JP2022091020A - Display device, display method and program - Google Patents

Abstract

To suppress a flicker on a screen of an output image after scene change and suppress white blur in a low gradation region.SOLUTION: A display device (1) of the present invention comprises a luminance value setting unit (13) which sets a luminance value of a first region in a lower gradation than a prescribed gradation in a first image after scene change to a luminance value of the first region of the output image, and sets a luminance value of a second region other than the first region to a luminance value within a range of a second threshold larger than a first threshold from the luminance value of the second region of the output image.SELECTED DRAWING: Figure 1

Description

The present invention relates to a display device that sets the brightness of an output image according to the presence or absence of a scene change in an input image.

In the display device, for example, Patent Document 1 discloses a technique for setting the brightness of an output image according to the presence or absence of a scene change in an input image. In the image processing apparatus disclosed in Patent Document 1, a gamma curve is generated as follows. When there is no scene change, the gamma curve for the frames after the next frame is generated by the first calculation based on the previous frame. On the other hand, when there is a scene change, a gamma curve is generated from the statistics of the scene-changed frame by a second calculation that can be processed in a shorter time than the first calculation. Further, the gamma curve obtained by the first calculation is estimated by the second calculation. That is, a gamma curve close to the gamma curve obtained by the first calculation is generated by the second calculation. Therefore, it is possible to reduce the change in brightness that occurs when the time-direction fluctuation suppression process in which the gamma curve is gently changed with a constant time constant is performed.

Japanese Unexamined Patent Publication No. 2014-11725

However, when changing from a bright scene to a dark scene, if you gently change the gamma curve from the previous scene, the black area of the dark scene will gradually turn black from the brightness of the previous scene, so it looks like it floats a little white. The phenomenon that the darkening is visually visible, so-called whitening, occurs.

One aspect of the present invention is to realize a display device capable of suppressing whitening in a low gradation region while suppressing screen flicker in an output image after a scene change when there is a scene change. ..

In order to solve the above problems, the display device according to one aspect of the present invention includes a scene change detection unit that detects whether or not an input image composed of a plurality of frames is switched in frame units, and the scene change. A luminance value setting unit that sets the luminance value of the first image for a frame detected by the detection unit as having a scene change, and a display control unit that displays an image on the display unit based on the luminance value of the first image. Including, the luminance value setting unit determines whether a predetermined region of the first image is a first region having a gradation lower than a preset gradation or a second region other than the first region. The area determination unit and the luminance value of the first region determined by the region determination unit are set to the luminance values within the first range of low gradation including the luminance value of the first region of the first image. The luminance value of the second region determined by the first luminance value setting unit and the region determination unit includes the luminance value of the second region of the first image and is higher than the upper limit value of the first range. It is characterized by including a second luminance value setting unit for setting a luminance value within the second range with the luminance value as a lower limit value.

The display method according to one aspect of the present invention is a display method for displaying the output image for the input image on the display device based on the output luminance set according to the change of the scene of the input image composed of a plurality of frames. Therefore, in advance, the scene change detection step for detecting the presence or absence of scene switching in the frame unit of the input image and the predetermined area of the first image for the frame detected by the scene change step as having a scene change are performed in advance. The area determination step for determining whether the first area has a gradation lower than the set gradation or the second area other than the first area, and the luminance value of the first area determined by the area determination step are determined. The first luminance value setting step for setting the luminance value within the first range of low gradation including the luminance value of the first region of the first image, and the luminance of the second region determined by the region determination step. A second luminance value setting in which the value is set to a luminance value in the second range including the luminance value of the second region of the first image and having a luminance value higher than the upper limit value of the first range as the lower limit value. It is characterized by including steps.

According to one aspect of the present invention, when there is a scene change, it is possible to suppress whitening in a low gradation region while suppressing screen flicker in the output image after the scene change.

It is a schematic block diagram of the display device which concerns on Embodiment 1 of this invention. It is a front view which shows the appearance of the display device shown in FIG. It is a flowchart which shows the flow of the gamma curve generation processing in the display device shown in FIG. It is a figure for demonstrating scene change detection. It is a figure for demonstrating the process of image comparison. This is the gamma curve of the frame before the scene change. This is the gamma curve of the frame after the scene change. It is a figure for demonstrating the number of reference frames at the time of setting brightness. It is a figure for demonstrating other processing of image comparison. It is a figure for demonstrating further other processing of image comparison. It is a schematic block diagram of the display device which concerns on Embodiment 2 of this invention. It is a flowchart which shows the flow of the display device gamma curve generation processing shown in FIG. It is a schematic block diagram of the display device which concerns on Embodiment 3 of this invention. It is a flowchart which shows the flow of the display device gamma curve generation processing shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, the configuration described in the present embodiment is not intended to limit the scope of the present invention to the present invention unless otherwise specified, and is merely an explanatory example.

[Embodiment 1]
Hereinafter, one embodiment of the present invention will be described in detail.

(Overview of display device)
The display device 1 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration of a display device 1 according to the present embodiment. Further, FIG. 2 is a perspective view showing the appearance of the display device 1.

As shown in FIG. 1, the display device 1 includes an image acquisition unit 11, a scene change detection unit 12, a luminance value setting unit 13, a gamma curve generation unit 14, a panel control unit 15, and a display panel 16.

The image acquisition unit 11 acquires an input image composed of a plurality of frames. The image acquired by the image acquisition unit 11 is a video signal such as an HDR signal. HDR signals include HDMI® signals, Tuner signals (signals received by tuners) and CVBS (Composite Video, Blanking,) based on the HDMI® (High-Definition Multimedia Interface) standard. and Sync: Composite video signal) It can be a signal or the like.

The image acquisition unit 11 has a storage unit 111 that temporarily stores the acquired input image for each frame, and an analysis unit 112 that analyzes the acquired input image for each frame. At least a part of the analysis information analyzed by the analysis unit 112 is sent to the scene change detection unit 12 in the subsequent stage. The analysis information includes at least a minimum luminance value, a maximum luminance value, an APL (Average Picture Level), and a histogram. On the other hand, the input image acquired by the image acquisition unit 11 and temporarily stored in the storage unit 111 is sent to the gamma curve generation unit 14 in the subsequent stage as information indicating the input luminance before correction for each frame.

