Patent Application
20190052853
The present invention relates to a display control device or the like configured to reduce color noise in an image to be displayed.
In recent years, a High Dynamic Range (HDR) signal having an abundant information amount ranging from low luminance to high luminance has been standardized in regard. to a signal of an image (video) to be displayed on a display apparatus such as a television receiver (television set). However, when an image based on the HDR signal is accurately displayed on the display apparatus, color noise may occur in a low luminance region of the image.
PTL 1: Japanese Unexamined Patent Application Publication No. 2007-312331 (Publication Date: Nov. 29, 2007)
PTL 2: Japanese Unexamined Patent Application Publication No. 2000-23181 (Publication Date: Jan. 21, 2000)
Techniques for reducing noise in an image (video) to be displayed on a display apparatus by using an averaging filter or the like are known. (for example, see PTL 1 and PTL 2 below). However, such techniques involve problems that an information amount of the image decreases, leading to a blurred image and/or loss of x sense of detail.
In view of the foregoing, it is an object of the present invention to realize a display control device or the like configured to reduce color noise in a low luminance region of an image without reducing as information amount of the image.
To achieve the object, a display control device according to one aspect of the present invention includes a saturation changing unit configured to reduce saturation of a pixel having luminance lower than luminance corresponding to a first value according to luminance of an image to be displayed while the luminance of the pixel is maintained.
Moreover, to achieve the object, a control method for a display control device according to an aspect of the present invention includes a saturation changing step of reducing saturation of a pixel having luminance lower than luminance corresponding to a first value according to luminance of an image to be displayed while the luminance of the pixel is maintained.
An aspect of the present invention provides the effect that color noise in a low luminance region of an image can be reduced without reducing the information amount of the image.
A first embodiment of the present invention will be described in detail below with reference to
First, a scheme of the present invention will be described with reference to
The noise reduction apparatus 1 shown in
Note that the present embodiment. describes the noise reduction apparatus 1 with which the television set 10 shown in
Next, main components of the television set 10 equipped with the noise reduction apparatus 1 will be described with reference to
As illustrated, the television set 10 includes a broadcast reception unit 11 configured to receive a broadcast stream, a control unit 12 configured to control overall components in the television set 10, a storage unit 13 configured to store various types of data to be used in the television set 10, and a display unit 14 configured to display video of a broadcast program. The broadcast reception unit 11 receives, for example, a broadcast stream containing a broadcast program broadcast in digital terrestrial broadcasting, satellite broadcasting, or the like. Moreover, the broadcast reception unit 11 includes, for example, an antenna and a tuner.
The control unit 12 includes a broadcast signal control unit 121, a brightness distribution generation unit 122 (maximum value specification unit), a luminance coefficient decision unit 123, a saturation coefficient decision unit 124, a hue coefficient decision unit 125, a computation coefficient calculation unit 126, a saturation correction unit 127 (saturation changing unit), and a video processing unit 128. Moreover, the storage unit 13 stores luminance coefficient, decision information 131, a luminance look-up table 132, a saturation look-up table 133, and a hue look-up table 134. Note that in
The broadcast signal control unit 121 outputs information of each frame of the broadcast program included in the broadcast stream, which is received, to each component in the control unit 12. Specifically, the broadcast signal control unit 121 outputs luminance information d1 denoting luminance of each pixel of a frame and chrominance information d2 denoting saturation and hue of each pixel of the frame to the saturation correction unit 127. Moreover, the broadcast signal control unit 121 outputs the luminance information d1 to the brightness distribution generation unit 122. Furthermore, the broadcast signal control unit 121 outputs the chrominance information d2 to the saturation coefficient decision unit 124 and the hue coefficient decision unit 125.
Note that when the broadcast signal control unit 121 acquires color component information (specifically, values of a red component, a green component, a blue component of each pixel of the frame), the broadcast signal control unit 121 converts the color component information into the luminance information d1 and the chrominance information d2 and outputs the luminance information d1 and the chrominance information d2 to each component of the above-described control unit 12. Here, as a method for converting the color component information into the luminance information d1 and the chrominance information d2, a known technique may be used.
