WO2009128201A1

WO2009128201A1 - Video signal processor and display device

Info

Publication number: WO2009128201A1
Application number: PCT/JP2009/001181
Authority: WO
Inventors: 大竹隆太郎; 太田義人; 小林隆宏
Original assignee: パナソニック株式会社
Priority date: 2008-04-18
Filing date: 2009-03-17
Publication date: 2009-10-22

Abstract

A motion judgment circuit (2) outputs a motion judgment signal indicating whether each portion of video is a still region or a motion region. When the motion judgment signal indicates the still region and when the motion judgment signal indicates the motion region and the magnitude of a motion vector is equal to or less than a threshold value, an overdrive circuit (6) does not bring a liquid crystal display panel (200) under overdrive control or reduces the correction amount. When the motion judgment signal indicates the motion region and the magnitude of the motion vector is more than the threshold value, the overdrive circuit (6) brings the liquid crystal display panel (200) under the overdrive control.

Description

Video signal processing device and display device

The present invention relates to a video signal processing device and a display device including the same.

Generally, a liquid crystal display panel is used for various display devices such as a television receiver, a monitor device, and a mobile phone. However, the liquid crystal display panel has a characteristic that the response speed of the video display with respect to the gradation change of the video signal is slow. Therefore, an afterimage is generated when a moving image is displayed.

Therefore, when the gradation of the video signal increases, the driving voltage of the liquid crystal display panel is set higher than the value corresponding to the gradation, and when the gradation of the video signal decreases, the driving of the liquid crystal display panel is performed. The voltage is set lower than the value corresponding to the gradation. Such driving is called overdrive. Overdrive improves the response characteristics of the liquid crystal display panel and can reduce afterimages (see, for example, Patent Document 1).
JP-A-6-189232

However, when an image is displayed on the liquid crystal display panel by overdrive, noise on the screen is also emphasized. As a result, the quality of the video deteriorates.

An object of the present invention is to provide a video signal processing device capable of improving the response speed of video display without enhancing noise, and a display device including the same.

(1) A video signal processing device according to an aspect of the present invention is a video signal processing device that processes an input video signal, and is a unit region that includes a predetermined number of pixels based on the input video signal. A detection unit that detects a motion vector every time, and the gradation of the video signal that is output when the gradation of the input video signal rises to be higher than the gradation after the rise of the input video signal The video signal is corrected so that the gradation of the video signal is corrected and the gradation of the output video signal is lower than the gradation after the decrease of the input video signal when the gradation of the input video signal is lowered. And a control unit that controls the correction amount by the correction unit based on the motion vector detected by the detection unit.

In the video signal processing apparatus, a motion vector is detected for each unit area by the detection unit based on the input video signal. When the gradation of the input video signal increases, the gradation of the video signal is adjusted by the correction unit so that the gradation of the output video signal becomes higher than the gradation after the input video signal increases. It is corrected. When the gradation of the input video signal falls, the gradation of the video signal is adjusted by the correction unit so that the gradation of the output video signal is lower than the gradation after the fall of the input video signal. It is corrected. In this case, the correction amount by the correction unit is controlled by the control unit based on the detected motion vector.

For the still image part, the size of the motion vector is zero. For the moving image portion, the magnitude of the motion vector is large. Further, the motion vector cannot be detected for the noise portion. Therefore, by controlling the correction amount by the correction unit based on the motion vector, it is possible to improve the response speed of video display without enhancing noise.

(2) The control unit performs gradation correction by the correction unit in the first case where the magnitude of the motion vector detected by the detection unit is larger than a predetermined threshold value, and is detected by the detection unit. When the magnitude of the motion vector is equal to or smaller than the threshold value or the motion vector cannot be detected in the second case, the correction by the correction unit is not performed or the correction amount by the correction unit is the first correction You may control a correction | amendment part so that it may become small compared with quantity.

In this case, in the first case where the magnitude of the motion vector is larger than the threshold value, the target unit area is regarded as a moving image portion, and the change in the gradation of the output video signal is emphasized. On the other hand, in the second case where the magnitude of the motion vector is less than or equal to the threshold value or the motion vector cannot be detected, the target unit region is regarded as a still image part or a noise part, The change in gradation of the output video signal is not emphasized or the degree of enhancement is reduced. As a result, it is possible to reliably improve the response speed of video display without enhancing noise.

(3) The video signal processing device further includes a determination unit that determines a still region and a motion region of the video based on a change in the value of a corresponding pixel of the plurality of frames, and the control unit determines the stillness determined by the determination unit Regardless of the detection result of the detection unit, the correction unit is controlled so that gradation correction by the correction unit is not performed or the correction amount by the correction unit is smaller than the correction amount in the first case. May be.

In this case, the still area and the motion area of the video are determined by the determination unit based on the change in the value of the corresponding pixel in the plurality of frames. For the static region, regardless of the motion vector, the control unit corrects the gradation so that the correction unit does not perform gradation correction or the correction amount by the correction unit is smaller than the correction amount in the first case. Be controlled.

Thereby, when the motion vector cannot be detected, when the accuracy of the motion vector is low, or when the motion vector is erroneously detected, it is possible to reliably prevent the gradation change in the still region from being emphasized. As a result, the video quality is improved.