The scene change detection unit 12 detects whether or not the scene of the input image is switched based on at least a part of the analysis information for each frame sent from the image acquisition unit 11. The signal indicating the detection result by the scene change detection unit 12 is sent to the luminance value setting unit 13 in the subsequent stage.

The luminance value setting unit 13 sets the luminance value in the output image of the frame to be the scene change detection target according to the signal indicating the detection result sent from the scene change detection unit 12. The luminance value setting unit 13 generates a correction signal for correcting the gamma curve from the set luminance value, and sends the generated correction signal to the gamma curve generation unit 14 in the subsequent stage. The details of the luminance value setting unit 13 will be described later.

The gamma curve generation unit 14 corrects the input brightness for each frame stored in the storage unit 111 sent from the image acquisition unit 11 based on the correction signal sent from the brightness value setting unit 13, and corrects the input brightness. Generates a gamma curve for each frame from. Information indicating the gamma curve generated by the gamma curve generation unit 14 is sent to the panel control unit 15 in the subsequent stage.

The panel control unit 15 sets the output luminance of each pixel of the display panel 16 based on the information indicating the gamma curve generated by the gamma curve generation unit 14. As a result, the image represented by the image signal is displayed on the display panel 16 with the original brightness.

The frame rate of the display panel 16 is 240 FPS (updated 240 times per second).

(Brightness value setting unit 13)
The brightness value setting unit 13 includes an image comparison unit 131, an area determination unit 132, a first brightness value setting unit 133, a second brightness value setting unit 134, a third brightness value setting unit 135, and a correction signal generation unit 136. .. In the luminance value setting unit 13, the first luminance value setting unit 133 and the second luminance value setting unit 134 set the luminance value of the output image (first image) for the frame detected as having a scene change. The third luminance value setting unit 135 sets the luminance value of the output image (second image) for the frame detected as having no scene change. The correction signal generation unit 136 generates a correction signal for correcting the gamma curve from the luminance value set by the first luminance value setting unit 133, the second luminance value setting unit 134, or the third luminance value setting unit 135.

When the signal indicating the detection result from the scene change detection unit 12 is a signal indicating that there is a scene change, the image comparison unit 131 compares the images before and after the scene change. Specifically, the image comparison unit 131 determines whether or not the image after the scene change is darker than the image before the scene change. Then, the image comparison unit 131 sends the result of the image comparison to the region determination unit 132 and the third luminance value setting unit 135 in the subsequent stage. The details of the image comparison by the image comparison unit 131 will be described later.

The area determination unit 132 determines the area when the signal from the image comparison unit 131 indicating the image comparison result is a signal indicating that the image after the scene change is darker than the image before the scene change. That is, is it the first region having a gradation lower than the preset gradation for each predetermined region of the first image corresponding to the frame targeted for scene change detection, that is, the frame detected as having a scene change? , It is determined whether it is a second area other than the first area. Here, the "predetermined area" may be set according to the type of the image after the scene change (an image of a night view, a landscape including the sea, etc.), or may be set to a preset size. good. Further, the "predetermined area" may be the entire area or a part of the image. This "region" may be one pixel or a set of a plurality of pixels.

When considering the accuracy of the area determination, it is preferable that the area determination is performed for each pixel in the entire area of the first image.

The first luminance value setting unit 133 sets the luminance value of the first region determined by the region determination unit 132 within the range of the first threshold value from the luminance value of the first region in the output image of the frame to be determined by the region. Set to the brightness value. That is, when the signal indicating the detection result from the scene change detection unit 12 is a signal indicating that there is a scene change, the first luminance value setting unit 133 outputs an output image (first image) for the frame detected as having a scene change. In, the luminance value of the first region of the gradation lower than the preset gradation is set to the luminance value within the first range of the low gradation including the luminance value of the first region of the output image.

Here, the first range means a range in which the luminance value is between 0 and 3 when the luminance value is represented by 256 gradations from 0 to 255 and the 0 gradation is black. The first range is not limited to the range where the luminance value is between 0 and 3, and the upper limit luminance value may be larger than 3. Further, the luminance value of the first region may be set to the same luminance value as that of the first region of the first image.

The second luminance value setting unit 134 sets the luminance value of the second region determined by the region determination unit 132 to be larger than the first threshold value from the luminance value of the second region in the output image of the frame to be determined by the region. 2 Set the brightness value within the threshold range. That is, the second luminance value setting unit 134 sets the luminance value of the second region other than the first region in the output image (first image) for the frame detected as having a scene change to the second image of the first image. The luminance value in the second range including the luminance value of the region and having the luminance value higher than the upper limit value of the first range as the lower limit value is set.

Here, in the second range, the luminance value is represented by 256 gradations from 0 to 255, and when 255 gradations are white, the upper limit luminance value defined in the first range (in the above example, the luminance value is the third floor). A brightness value larger than the key) is in the range of 4 to 255. If the upper limit brightness value of the first range changes, the lower limit brightness value of the second range also changes. Further, the second range may be set based on the first image information corresponding to the first image and the second image information corresponding to the second image for the frame past the frame for the first image.

The third luminance value setting unit 135 sets the luminance value in the output image (third image) for the frame when the signal indicating the detection result from the scene change detection unit 12 is a signal indicating no scene change. Further, the third luminance value setting unit 135 outputs to the frame when the signal indicating the image comparison result from the image comparison unit 131 is a signal indicating that the image after the scene change is not darker than the image before the scene change. The brightness value in the image (fourth image) is set. That is, the third luminance value setting unit 135 sets the luminance values of the third image for the frame without the scene change and the luminance value of each of the fourth images with the scene change and not darker than the image before the scene change.

The third luminance value setting unit 135 includes a reference frame number setting unit 1351 and an average value calculation unit 1352. That is, the reference frame number setting unit 1351 sets the number of reference frames used for correcting the input luminance according to the signal indicating the presence or absence of the scene change sent from the scene change detection unit 12. Here, the reference frame includes a current frame to be detected with or without a scene change, and a past frame composed of several frames that are continuously traced back to the past from the current frame. Then, the reference frame number setting unit 1351 sets the number of reference frames when there is a scene change to be smaller than the number of reference frames when there is no scene change. Specifically, the reference frame number setting unit 1351 sets the number of frames of the past frames constituting the reference frame so that the number of frames with the scene change is smaller than that without the scene change. The signal indicating the number of reference frames set by the reference frame number setting unit 1351 is sent to the average value calculation unit 1352 in the subsequent stage.