The brightness distribution generation unit 122 generates a brightness distribution (luminance histogram) of the frame based on the luminance information d1, which is acquired. For example, the brightness distribution generation unit 122 generates the brightness distribution shown in
The luminance coefficient decision unit 123 determines a luminance coefficient Ay (first coefficient) which is a coefficient according to the luminance of the frame received by the television set 10. Specifically, the luminance coefficient decision unit 123 first reads the luminance LUT 132 from the storage unit 13. The luminance LUT 132 stores information denoting the function of the luminance coefficient AY with respect to the luminance and, for example, stores the function shown in
As illustrated in
Subsequently, the luminance coefficient decision unit 123 determines a value Y1 and a value Y2 in the luminance LUT 132 and determines the luminance coefficient AY at each luminance of the frame. Specifically, the luminance coefficient decision unit 123 reads the luminance coefficient decision information 131 from the storage unit 13, and from the frame luminance maximum value Ymax and the luminance coefficient decision information 131, which is read, the luminance coefficient decision unit 123 defines the low luminance range in the frame.
The luminance coefficient decision information 131 includes a low luminance range decision coefficient B, noise reduction range decision information, and adjustment range decision information. The low luminance range decision coefficient B is a coefficient for determining the noise reduction range and. the adjustment range. In other words, the low luminance range decision coefficient B is a coefficient for defining the low luminance range in the frame. In the present embodiment, an example in which the low luminance range decision coefficient B=0.005 is described, but this example should not be construed as limiting. The noise reduction range decision information is information for determining the value Y1. In the present embodiment, the noise reduction range decision information is a computation formula, and an example in which Y1=Ymax×B is described. However, the noise reduction range decision information is not limited to this example as long as it is information which enables the value Y1 to be determined. The adjustment range decision information is information for determining the value Y2. In the present embodiment, the adjustment range decision information is a computation formula, and an example in which Y2=Y1×2 is described. However, the adjustment range decision information is not limited to this example as long as it is information which enables the value Y2 to be determined.
For example, when the frame luminance maximum value Ymax is 100 cd/m2, the luminance coefficient decision unit 123 determines 0.5 cd/m2 for the value Y1 and 1 cd/m2 for the value Y2. Then, the luminance coefficient decision unit 123 substitutes the value Y1, the value Y2, and the frame luminance maximum value Ymax into the luminance LUT 132 to determine the luminance coefficient AY with respect to the luminance of each pixel of the frame, which is received. As illustrated in
Moreover, it can also be said that the luminance coefficient decision unit 123 further determines a second threshold value (value Y1, second value) at the luminance of the image, and for a pixel included in a luminance range of 0 to the value Y1, the noise reduction apparatus 1 reduces saturation to 0, and for a pixel included in a luminance range of the value Y1 to the value Y2, the noise reduction apparatus 1 reduces the extent of reduction of the saturation as the luminance increases.
Finally, the luminance coefficient decision unit 123 outputs to the computation coefficient calculation unit 126 the luminance coefficient AY, which is determined.
Note that the function. stored in the luminance LUT 132 is not limited to the example in
Moreover, when the frame is overall bright (that is, when the frame luminance minimum value Ymin and the frame luminance maximum value Ymax are large), the value Y1 is also large. Thus, a pixel whose saturation originally does not have to be reduced may also be subjected to a reduction of saturation. Thus, when the frame luminance minimum value Ymin exceeds the prescribed value (for example, 5 cd/m2), the luminance coefficient decision unit 123 may determine the luminance coefficient AY is 0 regardless of the luminance of pixels of the frame. In this way, when the frame is overall bright, the noise reduction process based on the luminance is not performed, and therefore, it is possible to prevent excessive reduction of saturation.
The saturation coefficient decision unit 124 determines a saturation coefficient A5 which is a coefficient according to the saturation of the frame received by the television set 10. Specifically, when the saturation coefficient decision unit 124 acquires the chrominance information d2 from the broadcast signal control unit 121, the saturation.
coefficient decision unit 124 first calculates a saturation S of each pixel. Specifically, the chrominance information d2 acquired by the saturation coefficient decision unit 124 includes blue chrominance Cb denoting blue saturation and hue and red chrominance Cr denoting red. saturation and hue. Here, with reference to
Thus, the saturation coefficient decision unit 124 substitutes the blue chrominance Cb and the red chrominance Cr, which are acquired, into the computation formula S=(Cb2+Cr2)1/2 to calculate the saturation S. Note that this computation formula is a mere example, and the calculation method of the saturation S is not limited to this example. For example, the blue chrominance Cb and the red chrominance Cr, which are acquired, may be substituted into the computation formula S=|Cb|+|Cr| to calculate the saturation S. Note that |Cb| and |Cr| are respectively the absolute value of the blue chrominance Cb and the absolute value of the red chrominance Cr. That is, the saturation S increases as the absolute values of the blue chrominance Cb and the red chrominance Cr increase, and it is only required that the calculation method of the saturation S is a method that performs computation which can express this relationship.