(4) The control unit sets a target unit region in one frame among the plurality of frames and sets a plurality of candidate unit regions in other frames, and the difference between the target unit region and the corresponding pixel in each candidate unit region Calculates the sum of values as difference data, selects a candidate unit area corresponding to the smallest difference data among a plurality of candidate unit areas, and detects a motion vector based on the position of the target unit area and the selected candidate unit area May be.

In this case, the destination unit region of the target unit region or the source unit candidate region is determined by pattern matching. Thereby, a motion vector can be detected with a relatively small amount of data and simple processing.

(5) The control unit may determine the accuracy of the motion vector detected by the detection unit, and may control the correction unit so that the correction amount by the correction unit decreases as the accuracy of the determined motion vector decreases.

In this case, the lower the accuracy of the motion vector, the smaller the correction amount by the correction unit. Therefore, the possibility that the gradation change is emphasized based on the erroneously detected motion vector can be reduced. As a result, it is possible to prevent the video quality from being degraded.

(6) The control unit sets a target unit region in one frame among a plurality of frames and sets a plurality of candidate unit regions in other frames, and each pixel of the target unit region corresponds to each candidate unit region. Calculate the sum of the difference values with the pixel as difference data, select a candidate unit area corresponding to the smallest difference data among a plurality of candidate unit areas, and based on the position of the target unit area and the selected candidate unit area A motion vector may be detected, and the accuracy of the motion vector may be determined based on difference data corresponding to the selected candidate unit region.

Also, the smaller the difference data between the attention candidate unit area and the selected candidate unit area, the higher the accuracy of the motion vector. Therefore, it is possible to easily determine the accuracy of the motion vector based on the difference data corresponding to the selected candidate unit region.

(7) The control unit may change the correction amount by the correction unit based on the direction of motion of each unit area obtained from the motion vector detected by the detection unit.

In this case, it is possible to further improve the quality of the video by utilizing the fact that the human visual characteristics differ depending on the direction of movement of the object.

(8) A display device according to another aspect of the present invention includes a video signal processing device that processes an input video signal, and a display panel that displays video based on the video signal output from the video signal processing device. The video signal processing apparatus includes: a detection unit that detects a motion vector for each unit area configured by a predetermined number of pixels based on an input video signal; and a case where the gradation of the input video signal increases. Output when the gradation of the video signal is corrected and the gradation of the input video signal is lowered, while correcting the gradation of the video signal so that the gradation of the output video signal is higher than the gradation after the rising of the input video signal. The correction unit corrects the gradation of the video signal so that the gradation of the input video signal is lower than the gradation after the falling of the input video signal, and the correction unit based on the motion vector detected by the detection unit Control the amount of correction It is obtained by a that the control unit.

In this display device, a video is displayed on the display panel based on the video signal output from the video signal processing device. Therefore, it is possible to improve the response speed of displaying the moving image portion without enhancing noise.

According to the present invention, it is possible to improve the response speed of video display without enhancing noise.

FIG. 1 is a block diagram showing a configuration of a display device according to a first embodiment. FIG. 2 is a diagram showing the concept of motion determination by the motion determination circuit. FIG. 3 is a diagram showing the concept of motion vector detection by the motion vector detection circuit. FIG. 4 is a schematic diagram showing an example of a video block dividing method. FIG. 5 is a schematic diagram showing a method for calculating difference data. FIG. 6 is a diagram for explaining the operation of the overdrive controller. FIG. 7 shows an example of the function f (MV). FIG. 8 is a flowchart showing the operation of the overdrive controller. FIG. 9 is a block diagram showing the configuration of the overdrive circuit. FIG. 10 shows an example of the correction value table. FIG. 11 is a diagram showing an example of the gradation of the video signal of the previous frame, the video signal of the current frame, and the corrected video signal of the current frame. FIG. 12 shows an example of a candidate block setting method. FIG. 13 is a diagram illustrating another example of a candidate block setting method. FIG. 14 is a diagram illustrating an example of a motion vector detection method. FIG. 15 is a diagram illustrating an example of a motion vector detection method. FIG. 16 is a diagram illustrating an example of a motion vector detection method. FIG. 17 is a diagram for explaining the operation of the overdrive controller 5. FIG. 18A shows an example of the function g (DFD) of the control signal CT, and FIG. 18B shows another example of the function g (DFD) of the control signal CT. FIG. 19 is a flowchart showing the operation of the overdrive controller. FIG. 20 is a block diagram showing the configuration of the overdrive circuit in the display device according to the third embodiment.

(1) First Embodiment (a) Overall Configuration and Operation of Display Device FIG. 1 is a block diagram showing a configuration of a display device according to a first embodiment.

The display device shown in FIG. 1 includes a video signal processing device 100 and a liquid crystal display panel 200. The video signal processing apparatus 100 includes a motion detection unit 10 and an overdrive unit 20.

The video signal VD0 is input to the video signal processing apparatus 100. The video signal VD0 includes, for example, a red video signal (R), a green video signal (G), and a blue video signal (B). The value of the video signal VD0 represents gradation. The value of the video signal VD0 corresponds to the luminance of the pixel of the liquid crystal display panel 200. Hereinafter, the video signal VD0 input to the video signal processing apparatus 100 is referred to as a current frame video signal.

The motion detection unit 10 includes a frame memory 2, a motion determination circuit 2, and a motion vector detection circuit 3. The overdrive unit 20 includes a frame memory 4, an overdrive controller 5, and an overdrive circuit 6.