The mean value calculation unit 1352 refers to the totaled APL after totaling the APLs among the analysis information of each frame constituting the reference frame based on the signal indicating the number of reference frames sent from the reference frame number setting unit 1351. Divide by the number of frames to obtain the average value of APL. The average value of APL obtained by the average value calculation unit 1352 is sent to the correction signal generation unit 136 in the subsequent stage.

The correction signal generation unit 136 generates a correction signal for correcting the gamma curve from the luminance value set in the first luminance value setting unit 133, the second luminance value setting unit 134, or the third luminance value setting unit 135. The generated correction signal is sent to the gamma curve generation unit 14 in the subsequent stage.

(Gamma curve generation process)
The flow of the gamma curve generation process executed by the display device 1 having the above configuration will be described with reference to FIGS. 3 to 8. FIG. 3 is a flowchart showing the flow of the gamma curve generation process. FIG. 4 is a diagram for explaining scene change detection. FIG. 5 is a diagram for comparing the darkness of the output image before and after the scene change. FIG. 6 is a diagram showing a gamma curve of the output image of the frame before the scene change. FIG. 7 is a diagram showing a gamma curve of the output image of the frame after the scene change. FIG. 8 is a diagram for explaining the number of reference frames when the output luminance is set.

First, the scene change detection unit 12 determines whether or not there is a scene change (step S11). That is, the scene change detection unit 12 detects whether or not the input image of the current frame is an image that has undergone a scene change from the input image of the previous frame, that is, whether or not there is a scene change. Specifically, the scene change detection unit 12 detects the presence or absence of a scene change from the histogram of the analysis information sent from the image acquisition unit 11. For example, in four consecutive frames A, B, C, and D shown in FIG. 4, the histograms of the frames before and after are compared for each BIN (1 bit of binary data) to obtain the difference in frequency for each BIN. If the sum of the absolute values of the obtained differences is equal to or greater than the preset value, it is determined that there is a scene change in the latter frame of the two compared frames. Here, in the example shown in FIG. 4, when the setting value of the judgment standard is 3515, there is a scene change between the frame B and the frame C in which the total difference of the absolute values of the frequency difference is 4000. Is detected by the scene change detection unit 12. Further, when the total of the absolute value difference of the frequency difference is 0, and when it is 3000, both are smaller than 3515, so that the scene changes between the frame A and the frame B and between the frame C and the frame D. The scene change detection unit 12 detects that there was no such thing. The frame size assumed in FIG. 4 is 3840 × 2160 if the display device 1 is a 4KTV. If the display device 1 is an 8KTV, the size is 7860 × 4320.

Next, when it is detected in step S11 that there is a scene change (YES), the luminance value setting unit 13 proceeds to step S12. In step S12, it is determined whether or not the first image corresponding to the frame in which the scene change is detected by the image comparison unit 131 is darker than the second image corresponding to the frame immediately before the frame in which the scene change is detected. do. Here, the image comparison unit 131 determines whether or not the first image is darker than the second image by using the luminance histogram of the image. For example, the image of the scene A shown by the reference numeral 1051 in FIG. 5 is referred to as a second image before the scene change, and the image of the scene B shown by the reference numeral 1052 is referred to as a first image after the scene change. At this time, the image comparison unit 131 compares the darkness of the first image and the second image from the histogram of the brightness of the second image shown by reference numeral 1053 and the histogram of the brightness of the first image shown by reference numeral 1054. do. Here, the luminance is set to 256 gradations, and the threshold value B of the luminance value (gradation) is set in the histogram of each luminance. The threshold value B is, for example, 30 gradations. Therefore, in the image comparison unit 131, the proportion of pixels having a luminance value equal to or less than the preset threshold B in the luminance histogram of the first image is equal to or greater than the proportion of pixels having a luminance value equal to or less than the threshold B in the luminance histogram of the second image. When, it is determined that the first image is darker than the second image.

That is, in the image comparison unit 131, the proportion of pixels having a luminance value equal to or less than the preset threshold B in the luminance histogram of the first image is equal to or greater than the proportion of pixels having a luminance value equal to or less than the threshold B in the luminance histogram of the second image. When, it is determined that the first image is darker than the second image.

Therefore, if the image comparison unit 131 determines (YES) that the first image is darker than the second image in step S12, the process proceeds to step S13.

In step S13, the area determination unit 132 determines whether the first area has a gradation lower than the preset gradation with respect to the predetermined area of the first image corresponding to the frame detected as having a scene change. It is determined whether the area is a second area other than the first area. Here, when the brightness is 256 gradations, the preset gradation is set to the luminance value 3. Therefore, the first region is a region composed of pixels having a luminance value of 0 to 3. For example, in the first image shown by reference numeral 1052 in FIG. 5, the region indicated by reference numeral 1052a is one of the first regions. On the other hand, the second region is a region composed of pixels having a luminance value of 4 or more. As described above, each region may be one pixel or a set of a plurality of pixels. After the area is determined by the area determination unit 132, the process proceeds to step S14 and step S15.

In step S14, the luminance value of the first region determined in step S13 is set by the first luminance value setting unit 133. The first luminance value setting unit 133 sets the luminance value of the first region of the first image to the luminance value within the first range of low gradation including the luminance value of the first region of the first image. Here, when the luminance value is set to 256 gradations of 0 to 255, the luminance value 3 is set as the upper limit value, and the first range is set as the range of the luminance value 0 to 3.

In step S15, the luminance value of the second region determined in step S13 is set by the second luminance value setting unit 134. The second luminance value setting unit 134 includes the luminance value of the second region of the first image, the luminance value of the second region of the first image, and the luminance value higher than the upper limit value of the first range. Set the brightness value within the second range, which is the lower limit value. Here, when the luminance value is set to 256 gradations of 0 to 255, the luminance value 4 is set as the lower limit value, and the second range is set as the range of the luminance values 4 to 255.