Subsequently, the saturation coefficient decision unit 124 reads the saturation LUT 133 from the storage unit 13. The saturation LUT 133 stores information denoting the function of the saturation coefficient AS with respect to the saturation S and, for example, stores the function shown in
Note that the function stored in the saturation LUT 133 is not limited to the example shown in
The hue coefficient decision unit 125 determines a hue coefficient AH which is a coefficient according to the hue of the frame received by the television set 10. Specifically, when the hue coefficient decision unit 125 acquires the chrominance information d2 from the broadcast signal control unit 121, the hue coefficient decision unit 125 first calculates hue H of each pixel. As described above, the hue H corresponds to an angle formed between a straight line passing through the origin O and the point Cb on the horizontal axis and a straight line passing through the origin O and the point P in the planar coordinate system in
Subsequently, the hue coefficient decision unit 125 reads the hue LUT 134 from he storage unit 13. The hue LUT 134 stores information denoting the function of the hue coefficient AH with respect to the hue H and, for example, stores the function shown in
Note that the function stored in the hue LUT 134 is not limited to the example in
The computation coefficient calculation unit 126 calculates a computation coefficient AT (noise reduction coefficient) for reducing the saturation of each pixel of the frame based on the luminance coefficient AY, the saturation coefficient AS, and the hue coefficient AH. Specifically, the luminance coefficient AY, the saturation coefficient AS, and the hue coefficient AH, which are acquired, are substituted into the computation formula AT=AY×AA×AH to calculate the computation coefficient AT. Note that the computation formula for calculating the computation coefficient. AT is a mere example and is not limited to this example. The computation coefficient calculation unit 126 outputs the computation coefficient AT, which is calculated, to the saturation correction unit 127.
Here, the computation coefficient AT according to the present embodiment is a coefficient which is in proportion to the luminance coefficient A. That is, the computation. coefficient A according to the present embodiment is a value which increases as the luminance coefficient AY increases. Moreover, the computation coefficient AT according to the present embodiment is a coefficient which is in proportion to the saturation coefficient AS determined based on the function (see
The saturation correction unit 127 reduces, based on the computation coefficient AT, the saturation of a pixel which is included in pixels of the frame and whose luminance is included within the low luminance range. Specifically, the video processing unit 128 calculates blue chrominance Cb′ serving as a blue chrominance Cb after correction (in other words, after the saturation is reduced) and red chrominance Cr′ serving as a red chrominance Cr after correction (in other words, after the saturation is reduced) respectively from the blue chrominance Cb and the red chrominance Cr included in the chrominance information d2 acquired from the broadcast signal control unit 121 and the computation coefficient AT acquired from the computation coefficient calculation unit 126. More specifically, the blue chrominance Cb, the red chrominance Cr and the computation coefficient AT, which are acquired, are substituted into the computation formula Cb′=(1−AT)×Cb and the computation formula Cr′(1−AT)×Cr to calculate the blue chrominance Cb′ and the red chrominance Cr′. Then, the saturation correction unit 127 outputs the blue chrominance Cb′ and red chrominance Cr′, which are calculated, to the video processing unit 128.
Here, correction of the saturation by the saturation correction unit 127 will be described in detail. Detailed description will be given later, but the video processing unit 128 causes the display unit 14 to display a frame based on the luminance information d1, the blue chrominance Cb′, and the red chrominance Cr′ acquired from the saturation correction unit 127. As described above, the blue chrominance Cb′ and the red chrominance Cr′ are respectively obtained by multiplying the red chrominance blue Cb and the red chrominance Cr, which are acquired, by a value obtained by subtracting the computation coefficient AT from 1. Here, as described above, the saturation S is saturation that increases as the absolute value of the blue chrominance Cb and the absolute value of the red chrominance Cr increase (for example, the saturation S is saturation calculated based on the computation formula S=(Cb2+Cr2)1/2). That is, the saturation S corresponds to a value which changes alone with the value of the blue chrominance and the value of the red chrominance. As stated above, the saturation correction unit 127 changes the value of the blue chrominance Cb and the value of the red chrominance Cr to the blue chrominance Cb′ and the red chrominance Cr′, thereby changing the saturation of each pixel in the frame displayed on the display unit 14 from the saturation of each pixel of the frame, which is received.
