JP2001346071A - Device and method for processing video signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video signal processor and its processing method by which the noise level of a video signal is excellently reduced. SOLUTION: The video signal processor is provided with a sharpness circuit 14 for filtering an inputted luminance signal by a transversal filter 11, multiplying the filtered luminance signal by a prescribed coefficient, adjusting time delay which occurs in the transversal filter 11 and adding it to an original signal and a non-corelation detecting circuit 15 for discriminating a section only with noise from a section which comprises the change components of noise and the luminance signal through the use of a non-corelation detecting processing with respect to the luminance signal filtered by the filter 11. A noise removal processing for subtracting noise from the luminance signal is performed in the sharpness circuit 14 in the section only with noise, which is detected by the circuit 15.

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 apparatus and a video signal processing method suitable for use in, for example, a sharpness circuit for improving the sharpness of a video.

[0002]

2. Description of the Related Art In a television receiver, a video tape reproducing device, and a digital video disk reproducing device,
A sharpness circuit is known as a means having a function of improving sharpness.

Further, as a noise reduction circuit for these conventional television receivers, a noise level is detected,
By narrowing the sharpness adjustment amount in inverse proportion to the detected noise amount, raising the relatively high frequency signal gain,
There is a circuit that performs processing for improving sharpness to make noise less noticeable.

[0004]

However, in the above-described conventional noise reduction circuit, if there is noise in the signal, the noise is emphasized by the sharpness circuit, which may lead to deterioration of image quality. For this reason, there is a method of detecting a noise level and using a circuit for reducing the amount of sharpness adjustment in inverse proportion to the detected noise amount and making the noise inconspicuous.
In this case, the S / N ratio of the video signal cannot be directly improved, and the sharpness cannot be increased in the presence of noise. There was an inconvenience.

In addition, there is a coring sharpening technique in which sharpness is applied only to a signal of a certain level or more and a small amplitude signal such as noise is not applied to the sharpness function. However, this technique removes noise of a video signal. There was an inconvenience that you could not do that.

[0006] Therefore, the present invention has been made in view of such a point, and it is an object of the present invention to provide a video signal processing device and a video signal processing method that can favorably reduce the noise level of a video signal.

[0007]

A video signal processing apparatus according to the present invention filters an input luminance signal with a transversal filter, multiplies the filtered luminance signal by a predetermined coefficient, and applies the filtered signal to the transversal filter. A sharpness circuit that adjusts the resulting time delay and adds it to the original signal, and a section including only noise and a section including a change component of noise and a luminance signal by using a decorrelation detection process on the luminance signal filtered by the transversal filter. And in a section of only the noise detected by the decorrelation detection circuit, the sharpness circuit performs a noise removal process of subtracting the noise from the luminance signal.

Further, in the video signal processing method of the present invention, the input luminance signal is filtered by a transversal filter, the filtered luminance signal is multiplied by a predetermined coefficient, and the time delay generated by the transversal filter is adjusted. And a non-correlation that discriminates a luminance signal filtered by the transversal filter into a section including only noise and a section including noise and a change component of the luminance signal using a decorrelation detection process. In a section including only noise detected by the decorrelation detection process, a noise removal process of subtracting noise from a luminance signal in the sharpness process is performed.

Therefore, according to the present invention, the following operations are performed. According to the video signal processing device and the video signal processing method of the present invention, in the sharpness circuit, the luminance signal is subjected to decorrelation detection processing, discriminated into a section including only noise and a section including a change component of the noise and the luminance signal, In a section including only noise, noise removal processing of subtracting the noise from the luminance signal is performed.

According to the present invention, the processing for improving the sharpness by the sharpness is performed without deteriorating the image quality, while performing the noise removal processing on the noisy signal.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A video signal processing apparatus according to the present embodiment performs correlation detection to reduce noise by subtracting a noise component from a signal, and adds a sharpness component to a signal to reduce sharpness. Is to improve the sharpness.

The video signal processing apparatus according to the present embodiment is applied to a sharpness circuit built in a television receiver. That is, in a television receiver, a television broadcast is received, noise of a video signal included in the received broadcast wave is reduced, and the noise-reduced video signal is sharpened. Is displayed.

[0013] The present invention is not limited to this case, and a video signal supplied from an external or built-in video signal source (such as a video reproducing apparatus) to a television receiver is reduced in noise and sharpened for display processing. Be suited.