Next, the correction signal generation unit 136 generates a correction signal for correcting the gamma curve from the first luminance value set in step S14 and the second luminance value set in step S15 (step S18).

Subsequently, the gamma curve generation unit 17 generates a gamma curve that corrects the input luminance of the frame for which the presence or absence of a scene change is detected based on the correction signal generated in step S18 (step S19). Specifically, the gamma curve is generated as follows. For example, the gamma curve (y = f (x)) of the image of the scene A shown by reference numeral 1051 in FIG. 5 is taken as the gamma curve shown in FIG. Here, y is an output luminance value and x is an input luminance value. The gamma curve (y = f (x)) of the image of the scene B shown by the reference numeral 1052 of FIG. 5, which is the image after the scene change, has the input luminance value on the low gradation side and the high gradation side with the threshold value Xblk as the boundary. The setting of the output brightness value is different. For example, on the low gradation side, the value calculated from the output luminance value of the scene B is used as the output luminance value. Specifically, the luminance value set by the first luminance value setting unit 133 (the luminance value 3 is the first threshold value and the luminance value is in the range of 0 to 3) is used as the output luminance value. On the other hand, on the high gradation side, the output luminance value is set between the output luminance value of the scene A and the output luminance value of the scene B. Specifically, the brightness value set by the second brightness value setting unit 134 (the brightness value 4 larger than the first threshold value is set as the second threshold value, and the range of the brightness values 4 to 255) is used as the output brightness value. The gamma curve of the scene B is corrected by these output luminance values. Here, the threshold value Xblk is, for example, 30 gradations.

In the gamma curve corrected in this way, the brightness above the threshold value Xblk retains the influence of the previous frame in order to suppress a sudden change, but if it is less than the threshold value Xblk, it is replaced with the brightness calculated from the current frame. ..

The panel control unit 15 sets the brightness (output brightness) of each pixel of the display panel 16 from the gamma curve generated by the gamma curve generation unit 14.

By the above processing, an appropriate gamma curve is obtained for the first image which is determined to have a scene change and is determined to be a dark image. As a result, the first region, which is a low gradation region in the first image, can be immediately darkened, and the brightness of the second region, which is a region other than the low gradation region, can be gradually changed. As a result, in the first image after the scene change, it is possible to suppress the flicker of the screen and suppress the whitening in the low gradation region.

On the other hand, the process for obtaining an appropriate gamma curve for the first image determined to have a scene change and determined to be a dark image is as follows.

If it is determined (NO) by the image comparison unit 131 that the first image is not darker than the second image in step S12, the process proceeds to step S16. Here, an image in which the first image is not darker than the second image is referred to as a fourth image.

In step S16, the luminance value of the fourth image is set by the third luminance value setting unit 135. Specifically, the third brightness value setting unit 135 sets the number of reference frames as M by the reference frame number setting unit 1351, and the average value calculation unit 1352 calculates the average value of APL with the reference frame number M. The calculated average value of APL is set as the brightness value.

Next, the process proceeds to step S18, and the correction signal generation unit 136 generates a correction signal for correcting the input brightness of the gamma curve of the first image based on the brightness value of the fourth image set in step S16.

Subsequently, the gamma curve generation unit 17 generates a gamma curve that corrects the input luminance of the frame for which the presence or absence of a scene change is detected based on the correction signal generated in step S18 (step S19). The panel control unit 15 sets the brightness (output brightness) of each pixel of the display panel 16 from the gamma curve generated by the gamma curve generation unit 14.

The description of the gamma curve generation process up to this point is for the case where it is determined that there is a scene change in step S11, but the gamma curve generation process for the case where it is determined in step S11 that there is no scene change (NO) will be described below. do.

That is, when it is determined (NO) that there is no scene change in step S11, the process proceeds to step S17 and the brightness value of the third image is set. The third image is an image determined to have no scene change.

In step S17, the brightness value of the third image is set by the third brightness value setting unit 135. Specifically, the third brightness value setting unit 135 sets the number of reference frames to N by the reference frame number setting unit 1351, and calculates the average value of APL with the reference frame number N by the average value calculation unit 1352. The calculated average value of APL is set as the brightness value.

Here, the average value of APL calculated in steps S16 and S17 is an average value obtained by adding the APL for each frame constituting the reference frame by the number of reference frames and dividing by the number of reference frames. .. Here, in the case of step S16, the number of reference frames when it is detected that there is a scene change is as follows. For example, as shown by reference numeral 1082 in FIG. 8, the frame (n + 1) for which the presence or absence of a scene change is detected is set as the current frame, and this current frame and M-1 past frames retroactive from the current frame are used. The total number is M. Further, in the case of step S17, the number of reference frames when it is detected that there is no scene change is as follows. For example, as shown by reference numeral 1081 in FIG. 8, the frame (n) for which the presence or absence of a scene change is detected is set as the current frame, and this current frame and N-1 past frames retroactive from the current frame are used. There will be a total of N pieces. Here, N> M.

Next, the process proceeds to step S18, and the correction signal generation unit 136 generates a correction signal for correcting the input brightness of the gamma curve of the first image based on the brightness value of the third image set in step S17.

Subsequently, the gamma curve generation unit 17 generates a gamma curve that corrects the input luminance of the frame for which the presence or absence of a scene change is detected based on the correction signal generated in step S18 (step S19). The panel control unit 15 sets the brightness (output brightness) of each pixel of the display panel 16 from the gamma curve generated by the gamma curve generation unit 14.

In step S11, the method of determining the scene change by comparing the histograms of the frames before and after with each BIN to obtain the gradation difference and comparing the total of the gradation differences with the preset value has been described. , The judgment of the scene change is not limited to this. It does not matter if it is another scene change judgment method.

[Modification example]
As described above, the image comparison by the image comparison unit 131 is performed by the histogram of the brightness of the images before and after the scene change, and it is determined whether or not the first image after the scene change is darker than the second image before the scene change. Was there. However, whether or not the first image is darker than the second image is not determined by the luminance histogram, but the ratio of the region below the preset gradation in the entire region of the first image is a predetermined ratio. It may be done depending on whether or not it is the above.

