JPH07298096A - Gamma correction circuit - Google Patents

Abstract

PURPOSE:To provide a video display device of the PIP system in which gamma correction is separately applied to a main image and a sub-image. CONSTITUTION:The circuit is made up of a main analog signal processing section 1 applying analog signal processing to a main video signal, a main A/D converter section 2 implementing A/D conversion, an analog sub-signal processing section 4 applying analog signal processing to a video sub-signal, a digital signal processing section 3 receiving a digital signal from the main A/D converter section 2 at one input terminal and receiving a digital signal from a sub A/D converter section 5 at the other input terminal, a changeover section 11 connecting to an output of the digital signal processing section 3, a main gamma correction circuit 9 connecting to one output of the changeover section 11, a sub gamma correction circuit 15 connecting to the other output of the changeover section 11, a main APL detection section 7 detecting an average luminance of a main video image, a main correction table 8, a sub-APL detection section 13 detecting the average luminance of the video sub-signal and a correction sub-table 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gamma correction circuit for a main image and a sub image in a picture-in-picture type image display device.

[0002]

2. Description of the Related Art A program of a desired genre is broadcast by allowing a plurality of channels to be simultaneously viewed on a single television receiver or by changing a channel of a child image without changing a current program of a parent image. There is a picture-in-picture method (hereinafter referred to as PIP method) in which a sub-screen is displayed on the main screen for the purpose of searching whether or not it is present. As the input of the PIP method,
It is possible to use the main image as a video and the sub image as an antenna, the main and the sub as the video, and the use of two tuners as the main and sub antennas. As shown in FIG. 3, the composite video signal of the main image is input from the antenna, demodulated by the analog signal processing unit 1 for the main image, and A by the main A / D conversion unit 2.
A / D-converted and input to the digital signal processing unit 3, a sub-video composite video signal is demodulated by the sub-video analog signal processing unit 4, and A / D-converted by the sub-A / D conversion unit 5 to obtain a digital signal. It is input to the processing unit 3 and the output of the main A / D conversion unit 2 is input to the Y encoder 6 for gamma-correcting the main video signal. For example, a luminance signal level distribution for one frame is obtained and encoded. Then, the APL detection circuit 7 detects the average luminance of the luminance signal, the correction table 8 selects an appropriate correction coefficient corresponding to the average luminance, and inputs the correction coefficient to the gamma correction circuit 9, and A signal from the switching unit 11 switched by the read switching controller 10 is input to the gamma correction circuit 9 from the digital signal processing unit 3, and the gamma correction circuit 9 performs gamma correction to perform a gamma correction. It was configured to output to the display device of Ma Display like. However, the conventional P
Since the gamma correction of the IP screen was performed based on the video content of the main video, as shown in FIG. 4 (A), only the main video is displayed on the screen 31, or as shown in FIG. 4 (B). When the sub video 32 is displayed in the main video screen 31, there is no particular problem as long as the average luminance levels of the main video and the sub video are about the same. For example, as shown in FIG. When the average luminance level of the main image becomes extremely low compared to the average luminance level of the sub image, there is a problem that the screen of the sub image becomes darker accordingly. If the average luminance level of 1 is extremely higher than the average luminance level of the sub-image, the problem is that the screen of the sub-image becomes brighter accordingly.

[0003]

As described above, the PIP in which the gamma correction is performed based on the image content of the main image.
In the case of the screen of the system, there is a disadvantage that the brightness of the screen is controlled by the main image and the sub-image screen becomes difficult to see. Therefore, the present invention separately gamma-corrects the main image and the sub-image. An object of the present invention is to provide a PIP type video display device that enables the above.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a picture-in-picture type video display device for generating and displaying a sub-screen on a main screen. Main analog signal processing unit for processing and main A / D for A / D converting the analog signal
A conversion unit, a sub-analog signal processing unit that performs analog signal processing on the sub-video signal, a sub-A / D conversion unit that performs A / D conversion on the analog signal, and one input of the digital signal of the main A / D conversion unit. Input to the terminal and the other input terminal to the sub A /
A digital signal processing unit for inputting a digital signal of the D conversion unit, a switching unit connected to the output of the digital signal processing unit and switched by a switching signal of the digital signal processing unit, and connected to one output of the switching unit. The main gamma correction circuit includes a main gamma correction circuit, a sub gamma correction circuit connected to the other output, a main APL detection unit that detects the average luminance of the main image, and a correction coefficient according to the average luminance. A main correction table to be input to the sub video signal, a sub APL detection unit for detecting the average luminance of the sub video signal, and a correction coefficient according to the average luminance of the sub video signal, and the sub correction input to the sub gamma correction circuit. A table, and the output of the main gamma correction circuit and the sub gamma correction circuit is switched by a switching signal of the digital signal processing unit and is taken out as a video signal. And wherein the door.

