JPH0662278A - Video signal processor - Google Patents

Abstract

PURPOSE:To provide a video signal processor for performing contour correction processing by enlarging gradient at the contour part of a video signal without excessively adding undershoot and overshoot. CONSTITUTION:A control signal generating circuit 40 detects the undershoot and overshoot parts of the video signal which contour is corrected by a contour correcting circuit 20. At this detected part, the gain of a contour correcting signal is adjusted with a coefficient different from the other part by a contour correcting circuit 30 and thus, the contour correcting signal is provided corresponding to the video signal.

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 device for correcting a contour portion of a video signal.

[0002]

2. Description of the Related Art Conventionally, in a color television signal transmission system, the sharpness of an image reproduced by a receiver is lowered because the transmission band is limited. For example,
In the NTSC system, the luminance signal band is 0 to 4.2 [MHz]
Is restricted to. Therefore, even when the image is taken with an ideal image pickup tube, the signal at the time of black-and-white change of the luminance signal does not become sharper than a certain value at the rising and falling slopes of the signal on the receiver, and the contour part on the screen It looks a little blurry.

In order to improve such image blurring,
In recent years, in a video signal processing device, contour correction is performed by forming a secondary differential signal using a delay circuit and adding it to the original signal.

A conventional video signal processing device will be described below. FIG. 12 shows a block diagram of a conventional video signal processing device. In FIG. 12, 1 is a video signal input terminal, 21a and 21b are delay circuits for delaying the signal for a predetermined time, 22, 23 and 24 are multipliers, 25 and 27 are adders, and 26 is a contour correction level. The gain adjuster 2 is an output terminal. FIG. 13 shows operation waveforms at points a to i shown in FIG.

The operation of the video signal processing device configured as described above will be described with reference to FIGS. 12 and 13. First (FIG. 12), the video signal input from the input terminal 1 is supplied to the delay circuit 21a and the multiplier 22. The output signal of the delay circuit 21a is the delay circuit 21b and the multiplier 23.
And to the adder 27. The output signal of the delay circuit 21b is supplied to the multiplier 24. For example, input terminal 1 (point a)
When the video signal having the waveform of (FIG. 13 (a)) is input to (FIG. 13 (b)), (FIG. 13 (c)), the output signals of the delay circuits 21a and 21b (signals at points b and c) are )become that way.

The input video signal and the output signals of the delay circuits 21a and 21b (the signals at points a, b and c) are respectively multiplied by multipliers.
Supplied to 22, 23, 24. If the coefficients of the multipliers 22, 23, 24 are Ka = -1, Kb = 2, Kc = -1, the output signals of the multipliers 22, 23, 24 (signals at points d, e, f) are ( 13 (d)), (FIG. 13 (e)),
(Fig. 13 (f)). These three signals are added to the adder 25, and as a result, the output signal of the adder 25 (the signal at point g) is a signal waveform obtained by quadratic differentiation of the original signal as shown in FIG. 13 (g). Become.

The output signal of the adder 25 is adjusted in amplitude by the gain adjuster 26 with an arbitrary gain, and then added to the adder 27. For example, assuming that the gain is 2, the output signal of the gain adjuster 26 (the signal at the point h) is as shown in FIG. 13 (h). The output signal of the gain adjuster 26 is added to the adder 27 together with the output signal of the delay circuit 21a, and the output signal of the adder 27 (the signal at point i) is corrected for the contour as shown in FIG. 13 (i). The output signal 2 is output from the output terminal 2.

In the conventional video signal processing apparatus configured as described above, a signal with a sharp edge portion is obtained, and edge correction is performed.

[0009]

However, in the above-mentioned conventional configuration, undershoot and overshoot are added to improve the sharpness due to the effect of increasing the gradient of the contour portion, but if it is excessively performed, the contour portion of the image is There was a problem that the unnaturalness of the added white and black borders was conspicuous.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a video signal processing apparatus which makes a contour portion steep and corrects the contour without excessively adding an undershoot and an overshoot. To do.

[0011]

SUMMARY OF THE INVENTION A first invention is a signal level detection circuit for detecting a maximum signal level and a minimum signal level from an input video signal, and first and second contour corrections for processing the input video signal. A circuit and a control signal generation circuit for generating a control signal corresponding to the waveform of the contour-corrected video signal from the respective output signals of the first contour correction circuit and the signal level detection circuit.