Moreover, as described above, the computation coefficient AT is calculated through multiplication of the luminance coefficient AY, the saturation coefficient AS, and the hue coefficient AH. That is, the value of the computation coefficient AT increases as the value of each of the luminance coefficient AY, the saturation coefficient AS, and the hue coefficient AH increases. Here, since each of the luminance coefficient AY, the saturation coefficient AS, and the hue coefficient AH is a value larger than or equal to 0 and smaller than or equal to 1, the computation coefficient AT is also a value larger than or equal to 0 and smaller than or equal to 1, and in the same way, (1−AT) is also a value larger than or equal to 0 and smaller than or equal to 1. Thus, the value of the blue chrominance Cb′ and the value of the red chrominance Cr′ are respectively equal to the value of the blue chrominance Cb, which is acquired and the value of the red chrominance Cr, which is acquired (where computation coefficient AT=0), or the absolute value of the blue chrominance Cb′ and the absolute value of the red chrominance Cr′ are respectively smaller than the value of the blue chrominance Cb, which is acquired and the value of the red chrominance Cr, which is acquired (where 0<computation coefficient. AT≤1). Moreover, the absolute value of the blue chrominance Cb′ and the absolute value of the red chrominance Cr′ decrease as the value of the computation coefficient AT increases. That is, the saturation S based on the blue chrominance Cb′ and the red chrominance Cr′ (the saturation S of each pixel in the frame displayed on the display unit 14) decrease as the value of the computation coefficient AT increases and the difference from the saturation S of each pixel in the frame, which is received, increases (in other words, as the value of the luminance coefficient AY increases, the extent of reduction of the saturation S increases).
Moreover, as described above, the value of the luminance coefficient AY according to the present embodiment is 0 when the luminance of each pixel is not included within the low luminance range (range of 0 cd/m2 to Y2 cd/m2). That is, for each pixel whose luminance is not included within the low luminance range, the computation coefficient AT is 0, and therefore, the noise reduction apparatus 1 does not correct the saturation of the pixel (saturation is not reduced). That is, the noise reduction apparatus 1 according to the present embodiment reduces only the saturation of each pixel having luminance included within the low luminance range.
Moreover, as the luminance information d1, the luminance information d1 of the frame, which is received is output as is to the video processing unit 128. Thus, the frame displayed on the display unit 14 is the frame, which is received, and in which luminance of each pixel is maintained. Note that the broadcast signal control unit 121 may output the luminance information d1 to the video processing unit 128 but not to the saturation correction unit 127.
Moreover, the blue chrominance Cb′ and the red chrominance Cr′ are respectively calculated by multiplying the blue chrominance Cb and the red chrominance Cr by (1−AT), and therefore, Cr/Cb=Cr′/Cb′ holds true. Thus, the hue of each pixel of the frame displayed on the display unit 14 is the hue H of each pixel of the frame, which is received, the hue H being maintained.
The video processing unit 128 causes the display unit 14 to display the frame based on the luminance information d1, the blue chrominance Cb′, and the red chrominance Cr′, which are acquired. Thus, the display unit 14 displays the frame in which the saturation of a pixel having luminance included within the low luminance range is corrected (saturation is reduced).
As described above, the noise reduction apparatus 1 according to the present embodiment reduces the saturation. of the pixel having low luminance, and therefore, it is possible to reduce the occurrence of color noise in the pixel. Moreover, it is possible to perform a noise reduction process on only a pixel which requires the noise reduction. Moreover, since the luminance of each pixel is maintained, the occurrence of a blurred area or a dark area due to a reduction of the luminance can be reduced.