Hereinafter, the configuration of a sharpness circuit to which the video signal processing device of the present embodiment is applied will be described.
FIG. 1 is a diagram illustrating a configuration of a sharpness circuit to which the video signal processing device according to the present embodiment is applied. The luminance signal is
It is input to the sharpness circuit 14. This luminance signal is
This is a signal obtained by separating a luminance signal from a video signal (a video signal from an internal tuner or the like or a video signal from the outside) obtained by the television receiver by a luminance / chroma separation circuit. Alternatively, it is a luminance signal of the video signals supplied in a state where the luminance signal and the chroma signal are separated from an external video signal source.

In the video signal processing apparatus according to the present embodiment, the broken line in FIG. 1 is a diagram of a conventional sharpness circuit. The luminance signal is input to the transversal filter 11 within the broken line, and the transversal filter 11 outputs a sharpness component. The output is weighted by a variable gain amplifier 12, and the weighted signal is added to an original luminance signal by an adder 13. At this time, the weighting coefficient of the amplifier 12 is determined by, for example, data set by a user supplied from a microcomputer (hereinafter, referred to as “microcomputer”).

When there is noise, the decorrelation detection circuit 15 discriminates the luminance signal into a section including only noise and a section including a change component of the noise and the luminance signal. Then, a negative weighting coefficient is transferred from No. 15 and noise removal processing for subtracting noise from the luminance signal is performed.

FIG. 2 shows a transversal filter 11.
3 is a specific example of the circuit shown in FIG. In FIG.
The adder 24 outputs a sharpness component between the signal delayed by the delay element 21, the signal delayed by the delay element 21 and the delay element 22, and the input luminance signal.

FIG. 3 shows the decorrelation detection circuit 15 shown in FIG.
3 is a specific example of the circuit shown in FIG. Band-pass filter (BPF) 3 of the signal obtained at input terminal 31
2 (substantially the same characteristics as the transversal filter 11 of FIG. 1) is supplied to one input terminal of the differential amplifier 33 via the resistor R1. Further, a signal obtained by dividing the power supply voltage by the resistors R2 and R3 is supplied to the other input terminal of the differential amplifier 33. In the differential amplifier 33, a resistor R4 is connected between one input terminal and the output terminal on the inversion side, and operates as a comparator. The threshold level when operating as this comparator is determined by the resistor R
2 and R3. The voltage indicating the coefficient data from the microcomputer shown in FIG.
3 is supplied to the connection point.

The non-inverted output signal of the differential amplifier 33 is supplied to the base of the transistor Q1, and the non-inverted output signal is supplied to the base of the transistor Q2. The transistors Q1 and Q2 form an emitter follower circuit in which the emitters are connected to each other, and make the output of the differential amplifier 33 an absolute value. A resistor R5 is connected between the emitters of the transistors Q1 and Q2 and the ground potential portion, and a connection point between the transistors Q1 and Q2 and the resistor R5 is connected to the base of the transistor Q3. . This transistor Q
3 and the power supply potential section are connected by a resistor R6, and a decorrelation detection signal output terminal 34 is drawn from a connection point between the transistor Q3 and the resistor R6.

FIG. 4 specifically shows a circuit example of the adder 13 shown in FIG. In the adder 13 shown in FIG. 4, a circuit example of the equalizer 42 for delay adjustment and the adder 43 is shown. The luminance signal obtained at the input terminal 41 of the equalizer 42 is transferred to a transistor Q11 that constitutes the equalizer 42.
Supply to the base. A resistor R11 is connected between the collector of the transistor Q11 and the power supply potential portion, and a resistor R12 is connected between the emitter of the transistor Q11 and the ground potential portion. One end of a resistor R13 is connected to the emitter of the transistor Q11.
Is connected to one end of the capacitor C11, and the other end of the resistor R13 and the other end of the capacitor C11 are connected to the base of the transistor Q12. A resistor R14 is connected between the transistor Q12 and the power supply potential portion, and a resistor R14 is connected between the emitter of the transistor Q12 and the ground potential portion.
15 is connected, and the output of the equalizer -42 is drawn out from the connection point between the transistor Q12 and the resistor R14.

The transistor Q11 in the equalizer 42
Constitutes a delay circuit, which is capable of adjusting a slight shift in delay time by the time constant of the capacitor C11 and the resistor R13. Then, the inversion and the gain adjustment are performed by the transistor Q12 to obtain the output of the equalizer 42.