The frame memory 1 stores the video signal VD1 of the current frame. As a result, the video signal VD0 of the previous frame is output from the frame memory 1.

Based on the input current frame video signal VD1 and the previous frame video signal VD0 output from the frame memory 1, the motion determination circuit 2 determines whether each part of the video on one screen is a still area or a motion area. Determine. Each part of the video may be one pixel or a block composed of a plurality of pixels. The motion determination circuit 2 outputs a motion determination signal SM indicating a motion region or a still region.

The motion vector detection circuit 3 detects the motion vector of each block of the video of one screen based on the video signal VD1 of the current frame input and the video signal VD0 of the previous frame output from the frame memory 1. The motion vector indicates the moving direction and size of each moving image portion between the previous frame and the current frame. The motion vector detection circuit 3 outputs the detected motion vector MV.

The frame memory 4 stores the video signal VD1 of the current frame. As a result, the video signal VD0 of the previous frame is output from the frame memory 4.

The overdrive controller 5 outputs a control signal CT based on the motion determination signal SM output from the motion determination circuit 2 and the motion vector MV output from the motion vector detection circuit 3. The control signal CT will be described later.

The overdrive circuit 6 is based on the current frame video signal VD1, the previous frame video signal VD0 output from the frame memory 4, and the control signal CT output from the overdrive controller 5, and the current frame video signal. Correct VD1. The corrected video signal VD2 is output from the overdrive circuit 6 to the liquid crystal display panel 200. The liquid crystal display panel 200 displays a video based on the corrected video signal VD2.

(B) Concept of Motion Determination FIG. 2 is a diagram showing the concept of motion determination by the motion determination circuit 2. An example of the image of the previous frame is shown on the left side of FIG. 2, and an example of the image of the current frame is shown on the right side.

In the video in Figure 2, the house is stationary and the sun is moving to the right. In the image of the previous frame, noise n appears on the roof of the house.

The motion determination circuit 2 calculates the difference value between the video signal of the current frame and the video signal of the previous frame for each pixel, and determines that the pixel is a still region when the difference value is equal to or less than a predetermined threshold value. If the difference value is larger than the threshold value, the pixel is determined to be a motion region. Note that, for each block composed of a plurality of pixels, it may be determined whether the pixel of the block is a static region or a motion region.

According to the motion determination by the motion determination circuit 2, in the current frame image on the right side of FIG. 2, the shaded area is determined as a still area and the white portion is determined as a motion area. Thus, the noise n portion is determined to be a motion region.

(C) Concept of Motion Vector Detection FIG. 3 is a diagram showing the concept of motion vector detection by the motion vector detection circuit 3. An example of the image of the previous frame is shown on the left side of FIG. 3, and an example of the image of the current frame is shown on the right side.

In the video in Figure 3, the house is stationary and the sun is moving to the right. In the image of the previous frame, noise n appears on the roof of the house.

The motion vector detection circuit 3 detects a motion vector for each block composed of a predetermined number of pixels. In this case, the block of the previous frame that matches the block of interest of the current frame is detected by comparing the block of interest of the current frame with the entire range of the previous frame or each of a plurality of blocks within the predetermined range. Here, the target block refers to a block to be processed. The above operation is referred to as searching for the previous frame based on the current frame.

動き Calculate the motion vector from the block detected in the previous frame to the target block in the current frame. A motion vector is calculated for each block in the current frame while shifting the block of interest in the current frame.

Note that the current frame may be searched based on the previous frame. That is, the block of the current frame that matches the block of interest of the previous frame is detected by comparing the block of interest of the previous frame with the entire range of the current frame or each of a plurality of blocks within the predetermined range. To the motion vector detected from the current frame may be calculated. In this case, a motion vector is calculated for each block of the current frame while shifting the block of interest in the previous frame.

In the example of FIG. 3, the block BL1 of the previous frame matches the block BL2 of the current frame. Thereby, it is determined that the block BL1 of the previous frame has moved to the block BL2 of the current frame, and a motion vector MV1 from the block BL1 to the block BL2 is calculated.

On the other hand, in the current frame, there is no block that matches the block BL3 including noise n in the previous frame. Therefore, in the current frame, no motion vector is detected for the block BL3 in which the noise n of the previous frame exists.

(D) Motion Vector Detection Method Here, the details of the motion vector detection method by the motion vector detection circuit 3 will be described.

FIG. 4 is a schematic diagram showing an example of a video block dividing method. As shown in FIG. 4, the image of the previous frame and the image of the current frame are divided into a plurality of blocks. Each block is composed of a predetermined number of pixels such as 4 × 4 pixels, 4 × 8 pixels, 8 × 8 pixels, and the like.

In FIG. 4, each block is represented by a horizontal X coordinate and a vertical Y coordinate on the screen. For example, the coordinates of the upper left block of the screen are (X, Y) = (0, 0). The coordinates of the target block BL (3, 2) indicated by diagonal lines in the current frame are (3, 2).

The motion vector detection circuit 3 performs difference data described below between the block of interest BL (3, 2) of the current frame and each of the blocks in the entire range or a predetermined range (hereinafter referred to as a detection range) of the previous frame. Calculate the DFD. Hereinafter, a block to be compared with the block of interest is referred to as a candidate block.

