JP2910883B2 - Video signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention processes a video signal to display the video signal using a liquid crystal panel or a cathode ray tube.
The present invention relates to a video signal processing device .

[0002]

2. Description of the Related Art Conventionally, in various video display devices,
In order to display an image in an optimal state, a method of correcting characteristics unique to each image display device according to the level of an input signal or the like has been performed. In particular, a video display device using a transmissive or projection type liquid crystal panel can provide a bright display, and has been used as a display device instead of a cathode ray tube in a direct-view type liquid crystal television receiver or a projection type liquid crystal projection device. I have.

However, a liquid crystal panel has a narrower input voltage range capable of expressing a gradation than a cathode-ray tube, and thus tends to cause underexposure and overexposure. FIG. 2 shows the transmittance with respect to the applied voltage (V) of the liquid crystal panel, and the portion corresponding to ΔV of the electro-optical characteristics of the liquid crystal is the range of the input voltage. In order to cope with the problem that the width of the applied voltage that can be applied as such an input voltage is narrow, in a liquid crystal display device, AGC is applied to an input video signal in accordance with an input video level to control contrast, In some cases, video control such as brightness and gamma correction is performed to improve the image quality.

[0004]

The above conventional video signal processor
In the physical device, the screen area for extracting the video level detection signal which is the basis for controlling the video is set to the area of the normal screen (aspect ratio 4: 3), so that the landscape screen (aspect ratio 16: 9) In this video, black areas are formed on the upper and lower sides, and when such a video signal is input as a video level detection signal, it affects the detected video level, and there is a problem that appropriate video control is not performed.

[0005]

In order to solve the above-mentioned problem, the present invention detects a peak value, an average value, a black peak value, and a pedestal level value of a luminance signal of an input video signal at predetermined time intervals. A video signal processing device for controlling a contrast value, a brightness value or a gamma value of a video based on the detection data, a screen detection area setting means for specifying a detection area of a screen for detecting each of the detection data; Screen detection means for detecting whether the screen aspect ratio of the video signal is a normal screen or a landscape screen, and controlling the screen detection area setting means based on the screen information detected by the screen detection means to set the detection area to normal. Control means for switching between a screen and a landscape screen is provided.

[0006]

According to the above arrangement, when an input video signal is supplied, the screen detecting means detects screen information indicating whether the input video signal is a normal screen or a landscape screen from the luminance signal of the input video signal. Based on this screen information, a detection area for detecting each detection data optimal for the screen is set by the screen detection area setting means. Therefore, even if the input video signal is switched between the normal screen and the landscape screen, the optimum detection area is always set on the screen of the input video signal, and the peak value and the average value of the luminance signal of the input video signal are set from this detection area. , Black peak value, pedestal level value and the like are detected. Then, based on each of the detected data, the input video signal is corrected in accordance with the characteristics of the video display device.

[0007]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, an input video signal supplied from an input terminal T is sampled, quantized and converted into an 8-bit digital signal by an analog-to-digital (A / D) conversion circuit 1 and then converted to a Y / Y signal. The image signal is separated into a luminance signal Y and a chroma signal C by a C separation circuit 2, and further subjected to various kinds of video signal processing such as synchronization separation and demodulation by a video signal processing circuit 3, to thereby produce R, G, B signals and a horizontal synchronization signal H− The SYNC and the vertical synchronization signal V-SYNC are derived. The R, G, and B signals are corrected by an R, G, and B control circuit 14 according to a control signal described later, and supplied to a liquid crystal panel 15 to display an image.

In FIG. 3, reference numeral 4 denotes a screen area setting circuit used for detecting the luminance signal Y. The detection area of the video signal is controlled by a control signal from a landscape screen detection circuit 20 which will be described later.
(B) Set in the shaded area. That is, when the landscape screen detection circuit 20 determines that the input video signal is of a landscape screen, the screen area setting circuit 4 sets the detection area within the display area of the landscape screen shown by oblique lines in FIG. If the input video signal is determined not to be that of a horizontally long screen, it is determined that the input video signal is that of a normal screen, so that the screen area setting circuit 4 sets the detection area as shown in FIG. As shown by the diagonal lines, the display area is enlarged to the display area of the normal screen beyond the display area of the landscape screen.

In a detection area different between the landscape screen and the normal screen set by the screen area setting circuit 4, the peak value, the average value, and the black level of the luminance signal Y are respectively a peak detection circuit 5, an average value detection circuit 6, The pedestal level is detected by a pedestal detection circuit 8.