The output of the equalizer 42 is supplied to the base of a transistor Q13 forming the adder 43. The adder 43 is an adder composed of two transistors Q13 and Q14 and resistors R16, R17, R18 and R19. The other adder signal from the transversal filter 11 is supplied from the input terminal 44 to the base of the transistor Q14. Supplied. A resistor R16 is connected between the emitter of the transistor Q13 and the ground potential, and a resistor R19 is connected between the emitter of the transistor Q14 and the ground potential.
, A series circuit of resistors R17 and R18 is connected. The output terminal 45 of the addition signal is drawn out from the connection point between the resistors R17 and R18.

FIG. 5 shows the delay elements 21 and 22 shown in FIG.
FIG. 3 is a diagram showing an example of a circuit for timing adjustment of FIG. The signal obtained at the input terminal 51 is supplied to the base of the transistor Q21. A resistor R21 is connected between the emitter of the transistor Q21 and the ground potential portion, and a connection point between the transistor Q21 and the resistor R21 is connected to the resistor R22 and the resistor R22.
Supply to the input terminal of the amplifier 53 via the C delay line 52,
The output of the amplifier 53 is supplied to an output terminal 54 of the delay element. The input terminal of the amplifier 53 is grounded via a resistor R23.

Since the delay elements 21 and 22 are configured as shown in FIG. 5, since the terminating resistor is connected to the LC delay line 52, the signal level passing through the LC delay line 52 is attenuated to 1/2. I will. In order to compensate for this attenuation, the circuit shown in FIG.

Next, the operation of the subtraction type noise reduction type sharpness circuit to which the video signal processing apparatus of the present embodiment is applied will be described with reference to the timing chart shown in FIG.
Since the operation of the sharpness is not different from the conventional sharpness, the description of the operation is omitted. FIG. 6A
5 shows an example of a change in the level of the luminance signal input to the subtraction type noise reduction type sharpness circuit. This luminance signal has a section of the horizontal synchronizing signal h in a constant cycle, and sections immediately before and after the horizontal synchronizing signal h are called front porch f and back porch b, respectively, and are sections of a constant level. . In the video information section V, the signal level is in accordance with the luminance level at that time. Here, it is assumed that the noise N is superimposed on a part of the video information section V (in the figure, the noise N is emphasized).

The luminance signal is supplied to the band-pass filter 32 in the non-correlation signal detection circuit 15 so that only the high-frequency component is passed, so that a differential waveform shown in FIG. 6B is obtained. In the signal waveform of the high frequency component, the boundary between the horizontal synchronization signal and the front porch f and the back porch b, and the boundary between the video information section V and the front porch f and the back porch b,
As the signal changes, a noise component appears.

Here, assuming that the signal shown in FIG. 6B is subtracted from the signal shown in FIG. 6A as it is, noise components can be removed as shown in FIG. 6C. This results in a signal from which the high-frequency component at the falling portion has been removed, and the signal is not suitable as a video signal. For this reason, in the present example, a decorrelation signal detection circuit 15 is provided to detect decorrelation of a signal and to control signal subtraction based on the detection. Here, the decorrelation means detecting a signal change in horizontal scanning, such as rising or falling of a flat field (a signal with a constant luminance level).

More specifically, after the signal waveform of the high-frequency component shown in FIG. 6B is rectified as shown in FIG. 6D, the signal level is at a level (1 VF) lower than the threshold level as shown in FIG. 6E. At some point, that is, during the period when the luminance signal is lower than the threshold level, a negative coefficient is set in the weighting circuit of the variable gain amplifier 12 in the sharpness circuit, the signal is subtracted from the original signal, and the signal in between is subtracted by the adder 13. Perform processing. That is, the noise component can be subtracted. By doing so, the horizontal synchronization signal and the front porch f and the back porch b
In a portion where a signal change is detected and there is no correlation, such as a boundary between the image information section V and the front porch f or the back porch b, a sharpness component is added to the signal by the adder 13. In a section where there is no signal change and there is a correlation, a noise subtraction process is executed.

FIG. 6F shows a case where the threshold level can be set to a small threshold level T1 shown by a dotted line and a case where it can be set to a large threshold level T2 shown by a solid line. This allows
In a portion where a signal change is detected and there is no correlation, such as a boundary portion between the horizontal synchronization signal and the front porch f or the back porch b, or a boundary portion between the video information section V and the front porch f or the back porch b. , The signal is added with a sharpness component by the adder 13, and in a section where there is no signal change and there is a correlation, according to the threshold level small T1 shown by the dotted line or the threshold level large T2 shown by the solid line,
A noise subtraction process is performed.