A second invention is a signal level detection circuit for detecting a maximum signal level and a minimum signal level from an input video signal, first and second contour correction circuits for processing the input video signal, and the first invention. A control signal generation circuit for generating a control signal corresponding to the waveform of the contour-corrected video signal from the respective output signals of the contour correction circuit and the signal level detection circuit, and detecting the amplitude of the contour from the signal level detection circuit. A contour amplitude detecting circuit for generating a control signal corresponding to the level and a switching circuit for receiving the input video signal and the respective output signals of the second contour correcting circuit are provided.

[0013]

According to the first aspect of the present invention, with the above configuration, the amplitude value of the contour correction signal is adjusted with an arbitrary gain when the control signal generating circuit detects undershoot or overshoot. As a result, it is possible to make the contour portion steep and reduce the unnaturalness of the contour portion of the image without excessively adding undershoot and overshoot.

According to the second aspect of the invention, when the control signal generating circuit detects undershoot or overshoot, the amplitude value of the contour correction signal is adjusted with an arbitrary gain. Also, the contour amplitude detection circuit detects the contour amplitude value, and when the detected contour amplitude value is larger than a predetermined value, the contour-corrected video signal is output using the gain-adjusted contour correction signal. In other cases, the original video signal is output. This makes it possible to sharpen the contour portion without excessively adding undershoot and overshoot to reduce the unnaturalness of the contour portion of the image, and to correct the portion with a small amplitude value of the contour. No noise will be emphasized because no.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a video signal processing device in a first embodiment of the present invention.
In FIG. 1, 1 is a video signal input terminal, 10 is a signal level detection circuit, 20 is a first contour correction circuit, 30 is a second contour correction circuit, 40 is a control signal generation circuit, and 2 is an output terminal. Is.

The operation of the video signal processing apparatus configured as described above will be described. First, the video signal input from the input terminal 1 is detected by the signal level detection circuit 10, the first contour correction circuit 20, and the second contour. It is supplied to the correction circuit 30. The output signals of the signal level detection circuit 10 and the first contour correction circuit 20 are supplied to the control signal generation circuit 40. The output signal of the control signal detection circuit 40 is supplied to the control terminal of the second contour correction circuit 30, and the output signal of the second contour correction circuit 30 is output from the output terminal 2.

The signal level detection circuit 10 is constructed, for example, as shown in FIG. The input signal to the signal level detection circuit 10 is delayed by the delay circuits 11a, 11b, 11c and 11d at predetermined time intervals. Each delay circuit 11a, 11b, 11c, 11d
The output signal and the input signal to the signal level detection circuit 10 are supplied to the maximum signal level detection circuit 12, and the maximum signal level is detected. Similarly, each delay circuit 11a, 11b, 11c, 11d
The output signal and the input signal to the signal level detection circuit 10 are also supplied to the minimum signal level detection circuit 13 to detect the minimum signal level. These detection signals are supplied to the control signal generation circuit.

The first contour correction circuit 20 and the second contour correction circuit 30 are constructed, for example, as shown in (FIGS. 3A and 3B). Gain adjuster 36 of second contour correction circuit 30
The configuration is basically the same as that shown in the conventional example except that the output signal of the control signal generation circuit 40 is supplied to the gain control terminal of. Alternatively, the first contour correction circuit
The second contour correction circuit 20 and the second contour correction circuit 30 are used in common, for example, as shown in FIG. Here (Fig. 3)
An example of the configuration shown in FIG.

The control signal generation circuit 40 is constructed, for example, as shown in FIG. The maximum signal level and the output signal of the first contour correction circuit 20 are supplied to the comparator 41, and the amplitude values are compared. Similarly, the minimum signal level and the output signal of the first contour correction circuit 20 are supplied to the comparator 42 to compare the amplitude values. The output signals of the comparators 41 and 42 are supplied to the coefficient generator 43, and the output signals thereof are supplied to the gain control terminal of the gain adjuster 36 of the second contour correction circuit 30.