In this example, difference data DFD (0, 0) to DFD (M, N) between the target block BL (3, 2) of the current frame and the candidate blocks BL (0, 0) to BL (M, N) of the previous frame. ) Respectively. Here, M is the X coordinate of the rightmost block in the detection range, and N is the Y coordinate of the lowermost block in the detection range. The motion vector detection circuit 3 selects the minimum difference data from the calculated difference data DFD (0, 0) to DFD (M, N), and the selected difference data is equal to or less than a predetermined threshold value. In this case, the candidate block of the previous frame corresponding to the difference data is determined to be the block from which the target block of the current frame is moved. Then, the motion vector detection circuit 3 calculates the direction and distance from the position of the movement source block to the position of the target block as a motion vector.

For example, if the difference data DFD (6, 0) between the target block BL (3, 2) of the current frame and the candidate block BL (6, 0) of the previous frame is the minimum and not more than the threshold value, the previous frame Candidate block BL (6, 0) is determined to be the source block. In this case, the motion vector is calculated as (−3, 2) in terms of the X and Y coordinates of the block. The calculated motion vector is given to each of the plurality of pixels of the block of interest. Therefore, the plurality of pixels in the block of interest have the same motion vector.

Note that the pixels on the screen may be represented by the horizontal x-coordinate and the vertical y-coordinate, and the motion vector MV may be represented by the pixel x-coordinate and y-coordinate.

(E) Difference Data Calculation Method FIG. 5 is a schematic diagram showing a difference data calculation method. The candidate block CD of the previous frame is shown on the left side of FIG. 5, and the target block OB of the current frame is shown on the right side.

In the example of FIG. 5, each block consists of 4 × 4 pixels. Each pixel in one block is represented by a horizontal x coordinate and a vertical y coordinate. In the example of FIG. 5, 16 pixels of each block are represented using coordinates (0, 0) to (3, 3).

Here, the motion vector detection circuit 3 calculates a difference value diff between each pixel in the target block OB of the current frame and a corresponding pixel in the candidate block CD of the previous frame. Specifically, a difference value diff _{(0, 0)} between the value of the pixel at the coordinate (0, 0) in the candidate block CD and the value of the pixel at the coordinate (0, 0) in the target block OB is calculated. A difference value diff _{(0, 1)} between the value of the pixel at the coordinate (0, 1) in the candidate block CD and the value of the pixel at the coordinate (0, 1) in the target block OB is calculated. Similarly, difference values diff _{(0, 2)} to diff _{(3, 3)} of corresponding pixels in the candidate block CD and the target block OB are calculated.

The motion vector detection circuit 3 calculates difference data DFD between the current block of interest block OB and the previous frame candidate block CD by the following equation.

DFD = diff _(0,0) + diff _(0,1) + ... + diff _(3,3)
From the above equation, if the values of all the pixels in the target block OB of the current frame and the values of all the pixels of the candidate block CD of the previous frame completely match, the difference data DFD is zero.

(F) Operation of Overdrive Controller 5 FIG. 6 is a diagram for explaining the operation of the overdrive controller 5. In FIG. 6, the left column indicates the state of the motion determination signal SM and the motion vector MV input to the overdrive controller 5, and the right column indicates the value of the control signal CT output from the overdrive controller 5. . Here, it is assumed that a still region and a motion region are determined for each pixel.

When the motion determination signal SM for the target pixel indicates a still region, the value of the control signal CT is 0. Here, the target pixel means a pixel to be processed.

If the motion determination signal SM for the pixel of interest indicates a motion region and the magnitude of the motion vector MV is equal to or smaller than a predetermined threshold value T or the motion vector MV cannot be detected, the control signal CT The value of is 0. The threshold value T is set to an arbitrary real value greater than or equal to zero. Here, the motion vector MV cannot be detected means that one motion vector MV cannot be specified for the block of interest. For example, when there is no candidate block that matches or is similar to the block of interest, it matches or is similar to the block of interest. This is a case where a plurality of candidate blocks to be detected are detected.

Furthermore, when the motion determination signal SM for the pixel of interest indicates a motion region and the magnitude of the motion vector MV is greater than the threshold value T, the value of the control signal CT is the value of a predetermined function f (MV). Become.

FIG. 7 is a diagram illustrating an example of the function f (MV). The vertical axis in FIG. 7 indicates the value of the function f (MV), and the horizontal axis indicates the magnitude of the motion vector MV.

In the example shown in FIG. 7, the value of the control signal CT increases from the threshold value T to m1 of the motion vector MV, and the value of the control signal CT becomes constant in the range of the motion vector MV from m1 to m2. The value of the control signal CT decreases from the magnitude m2 to m3 of the motion vector MV.

FIG. 8 is a flowchart showing the operation of the overdrive controller 5.

In FIG. 8, first, the overdrive controller 5 determines whether or not the motion determination signal SM for the target pixel of the target block indicates a still region (step S1).

When the motion determination signal SM does not indicate a still region, that is, when the motion determination signal SM indicates a motion region, the overdrive controller 5 determines whether the magnitude of the motion vector MV is equal to or less than the threshold value T or the motion vector It is determined whether MV cannot be detected (step S2).

When the magnitude of the motion vector MV is larger than the threshold value T, the overdrive controller 5 sets the value of the control signal CT to the value of the function f (MV) (step S3).