Next, with reference to
First, the broadcast signal control unit 121 stands by for the reception of a frame of a broadcast program (step S1, hereinafter “step” is omitted). When receiving the frame (if YES is determined in S1), the broadcast signal control unit 121 outputs a luminance information d1 and a chrominance information d2 to the saturation correction unit 127. Moreover, the broadcast signal control unit 121 outputs the luminance information d1 to the brightness distribution generation unit 122. Furthermore, the broadcast signal control unit 121 outputs the chrominance information d2 to the saturation coefficient decision unit 124 and the hue coefficient decision unit 125.
Subsequently, the brightness distribution generation unit 122 generates a brightness distribution based on the luminance information d1, which is acquired (S2). Then, the brightness distribution generation unit 122 refers to the brightness distribution, which is generated, to specify a frame luminance maximum value Ymax and a frame luminance minimum value Ymin, and the brightness distribution generation unit 122 outputs the frame luminance maximum value Ymax and the frame luminance minimum value Ymin to the luminance coefficient decision unit 123.
Subsequently, the luminance coefficient decision unit 123 defines a low luminance range in the frame, which is received (S3). Specifically, the luminance coefficient decision unit 123 calculates, from the frame luminance maximum value Ymax, which is acquired and the low luminance range decision coefficient B read from the storage unit 13, a value Y1 and a value Y2 in a function stored in the Luminance LUT 132 read from the storage unit 13 so as to define the low luminance range (in other words, a specific numerical value of the value Y2). Then, the luminance coefficient decision unit 123 determines a luminance coefficient AY (S4). Specifically, the value Y1, value Y2, and the frame luminance maximum value Ymax are substituted into the function stored in the luminance LUT 132, which is read, to determine the luminance coefficient AY with respect to the luminance of each pixel of the frame, which is received. Note that, as described above, the luminance coefficient AY for luminance which is not included within the low luminance range is 0. The luminance coefficient decision unit 123 outputs, to the computation coefficient calculation unit 126, the luminance coefficient AY, which is determined.
Subsequently, the saturation coefficient decision unit 124 determines a saturation coefficient AS (S5). Specifically, the saturation coefficient decision unit 124 calculates the saturation S from a blue chrominance Cb and a red chrominance C, included in the chrominance information d2, which is acquired, and the saturation coefficient decision unit 124 substitutes the saturation S, which is calculated, into function stored in the saturation LUT 133 read from the storage unit 13 to determine the saturation coefficient AS with respect to the saturation of each pixel of the frame, which is received. The saturation coefficient decision unit 124 outputs, to the computation coefficient calculation unit 126, the saturation coefficient AS, which is determined.
Subsequently, the hue coefficient decision unit 125 determines a hue coefficient AH (S6). Specifically, the hue coefficient decision unit 125 calculates the hue H from the blue chrominance Cb and the red chrominance Cr included in the chrominance information d2, which is acquired, and the hue coefficient decision unit 125 substitutes the hue H, which is calculated, a function stored in the hue LUT 134 read from the storage unit 13 to determine the hue coefficient AH with respect to the hue of each pixel of the frame, which is received. The hue coefficient decision unit 125 outputs, to the computation coefficient calculation unit 126, the hue coefficient AE, which is determined.
Note that it is only required that the processes in S4, S5, and S6 are performed after the process in S3 and before the process in S7, and the order of the processes is not limited to a particular order. Alternatively, the processes in S4, S5, and S6 may be simultaneously performed.
Subsequently, the computation coefficient calculating unit 126 calculates a computation coefficient AT from the luminance coefficient AY, the saturation coefficient AS, and the hue coefficient AH, which are acquired (S7). Then, the computation coefficient calculation unit 126 outputs, to the saturation correction unit 127, the computation coefficient AT, which is calculated.
Subsequently, the saturation correction unit 127 corrects the saturation of the frame, which is received, based on the computation coefficient, which is acquired (S8, saturation changing step). More specifically, the saturation correction unit 127 substitutes the blue chrominance Cb, the red chrominance Cr, and the computation coefficient AT, which are acquired, into the computation formula Cb′=(1−AT)×Cb and the computation formula Cr′=(1−AT)×Cr to calculate the blue chrominance Cb′ and the red chrominance Cr′. Then, the saturation correction unit 127 outputs, to the video processing unit 128, the luminance information d1, which is acquired, and the blue chrominance Cb′ and red chrominance Cr′, which are calculated.