The operation of the video signal processing device having the above construction will be described with reference to the waveform chart of FIG. First, for example, when the video signal shown in FIG. 6 (a) is input to the input terminal 1, the video signal is delayed by the delay circuits 11a and 11a of the signal level detection circuit 10.
The output signals (signals at points b, c, d, and e) delayed by b, 11c, and 11d are (Fig. 6 (b),
As shown in (c), (d) and (e). The input video signal and the output signals (signals at the points a, b, c, d, and e) of the delay circuits 11a, 11b, 11c, and 11d are supplied to the maximum signal level detection circuit 12 and the minimum signal level detection circuit 13, respectively. Signal level (Fig. 6 (f)) and minimum signal level (Fig. 6)
(G)) is detected.

The input video signal supplied to the first contour correction circuit 20 has a gain of, for example, the coefficients of the multipliers 21a, 21b and 21c set to Ka = -1, Kb = 2 and Kc = -1. When the setting value is 2, the output signal of the adder 25 (the signal at the point h) becomes as shown in FIG. 6 (h), and the gain adjuster
The output signal of 26 (the signal at point i) is as shown in FIG. 6 (i). This signal is added by the adder 27 to the output signal of the delay circuit 21b (similar to the signal at the point c), and the added output (j
The point) becomes a signal as shown in (FIG. 6 (j)). The input video signal supplied to the second contour correction circuit 30 is processed in the same manner, and at the point m, a signal having the same waveform as the signal at the point h is obtained.

The control signal generation circuit 40 receives the maximum signal level, the minimum signal level, and the signal contour-corrected by the first contour correction circuit 20, and adds the signal to the input video signal by the first contour correction circuit 20. Undershoot and overshoot parts are detected and a predetermined coefficient is output. First, the input maximum signal level (signal at point f) and the output signal of the first contour correction circuit 20 (signal at point j) are supplied to the comparator 41 and their amplitude values are compared. For example, if the output signal of the first contour correction circuit 20 (the signal at the point j) is higher than the maximum signal level (the signal at the point f), "1" is output, and otherwise "0". If “” is output, the output signal of the comparator 41 (the signal at the k point) is as shown in FIG. 6 (k).

Similarly, the minimum signal level (signal at point g)
And the output signal of the first contour correction circuit 20 (the signal at the point j) is supplied to the comparator 42 and the amplitude values are compared. For example, the first
If the output signal of the contour correction circuit 20 (the signal at the point j) is lower than the minimum signal level (the signal at the point g), "1"
Is output and "0" is output in all other cases, the comparator 42 outputs the signal (Fig. 6 (l)). The output signals of the comparators 41 and 42 (the signals at the k and l points) are supplied to the coefficient generator 43. The coefficient generator 43 outputs a coefficient K for setting the gain of the gain adjuster 36 of the second contour correction circuit 30 in accordance with the output signals (signals at points k and l) of the comparator 41 and the comparator 42.

The coefficient generator 43 sets the coefficient K to K = 0.5 in the case of (k = “1” and l = “0”) or (k = “0” and l = “1”), and otherwise. If K = 2 in the case of, in this case, the output signal of the adder 35 (signal at point m)
Is a partially different coefficient in the gain adjuster 36 (K = 0.5 in the chute part, K = 2 in other rising parts, etc.)
The gain is adjusted by and the contour correction signal as shown in FIG. 6 (n) is obtained at the n point. This signal is added by the adder 37 to the output signal of the delay circuit 31b (similar to the signal at point c),
The contour-corrected video signal (FIG. 6 (o)) is output from the output terminal 2.

The manner in which the contour is corrected will be described with reference to FIG. 7 (FIG. 7). The contour correction device described in the conventional example performs contour correction by adding a contour correction component to an input video signal, and the correction amount is controlled by adjusting the amplitude of this correction component with an arbitrary gain. (Fig. 7
As shown in (a), the larger the gain is set, the steeper the signal waveform in the rising period becomes, and at the same time, the amount of undershoot and overshoot added increases.

However, if excessively performed, white or black edging cannot be ignored with respect to the original image in a fine image or a portion where the amplitude of the contour is small, and image unnaturalness becomes conspicuous. Therefore, the video signal processing apparatus according to the present embodiment independently adjusts the gains of the correction component of the undershoot and overshoot when added to the input video signal and the rising period, and adds the gain to the input video signal. To do. Therefore, as shown in FIG. 7B, the amount of undershoot and overshoot added is suppressed while the signal waveform in the rising period remains steep.