In step S1, if the motion determination signal SM indicates a still region, the overdrive controller 5 sets the value of the control signal CT to 0 (step S4). On the other hand, if the magnitude of the motion vector MV is equal to or smaller than the threshold value T in step S2 or the motion vector MV cannot be detected, the overdrive controller 5 sets the value of the control signal CT to 0 (step S4). .

Steps S1 to S4 are performed for all the pixels in each block of interest.

Thus, the value of the control signal CT is set based on the motion determination signal SM and the motion vector MV. Thereby, the value of the control signal CT becomes 0 for the noise portion.

(G) Configuration and Operation of Overdrive Circuit 6 FIG. 9 is a block diagram showing the configuration of the overdrive circuit 6. FIG. 10 shows an example of the correction value table. The correction value table is not limited to one type, and a plurality of types may be provided corresponding to the red video signal (R), the green video signal (G), and the blue video signal (B).

As shown in FIG. 9, the overdrive circuit 6 includes a correction value generation unit 61, an adder 62, and a multiplier 63. The correction value generation unit 61 stores a correction value table shown in FIG. The correction value generator 61 reads out and outputs the correction value AM0 from the correction value table based on the video signal VD0 of the previous frame and the video signal VD1 of the current frame.

As shown in FIG. 10, correction values are set in the correction value table according to the gradation of the video signal VD0 of the previous frame and the gradation of the video signal VD1 of the current frame. The correction value in the correction value table has a larger absolute value as the difference between the gradation of the video signal VD1 of the current frame and the gradation of the video signal VD0 of the previous frame is larger. When the gradation of the video signal VD1 of the current frame is higher than the gradation of the video signal VD0 of the previous frame, the correction value has a positive sign, and the gradation of the video signal VD0 of the previous frame is the current frame. If the gradation is higher than the gradation of the video signal VD1, the correction value has a negative sign.

The multiplier 63 in FIG. 9 multiplies the correction value AM0 output from the correction value generation unit 61 by the value of the control signal CT, and outputs the multiplication result as the correction value AM1. The adder 62 adds the correction value AM1 output from the multiplier 63 to the video signal VD0 of the previous frame, and outputs the addition result as the corrected video signal VD2 of the current frame.

FIG. 11 is a diagram showing an example of gradations of the video signal VD0 of the previous frame, the video signal VD1 of the current frame, and the corrected video signal VD2 of the current frame. The vertical axis in FIG. 11 is the gradation of the target pixel of the video signals VD0, VD1, and VD2, and the horizontal axis is the frame.

In the example of FIG. 11, the pixel of interest is a motion region, and the magnitude of the motion vector MV is larger than the threshold value T. When the gradation of the video signal VD1 of the current frame is higher than the gradation of the video signal VD0 of the previous frame, the gradation of the video signal VD2 of the current frame is higher than the gradation of the video signal VD1 of the current frame. It is corrected as follows. Thereby, the gradation change of the video signal is emphasized.

On the other hand, when the gradation of the video signal VD1 of the current frame is lower than the gradation of the video signal VD0 of the previous frame, the gradation of the video signal VD2 of the current frame is higher than the gradation of the video signal VD1 of the current frame. It is corrected to be lower. Thereby, the gradation change of the video signal is emphasized.

When the target pixel is a still region, or when the target pixel is a motion region and the motion vector MV is equal to or less than the threshold value T, the gradation of the video signal VD2 of the current frame is the same as that of the video signal VD1 of the current frame. It becomes equal to the gradation. That is, the gradation change of the video signal is not emphasized.

(H) Effect of First Embodiment As described above, the value of the control signal CT is set based on the motion determination signal SM and the motion vector MV. Thereby, the control signal CT becomes 0 for the noise portion. In this case, in the overdrive circuit 6, overdrive control of the video signal VD1 is not performed for the still region and the noise portion, and the video signal VD1 is output as it is as the video signal VD2. Therefore, the response speed of displaying the moving image portion on the screen of the liquid crystal display panel 200 is improved without enhancing the noise. As a result, an afterimage is prevented from occurring when there is a moving image portion in the video.

When the motion determination signal SM indicates a still region, the control signal CT becomes 0 regardless of the motion vector MV. Thereby, when the motion vector MV cannot be detected, when the accuracy of the motion vector MV is low, or when the motion vector MV is erroneously detected, it is reliably prevented that the gradation change in the still image portion is emphasized. be able to.

(2) Second Embodiment Next, a second embodiment of the present invention will be described. The display device according to the second embodiment is different from the display device according to the first embodiment in the following points.

In the second embodiment, the overdrive circuit 6 changes the value of the control signal CT based on the accuracy (reliability) of the motion vector MV output from the motion vector detection circuit 3.

(A) Accuracy of Motion Vector MV First, the accuracy of the motion vector MV will be described. 12 and 13 are diagrams illustrating an example of a candidate block setting method.

Here, in order to simplify the explanation, it is assumed that one screen SC is composed of 8 pixels and 8 lines as shown in FIGS. Each block is assumed to be composed of 4 × 4 pixels. In the example of FIG. 12, the four candidate blocks A, B, C, and D are set so as not to overlap each other. In the example of FIG. 13, the four candidate blocks A, B, C, and D are set to overlap each other.

In the following description, four candidate blocks A, B, C, and D are set as in the example of FIG. Also, the current frame is searched with reference to the previous frame.

