JPH0698200A - Video signal processor - Google Patents

Abstract

PURPOSE:To stably superimpose and extract a reference signal even for a signal whose flyback period is short. CONSTITUTION:A superimposing part 10 selectively superimposes the reference signal for a gain control and for a direct current reproduction on an input video signal at every flyback period in one horizontal canning period. A first feedback control part 15 extracts the reference signal for the direct current reproduction from the output of an amplifying circuit 13, and controls the direct current reproduction of a video signal. A second feedback control part 16 extracts the reference signal for the gain control, and controls the gain of an entire processing system. The timing of the superimpose and extraction of the reference signal by the superimposing part 10 and the feedback control parts 15 and 16 is prepared by a timing generating part 17. Thus, the plural reference signals are selectively superimposed in each flyback period, so that it is possible to facilitate a countermeasure to the video signal processing of a high scanning frequency, and the stabilization and high precision of the feedback control can be attained.

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 such as a color television receiver.

[0002]

2. Description of the Related Art As a conventional video signal processing device, there is, for example, a structure shown in FIG. In FIG. 12, 128
Is a reference signal generator that generates a reference signal for controlling the brightness and contrast of the display image, 120 is a superimposing unit that superimposes the reference signal from the reference signal generating unit 128 in the blanking period of the video signal, and 121 is the video signal. , A gain control unit for controlling the contrast by controlling the amplitude of the video signal, a first direct current reproduction unit 122 for direct current reproduction of the video signal, an amplifier circuit 123 for performing various processes of the video signal, and an amplifier circuit 1
A second signal generator for extracting a reference signal for controlling the brightness from the output of 23 and controlling the first DC regenerator 122;
Reference numeral 127 denotes a first signal generator that extracts a reference signal for controlling the contrast from the output of the amplifier circuit 123 and controls the gain controller 121; and 124, a second DC regenerator that controls the cutoff level of the CRT. 125 drives the CRT and detects the cathode current, and detects the second DC regeneration unit 12
4 is a current detection unit for controlling the control unit 4.

Next, the operation of this video signal processing device will be described. The video signal is supplied by the superimposing unit 120 to the reference signal generator
The reference signal generated by 28 is superimposed on the blanking period of each video signal of GBR. The video signal processed by the amplifier circuit 123 is sampled and held by the second signal generator 126 only in the portion of the luminance level reference signal,
Based on this information, direct current regeneration is performed by the first direct current regeneration unit 122.

The output of the amplifier circuit 123 is sampled and held by the first signal generator 127 only for the contrast reference signal, and this information is used to control the gain controller 121.
Is controlled. The output of the amplifier circuit 123 is DC-regenerated by the second DC regenerator 124, and then the current detector 125 drives the CRT and is sampled and held at the same time. Based on this information, the second DC regenerator 124 is controlled to cut off. The level is kept constant.

As described above, since the brightness and the contrast are feedback-controlled by the independent reference signals, the tracking of R, G, and B can be accurately performed even when the brightness is changed, so that the chromaticity changes. There is no. Further, since the cathode current variation is monitored by the feedback control, the variation of the cathode current due to the change of the CRT characteristic with time is automatically dealt with and the variation is suppressed.

[0006]

However, in the above-mentioned conventional configuration, it is necessary to carry a plurality of reference signals within the horizontal blanking period, so that the horizontal scanning line frequency is high and the blanking period is short, such as in a computer. In the case of a signal, there is a problem that the reference signal cannot be accurately superimposed and extracted.

In view of the above point, an object of the present invention is to provide a video signal processing apparatus capable of stably superimposing and extracting a reference signal even on a signal having a short blanking period.

[0008]

A video signal processing apparatus according to claim 1, wherein a timing for selectively superimposing a plurality of reference signals on the video signal and a reference signal superposed on the video signal are selectively extracted. Timing generating means for generating a timing for performing, a superimposing means for selectively superimposing a plurality of reference signals on the blanking period of the video signal by a signal from the timing generating means, and a superimposing means for superimposing by a signal from the timing generating means. The extraction means selectively extracts the reference signal, and the control means performs the contrast control and the brightness control of the video signal by the reference signal extracted by the extraction means.