Specifically, as shown in FIG. 9, in the entire region of the first image 1091 after the scene change, the region (first region) 1091a of the preset gradation (for example, the gradation 3 of 256 gradations) or less. If the ratio is a predetermined ratio (for example, a quarter of the total area), it is determined that the first image 1091 is darker than the image before the scene change. For example, if the area of the first region 1091a having a gradation of 3 or less in the entire region of the first image 1091 is one-third or more of the area of the remaining region (second region) 1091b, the first image 1091 is It is determined that the image is darker than the second image before the scene change. Here, in FIG. 9, for convenience of explanation, the first region 1091a and the second region 1091b are rectangular regions having the same width but different heights H. Therefore, since the height ratio of the first region 1091a, which is a black area, is 1 / 4H, it can be seen that it is 1/4 of the area of the first image 1091.

Further, as shown in FIG. 9, if the first region 1091a, which is a black area, is above the first image 1091, it is assumed that the black area is reflected in the first image 1091 in a band shape, and that the night sky, other characters, and the black characters are reflected. It can be assumed that there are lines, subtitle areas, etc. Further, if the first region 1091a, which is a black area, is below the first image 1091, it can be assumed that the first image 1091 has a night sea or a band.

By the way, in the first embodiment, when the first image after the scene change is darker than the second image before the scene change, the brightness by the first brightness value setting unit 133 is set in order to make it difficult for the black area to appear white. I am trying to set the value. However, even if the first image is not darker than the second image, the luminance value may be set by the first luminance value setting unit 133. For example, if a black area exists, whitening may occur in the existing black area. In such a case, the first luminance value setting unit 133 sets the luminance value.

For example, even if the first image after the scene change is not darker than the second image before the scene change, if a black area having a predetermined shape exists, the black area will appear white. In this case, the predetermined shape of the black area is, for example, the shape of the "mountain" shown by the reference numeral 1101 in FIG. 10, the shape of the "tree" shown by the reference numeral 1102, the shape of the "person" shown by the reference numeral 1103, or the shape of the reference numeral 1104. There are a square shape shown, a triangular shape shown by reference numeral 1105, and the like. Therefore, if the black area has a predetermined shape, the brightness value of the black area is set to the first luminance even if the first image is not darker than the second image in order to make it difficult for the black area to appear white. It needs to be set by the value setting unit 133. In this case, the image comparison unit 131 makes the first image darker than the second image when the region below the preset gradation has a predetermined shape in the first image determined to have a scene change. Judge. As a result, the first luminance value setting unit 133 sets the luminance value of a predetermined shape.

In the second embodiment below, there is a scene change, but the first image is not darker than the second image, and the first image has a black area having a predetermined shape or a black area having a predetermined area or more. An example of setting the brightness value of the output image will be described.

[Embodiment 2]
Other embodiments of the present invention will be described below. For convenience of explanation, the same reference numerals are given to the members having the same functions as the members described in the above-described embodiment, and the description thereof will not be repeated.

(Overview of display device)
The display device 2 according to the present embodiment will be described with reference to FIG. FIG. 11 is a block diagram showing the configuration of the display device 2 according to the present embodiment.

As shown in FIG. 11, the display device 2 has substantially the same configuration as the display device 1 of the first embodiment, and is different in the configuration of the luminance value setting unit 23. Therefore, in the present embodiment, the details of the configuration other than the luminance value setting unit 23 of the display device 2 will be omitted.

(Brightness value setting unit 23)
As shown in FIG. 11, the luminance value setting unit 23 does not include the image comparison unit 131, unlike the luminance value setting unit 13 of the first embodiment, and includes the image determination unit 231, the area determination unit 132, and the first luminance value setting. It includes a unit 133, a second luminance value setting unit 134, a third luminance value setting unit 135, and a correction signal generation unit 136. Here, the image determination unit 231 will be described. Since the operations of the area determination unit 132, the first luminance value setting unit 133, the second luminance value setting unit 134, the third luminance value setting unit 135, and the correction signal generation unit 136 are the same as those in the first embodiment. The explanation is omitted.

When the signal indicating the detection result from the scene change detection unit 12 is a signal indicating that there is a scene change, the image determination unit 231 is the first for the frame targeted for the scene change detection, that is, the frame detected as having the scene change. 1 Determine whether the image is dark or not. That is, the image determination unit 231 does not make a relative comparison and determination as to whether or not the first image is dark, but makes an absolute determination using an arbitrary standard.

For example, the image determination unit 231 may determine that the output image is dark when the proportion of pixels having a luminance value or less set in advance is equal to or greater than a predetermined proportion in the histogram of the luminance of the output image.

Alternatively, the image determination unit 231 determines that the first image is dark when the ratio of the region below the preset gradation to the predetermined region of the first image is equal to or greater than the predetermined ratio. May be good.

Further, the image determination unit 231 may determine the first image as a dark image when the region having a gradation or less set in advance has a predetermined shape with respect to the predetermined region of the first image. good. Here, the predetermined shape is, for example, the shape of the "mountain" shown by the reference numeral 1101 in FIG. 10, the shape of the "tree" shown by the reference numeral 1102, and the shape of the "person" shown by the reference numeral 1103. Alternatively, there are a square shape shown by reference numeral 1104, a triangular shape shown by reference numeral 1105, and the like.

(Gamma curve generation process)
The flow of the gamma curve generation process executed by the display device 2 having the above configuration will be described with reference to FIG. FIG. 12 is a flowchart showing the flow of the gamma curve generation process. The gamma curve generation process is substantially the same as the flowchart shown in FIG. 3 of the first embodiment. Therefore, here, only step S22, which is different from the flowchart shown in FIG. 3 of the first embodiment, will be described.

In step S22, the image determination unit 231 of the luminance value setting unit 23 determines whether or not the first image is dark from the image detected as having a scene change. Here, the image determination unit 231 determines that the first image is dark when the proportion of pixels equal to or less than the preset luminance value is equal to or greater than the predetermined proportion in the histogram of the luminance of the first image.

In step S22, the process after the image determination unit 231 determines that the first image is dark (YES), the process after the first image is determined not to be dark (NO), and in step S11, there is no sea change. Since the processing for the detected image is the same as the flowchart shown in FIG. 3 of the first embodiment, the description thereof will be omitted.

