JPS63122374A - Video signal processor - Google Patents

Abstract

PURPOSE:To project a picture of an optimum contrast constantly to input video signals of different amplitudes and black levels by detecting the amplitude and the black level of the input video signal and making the amplitude and the black level of the video signal constant according to this detected signal. CONSTITUTION:The detected signals from a black level maximum value detecting circuit 31 and a black level average value detecting circuit 32 are supplied to a black level control signal forming circuit 33, the quantity of the dynamic change of the black level of the video signal is compared with the quantity of the static change to form a black level control signal suitable for the picture. Then, it is supplied to a black level control circuit 3 and the black level of the input video signal is automatically controlled. Thereby, the picture of the optimum contrast can be constantly projected to the input video signals of the different black levels and the amplitudes.

Description

[Detailed description of the invention] It is related to

BACKGROUND OF THE INVENTION FIG. 6 shows a block diagram of a conventional FFL signal processing device for a television receiver. A video signal is input to the input terminal 2°, and the contrast circuit 21 controls the gain of the video signal to control the amplitude of the video signal applied to the ORτ 26. In the image quality adjustment circuit 22, since the electron beam of the CRT 2B has a finite size, the high-frequency component of the on-screen optical output signal decreases, so the deterioration of the high-frequency component is corrected. In order to perform correct color reproduction, the DC component reproducing circuit 23 performs DC component reproduction so that the pedestal level of the signal does not change due to the average brightness (APL) of the video signal. Further, in the DC component regeneration circuit 23, the brightness is adjusted by changing the DC potential that provides the pedestal level. In the video amplifier circuit 24, CRT25fr
, the video signal is amplified to excite it, and the CRTi is driven.

Problems to be Solved by the Invention However, in the above configuration, the contrast circuit 21 . Since the amplitude and brightness adjustment means of the DC component reproducing circuit 23 are fixed at a certain set level, when the amplitude and black level of the input video signal fluctuate as in general broadcasting, the contrast circuit 21. There is a problem in that the optimum image quality, that is, gradation, contrast, and brightness cannot be obtained unless the set level of the DC component regeneration circuit 23 is changed.

In view of this, an object of the present invention is to provide a video signal processing device that can always display an optimal image even if the amplitude and black level of an input video signal vary.

Means for Solving the Problems The present invention provides black level detection means for detecting the black level in a video signal, black level constant means for keeping the black level in the video signal constant using the black level detection signal, and The present invention is a video signal processing device including an amplitude detection means for detecting the amplitude of the video signal from the black level constant means, and an amplitude constant means for making the amplitude of the video signal constant using the amplitude detection signal.

Effect of the present invention With the above-described configuration, the amplitude and black level of the input video signal are detected, and the amplitude and black level of the video signal are made constant using this detection signal. It is possible to always project an image with the optimum contrast even on objects.

Embodiment FIG. 1 shows a basic conceptual diagram of a video signal processing apparatus according to the present invention. In FIG. 1, 1 is an input terminal for inputting a video signal, 2 is a black level detection circuit for detecting the black level in the video signal, and 3 is for controlling the black level of the video signal using the black level detection signal. Black level control circuit, 4
F! , an amplitude detection circuit that detects the amplitude of the signal from the black level control circuit, 5 an amplitude control circuit that controls the amplitude of the video signal using the amplitude detection signal, and e an output terminal.

The input/output characteristic diagram of FIG. 2 will be used to explain the operation of the video signal processing device having the basic concept configured as described above. When a video signal with a floating black level is supplied to the input terminal 1 as shown by the solid line in FIG. 3 to control the black level to the normal level. Further, the amplitude detection circuit 4 detects the amplitude of the video signal from the black level from the black level control circuit 3, and supplies this detection signal to the amplitude control circuit 6, so that the amplitude of the video signal is kept constant. It is controlled to be constant. Therefore, the video signal outputted from the output terminal 6 is a video signal in which the black level and the amplitude of the video signal are set normally, as shown by the broken line in FIG. 2C. Second
Similarly, when a video signal with a depressed black level is supplied to the input terminal 1 as shown by the solid line in the figure, the black level detection circuit 2
and the amplitude detection circuit 4 detects the black level and amplitude, and supplies this detection signal to the black level control circuit 3 and the amplitude control circuit 6 to control the black level and amplitude, as shown by the broken line in Figure 2. A video signal whose black level and video signal amplitude have been properly set is output from the output terminal 6. Similarly, when the amplitude of the video signal is small as shown by the solid line in FIG. By controlling the amplitude to be constant, a video signal whose amplitude is set normally as shown by the broken line C in FIG. 2 is output to the output terminal 6.
is output from. Since the subsequent operation is the same as that described above for supplying the signal to the input terminal in FIG. 6, the explanation will be omitted.