As described above, according to the first embodiment of the present invention, the undershoot detected by the control signal generating circuit 40 and the gain of the overshoot portion are adjusted by a coefficient different from those of the other portions, so that the undershoot occurs. It is possible to make the contour portion steep without excessively adding an overshoot and reduce the unnaturalness of the contour portion of the image.

FIG. 8 shows a block diagram of a video signal processing apparatus in the second embodiment of the present invention. (Fig. 1)
The configuration is basically the same as that of the first embodiment of the present invention shown in FIG. 2, except that the contour amplitude detection circuit 50 which receives the output signal of the signal level detection circuit 10 as an input, the input video signal and the second
That is, a switching circuit 60 is added which receives the output signal of the contour correction circuit 30 and is controlled by the output signal of the contour amplitude detection circuit 50.

The operation of the video signal processing device having the above construction will be described with reference to the waveform chart of FIG. Second contour correction circuit
The detailed operation until obtaining the output signal of 30 (FIG. 9 (o)) is the same as that described in the first embodiment of the present invention.

The contour amplitude detection circuit 50 is composed of a subtracter 51 and a comparator 52 as shown in FIG. 10, for example, and has the maximum signal level (signal at the point f) input to the contour amplitude detection circuit 50. The minimum signal level (signal at point g) is subtracted by the subtractor 51 and the subtraction output (FIG. 9 (p)) is supplied to the comparator 52. This signal is a threshold value T preset by the comparator 52.
It is compared with h and a signal indicating the comparison result is output. For example, if the output signal of the subtracter 51 (the signal at the point p) is larger than Th, "1" is output, and otherwise, "1" is output.
Assuming that 0 "is output, the output signal (q
The signal at the point) is as shown in FIG. 9 (q). This signal is used as the output signal of the contour amplitude detection circuit 50 and the switching circuit 60
It is supplied to the control terminal of.

The switching circuit 60 is composed of a timing adjuster 61 and a selector 62, for example, as shown in FIG. In the switching circuit 60, the output signal of the contour amplitude detection circuit 50 (signal at point q) is used as a control signal, and when q = 1, the output signal of the second contour correction circuit 30 (signal at point o) is switched to, and q When = 0, the timing adjuster 61
It switches to the input video signal that is timed with the signal at the point and outputs it. That is, the output signal of the subtracter 51 (the signal at the p point) represents the amplitude value of the contour, and this value is T
If it is larger than h, the signal is switched to the contour-corrected signal, and in other cases, the signal is switched to the contour-uncorrected signal, and the signal shown in FIG. 6 (r) is output from the output terminal 2.

As described above, according to the second embodiment of the present invention, the undershoot detected by the control signal generating circuit 40 and the gain of the overshoot section are adjusted by a coefficient different from those of the other sections. , It is possible to make the contour portion steep without excessively adding an overshoot, reduce the unnaturalness of the contour portion of the image, and further, when the amplitude change of the contour is small, correction is not performed. No noise is emphasized.

In the first embodiment of the present invention, the output signal of the contour amplitude detecting circuit 50 is also supplied to the coefficient generator 43 of the control signal generating circuit 40 to consider the magnitude of the contour amplitude value. You may set a coefficient.

In the first and second embodiments of the present invention, the image signal is extracted in the horizontal direction, but the present invention is not limited to this. For example, the image signal may be extracted in the vertical direction or the oblique direction. . Further, in detecting the maximum signal level and the minimum signal level, the image signals at the positions of five points arranged in the horizontal direction are selected, but the predetermined direction and the number of points may be set. Further, the number of generated coefficients is not limited to two, and various kinds may be set according to the magnitude of the amplitude value of the shoot part, or undershoot and overshoot may be set independently. Absent.

[0035]

As described above, according to the first invention, the signal level detection circuit for detecting the maximum signal level and the minimum signal level from the input video signal, and the first and second signal processing circuits for processing the input video signal are provided. By providing a contour correction circuit and a control signal generation circuit that generates a control signal corresponding to the waveform of the contour-corrected video signal from the output signals of the first contour correction circuit and the signal level detection circuit, undershoot It is possible to make the contour portion steep without excessively adding an overshoot and reduce the unnaturalness of the contour portion of the image.