Finally, the video processing unit 128 causes the display unit 14 to display a corrected frame (S9). Specifically, the video processing unit 128 causes the display unit 14 to display a frame based on the luminance information d1, the blue chrominance Cb′, and the red chrominance Cr′, which are acquired. Thus, the display unit 14 displays the frame in which the saturation of a pixel having luminance included within the low luminance range is corrected (saturation is reduced).
The low luminance range decision coefficient B included in the above-described luminance coefficient decision information 131 is a fixed value regardless of the frame luminance maximum value Ymax, but the low luminance range decision coefficient B may be a value according to the frame luminance maximum value Ymax. The variation will be described in detail with reference to
Note that a function for specifying the low luminance range decision coefficient B is not limited to the example shown in the figure. Note that in order to enable the noise reduction process to be performed on only pixels in which the occurrence of color noise is concerned (in other words, pixels whose value of luminance is small) even when the value of the frame luminance maximum value Ymax is large, a function as illustrated in the figure is desirable in which the low luminance range decision coefficient B gradually decreases as the frame luminance maximum value Ymax increases when the frame luminance maximum value Ymax is larger than or equal to the prescribed value.
Another embodiment of the present invention will be described below with reference to
As illustrated in
The broadcast signal control unit 121a has the function of the above-described broadcast signal control unit 121 and additionally, outputs a maximum luminance information d3 included in the broadcast stream to the luminance coefficient decision unit 123a. Note that the present embodiment describes an example in which the maximum luminance information d3 is information denoting the highest luminance in the content. That is, in the present embodiment, the maximum luminance information d3 corresponds to one value with respect to one content. Moreover, the maximum luminance information d3 is information included in a first frame in the content. Thus, when the broadcast signal control unit 121a acquires the first frame in the content, the broadcast signal control unit 121a outputs the maximum luminance information d3 included in the frame to the luminance coefficient decision unit 123a.
Note that the maximum luminance information d3 does not have to correspond to one value with respect to one content. For example, when the content is divided into several segments, the maximum luminance information d3 may be information denoting the highest luminance in each segment. In this case, the number of pieces of the maximum luminance information d3 existing for one content corresponds to the number of segments. Moreover, in this case, the maximum luminance information d3 is included in the first frame in each segment.
Alternatively, for example, the maximum luminance information d3 may be information denoting the highest luminance in each frame. In this case, the number of pieces of the maximum luminance information d3 existing for one content corresponds to the number of frames. Moreover, in this case, the maximum luminance information d3 is included in each frame. Note that when the maximum luminance information d3 is information denoting the highest luminance in each frame, it is highly possible that the value of the maximum luminance information d3 and a frame luminance maximum value Ymax are equal to each other. Note that the maximum luminance information d3 is a value configured on a transmission side of the content whereas the frame luminance maximum value Ymax is the highest luminance in a brightness distribution generated by the noise reduction apparatus 1a (i.e., a value specified on a reception side of the content), and therefore, the value of the maximum luminance information d3 and the frame luminance maximum value Ymax may be different values. Note that the maximum luminance information d3 may hereinafter be denoted as a maximum luminance value MaxCLL.
The luminance coefficient decision unit 123a is different from the luminance coefficient decision unit 123 in the following points. That is, the luminance coefficient decision unit 123a corrects a low luminance range decision coefficient B read from a storage unit 13 based on the maximum luminance information d3 and the frame luminance maximum value Ymax which are acquired (calculates a low luminance range decision coefficient B′ after correction). Specifically, the luminance coefficient decision unit 123a substitutes the maximum luminance value MaxCLL, which is acquired, the frame luminance maximum value Ymax, and the low luminance range decision coefficient B read from the storage unit 13 into the computation formula B′=Ymax/MaxCLL×B to calculate the low luminance range decision coefficient B′ after correction.
Then, based on the low luminance range decision coefficient B′, which is calculated, a value Y1 and a value Y2 are calculated. Note that a specific method for calculating the value Y1 and the value Y2 has been described in the first embodiment, and thus the description thereof is omitted here.