The peak value, average value, and black level of the luminance signal Y detected by the peak detection circuit 5, the average value detection circuit 6, and the black level detection circuit 7 are corrected by a pedestal level detection circuit 8 by a correction operation circuit 9. According to the derived pedestal level, a correction operation is performed to a true video signal level excluding the synchronization signal level, and the operation result is stored in the peak data register 10, the average value register 11, and the black level data register 12, respectively.

The peak value, average value, and black level of the luminance signal Y derived from the peak data register 10, the average value register 11, and the black level data register 12 are supplied to an image control operation circuit 13. In step 13, a control signal such as a contrast control signal, a brightness control signal, or a gamma correction control signal for correcting the R, G, and B signals in accordance with the characteristics of the liquid crystal panel 15 is calculated. It is supplied to the control circuit 14 to correct the R, G, B signals.

On the other hand, a landscape screen detection circuit 20 surrounded by a dashed line detects that the input video signal is a landscape screen with an aspect ratio of 16: 9, and the detected output signal is a video signal processing circuit 3. Are supplied to the screen area setting circuit 4 together with the horizontal synchronizing signal H-SYNC and the vertical synchronizing signal V-SYNC derived from a synchronizing signal separating circuit (not shown). The setting is made so as to be performed in an area suitable for a vertically long screen as shown by the diagonal lines in FIG. 3B described above. Set to be performed in an area suitable for the screen.

Next, the landscape screen detection circuit 20 will be described. The luminance signal Y separated by the Y / C separation circuit 2
Are guided to a screen area setting circuit 34 for setting an area for detection of the luminance signal Y, and a detection area,
Is set. That is, the above-mentioned detection area is formed in the upper part and the lower part of the display screen, and its position is provided outside the horizontal screen display area shown by the dotted line in the center part of the display screen.

Then, the peak value, black level and average value of the luminance signal Y are calculated for each of the detection areas shown in FIG.
24 and average value detection circuits 25 and 26, and each of these detection outputs is corrected by the correction operation circuit 27 in accordance with the pedestal level detected by the pedestal level detection circuit 37 in the same manner as in the case of the correction operation circuit 9 above. The outputs are peak data registers 28, 29, black level data registers 30, 31, and average value data register 32, respectively.
Write 33.

The peak data and the black level data from the peak data registers 28 and 29 and the black level data registers 30 and 31 are supplied to a coincidence detecting circuit 38, and the coincidence detecting circuit 38 generates a white peak for each of the detection areas. It is detected that the level coincides with the black peak level, and the average value data in the detection area from the average value data registers 32, 32 is led to an average video level determination circuit 35, and the average video level determination circuit 35 At 35, it is detected that the average level data is, for example, 5% or less.

The detection outputs of the coincidence detection circuit 34 and the average video level determination circuit 35 are output from the landscape screen determination circuit 3 respectively.
6, when the white peak level coincides with the black peak level in both the detection areas and the average value level data satisfies the above condition, the landscape screen determination circuit 36 determines that the landscape screen is the landscape screen, and If the condition is not satisfied, it is determined that the screen is not a landscape screen but a normal screen.

The judgment output of the landscape screen discrimination circuit 36 is guided to the screen area setting circuit 4 as a control signal. When the screen setting circuit 4 determines that the screen is a landscape screen, the detection area of the luminance signal is plotted. 3 (b) is set in the shaded area, and when it is determined that the screen is not a landscape screen, that is, in the case of a normal screen, the area is set in the shaded area in FIG. 3 (a).

[0018]

According to the present invention as described in the foregoing, the peak value of the luminance signal of the input video signal detected in order to correct the input image signal, the average value, the black level of the peak value
And the detection area of the pedestal level can be optimized by switching between the horizontal screen and the normal screen. It is possible to always perform optimal video control.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is an electro-optical characteristic diagram of a liquid crystal panel.

FIG. 3 is an explanatory diagram of a signal detection area according to the present invention.

FIG. 4 is an explanatory diagram of a detection area used for screen detection according to the present invention.

[Explanation of symbols]

 4, 34 screen area setting circuit 5 peak detection circuit 6 average value detection circuit 7 black level detection circuit 13 video control operation circuit 14 R, G, B control circuit 20 landscape screen detection circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 7/015 H04N 7/00 A

Claims (1)

(57) [Claims] A peak value, an average value, a black peak value, and a pedestal level value of a luminance signal of an input video signal are detected at predetermined intervals, and a contrast value, a brightness value, or a gamma value of the video is determined based on the detected data. In the video signal processing device which is controlled, a screen detection area setting means for specifying a detection area of a screen for detecting each of the detection data, and whether a screen aspect ratio of the input video signal is a normal screen or a landscape screen And a control means for controlling the screen detection area setting means based on the screen information detected by the screen detection means to switch the detection area between a normal screen and a landscape screen. Video featuring
Signal processing device.