According to a second aspect of the present invention, there is provided a video signal processing device, wherein a reference signal generating means for generating a contrast reference signal for contrast control and a brightness reference signal for brightness control, and horizontal synchronizing pulses are counted for each blanking period. Timing generating means for generating the timing of superimposing and sampling the reference signal, superimposing means for selectively superimposing two reference signals in the blanking period of the video signal by the signal from the timing generating means, and this superimposing means. First feedback control means for extracting and holding a brightness reference signal from the superimposed video signal by a signal from the timing generation means and outputting a signal for controlling the clamp level of direct current reproduction, and the first feedback control means. Direct current reproduction means for performing direct current reproduction with the signal of Second feedback control means for extracting and holding the contrast reference signal and outputting a signal for controlling the gain by the signal from the ring generating means, and gain control means for controlling the gain by the signal of the second control means. Is equipped with.

A video signal processing device according to a third aspect is the video signal processing device according to the second aspect, in which the average value level of the input video signal is detected and the direct current reproduction output from the first feedback control means is performed. Is provided with clamp level correcting means for correcting the signal for controlling the clamp level according to the change of the average value level. The video signal processing device according to claim 4 is the video signal processing device according to claim 2, wherein the difference between the average value level of the input video signal and the average value level of the video signal output from the DC reproducing means is detected. However, the present invention is characterized in that clamp level correction means is provided for correcting the signal for controlling the clamp level for DC regeneration output from the first feedback control means in accordance with the change in the difference in average value level.

[0011]

According to the present invention, since a plurality of reference signals are selectively superposed on the blanking period of the video signal, only one reference signal exists in one blanking period. In addition, the reference signals do not interfere with each other and superimposition and extraction of the reference signals are easy, and stable processing can be performed even for signals with a short blanking period. In addition, it is possible to easily deal with the case where the number of types of reference signals is increased.

Further, according to the third aspect of the invention, the direct current reproduction is dynamically performed such that the clamp level control of the direct current reproduction is corrected according to the change of the average value level of the input video signal. Since it is performed, the pedestal level can be stabilized within the entire scanning period. In addition, claim 4
According to the configuration described above, the control of the clamp level of the DC reproduction is corrected according to the change in the difference between the average value level of the input video signal and the average value level of the video signal output from the DC reproduction means. As described above, since the direct current is reproduced dynamically by the feedback loop, it is possible to stabilize the pedestal level of any input video signal within the entire scanning period and perform stable video signal processing.

[0013]

Embodiments (corresponding to claims 1 and 2) A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the first of the present invention.
3 is a block diagram of a video signal processing device according to the embodiment of FIG. In FIG. 1, 14 is a reference signal generator that generates a brightness reference signal and a contrast reference signal from an external input voltage, and 17 is a timing generator that counts horizontal synchronizing signals and generates superimposition and extraction timing for each blanking period. , 10 is a superimposing section for selecting one of the brightness reference pulse and the contrast reference pulse from the reference signal generating section 14 by the timing pulse from the timing generating section 17 and superimposing it on the video signal, and 11 is a gain control for controlling the gain. , 12 is a direct current regeneration unit for performing direct current regeneration, 13 is an amplification circuit, and 15 is a direct current regeneration unit 12 for extracting and holding a brightness reference signal from the output of the amplification circuit 13 according to a timing signal from the timing generation unit 17.
The first feedback control section 16 for controlling the gain control section 16 controls the gain control section 11 by extracting and holding the brightness reference signal and the contrast reference signal from the output of the amplifier circuit 13 according to the timing signal from the timing generation section 17. A feedback control unit, A is extraction means in claim 1, and B is control means in claim 1.

The operation of the video signal processing apparatus of this embodiment constructed as described above will be described with reference to FIGS. First, the superposition unit 10 will be described with reference to FIGS. FIG. 2 shows the superposition unit 10 in FIG.
It shows the details of. Further, FIG. 3 shows operation waveforms of the superposition unit 10.