By the above processing, it is possible to obtain an appropriate gamma curve for the first image determined to have a scene change and to be determined to be dark. As a result, the first region, which is a low gradation region in the first image, can be immediately darkened, and the brightness of the second region, which is a region other than the low gradation region, can be gradually changed. As a result, in the output image after the scene change, it is possible to suppress the flicker of the screen and suppress the whitening in the low gradation region.

[Embodiment 3]
Other embodiments of the present invention will be described below. For convenience of explanation, the same reference numerals are given to the members having the same functions as the members described in the above-described embodiment, and the description thereof will not be repeated.

(Overview of display device)
The display device 3 according to the present embodiment will be described with reference to FIG. FIG. 13 is a block diagram showing the configuration of the display device 3 according to the present embodiment.

As shown in FIG. 13, the display device 3 has substantially the same configuration as the display device 1 of the first embodiment, and is different in the configuration of the luminance value setting unit 33. Therefore, in the present embodiment, the details of the configuration other than the luminance value setting unit 33 of the display device 3 will be omitted.

(Brightness value setting unit 33)
As shown in FIG. 13, the brightness value setting unit 33 does not include the image comparison unit 131, unlike the brightness value setting unit 13 of the first embodiment, and includes the area determination unit 331, the first brightness value setting unit 133, and the second. It includes a luminance value setting unit 134, a third luminance value setting unit 332, and a correction signal generation unit 136. Here, the area determination unit 331 and the third luminance value setting unit 332 will be described. Since the operations of the first luminance value setting unit 133, the second luminance value setting unit 134, and the correction signal generation unit 136 are the same as those in the first embodiment, the description thereof will be omitted.

When the signal indicating the detection result from the scene change detection unit 12 is a signal indicating that there is a scene change, the area determination unit 331 determines the area as follows. Whether the first area has a gradation lower than the preset gradation with respect to the predetermined area of the first image corresponding to the frame targeted for scene change detection, that is, the frame detected as having a scene change. It is determined whether the area is a second area other than the first area. Here, the predetermined area may be the entire area or a part of the image. Further, the area may be one pixel or a set of a plurality of pixels.

The first luminance value setting unit 133 sets the luminance value of the first region determined by the region determination unit 331. The second luminance value setting unit 134 sets the luminance value of the second region determined by the region determination unit 331.

When the third luminance value setting unit 332 receives the signal indicating no scene change sent from the scene change detection unit 12, the current frame and the past frame consisting of several frames continuously retroactively from the current frame. The brightness value of the third image of the current frame is set with reference to.

(Gamma curve generation process)
The flow of the gamma curve generation process executed by the display device 3 having the above configuration will be described with reference to FIG. FIG. 14 is a flowchart showing the flow of the gamma curve generation process. The gamma curve generation process is substantially the same as the flowchart shown in FIG. 3 of the first embodiment. Therefore, only step S32, which is different from the flowchart shown in FIG. 3 of the first embodiment, will be described.

The area determination unit 331 of the luminance value setting unit 33 has a gradation lower than the preset gradation with respect to a predetermined area of the first image corresponding to the frame detected as having a scene change in step S32. It is determined whether it is the first region or the second region other than the first region. Here, when the brightness is 256 gradations, the preset gradation is set to the luminance value 3. Therefore, the first region is a region composed of pixels having a luminance value of 0 to 3. After the area is determined by the area determination unit 331, the process proceeds to step S33 and step S34.

Here, the processes in steps S33 and S34, and the subsequent processes in steps S36 and S37 are the same processes as in steps S14, S15, S18, and S19 of FIG. 3 of the first embodiment, respectively, as described above. The explanation is omitted. Further, the process after it is determined in step S31 that there is no scene change, that is, the process in step S35 is the same process as step S17 in FIG. 3 of the first embodiment, and thus the description thereof will be omitted.

By the above processing, an appropriate gamma curve is obtained for an input image having a region determined to have a scene change and determined to be dark. As a result, the first region, which is a low gradation region in the first image, can be immediately darkened, and the brightness of the second region, which is a region other than the low gradation region, can be gradually changed. As a result, in the output image after the scene change, it is possible to suppress the flicker of the screen and suppress the whitening in the low gradation region.

[Example of implementation by software]
The control block of the display device 1 (particularly the brightness value setting unit 13, the gamma curve generation unit 14 and the panel control unit 15), and the control block of the display device 2 (particularly the brightness value setting unit 23, the gamma curve generation unit 14 and the panel control unit 15). ) And the control block of the display device 3 (particularly, the luminance value setting unit 33, the gamma curve generation unit 14 and the panel control unit 15) are realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like. It may be realized by software.

In the latter case, the display devices 1, 2, and 3 include a computer that executes a program instruction, which is software that realizes each function. The computer includes, for example, at least one processor (control device) and at least one computer-readable recording medium that stores the program. Then, in the computer, the processor reads the program from the recording medium and executes it, thereby achieving the object of the present invention. As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, a "non-temporary tangible medium", for example, a ROM (Read Only Memory) or the like, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. Further, a RAM (Random Access Memory) for expanding the above program may be further provided. Further, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. It should be noted that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

〔summary〕
In the display device according to the first aspect of the present invention, the scene change detection unit 12 that detects the presence or absence of scene switching in the input image composed of a plurality of frames and the scene change detection unit 12 indicate that there is a scene change. A luminance value setting unit 13 that sets the luminance value of the first image for the detected frame, and a display control unit (gamma curve generation unit 14, panel control) that displays an image on the display unit based on the luminance value of the first image. The luminance value setting unit 13 includes a unit 15) and a first region having a gradation lower than a preset gradation with respect to a predetermined region of the first image, or a region other than the first region. The area determination unit 132 that determines whether it is the second region and the luminance value of the first region determined by the region determination unit 132 are the second of the low gradation including the luminance value of the first region of the first image. The luminance value of the second region determined by the first luminance value setting unit 133 and the region determination unit 132 to set the luminance value within one range includes the luminance value of the second region of the first image. Moreover, it is characterized by including a second luminance value setting unit 134 for setting a luminance value in the second range having a luminance value higher than the upper limit value of the first range as a lower limit value.