As described above, correcting the low luminance range decision coefficient B in accordance with the maximum luminance information d3 and the frame luminance maximum value Ymax enables the definition of the low luminance range in a frame of a relatively dark scene in the content to be changed. This will be described with reference to
In contrast, if, when the frame luminance maximum value Ymax is smaller than the maximum luminance in the content, the low luminance range is set to a luminance range of 0% to 1% with respect to the frame luminance maximum value Ymax, noise reduction may be performed on a pixel which does not need the noise reduction. Thus, the noise reduction apparatus 1a according to the present embodiment further narrows the low luminance range when the frame luminance maximum value Ymax is smaller than the maximum luminance in the content. Thus, it is possible to perform noise reduction on only a pixel which requires the noise reduction. A specific example will he described in
As described above, the noise reduction apparatus 1a according to the present embodiment corrects the low luminance range decision coefficient B in accordance with the ratio (Ymax/MaxCLL) of the maximum luminance value MaxCLL and the frame luminance maximum value Ymax. This defines an appropriate low luminance range for each frame, and thus, it is possible to perform the noise reduction on only a pixel which requires the noise reduction.
The above-described luminance coefficient decision unit 123a uses the maximum luminance value MaxCLL to correct the low luminance range decision coefficient B. However, a method for using the maximum luminance value MaxCLL is not limited to this example. For example, the luminance coefficient decision unit 123a. may use the maximum luminance value MaxCLL instead of the frame luminance maximum value Ymax to calculate the value Y1 and the value Y2. In this example, the computation formula for calculating the value Y1 is Y1=MaxCLL×B.
Moreover, the noise reduction apparatus 1a may define a suitable low luminance range for each frame of a content based on average luminance information (Maximum Frame Average Light Level, hereinafter, the average luminance information may be referred to as an average luminance value MaxFALL) instead of the maximum luminance information d1, the average luminance information being included in the broadcast stream and denoting the average luminance in the content (average value of luminance of content). Note that a specific process performed by the luminance coefficient decision unit 123a of this case is similar to the above-described process except that the maximum luminance value MaxCLL in the above-described process is replaced with the average luminance value MaxFALL, and therefore, the description thereof is omitted here.
Alternatively, the noise reduction apparatus 1a may define a suitable low luminance range for each frame of content based on maximum luminance information (Max Display Mastering Luminance) at the time of creating the content instead of the maximum luminance information d3. The maximum luminance information (Max Display Mastering Luminance) is included in the broadcast stream and denoting the maximum luminance in a monitor (display apparatus) used at the time of creation of the content by a creator of the content. Note that a specific process performed by the luminance coefficient decision unit 123a of this case is similar to the above-described process except that the maximum luminance value MaxCLL in the above-described process is replaced with the maximum luminance information at the time of content creation, and therefore, the description thereof is omitted here.
Still another embodiment of the present invention will be described below with reference to
As illustrated in
When acquiring the remote control signal from the remote control reception unit 15, the remote control signal control unit 129 specifies an operation instruction included in the remote control signal and outputs the operation instruction to the luminance coefficient decision unit 123b or the computation coefficient calculation unit 126b. Specifically, when the operation instruction, which is specified, is a correction instruction d4 of the low luminance range decision coefficient B, the remote control signal control unit 129 outputs the correction instruction d4 to the luminance coefficient decision unit 123b. When the operation instruction, which is specified, is a correction instruction d5 of the computation coefficient AT, the remote control signal control unit 129 outputs the correction instruction d5 to the computation coefficient calculation unit 126b.
When the operation instruction, which is specified, is a user interface (hereinafter referred to as UI) display instruction d6 which causes a display unit 14 to display a UI for correcting the low luminance range decision coefficient B and/or the computation coefficient AT, the remote control signal control unit 129 outputs the UI display instruction d6 to the video processing unit 128b.
The luminance coefficient decision unit 123b is different from the luminance coefficient decision unit 123 in the following points. That is, the luminance coefficient decision unit 123b corrects the low luminance range decision coefficient B, which is read, based on the correction instruction d4, which is acquired. For example, when the correction instruction d4 is an instruction to multiply the low luminance range decision coefficient by 2, the luminance coefficient decision unit 123b calculates a low luminance range decision coefficient B″ corresponding to the low luminance range decision coefficient B multiplied by 2 in accordance with the instruction and determines a luminance coefficient AY based on the low luminance range decision coefficient B″.
Note that the luminance coefficient decision unit 123b may be configured, as the luminance coefficient decision unit 123a described in the second embodiment, to correct a low luminance range decision coefficient B′ based on a maximum luminance value MaxCLL and a frame luminance maximum value Ymax which are acquired. In this case, the luminance coefficient decision unit 123b further corrects the low luminance range decision coefficient B in accordance with the correction instruction d4, which is acquired.