In FIG. 2, 20 is a switch for controlling the video signal a, 21 is a switch for controlling the contrast reference signal b, and 22 is a switch for controlling the brightness reference signal c. The input video signal a is set to 0 by the switch 20 only in the portion where the reference pulse is superposed on the signal d from the timing generator 17. The contrast reference signal b and the brightness reference signal c are superimposed on the 0 portion of the video signal at the timing of the signal e and the brightness reference signal c at the timing of the signal f. As a result, the contrast reference signal b and the brightness reference signal c become the video signal g which is alternately superposed every 1H in the blanking period of each of the R, G and B video signals.

Next, the first feedback control section 15 will be described with reference to FIGS. FIG. 4 shows the details of the first feedback control section 15, and FIG. 5 explains its operation. Figure 4
In FIG. 3, h is a brightness control signal for setting the brightness, 41 is a level shift unit for converting the output of the amplifier circuit 13 into a level that is easy to process, and 42 is a brightness generated by the signal from the timing generation unit 17 for the level-shifted signal. A sample and hold circuit for extracting and holding the reference signal, 43 is the extracted signal and the brightness control signal h
Is a comparator that controls the DC regenerating unit 12 so as to be equal to each other.

In the output signal i from the amplifier circuit 13, the contrast reference pulse and the brightness reference pulse are alternately superimposed every 1H in the blanking period portion. sample·
The hold circuit 42 extracts and holds the portion of the brightness reference signal at the timing of the signal j from the timing generator 17, and outputs a waveform like the signal k. Comparator 4
At 3, the peak value of the signal k and the brightness control signal h are compared and the video signal is clamped so that they are equal to each other, and the luminance is kept constant.

Next, the second feedback control section 16 will be described with reference to FIGS. 6 and 7. FIG. 6 shows the details of the second feedback control section 16, and FIG. 7 explains the operation thereof. Figure 6
In FIG. 1, 1 is a contrast control signal for setting the contrast, 60 is a level shift unit for converting the output signal i from the amplifier circuit 13 into an appropriate magnitude, and 61 is a contrast reference according to the timing generated by the timing generation unit 17. A sample and hold circuit that extracts and holds a signal, 62 is a sample and hold circuit that extracts and holds a brightness reference signal at the timing generated by the timing generator 17, and 64 is a sample and hold circuit for the outputs of the sample and hold circuits 61 and 62. A subtractor 63 that takes a difference compares a signal p output from the subtractor 64 with a contrast control signal 1 and controls the gain control unit 11 so that they are equal to each other.

The output signal i of the amplifier circuit 13 is sampled by the timing signal m from the timing generator 17.
The hold circuit 61 extracts and holds the contrast reference signal, and the timing signal j from the timing generator 17 causes the sample and hold circuit 62 to extract and hold the brightness reference signal. Then, the subtractor 64 causes the sample and hold circuits 61 and 62 to
The difference between the outputs n and o is calculated and compared with the contrast control signal 1 by the comparator 63, and the gain controller 11 is controlled so as to be equal.

As described above, since the pedestal level is set to the peak value of the brightness reference signal by the first feedback control loop, the difference between the outputs n and o of the sample and hold circuits 61 and 62, that is, the output of the subtracter 64. The change in the signal p is the change in the gain of the amplifier circuit 13, and the contrast is kept constant by comparing the output signal p of the subtractor 64 and the contrast control signal 1 and controlling the gain control unit 11 so that they become equal. Be done.

As described above, according to this embodiment, the contrast reference signal and the brightness reference signal are selectively overlapped with the blanking period of the video signal, so that one reference signal is provided in one blanking period. Since the reference signals do not interfere with each other, the reference signals can be easily superimposed and extracted, and a signal having a short retrace line period can be stably processed. In addition, it is possible to easily deal with the case where the number of types of reference signals is increased.

[Second Embodiment; Corresponding to Claims 1 and 3] Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a block diagram of a video signal processing device according to the second embodiment of the present invention. In this second embodiment, the first
6 is different from that of the first embodiment in that the clamp level includes a detection unit 81 that detects the average value level of the video signal, and an adder 80 that adds the signal from the detection unit 81 and the signal from the first feedback control unit 15. 1 is that the correction means is provided and the direct-current regeneration section 12 is dynamically controlled. The other parts are shown in FIG.
The description is omitted because it has the same configuration as.