As described above, even if the black level and amplitude of the input video signal vary, a regular video signal is always output.

As described above, the black level and amplitude of the video signal are detected,
By keeping the black level and amplitude of the video signal constant using this detection signal, it is possible to always project an image with the optimal contrast even when the input video signal has a different black level and amplitude. There was a drawback that the image was distorted due to variations in level and amplitude.

Therefore, in the present invention, a first loop detects and controls the maximum black level and amplitude of the video signal, and a second loop detects and controls the average black level and amplitude of the video signal. The above-mentioned drawbacks are solved by controlling with a double loop configuration.

FIG. 3 shows a block diagram of a video signal processing device according to a first embodiment of the present invention.

In FIG. 3, 32 is a black level average value detection circuit that detects the average value of the black level within the effective display area of the input video signal from the input terminal 1, and 31 is the effective display area of the signal from the black level control circuit 3. 33 is a black level control signal generating circuit that generates a black level control signal from the black level maximum value detection signal and the black level average value detection signal; 34; 355 is an amplitude maximum value detection circuit that detects the maximum value of the amplitude of the signal from the amplitude control circuit 6; and 355 is an amplitude average value detection circuit that detects the average value of the amplitude of the signal from the black level control circuit 3.

The operation of the video signal processing device of this embodiment configured as described above will be described below. First, let's talk about black level control. The input video signal from the input terminal 1 is supplied to a black level average value detection circuit 32, and the average black level within the effective display area of the video signal is detected. That is, the black level average value detection circuit 32 extracts static black level fluctuations of the input video signal. The video signal whose black level has been controlled from the black level control circuit 3 is supplied to a black level maximum value detection circuit 31, and the blackest shadow within the effective display area of the video signal is produced.

That is, the maximum black level detection circuit 32 extracts dynamic black level fluctuations of the input video signal.

The detection signals from the black level maximum value detection circuit 31 and the black level average value detection circuit 32 are supplied to a black level control signal generation circuit 33, which detects the dynamic amount of change and the static amount of change in the black level of the video signal. A black level control signal suitable for the image is created by comparing the two.

The black level control signal from the black level control signal generation circuit 33 is supplied to the black level control circuit 3, and the black level of the input video signal is automatically controlled. Next, the amplitude side will be described. The signal from the amplitude control circuit 5 is supplied to the maximum amplitude value detection circuit 34, and the maximum amplitude level of the video signal is detected. That is, the maximum amplitude value detection circuit 34 extracts the dynamic amplitude fluctuations of the video signal accompanying the black level control and the dynamic amplitude fluctuations of the input video signal. The signal from the black level control circuit M3 is supplied to an amplitude average value detection circuit 35, and the average level of the amplitude of the video signal is detected. In other words, amplitude average value detection port @3
6, static amplitude fluctuations of the video signal are extracted. The detection signals from the amplitude maximum value detection circuit 34 and the amplitude average value detection circuit 36 are sent to the amplitude control signal generation circuit 36.
The dynamic and static changes in the amplitude of the video signal are compared to create an amplitude control signal suitable for the image. The amplitude control signal from the amplitude control signal generation circuit 36 is supplied to the amplitude control circuit 6,
The amplitude of the video signal is automatically controlled.

Next, in order to explain in more detail, a specific circuit shown in FIG. 4 and a waveform diagram shown in FIG. 5 will be used. Input terminal 1 is shown in Figure 6a.
As shown in the figure, a video signal with a raised black level is input.

The input video signal is supplied to the clamp circuit 7, and is clamped by applying a clamp pulse shown in FIG. 6 to the input terminal 17. The unclamped video signal is supplied to an extraction circuit 1o to detect the black level, and a pulse having a timing period shown in FIG. The signal shown in Figure d is output. The average value detection circuit 11 detects the average level of the black level within the display area from the signal from the extraction circuit 1o.