14 to 17 are diagrams showing an example of a method for detecting the motion vector MV.

As shown in FIG. 14, a candidate block of the current frame that matches the target block OB of the previous frame is detected by comparing the target block OB of the previous frame with each of the candidate blocks A, B, C, and D of the current frame. Then, the motion vector from the target block OB of the previous frame to the candidate block detected in the current frame is calculated.

In FIG. 15, it is assumed that the object of the target block OB in the previous frame moves 4 pixels in the horizontal direction and 4 pixels in the vertical direction. For example, the gradation of the target block OB in the previous frame is set to 255, and the gradation of the other part is set to 0. In this case, the gradation of candidate blocks A, B, and C is 0, and the gradation of candidate block D is 255.

Also in this example, the pixels in each block are represented by the x and y coordinates in each block. A difference value diff _(0,0) between the value (gradation) of the pixel at the coordinate (0,0) in the target block OB and the value of the pixel at the coordinate (0,0) in the candidate block A is calculated, and the target A difference value diff _{(0, 1)} between the value of the pixel at the coordinate (0, 1) in the block OB and the value of the pixel at the coordinate (0, 1) in the candidate block A is calculated. Similarly, the difference between the pixel values at coordinates (0, 2) to (3, 3) in the target block OB and the pixel values at coordinates (0, 2) to (3, 3) in the candidate block A The values diff _{(0, 2)} to diff _{(3, 3)} are respectively calculated.

Further, difference data DFD _OA between the target block OB and the candidate block A is calculated by the following equation.

DFD _OA = diff _(0,0) + diff _(0,1) + ... + diff _(3,3)
Similarly, difference data DFD _OB between the target block OB and the candidate block B, difference data DFD _OC between the target block OB and the candidate block C, and difference data DFD _OD between the target block OB and the candidate block D are calculated. .

In the above example, DFD _OA = DFD _OB = DFD _OC = 255 × 16 = 4080, and DFD _OD = 0. Therefore, since the difference data DFD _OD is minimum, it is detected that the object of the target block OB in the previous frame has moved to the candidate block D in the current frame. In this case, when the motion vector MV is expressed by the x coordinate and y coordinate of the pixel, MV = (4, 4).

In FIG. 16, it is assumed that the object of the target block OB in the previous frame moves 3 pixels in the horizontal direction and 3 pixels in the vertical direction. Here, for example, the gradation of the target block OB in the previous frame is set to 255, and the gradation of the other part is set to 0. In this case, the gradation of 15 pixels of the candidate block A, 13 pixels of the candidate block B, 13 pixels of the candidate block C, and 7 pixels of the candidate block D becomes 0, and 1 of the candidate block A The gradation of the three pixels, the three pixels of the candidate block B, the three pixels of the candidate block C, and the nine pixels of the candidate block D are 0.

Also in this embodiment, difference data _{DFD OA} between the target block OB and the candidate block A, the difference data _{DFD OB} between the target block OB and the candidate block B, the block of interest OB and the difference data _{DFD OC} of the candidate block C, and the block of interest OB And the difference data DFD _OD between the candidate block D and the candidate block D is calculated.

As a result, DFD _OA = 255 × 15 = 3825, DFD _OB = DFD _OC = 255 × 13 = 3315, and DFD _OD = 255 × 7 = 1785. In this case, since the difference data DFD _OD is minimized, it is detected that the object of the target block OB in the previous frame has moved to the candidate block D in the current frame. In this case, when the motion vector MV is expressed by the x coordinate and y coordinate of the pixel, MV = (4, 4). However, MV = (4, 4) is not accurate, and the accurate motion vector MV is (3, 3).

Thus, the accuracy of the motion vector MV tends to be lower as the minimum difference data DFD is larger.

(B) Operation of Overdrive Controller 5 As described above, when the motion vector MV is detected in units of blocks, the accuracy of the detected motion vector MV is different. However, it has been found that there is a certain degree of correlation between the accuracy of the detected motion vector MV and the difference data DFD. Specifically, the smaller the difference data DFD corresponding to the detected motion vector MV, the higher the accuracy of the detected motion vector MV. Also, the greater the difference data DFD corresponding to the detected motion vector MV, the lower the accuracy of the detected motion vector MV.

Therefore, in the present embodiment, the correction value by the overdrive circuit 6 is controlled based on the accuracy of the motion vector MV.

FIG. 17 is a diagram for explaining the operation of the overdrive controller 5. In FIG. 17, the left column indicates the state of the motion determination signal SM and the motion vector MV input to the overdrive controller 5, and the right column indicates the value of the control signal CT output from the overdrive controller 5. .

When the motion determination signal SM for the target pixel indicates a still region, the value of the control signal CT is 0.

When the motion determination signal SM for the pixel of interest indicates a motion region and the magnitude of the motion vector MV is equal to or smaller than a predetermined threshold T or when the motion vector MV cannot be detected, the control signal CT The value is 0.

Furthermore, when the motion determination signal SM for the pixel of interest indicates a motion region and the magnitude of the motion vector MV is larger than the threshold value T, the value of the control signal CT is the value of a predetermined function g (DFD). Become.

FIGS. 18A and 18B are diagrams illustrating an example of a function g (DFD) of the control signal CT. 18A and 18B, the vertical axis indicates the value of the function g (DFD), and the horizontal axis indicates the value of the difference data DFD.