In order to explain the operation of the video signal processing apparatus of this embodiment having the above structure,
The operation waveform diagram of FIG. 9 is used. The superimposed reference signal is omitted in FIG. In the video signal processing apparatus according to the first embodiment, when a signal having a large average value level as shown by q in FIG. 9 is applied as a video signal, a horizontal sag is generated in the waveform as shown by r in FIG. , The direct current reproduction is disturbed. This is because feedback is applied by the brightness reference signal every 2H and the clamp level for DC reproduction is determined, so that it is not possible to cope with a sudden average video signal level. In the case of a general image, such abrupt change cannot occur, so no particular problem occurs, but in the case of a video signal such as computer graphics, it can cause a problem.

In the second embodiment, in order to solve the problem of the first embodiment, the average value level of the video signal is detected by integrating the input video signal (waveform s in FIG. 9). By controlling the clamp level of the DC reproduction by canceling the horizontal sag generated in the amplifier circuit, it is possible to prevent the DC reproduction from being disturbed (waveform t in FIG. 9). However, since this correction is an open loop, external adjustment is necessary to make the horizontal sag just cancel. The waveform s in FIG. 9 is a waveform obtained by integrating the input signal q, and the waveform t is obtained by correcting the waveform r in which the DC reproduction is disturbed by the zag generated in the amplifier circuit with the waveform s.

[Third Embodiment: Corresponding to Claims 1 and 4] Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a block diagram of a video signal processing device according to the third embodiment of the present invention. In FIG. 10, 101 is a detector for detecting the average level of the difference between the input video signal and the output video signal from the amplifier circuit 13, and 100 is the output signal of the detector 101 and the control signal from the first feedback controller. This is an adder for adding and controlling the DC regeneration unit 12, and the other configuration is similar to that of the second embodiment shown in FIG.

The third embodiment is provided with a clamp level correction means consisting of the detection unit 101 and the adder 100. The difference from the second embodiment is that the detection unit 101 has an input video signal and an amplification circuit. The average level of the difference from the output video signal from 13 has been detected. In the video signal processing apparatus of this embodiment configured as described above, the operation waveform diagram of FIG. 11 is used to explain the operation thereof. In FIG. 11, the superimposed reference signal is omitted.

In FIG. 11, u is an input video signal, v is an output signal of the amplifier circuit 13, and w is an output video signal of the detector 101. Since the feedback loop is configured so that the average values of the input video signal and the output video signal are equal to each other as shown in this figure, the pedestal level can always be stabilized.
As described above, according to the third embodiment, the DC reproduction can be performed not only in the blanking period but also in the entire scanning period, so that stable video signal processing can be always performed even for a video signal whose level changes drastically. .

The first to third embodiments are examples of television receivers and do not limit the equipment in which the present apparatus is incorporated. Further, in the first to third embodiments, the timing reference of the timing generator 17 has been described using the synchronizing pulse, but it goes without saying that the retrace pulse from the deflection circuit or the like may be used as the reference.

In the first to third embodiments, the case has been described in which the brightness reference signal and the contrast reference signal are alternately superposed on the video blanking period, but the ratio of superimposing the brightness reference pulse is increased to increase the video signal. It goes without saying that it can be stabilized against changes in the average value level of. Further, in the first to third embodiments, the case where two of the brightness reference signal and the contrast reference signal are superimposed on the reference signal has been described, but it goes without saying that two or more reference signals may be used.

Further, in the second and third embodiments, the correction associated with the change of the average value level of the video signal is performed by the direct current reproducing section 12 in the preceding stage of the amplifier circuit 13, but it may be performed by other portions. Not to mention good things.

[0031]

According to the video signal processing device of the present invention, a plurality of reference signals are selectively superposed on the blanking period of the video signal. Since only the signals exist, the reference signals do not interfere with each other, the reference signals can be easily superimposed and extracted, and the signals having a short blanking period can be stably processed. In addition, it is possible to easily deal with the case where the number of types of reference signals is increased.