Similarly, the signal from the black level control circuit 3 is output to the extraction circuit 8.
All the signals of only the effective display area of the video are extracted, and the maximum value detection circuit 9 detects the blackest level within the display area.

The detection signals from the maximum value detection circuit 9 and the average value detection circuit 11 are supplied to a comparator 12, which compares and weights the black level maximum value detection signal and the black level average value detection signal. , a signal suitable for the amount of change in black level and response speed is output.

The comparison output from the comparator 12 is supplied to a limiter circuit 13, and after being limited within a predetermined range, it is sent to a black level control circuit 3.
is supplied to The black level control circuit 3 supplies the input terminal 18 with a pulse having the timing shown in FIG. It is held at a DC potential. Therefore, as shown in FIG. 6f, the black level control circuit 3 outputs a video No. 6 in which the black level within the effective display area of the video signal is equal to the pedestal level. The signal from the black level control circuit 3 is supplied to an amplitude control circuit 6, and the amplitude is controlled. The maximum level of the signal amplitude of the signal from the amplitude control circuit 6 is detected by the amplitude maximum value detection circuit 34. Further, the average level of the signal amplitude of the signal from the black level control □□ circuit 3 is detected by an amplitude average value detection circuit 36.

The detection signal from the amplitude average value detection circuit 36 is supplied to the addition circuit 14, which adds the detection signal and the reference potential. The signals from the adding circuit 14 and the maximum amplitude detection circuit 34 are supplied to the comparator 16, which compares and weights the maximum amplitude detection signal and the average detection signal, thereby determining the amount of change in amplitude and the response speed. A suitable signal is output. Comparison output UIJ transmitter circuit 16 from the comparator 16
is supplied to the amplitude control circuit 6 after being limited within a predetermined range.
is supplied to Therefore, the amplitude control circuit 6 outputs from the output terminal 6 a video signal with an amplitude v2 from the black level, that is, a video signal equal to the amplitude of the input video signal, as shown in FIG. The same operation is performed when the level sinks.

As described above, according to this embodiment, control can be performed according to the average black level signal and the average amplitude signal from the average fixed point level detection circuit 20 and the average value amplitude detection circuit 21.
When the black level and amplitude of the video signal suddenly change, it is possible to suppress the sudden change in the black level and amplitude of the video signal, and always display an image with the optimum contrast.

As described in detail, according to the present invention, even when input video signals have different black levels and amplitudes, contrast,
It is possible to automatically display an image with the optimum contrast without having to adjust the brightness, which has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of a video signal processing device according to an embodiment of the present invention, Fig. 2 is an operational characteristic diagram of the embodiment, Fig. 3 is a block diagram of the embodiment, and Fig. 4 is the embodiment. FIG. 6 is an operational waveform diagram for explaining its operation, and FIG. 6 is a block diagram of a conventional video signal processing device. 3... Black level control circuit, 6... Amplitude control circuit, 31... Black level maximum value detection circuit,
32... Black level average value detection circuit, 33...
. . . Black level control signal generation circuit, 34 . . . Maximum amplitude detection circuit, 36 . . . Average amplitude detection circuit, 36 . . . . Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure! Figure 2 Grave Level Table Level 3 Figure Craftsmanship Bell Techniques and Circuits Demand is Bankede Circuit-P
N樗Figure 5

Claims (1)

[Claims] a black level control means for controlling the black level of the video signal; an amplitude control means for controlling the amplitude of the video signal from the black level control means; and a maximum black level within the effective display area of the signal from the black level control means. black level maximum value detection means for detecting a black level average value, black level average value detection means for detecting an average value of black levels within an effective display area of the input video signal, the black level maximum value detection means and the black level average value black level control signal generating means for generating a black level control signal from the black level detection signal from the detecting means; input means for inputting the black level control signal from the black level control signal generating means into the black level controlling means; , amplitude maximum value detection means for detecting the maximum value of the signal amplitude from the amplitude control means, amplitude average value detection means for detecting the average value of the signal amplitude from the black level control means, and the amplitude maximum value detection means; An amplitude control signal generating means for generating an amplitude control signal from the amplitude detection signal from the amplitude average value detecting means, and an input means for inputting the amplitude control signal from the amplitude control signal generating means to the amplitude controlling means. Video signal processing device.