[0005]

With the above-described structure, the R, G, and B primary color signals from the analog signal processing unit, which are separated into the luminance signal and the color signal for each of the main image and the sub image, are processed by the A / D conversion unit. The A / D-converted signal is stored in the digital signal processing unit, and the Y encoder encodes the luminance signal level of the original signal from the digital R, G, B signals and inputs it to the APL circuit. Video data output from the switching unit by detecting the average luminance value of the detected signal, correcting data based on the detected result is selected from the correction table and gamma correction is performed, and stored in the digital signal processing unit. Are switched by a switching signal from the digital signal processing unit, gamma-corrected by the main and sub-gamma correction circuits, and output as video data. .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gamma correction circuit according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of essential parts of an embodiment of a gamma correction circuit according to the present invention. In the figure,
1 is a main analog signal processing unit which inputs a composite video signal on the main video side and separates it into a luminance signal and a color signal,
The signals are converted into Y-R, Y-B, and Y signals, and converted into R, G, and B primary color signals. Reference numeral 2 is a main A / D conversion unit, and the R, G,
The B primary color signal is converted into, for example, a digital signal of about 8 bits, and the converted output is input to the main input terminal of the digital signal processing unit 3. 4 is a sub-analog signal processing unit,
A composite video signal on the sub-picture side is input, separated into a luminance signal and a color signal, converted into YR, YB, and Y signals and converted into R, G, and B primary color signals. 5 is a sub A / D
The conversion unit converts the R, G, and B primary color signals into, for example, a digital signal of about 8 bits, and inputs the converted output to the main input terminal of the digital signal processing unit 3. A main Y encoder 6 receives the output of the main A / D converter 2 and encodes it to generate a luminance signal, and a main APL circuit 7 detects the average level of the luminance signal. A main correction table 8 has a correction coefficient and is stored in the main gamma correction circuit 9. A sub Y encoder 12 includes the sub A / D converter 5
The sub-APL circuit 13 detects the average level of the luminance signal and the correction table 14 has a correction coefficient and is stored in the sub-gamma correction circuit 15. The digital signal processing unit 3 generates a switching signal from the switching signal output terminal 10, inputs the switching signal to the switching control terminal 16 of the switching unit 11, and outputs one video output of the switching unit 11 to the main gamma correction circuit. 9 and the video output of the other is input to the sub gamma correction circuit 15, one of the switching signals is input to the output control terminal 17 of the main gamma correction circuit, and the other is inverted in polarity by the inverter 15. The output is the output control terminal 1 of the sub-gamma correction circuit.
8 and the outputs of the main gamma correction circuit 9 and the sub gamma correction circuit 15 are switched and displayed on the PIP screen. The setting unit 19 inputs into the digital signal processing unit 3 the display setting position and size of the sub-picture input from a setting terminal device (not shown) such as a remote controller or a keyboard.

Next, the operation of the gamma correction circuit having the above configuration will be described. The output of the sub A / D conversion unit 5 is thinned out at a predetermined ratio, the screen is reduced, and then written in the other video memory (not shown) of the digital signal processing unit 3. The digital signal processing section 3 is operated according to the setting data of the sub-screen display position (usually the right or left point of the upper end of the sub-picture screen in the output picture screen) inputted from the setting section 19 such as a remote controller or a keyboard. The output of the screen of the video and the sub video is switched, and one of the switching signals is input to the output control terminal 17 of the main gamma correction circuit and the other is input to the inverter 15, and the inverted output of the inverter 15 is corrected to the sub gamma correction. It is input to the output control terminal 18 of the circuit, and the gamma-corrected outputs of the main gamma correction circuit 9 and the sub-gamma correction circuit 15 are switched and displayed at a predetermined position on the PIP screen.