Further, the video signal processing apparatus according to the third aspect of the invention dynamically corrects the DC level of the DC level by correcting the clamp level control of the DC level according to the change of the average level of the input video signal. Therefore, the pedestal level can be stabilized within the entire scanning period. Also,
According to a fourth aspect of the present invention, in the video signal processing device, the clamp level of the direct current reproduction is controlled according to the change in the difference between the average value level of the input video signal and the average value level of the video signal output from the direct current reproducing means. Since dynamic DC reproduction is performed by a feedback loop such as correction, it is possible to stabilize the pedestal level of any input video signal within the entire scanning period and perform stable video signal processing.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a detailed configuration of a superimposing unit in the embodiment.

FIG. 3 is an operation waveform diagram showing an operation of a superimposing unit in the embodiment.

FIG. 4 is a block diagram showing a detailed configuration of a first feedback control unit in the embodiment.

FIG. 5 is an operation waveform diagram showing an operation of the first feedback control unit in the embodiment.

FIG. 6 is a block diagram showing a detailed configuration of a second feedback control unit in the embodiment.

FIG. 7 is an operation waveform diagram showing an operation of the second feedback control unit in the embodiment.

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

FIG. 9 is an operation waveform chart showing the operation of the detection unit in the embodiment.

FIG. 10 is a block diagram showing a configuration of a video signal processing device according to a third embodiment of the present invention.

FIG. 11 is an operation waveform diagram showing the operation of the detection unit in the embodiment.

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

[Explanation of symbols]

 A extraction means B control means 10 superposition section (superposition means) 11 gain control section (gain control means) 12 direct current regeneration section (direct current regeneration means) 13 amplifier circuit 14 reference signal generation section (reference signal generation means) 15 first feedback Control unit (first feedback control unit) 16 Second feedback control unit (second feedback control unit) 17 Timing generation unit (timing generation unit) 80 Adder (clamp level correction unit) 81 Detection unit (clamp level correction) Means) 100 adder (clamp level correction means) 101 detection unit (clamp level correction means)

Claims (4)

[Claims] 1. A timing generating means for generating timing for selectively superimposing a plurality of reference signals on a video signal and timing for selectively extracting a reference signal superimposed on a video signal, and timing generation means. Superimposing means for selectively superimposing a plurality of reference signals by the signal from the means in the blanking period of the video signal, and extracting means for selectively extracting the reference signal superimposed by the signal from the timing generating means, A video signal processing device, comprising: a control means for performing contrast control and brightness control of a video signal according to the reference signal extracted by the extraction means. 2. A reference signal generating means for generating a contrast reference signal for contrast control and a brightness reference signal for brightness control, and timing for superimposing and sampling the reference signal for each blanking period by counting horizontal synchronizing pulses. And a superimposing means for selectively superimposing the two reference signals in the blanking period of the video signal by the signal from the timing generating means, and the timing from the superimposing video signal by the superimposing means. First feedback control means for extracting and holding the brightness reference signal by the signal from the generating means and outputting a signal for controlling the clamp level of direct current regeneration, and direct current regeneration by the signal of this first feedback control means From the direct current reproduction means and the timing generation means from the superimposed video signal An image including second feedback control means for extracting and holding a contrast reference signal by the signal of (1) and outputting a signal for controlling the gain, and gain control means for controlling the gain by the signal of the second control means. Signal processing device. 3. An average value level of an input video signal is detected, and a signal for controlling a clamp level of direct current reproduction output from the first feedback control means is corrected according to the change of the average value level. 3. The video signal processing device according to claim 2, further comprising a clamp level correcting means for performing the above. 4. A DC reproduction clamp level output from the first feedback control means by detecting a difference between the average value level of the input video signal and the average value level of the video signal output from the DC reproduction means. 3. The video signal processing apparatus according to claim 2, further comprising a clamp level correction unit that corrects a signal for controlling the signal according to a change in the difference between the average value levels.