandpass filter circuit 18. Signal C (t-
29τ), the output signal of the bandpass filter circuit −−1 / 4 · C (t) + ½ · C (t−29τ) −1 / 4 · C (t−58τ) is 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-29 [tau]) + 1/4 * C (t-58 [tau]), 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.

Example 10. FIG. 16 is a block circuit diagram showing a tenth embodiment of the video signal processing circuit of the present invention.
The same reference numerals as those used in FIG. In FIG. 16, 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 20 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 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 here,
The description of the operation is omitted.

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 in which the full-wave rectified color difference signal has a higher potential 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 by the 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.

[0086]

As described above, according to the video signal processing circuit of claim 1, the potential of the luminance signal is lower than the second potential in the bright image portion where the potential is higher than the first predetermined potential or near the black level.
Portion have including synchronization signal as a luminance signal, the potential of the luminance signal is rather low than the first predetermined potential, and a second potential
It is configured to select the output signal of the low-pass filter circuit that removes the interference and noise components when it is high , so that the interference and noise components of the video signal are removed and the attenuation of the high-frequency components of the image is minimized. Due to deterioration of the sync signal
It has an excellent effect of preventing instability of an image .

Further, in the video signal processing circuit according to claim 2, the potential of the luminance signal is set to a signal level at which vertical stripe interference is not noticeable.
The luminance signal is left as it is , and the potential of the luminance signal is vertically striped , in a bright image portion higher than the corresponding first predetermined potential or in a portion including a synchronization signal lower than the second potential near the black level.
When the interference is lower than the first predetermined potential corresponding to the inconspicuous signal level and higher than the second potential, the output signal of the low-pass filter circuit in which the interference and noise components are removed is selected. In addition to removing the interference and noise component of the video signal, the high frequency component of the image is minimized to be attenuated, and further, the instability of the image due to the deterioration of the synchronization signal is prevented.

Further, in the video signal processing circuit according to the third aspect, the brightness signal is kept as it is during a period around the bright image portion where the potential of the brightness signal is higher than a predetermined potential or the synchronizing signal.
The output signal of the filter circuit is selected during the period when the potential of the luminance signal is lower than the predetermined potential and is not included in the period centered on the synchronization signal, so the interference and noise components of the video signal are removed. At the same time, the excellent effect of suppressing the attenuation of the high frequency component of the image to the minimum and preventing the instability of the image due to the deterioration of the synchronizing signal is exerted.

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[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 operation 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 video signal processing circuit according to a third embodiment 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 video signal processing circuit according to a seventh embodiment 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 example.

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 the video signal processing circuit of the present invention.

FIG. 14 is an eighth and a first video signal processing circuit of the present invention.
It 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 the 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 present 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 14 Second potential generation circuit 15 Sync signal separation circuit 16 Phase adjustment circuit 17 Control circuit 18 Bandpass filter circuit 19 Delay circuit 21 Subtraction circuit

Claims (3)

(57) [Claims] 1. A low-pass filter circuit for removing an interference component or a noise component contained in a luminance signal in a composite video signal, and selecting either the luminance signal or an output signal of the low-pass filter circuit. And a switching circuit for outputting the luminance signal when the signal level of the luminance signal is higher than a predetermined value.
If it is lower than near the black level of the luminance signal,
The output level of the luminance signal is lower than the predetermined value.
One, is higher than the black level near the luminance signal is a video signal, characterized in that a control circuit for controlling the switching circuit to the same output as such so that the output signal of the low-pass filter circuit Processing circuit. 2. The predetermined value is a signal in which vertical stripe interference is not noticeable.
The image signal processing circuit according to claim 1, wherein the image signal processing circuit corresponds to a level . 3. A low pass filter circuit for removing an interference component or a noise component contained in a luminance signal in a composite video signal, and selecting either the luminance signal or an output signal of the low pass filter circuit. And a switching circuit for outputting the signal, and a period in which the signal level of the luminance signal is higher than a predetermined value
The luminance signal is output during the period including the synchronization signal of the luminance signal .
The output is the same as the output, and the signal level of the luminance signal is lower than the predetermined value, and
A video signal processing circuit period that does not include a synchronization signal, characterized in that a control circuit for controlling the switching circuit such that the same output as the output signal of the low-pass filter of the composite video signal.