In the example shown in FIGS. 18A and 18B, when the difference data DFD is 0, the value of the function g (DFD) is 1, and as the difference data DFD increases from 0, the value of the function g (DFD) is When the difference data DFD decreases to the predetermined value d, the value of the function g becomes zero.

As indicated by a solid line in FIG. 18A, the value of the function g (DFD) may decrease continuously and linearly as the difference data DFD increases from 0. In FIG. As indicated by a chain line, the value of the function g (DFD) may decrease continuously and in a curve as the difference data DFD increases from zero. Further, as indicated by a solid line in FIG. 18B, the value of the function g (DFD) may decrease stepwise as the difference data DFD increases from zero.

FIG. 19 is a flowchart showing the operation of the overdrive controller 5.

In FIG. 19, first, the overdrive controller 5 determines whether or not the motion determination signal SM for the target pixel indicates a still region (step S11).

When the motion determination signal SM does not indicate a still region, that is, when the motion determination signal SM indicates a motion region, the overdrive controller 5 determines whether the magnitude of the motion vector MV is equal to or less than the threshold value T or the motion vector It is determined whether MV is undetectable (step S12).

When the magnitude of the motion vector MV is larger than the threshold value T, the overdrive controller 5 sets the value of the control signal CT to the value of the function g (DFD) (step S13).

In step S11, when the motion determination signal SM indicates a still region, the overdrive controller 5 sets the value of the control signal CT to 0 (step S14). If the magnitude of the motion vector MV is equal to or smaller than the threshold value T in step S12 or the motion vector MV cannot be detected, the overdrive controller 5 sets the value of the control signal CT to 0 (step S14). .

Steps S11 to S14 are performed for all the pixels in each block of interest.

(C) Effects of Second Embodiment In the second embodiment, the following effects are obtained in addition to the effects similar to those of the first embodiment.

As described above, the correction value AM1 in the overdrive control of the video signal VD1 in the overdrive circuit 6 is controlled based on the accuracy of the motion vector MV. That is, when the accuracy of the motion vector MV is high, the absolute value of the correction value AM1 in the overdrive control is large, and when the accuracy of the motion vector MV is low, the absolute value of the correction value AM1 in the overdrive control is small. Become. As a result, the image quality of the video does not deteriorate.

(3) Third Embodiment Next, a third embodiment of the present invention will be described. The display device according to the third embodiment is different from the display devices according to the first and second embodiments in the following points.

FIG. 20 is a block diagram showing a configuration of the overdrive circuit 6 in the display device according to the third embodiment.

20 differs from the overdrive circuit 6 shown in FIG. 9 in that it further includes a multiplier 65. The overdrive circuit 6 shown in FIG. The multiplier 65 is supplied with a control signal CT ′. The multiplier 65 multiplies the correction value AM1 output from the multiplier 63 by the value of the control signal CT ', and outputs the multiplication result as a correction value AM3. The adder 62 adds the correction value AM3 output from the multiplier 65 to the video signal VD0 of the previous frame, and outputs the addition result as the corrected video signal VD2 'of the current frame. Therefore, the correction value AM3 increases as the value of the control signal CT ′ increases. Hereinafter, the control signal CT ′ will be described.

The human visual acuity in the vertical direction is inferior to that in the horizontal direction. Therefore, in the present embodiment, different overdrive control is performed on the moving object in the left-right direction and the moving object in the up-down direction. That is, when the motion vector MV indicates the left-right direction, the value of the control signal CT ′ is set large, and when the motion vector MV indicates the vertical direction, the value of the control signal CT ′ is set small. To do.

For example, when MVX is the magnitude of the horizontal component of the motion vector MV, the value of the control signal CT ′ is set to CT ′ = α · MVX ² . When MVY is the magnitude of the vertical component of the motion vector MV, the value of the control signal CT ′ may be set to CT ′ = α · (MVX ² ) / (MVY ² ).

Thus, in the video signal processing apparatus 100 according to the present embodiment, overdrive control for an object moving in the left-right direction can be emphasized compared to overdrive control moving in the up-down direction. As a result, it is possible to display an image that is visually uncomfortable on the screen of the liquid crystal display panel 200.

(4) Other Embodiments In the first to third embodiments, when the motion determination signal SM indicates a still region, or when the motion determination signal SM indicates a motion region and the magnitude of the motion vector MV is reduced. The correction value AM1 in the overdrive control is set to 0 when the threshold value T is equal to or less than the threshold value T or the motion vector MV cannot be detected. However, the correction value in this case is not limited to 0. When the motion determination signal SM indicates a still region, or when the motion determination signal SM indicates a motion region and the magnitude of the motion vector MV is equal to or smaller than the threshold value T or the motion vector MV cannot be detected, The correction value AM1 in the drive control may be set smaller than the correction value AM1 when the motion determination signal SM indicates the motion region and the magnitude of the motion vector MV is larger than the threshold value T.

In the first to third embodiments, the motion determination circuit 2 may not be provided when the motion vector MV cannot be detected by the motion vector detection circuit 3 at a low frequency. In this case, when the magnitude of the motion vector MV is equal to or smaller than the threshold value T, the value of the control signal CT becomes zero. Thereby, since overdrive control by the overdrive circuit 6 is not performed on the noise portion, it is possible to prevent the noise from being emphasized.