According to the above configuration, the first luminance value setting unit is the luminance value of the first region (low gradation region) having a gradation lower than the preset gradation in the first image for the frame in which the scene change is detected. Is set to a luminance value within the first range of low gradation including the luminance value of the first region of the first image, and the second luminance value setting unit is other than the first region of the first image. The luminance value of the second region is set to the luminance value in the second range including the luminance value of the second region of the first image and having the luminance value higher than the upper limit value of the first range as the lower limit value. .. As a result, the first region, which is a low gradation region in the first image, can be immediately darkened, and the brightness of the second region, which is a region other than the low gradation region, can be gradually changed. In the first image after the scene change, it is possible to suppress whitening in a low gradation region while suppressing flicker on the screen.

In the display device according to the second aspect of the present invention, in the first aspect, the first brightness value setting unit 133 sets the brightness value of the first region to the same brightness value as the first region of the first image. Then, the second brightness value setting unit 134 is based on the first image information corresponding to the first image and the second image information corresponding to the second image for the frame past the frame for the first image. , The second range may be set.

According to the above configuration, the first luminance value setting unit sets the luminance value of the first region to the same luminance value as the first region of the first image, and the second luminance setting unit sets the brightness value of the first region. The second range is set based on the first image information corresponding to one image and the second image information corresponding to the second image for a frame past the frame for the first image. As a result, the first region, which is a low gradation region in the first image, can be immediately darkened in the same manner as the first region of the first image, and the second region, which is a region other than the low gradation region, can be darkened immediately. Since the brightness can be changed gently, it is possible to suppress the flicker of the screen and more reliably suppress the whitening in the low gradation region in the output image after the scene change.

The display device according to the third aspect of the present invention determines the brightness of the first image and the second image with respect to the frame immediately before the frame detected by the scene change detection unit 12 as having a scene change in the first aspect. An image comparison unit 131 for comparison is provided, and when the image comparison unit 131 determines that the first image is darker than the second image, the region determination unit 132 relates to a predetermined region of the first image. Therefore, it is determined whether the first region has a gradation lower than the preset gradation or the second region other than the first region, and the first luminance value setting unit 133 is determined by the region determination unit 132. The brightness value of the first region is set to the brightness value within the first range, and the second brightness value setting unit 134 sets the brightness value of the second region determined by the region determination unit 132. The brightness value may be set within the second range.

According to the above configuration, when it is determined that the first image is darker than the second image, the first luminance value setting unit sets the luminance value of the first region in the first image to the said output image. The luminance value in the first range including the luminance value of the first region is set, and the second luminance value setting unit outputs the luminance value of the second region other than the first region in the first image. The luminance value in the second range including the luminance value in the second region of the image and having the luminance value higher than the upper limit value in the first range as the lower limit value is set. As a result, the first region, which is a low gradation region in the output image darker than before the scene change, can be immediately darkened in the same manner as the first region of the output image, and is a region other than the low gradation region. Since the brightness of the second region can be gradually changed, it is possible to suppress the flicker of the screen in the output image after the scene change and more reliably suppress the whitening in the low gradation region.

In the display device according to the fourth aspect of the present invention, in the third aspect, in the image comparison unit 131, the ratio of pixels having a luminance value equal to or less than a preset threshold in the luminance histogram of the first image is the second image. When it is equal to or more than the ratio of pixels having a brightness value equal to or less than the threshold value in the brightness histogram of the first image, it may be determined that the first image is darker than the second image.

According to the above configuration, the image comparison unit displays the first image from the second image when the ratio of pixels equal to or less than the preset brightness value is equal to or higher than a predetermined ratio in the histogram of the brightness of the first image. Is also determined to be a dark image, which is an effective determination method when the entire first image is dark.

In the above aspect 1 or 2, the display device according to the fifth aspect of the present invention further includes an image determination unit 231 for determining whether or not the first image is dark, and the image determination unit 231 allows the first image to be displayed. When it is determined that it is dark, the area determination unit 132 has a first region having a gradation lower than a preset gradation or a second region other than the first region with respect to a predetermined region of the first image. The first luminance value setting unit 133 determines whether it is a region, sets the luminance value of the first region determined by the region determination unit 132 to the luminance value within the first range, and sets the second luminance value. The value setting unit 134 may set the luminance value of the second region determined by the region determination unit 132 to the luminance value within the second range.

According to the above configuration, in the image determination, when the ratio of the region of the preset gradation or less in the entire region of the first image is equal to or more than the predetermined ratio, the first image is darker than the second image. Therefore, even if the entire image is not dark, it is an effective judgment method when a part of the area is dark.

In the display device according to the sixth aspect of the present invention, in the fifth aspect, when the image determination unit 231 has a predetermined ratio or more of pixels having a luminance value or less set in advance in the luminance histogram of the first image. In addition, the first image may be determined to be dark.

According to the above configuration, the image determination unit determines that the output image is dark when the proportion of pixels equal to or less than the preset luminance value is equal to or greater than the predetermined proportion in the histogram of the luminance of the first image. It can be appropriately determined that the entire image is dark.

In the display device according to the seventh aspect of the present invention, in the fifth aspect, the image determination unit 231 has a predetermined ratio or more of a region having a gradation or less set in advance with respect to a predetermined region of the first image. At this time, the first image may be determined to be dark.

According to the above configuration, the image determination unit determines that the first image is dark when the ratio of the region below the preset gradation to the predetermined region of the first image is equal to or more than the predetermined ratio. Therefore, it can be appropriately determined that the entire image is dark.

In the display device according to the eighth aspect of the present invention, in the fifth aspect, when the image determination unit 231 has a predetermined shape in a region having a gradation or less set in advance with respect to a predetermined region of the first image. In addition, the first image may be determined to be a dark image.

According to the above configuration, the image determination unit determines that the first image is a dark image when the region having a predetermined gradation or less has a predetermined shape with respect to the predetermined region of the first image. Therefore, even if the entire image is not dark, it is an effective determination method when the dark area has a predetermined shape.