FIG. 7 is a diagram showing an example of the band of the luminance signal handled by the noise reduction type sharpness circuit to which the video signal processing device of the present embodiment is applied, and the pass band characteristics of the transversal filter 11. The horizontal axis indicates frequency, and the vertical axis indicates signal gain. When the luminance signal input to the sharpness circuit of the present embodiment has a bandwidth of about 4 MHz, the transversal filter 11 has, for example, a pass band of 2 MHz or more. In addition, the bandpass filter 32 for detecting the correlation has a filter characteristic of passing a frequency slightly lower than the passband of the transversal filter 11 and passing the same upward. The reason why the pass band of the band-pass filter 32 is set wider than that of the transversal filter 11 is to reliably detect signal non-correlation (change in signal luminance) in a wide frequency range.

Next, the noise reduction processing operation of the noise reduction type sharpness circuit to which the video signal processing apparatus of the present embodiment is applied will be described with reference to the flowchart of FIG. In FIG. 8, first, in step S101, when a luminance signal is input, band limiting processing of the transversal filter 11 is performed, and at the same time, step S10 is performed.
At 2, a decorrelation detection process is performed. Here, step S
In the non-correlation detection processing of 102, it is determined whether or not correlation is detected (large). In step S103, when it is detected that the correlation is large, it is determined that the signal component is small. The coefficient of the amplifier (AMP) is negatively selected, and the noise subtraction processing is executed in the addition processing in step S106.

In step S102, it is determined whether or not no correlation (small) is detected in the decorrelation detection process. In step S104, when it is detected that the correlation is small, it is determined that there is a signal component. Step S10 as small processing
The coefficient of the amplifier (AMP) of No. 5 is positively selected, and in step S106, the high-frequency component of the luminance signal is added and emphasized in the addition processing to increase the sharpness.

In the sharpness circuit constituted by the video signal processing apparatus of the present embodiment, the signal and the noise component can be detected by the correlation detection circuit. Therefore, the sharpness component is not added to the noise that degrades the image quality without adding the sharpness component. Can be reduced.

In the video signal processing apparatus according to the present embodiment, since the noise reduction amount can be set by the microcomputer, the noise reduction amount can be arbitrarily changed. It is also possible to have a function of ring sharpness.

By applying the above-described video signal processing apparatus of the present embodiment to noise reduction processing of a received video signal, it is possible to satisfactorily reduce white noise in a weak electric field.

[0036]

According to the video signal processing apparatus of the present invention, an input luminance signal is filtered by a transversal filter, the filtered luminance signal is multiplied by a predetermined coefficient, and a time delay generated by the transversal filter is reduced. A sharpness circuit for adjusting and adding to the original signal, and a luminance signal filtered by the transversal filter are discriminated into a section including only noise and a section including a change component of the noise and the luminance signal using a decorrelation detection process. In the section including only the noise detected by the decorrelation detection circuit, a noise removal process of subtracting the noise from the luminance signal in the sharpness circuit is performed.
With the simple configuration, it is possible to effectively remove the noise of the video signal.

Further, in the video signal processing apparatus according to the present invention, when the decorrelation detecting circuit determines that the luminance signal has no correlation and includes only noise, the coefficient in the sharpness circuit is set to a negative value. Therefore, in a section where there is no change in the luminance signal based on the correlation of the luminance signal and only the noise is present, the noise reduction processing for stopping the sharpness function and removing the noise is performed, and the noise level included in the input luminance signal is reduced over a wide band. There is an effect that it can be effectively reduced.

Further, in the video signal processing apparatus according to the present invention, when the decorrelation detecting circuit determines that the section has a correlation with the luminance signal and includes a noise and a change component of the luminance signal, Since the coefficient is set to be positive, the change in the luminance signal based on the correlation of the luminance signal is large, and in the section of the signal component, the high-frequency component of the luminance signal is added and emphasized, so that the sharpness can be improved by ordinary sharpness. It has the effect of being able to.

Further, in the video signal processing method according to the present invention, the input luminance signal is filtered by a transversal filter, the filtered luminance signal is multiplied by a predetermined coefficient, and a time delay generated in the transversal filter is adjusted. , A non-correlation that discriminates a luminance signal filtered by the transversal filter into a section including only noise and a section including noise and a change component of the luminance signal by using a decorrelation detection process. In the section of only the noise detected by the decorrelation detection processing, the noise removal processing of subtracting the noise from the luminance signal in the sharpness processing is performed. The effect that the noise of the video signal can be removed well Unlikely to.