According to the second invention, a signal level detection circuit for detecting the maximum signal level and the minimum signal level from the input video signal, and first and second contour correction circuits for processing the input video signal, A control signal generation circuit that generates a control signal corresponding to the waveform of the contour-corrected video signal from the output signals of the first contour correction circuit and the signal level detection circuit; and the contour amplitude is detected from the signal level detection circuit. However, by providing a contour amplitude detection circuit that generates a control signal corresponding to the level and a switching circuit that receives the input video signal and the output signal of the second contour correction circuit as input, undershoot and overshoot can be prevented. In addition to making the contour part steep without adding too much, it is possible to reduce the unnaturalness of the contour part of the image.
Further, since the correction is not performed when the change in the amplitude of the contour is small, noise or the like is not emphasized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a video signal processing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a signal level detection circuit.

FIG. 3A is a configuration diagram of a first contour correction circuit, and FIG. 3B is a configuration diagram of a second contour correction circuit.

FIG. 4 is a configuration diagram when a contour correction circuit is shared.

FIG. 5 is a configuration diagram of a control signal generation circuit.

FIG. 6 is an operation waveform diagram of the first embodiment of the present invention.

7A is a characteristic diagram for explaining how the contour is corrected; FIG. 7B is a characteristic diagram for explaining how the contour is corrected according to the present embodiment.

FIG. 8 is a configuration diagram of a video signal processing device according to a second embodiment of the present invention.

FIG. 9 is an operation waveform diagram of the second embodiment of the present invention.

FIG. 10 is a configuration diagram of a contour amplitude detection circuit.

FIG. 11 is a configuration diagram of a switching circuit.

FIG. 12 is a block diagram of a conventional video signal processing device.

FIG. 13 is an operation waveform diagram of a conventional example.

[Explanation of symbols]

 10 signal level detection circuit 20 first contour correction circuit 30 second contour correction circuit 40 control signal generation circuit 50 contour amplitude detection circuit 60 switching circuit 70 contour correction circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Ueda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hideaki Yamauchi, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A signal level detection circuit for detecting a maximum signal level and a minimum signal level from an input video signal, first and second contour correction circuits for processing the input video signal, and the first contour correction circuit. And a control signal generation circuit that generates a control signal corresponding to the waveform of the contour-corrected video signal from each output signal of the signal level detection circuit, and the correction amount of the second contour correction circuit is generated by the control signal generation circuit. A video signal processing device characterized by performing contour correction according to a waveform of a video signal by controlling with an output signal of a circuit. 2. A signal level detection circuit for detecting a maximum signal level and a minimum signal level from an input video signal, first and second contour correction circuits for processing the input video signal, and the first contour correction circuit. And a control signal generation circuit for generating a control signal corresponding to the waveform of the contour-corrected video signal from each output signal of the signal level detection circuit, and the amplitude of the contour is detected from the signal level detection circuit to correspond to the level. A contour amplitude detection circuit that generates a control signal and a switching circuit that receives the input video signal and each output signal of the second contour correction circuit are provided, and the correction amount of the second contour correction circuit is controlled by the control circuit. By controlling the output signal of the signal generating circuit, contour correction according to the waveform of the video signal is performed, and the switching circuit is controlled by the output signal of the contour amplitude detecting circuit. A video signal processing apparatus characterized by switching and outputting a signal corresponding to the amplitude level of the contour by the. 3. The switching circuit switches to the output signal of at least the second contour correction circuit when the amplitude value of the contour is larger than a predetermined value according to the output signal of the contour amplitude detection circuit, and adjusts the timing otherwise. 3. The video signal processing device according to claim 2, wherein the input video signal is switched to another input video signal. 4. The contour amplitude detection circuit includes a subtractor that takes a difference between a maximum signal level and a minimum signal level, and a first comparator that compares an output signal of the subtractor with a predetermined value. The video signal processing device according to claim 2. 5. A signal level detection circuit, a maximum signal level detection circuit for detecting a maximum signal level from output signals of a plurality of delay circuits for delaying an input video signal at predetermined time intervals, and outputs of the plurality of delay circuits. 3. A video signal processing device according to claim 1, further comprising a minimum signal level detection circuit for detecting the minimum signal level from the signal. 6. The control signal generating circuit comprises a second comparator for comparing the maximum signal level with the contour-corrected video signal, and a third comparator for comparing the minimum signal level with the contour-corrected video signal. And a coefficient generator that detects a shoot portion of the contour-corrected video signal from the output signals of the second and third comparators and outputs a predetermined coefficient. The described video signal processing device.