The display method according to aspect 9 of the present invention is a display method for displaying the output image for the input image on the display device based on the output luminance set according to the change of the scene of the input image composed of a plurality of frames. Therefore, with respect to a scene change detection step for detecting the presence or absence of scene switching in frame units of the input image and a predetermined area of the first image for the frame detected by the scene change detection step as having a scene change. The area determination step for determining whether the first area has a gradation lower than the preset gradation or the second area other than the first area, and the luminance value of the first area determined by the area determination step. The first luminance value setting step for setting the luminance value within the first range of low gradation including the luminance value of the first region of the first image, and the second region determined by the region determination step. A second luminance value in which the luminance value is set to a luminance value in the second range including the luminance value in the second region of the first image and having a luminance value higher than the upper limit value of the first range as the lower limit value. It is characterized by including a setting step.

According to the above configuration, the first luminance value setting step is the first region (low gradation region) of the gradation lower than the preset gradation in the first image for the frame in which the scene change is detected. The luminance value is set to a luminance value within the first range including the luminance value of the first region of the first image, and the second luminance value setting step is a second other than the first region of the first image. The luminance value of the region is set to the luminance value in the second range including the luminance value of the second region of the first image and having the luminance value higher than the upper limit value of the first range as the lower limit value. As a result, the first region, which is a low gradation region in the first image, can be immediately darkened, and the brightness of the second region, which is a region other than the low gradation region, can be gradually changed. In the output image after the scene change, it is possible to suppress the whitening in the low gradation region while suppressing the flicker of the screen.

The display device according to each aspect of the present invention may be realized by a computer, and in this case, the display device is realized by the computer by operating the computer as each part (software element) provided in the display device. Display control programs for display devices and computer-readable recording media on which they are recorded also fall within the scope of the present invention.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention. Further, by combining the technical means disclosed in each embodiment, new technical features can be formed.

1, 2, 3 Display device 11 Image acquisition unit 12 Scene change detection unit 13 Luminance value setting unit 14 Gamma curve generation unit (display control unit)
15 Panel control unit (display control unit)
16 Display panel 17 Gamma curve generation unit 23 Brightness value setting unit 33 Brightness value setting unit 111 Storage unit 112 Analysis unit 131 Image comparison unit 132 Area determination unit 133 First brightness value setting unit 134 Second brightness value setting unit 135 Third brightness Value setting unit 1351 Reference frame number setting unit 1352 Average value calculation unit 136 Correction signal generation unit 231 Image judgment unit 331 Area determination unit 332 Third luminance value setting unit B Threshold Xblk Threshold

Claims (10)

A scene change detector that detects the presence or absence of scene switching in frame units for an input image composed of multiple frames, and a scene change detector.
A luminance value setting unit that sets the luminance value of the first image for a frame detected by the scene change detector as having a scene change, and a luminance value setting unit.
A display control unit that displays an image on the display unit based on the luminance value of the first image is included.
The brightness value setting unit is
A region determination unit for determining whether a first region having a gradation lower than a preset gradation or a second region other than the first region is determined for each predetermined region of the first image.
A first luminance value setting that sets the luminance value of the first region determined by the region determination unit to a luminance value within the first range of low gradation including the luminance value of the first region of the first image. Department and
The luminance value of the second region determined by the region determination unit includes the luminance value of the second region of the first image, and the luminance value higher than the upper limit value of the first range is set as the lower limit value. A display device including a second luminance value setting unit for setting a luminance value within the second range. The first luminance value setting unit sets the luminance value of the first region to the same luminance value as that of the first region of the first image.
The second luminance value setting unit is based on the first image information corresponding to the first image and the second image information corresponding to the second image for a frame past the frame for the first image. 2. The display device according to claim 1, wherein a range is set. It is provided with an image comparison unit that compares the brightness of the first image with the second image with respect to the frame immediately before the frame detected by the scene change detection unit as having a scene change.
When the image comparison unit determines that the first image is darker than the second image,
The area determination unit determines whether the predetermined area of the first image is a first area having a gradation lower than a preset gradation or a second area other than the first area.
The first luminance value setting unit sets the luminance value of the first region determined by the region determination unit to the luminance value within the first range.
The display device according to claim 1, wherein the second luminance value setting unit sets the luminance value of the second region determined by the region determination unit to the luminance value within the second range. .. The image comparison unit is
When the proportion of pixels having a luminance value equal to or less than a preset threshold in the luminance histogram of the first image is equal to or greater than the proportion of pixels having a luminance value equal to or less than the threshold in the luminance histogram of the second image, the first image is used. The display device according to claim 3, wherein the image is determined to be darker than the second image. An image determination unit for determining whether or not the first image is dark is further provided.
When the first image is determined to be dark by the image determination unit,
The area determination unit determines whether the predetermined area of the first image is a first area having a gradation lower than a preset gradation or a second area other than the first area.
The first luminance value setting unit sets the luminance value of the first region determined by the region determination unit to the luminance value within the first range.
The first or second aspect of the present invention, wherein the second luminance value setting unit sets the luminance value of the second region determined by the region determination unit to the luminance value within the second range. Display device. The image judgment unit is
The display according to claim 5, wherein in the histogram of the brightness of the first image, when the ratio of pixels having a luminance value or less set in advance is equal to or more than a predetermined ratio, the first image is determined to be dark. Device. The image judgment unit is
The fifth aspect of claim 5, wherein the first image is determined to be dark when the ratio of the region having a gradation or less set in advance to the predetermined region of the first image is equal to or more than the predetermined ratio. Display device. The image judgment unit is
The fifth aspect of claim 5, wherein the first image is determined to be a dark image when the region having a gradation or less set in advance has a predetermined shape with respect to the predetermined region of the first image. Display device. It is a display method for displaying an output image for the input image on a display device based on the output brightness set according to the change of the scene of the input image composed of a plurality of frames.
A scene change detection step that detects the presence or absence of scene switching in frame units of the input image, and
For each predetermined region of the first image for the frame detected by the scene change detection step, the first region has a gradation lower than the preset gradation or the second region other than the first region. The area determination step to determine whether
First luminance value setting for setting the luminance value of the first region determined by the region determination step to the luminance value within the first range of low gradation including the luminance value of the first region of the first image. Steps and
The luminance value of the second region determined by the region determination step includes the luminance value of the second region of the first image, and the luminance value higher than the upper limit value of the first range is set as the lower limit value. A display method including a second luminance value setting step for setting a luminance value within two ranges. A control program for operating a computer as the display device according to any one of claims 1 to 8, wherein the computer functions as each of the above-mentioned parts.

Images