In the video signal processing method according to the present invention, in the above-described non-correlation detection processing, when it is determined that there is no noise signal in the luminance signal without correlation, the coefficient in the sharpness processing is set to a negative value. Therefore, in a section where there is no change in the luminance signal based on the correlation of the luminance signal and only the noise is present, the noise reduction processing for stopping the sharpness function and removing the noise is performed, and the noise level included in the input luminance signal is reduced over a wide band. There is an effect that it can be effectively reduced.

Further, in the video signal processing method according to the present invention, in the above-described non-correlation detection processing, when it is determined that the section includes a correlation between the luminance signals and includes noise and a change component of the luminance signal, Since the coefficient is set to be positive, the change in the luminance signal based on the correlation of the luminance signal is large, and in the section of the signal component, the high-frequency component of the luminance signal is added and emphasized, so that the sharpness can be improved by ordinary sharpness. It has the effect of being able to.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a sharpness circuit applied to a video signal processing device according to an embodiment.

FIG. 2 is a circuit diagram showing a circuit example of a transversal filter of a sharpness circuit.

FIG. 3 is a circuit diagram illustrating a circuit example of a decorrelation signal detection circuit of the sharpness circuit;

FIG. 4 is a circuit diagram illustrating a circuit example of an equalizer and an adder of a sharpness circuit;

FIG. 5 is a circuit diagram showing a circuit example of a delay element of the transversal filter.

6 is a timing chart showing the operation of the subtraction type noise reduction circuit. FIG. 6A shows an input luminance signal, and FIG.
6C is a differential waveform of the luminance signal, FIG. 6C is a subtraction signal of the differential waveform from the luminance signal, FIG. 6D is an absolute value signal of the differential waveform, and FIG.
E is a noise subtracted signal below the threshold level (1 VF), and FIG. 6F is a differential waveform applicable to a small threshold level or a large threshold level.

FIG. 7 is a diagram illustrating an example of a luminance signal band and a pass band characteristic of a transversal filter.

FIG. 8 is a flowchart of a sharpness process.

[Explanation of symbols]

11 transversal filter, 12 amplifier, 13 adder, 14 sharpness circuit, 15
…… Decorrelation detection circuit,

Claims (6)

[Claims] 1. A sharpness filter for filtering an input luminance signal by a transversal filter, multiplying the filtered luminance signal by a predetermined coefficient, adjusting a time delay caused by the transversal filter, and adding the resultant to an original signal. And a decorrelation detection circuit for discriminating a luminance signal filtered by the transversal filter into a section including only noise and a section including a noise and a change component of the luminance signal using a decorrelation detection process. A video signal processing device that performs a noise removal process of subtracting noise from a luminance signal in the sharpness circuit in a section including only noise detected by a decorrelation detection circuit. 2. The video signal processing apparatus according to claim 1, wherein the decorrelation detecting circuit sets the coefficient in the sharpness circuit to a negative value when it is determined that the section has no correlation with the luminance signal and includes only noise. A video signal processing device. 3. The video signal processing device according to claim 2, wherein the decorrelation detecting circuit determines the coefficient in the sharpness circuit when the section has a correlation with the luminance signal and includes a noise and a change component of the luminance signal. A video signal processing device, wherein is set to be positive. 4. A sharpness process for filtering an input luminance signal by a transversal filter, multiplying the filtered luminance signal by a predetermined coefficient, adjusting a time delay caused by the transversal filter, and adding the resultant to an original signal. And a decorrelation detection process for discriminating a luminance signal filtered by the transversal filter into a section including only noise and a section including a change component of the noise and the luminance signal by using a decorrelation detection process. A video signal processing method for performing a noise removal process of subtracting noise from a luminance signal in the sharpness process in a section including only noise detected by the detection process. 5. The video signal processing method according to claim 4, wherein in the decorrelation detection processing, when it is determined that the section has only a noise without a correlation in a luminance signal, the coefficient in the sharpness processing is set to a negative value. A video signal processing method comprising: 6. The video signal processing method according to claim 5, wherein in the decorrelation detection processing, when it is determined that the section includes a correlation between luminance signals and includes noise and a change component of the luminance signal,
A video signal processing process, wherein the coefficient in the sharpness process is set to be positive.