In the first to third embodiments, the motion determination circuit 2 determines the still region and the motion region of the video based on the difference value between the corresponding pixels of the previous frame and the current frame. However, the present invention is not limited to this. Instead, the still region and the motion region of the video may be determined using other methods. For example, the still region and the motion region of the video may be determined based on the pixels of three or more frames. Further, the still region and the motion region may be determined for each unit region composed of one pixel, or the still region and the motion region may be determined for each unit region composed of a plurality of pixels.

Furthermore, in the first to third embodiments, the motion vector detection circuit 3 detects the motion vector MV based on the comparison (pattern matching) between the block of interest and the candidate block. However, the present invention is not limited to this. The motion vector may be detected using other methods. For example, a method of detecting a motion vector based on the gradient of the gradation of the video signal may be used. Alternatively, a pixel-by-pixel motion vector may be detected using a pixel sequential method.

All components of the video signal processing device 100 may be configured by hardware such as an electronic circuit, or some components of the video signal processing device 100 may be hardware such as a CPU (Central Processing Unit) and a semiconductor memory. Software and software such as software may be used.

The video signal processing apparatus according to the present invention is not limited to a liquid crystal display panel, and can be used for various other display panels that require an improvement in display response speed with respect to a change in gradation of a video signal.

(5) Correspondence between each constituent element of claim and each element of the embodiment Hereinafter, an example of correspondence between each constituent element of the claim and each constituent element of the embodiment will be described. It is not limited to examples.

In the above embodiment, the motion vector detection circuit 3 is an example of a detection unit, the overdrive circuit 6 is an example of a correction unit, the overdrive controller 5 is an example of a control unit, and the motion determination circuit 2 is a determination unit. The liquid crystal display panel 200 is an example of a display panel, a block is an example of a unit area, an attention block is an example of an attention unit area, and a candidate block is an example of a candidate unit area.

As the constituent elements of the claims, various other elements having configurations or functions described in the claims can be used.

The present invention can be used for a display device using a display panel such as a liquid crystal display panel.

Claims

A video signal processing apparatus for processing an input video signal,
A detection unit that detects a motion vector for each unit region configured by a predetermined number of pixels based on an input video signal;
When the gradation of the input video signal rises, the gradation of the video signal is corrected and input so that the gradation of the output video signal is higher than the gradation after the input video signal rises. A correction unit that corrects the gradation of the video signal so that the gradation of the video signal that is output when the gradation of the video signal is lower than the gradation after the decrease of the input video signal;
A video signal processing apparatus comprising: a control unit that controls a correction amount by the correction unit based on a motion vector detected by the detection unit.
The control unit performs gradation correction by the correction unit in the first case where the magnitude of the motion vector detected by the detection unit is larger than a predetermined threshold, and the detection unit detects the motion vector. In the second case where the magnitude of the motion vector is less than the threshold value or the motion vector cannot be detected, the correction by the correction unit is not performed or the correction amount by the correction unit is A video signal processing apparatus that controls the correction unit to be smaller than a correction amount in the first case.
A determination unit that determines a still region and a motion region of a video based on a change in a value of a corresponding pixel of a plurality of frames;
The control unit may not perform gradation correction by the correction unit or a correction amount by the correction unit for the still region determined by the determination unit regardless of the detection result of the detection unit. The video signal processing apparatus according to claim 2, wherein the correction unit is controlled to be smaller than a correction amount in the case of 1.
The control unit sets a target unit area in one of a plurality of frames and sets a plurality of candidate unit areas in another frame, and calculates a difference value between corresponding pixels in the target unit area and each candidate unit area. Is calculated as difference data, a candidate unit area corresponding to the smallest difference data is selected from among the plurality of candidate unit areas, and a motion vector is calculated based on the position of the target unit area and the selected candidate unit area. The video signal processing device according to claim 1, wherein the video signal processing device is detected.
The control unit determines the accuracy of the motion vector detected by the detection unit, and controls the correction unit so that the correction amount by the correction unit decreases as the accuracy of the determined motion vector decreases. The video signal processing apparatus according to 1.
The control unit sets a target unit region in one frame among a plurality of frames and sets a plurality of candidate unit regions in another frame, and each pixel of the target unit region and a corresponding pixel of each candidate unit region The difference value is calculated as difference data, a candidate unit region corresponding to the smallest difference data among the plurality of candidate unit regions is selected, and based on the position of the target unit region and the selected candidate unit region The video signal processing apparatus according to claim 5, wherein the motion vector is detected and the accuracy of the motion vector is determined based on difference data corresponding to the selected candidate unit region.
The video signal processing apparatus according to claim 1, wherein the control unit changes a correction amount by the correction unit based on a direction of motion of each unit area obtained from a motion vector detected by the detection unit.
A video signal processing device for processing an input video signal;
A display panel for displaying video based on the video signal output from the video signal processing device,
The video signal processing device detects a motion vector for each unit region composed of a predetermined number of pixels based on an input video signal;
When the gradation of the input video signal rises, the gradation of the video signal is corrected and input so that the gradation of the output video signal is higher than the gradation after the input video signal rises. A correction unit that corrects the gradation of the video signal so that the gradation of the video signal that is output when the gradation of the video signal is lower than the gradation after the decrease of the input video signal;
And a control unit that controls a correction amount by the correction unit based on a motion vector detected by the detection unit.