Main APL detector 7 and sub APL detector 1
3, the A / D-converted luminance data for one frame is divided into necessary pixels and input, and the pixels are thinned out to, for example, 1/16, and the luminance data levels of the respective pixels are added. By dividing by, it can be expressed as a plurality of bits of integrated luminance data. Also, APL
The detection circuits 7 and 13 compare the value of the luminance integrated data with the set value to compare the average level of the luminance for each frame with the set luminance level, and the data based on the comparison result is used in the correction table 8 And 14 are output. The correction tables 8 and 14 select the corresponding data from the correction table based on the output data from the APL circuit. For example, when the result detected by the APL circuit is the brightest, a binary 11111 is output. Then
When it is the darkest, 00000 is output to the upper address of the gamma correction circuit. The digital signal processing unit 3 stores the main video and the sub video data, reads the respective video data at a predetermined timing and outputs them to the switching unit 11, and the switching unit 11 outputs the switching signal of the digital signal processing unit 3. The video data from the switching unit 11 is switched based on the input data to the main gamma correction circuit 9 and the sub gamma correction circuit 15, and the gamma correction is performed based on the respective correction data. Correction circuit 15
Output is switched based on the switching signal from the digital signal processing unit 3 and is output to the lower address of the gamma correction circuit. In this way, a predetermined address is selected by the luminance data input to the lower address of the gamma correction circuit and the correction data from the correction table input to the upper address, and the preset correction is applied to the main and sub addresses. It is output as a screen on the PIP screen.

FIG. 2 is a diagram of a PIP screen by the gamma correction circuit having the above-mentioned configuration. FIG. 2A shows a case where only the main image is displayed on the screen 31, and FIG.
Is a diagram in which a sub-picture screen 32 is displayed in the main picture screen 31. In this case, if the luminance levels of the main and sub-pictures are the same, no particular problem occurs, but, for example, , If the average luminance level of the main image suddenly becomes lower than the average luminance level of the sub-image, in the conventional case, the screen of the sub-image becomes darker accordingly. Since the sub-picture is gamma-corrected independently of the main picture as in C), it means that the screen of the sub-picture remains bright. It is also possible to reverse the main video and the sub-video by designating the switching of the main video and the sub-video by the setting unit 19 to form a PIP screen in which the main video in the conventional sub-video screen is inserted. Becomes

[0010]

As described above, in the gamma correction circuit according to the present invention, the main image and the sub-image are separately subjected to gamma correction, so that the brightness of each screen can be made appropriate. The screen becomes easier to see. Also,
Since it is possible to reverse the main video and the sub-video and create the PIP screen in which the main video in the conventional sub-video screen is inserted, the flexibility of screen creation is increased.

[Brief description of drawings]

FIG. 1 is a block diagram of a gamma correction circuit according to the present invention.

FIG. 2 is an explanatory diagram of a screen of a gamma correction circuit according to the present invention.

FIG. 3 is a block diagram of a conventional gamma correction circuit.

FIG. 4 is an explanatory diagram of a screen of a conventional gamma correction circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Analog signal processing unit 2 A / D conversion unit 3 Digital signal processing unit 4 Block for generating sub-picture signal 5 A / D conversion unit 6 Encoder 7 APL circuit 8 Decoder 9 Gamma correction circuit

Claims (2)

[Claims] 1. In a picture-in-picture type video display device for generating and displaying a sub-screen on a main screen, a main analog signal processing section for analog-signal processing a main video signal, and an A / D converter for processing the analog signal. Main A / D for D conversion
A conversion unit, a sub-analog signal processing unit that performs analog signal processing on the sub-video signal, a sub-A / D conversion unit that performs A / D conversion on the analog signal, and one input of the digital signal of the main A / D conversion unit. Input to the terminal and the other input terminal to the sub A /
A digital signal processing unit for inputting a digital signal of the D conversion unit, a switching unit connected to the output of the digital signal processing unit and switched by a switching signal of the digital signal processing unit, and connected to one output of the switching unit. The main gamma correction circuit includes a main gamma correction circuit, a sub gamma correction circuit connected to the other output, a main APL detection unit that detects the average luminance of the main image, and a correction coefficient according to the average luminance. A main correction table to be input to the sub video signal, a sub APL detection unit for detecting the average luminance of the sub video signal, and a correction coefficient according to the average luminance of the sub video signal, and the sub correction input to the sub gamma correction circuit. A table, and the output of the main gamma correction circuit and the sub gamma correction circuit is switched by a switching signal of the digital signal processing unit and is taken out as a video signal. Gamma correction circuit, wherein the door. 2. The gamma correction circuit according to claim 1, wherein the main image can be a sub-screen and the sub-image can be a main screen.