Note that it is only required that the correction instruction d4 is an instruction to change (correct) the low luminance range, and the value corrected in accordance with the instruction is not limited to the low luminance range decision coefficient B. For example, the luminance coefficient decision unit 123b may correct the maximum luminance value MaxCLL according to the correction instruction d4.
The computation coefficient calculation unit 126b is different from the computation coefficient calculation unit 126 in the following points. That is, the computation coefficient calculation unit 126b corrects the computation coefficient AT, which is calculated, in accordance with the correction instruction d5, which is acquired. For example, when the correction instruction d5 is an instruction to multiply the computation coefficient AT by 0.5, the computation coefficient calculation unit 126b calculates a computation coefficient computation coefficient AT corresponding to the computation coefficient AT multiplied by 0.5 in accordance with the instruction and outputs the computation coefficient. AT′ to a saturation correction unit 127.
The video processing unit 128b is different from the video processing unit 128 in the following points. That is, when the video processing unit 128b acquires the UI display instruction d6 from the remote control signal control unit 129, the video processing unit 128b causes the display unit 14 to display a UI for correcting the low luminance range decision coefficient B and/or the computation coefficient AT. The UI is not particularly limited this example as long as it can receive the correction of the low luminance range decision coefficient B and/or the computation coefficient AT. The UI may be, for example, a UI illustrated in
For example, the video processing unit 128b may, as illustrated in
When the remote control signal control unit 129 acquires a remote control signal denoting that the handle section 411 of the UI 141 has moved from the left end to the right end of the slider section 412 in
Alternatively, for example, the video processing unit 128b may, as illustrated in
Note that the UI 142 includes text denoting “narrow” as the lower limit indication 413 and includes text denoting “wide” as the upper limit indication 414. Moreover, the UI 142 further includes an intermediate display 415 (text denoting “medium”) denoting a position corresponding to the center of the slider section 412. On the other hand, the UI 143 includes text denoting “small” as the lower limit indication 413 and includes text denoting “large” as the upper limit indication 414. Moreover, similarly to the UI 142, the UI 143 includes text “intermediate” as the intermediate display 415. Moreover, the display unit 14 displays, adjacently to the UI 142 and the UI 143 respectively, text “reduction range” and “reduction amount” denoting a process executed by an operation performed on the remote controller 20 by a user when a screen shown in
When the remote control signal control unit 129 acquires a remote control signal denoting that the handle section 411 of the UI 142 has moved from the left end to the right end of the slider section 412 in
When the remote control signal control unit 129 acquires a remote control signal denoting that the handle section 411 of the UI 143 has moved from the left end to the right end of the slider section 412 in
Note that the remote control signal control unit 129 may be configured to output the remote control signal acquired from the remote control reception unit 15 as is to the luminance coefficient decision unit 123b, the computation coefficient calculation unit 126b, or the video processing unit 128b. In the case of this example, the remote control signal control unit 129 determines an output destination to which the remote control signal, which is acquired, is to be output, and the remote control signal control unit 129 outputs the remote control signal to the output destination, which is determined. Moreover, the luminance coefficient decision unit 123b and the computation coefficient calculation unit 126b correct the low luminance range decision coefficient B or the computation coefficient AT in accordance with the remote control signal. Moreover, the video processing unit 128b causes the display unit 14 to display a UI according to the remote control signal.
Moreover, in the present embodiment, the remote controller 20 and the remote control reception unit 15 have been described as examples of components for receiving an input operation performed by a user, but the components for receiving the input operation given by the user are not limited to these examples. For example, the component may be a physical button provided to the television set 10b or a touch screen superimposed on the display unit 14. Alternatively, the remote controller 20 may include only the physical button as illustrated in
The television set 10b according to the present embodiment may enable a user to select a display mode of a content and may correct the low luminance range decision coefficient B or the maximum luminance value MaxCLL in accordance with the display mode selected by the user. In the case of this example, the video processing unit 128b may cause the display unit 14 to display a UI which enables a user to select the display mode of the content. The UI is not particularly limited to this example as long as it enables a user to select the display mode of the content, but the UI may be, for example, the UI illustrated in
A UI 144a, a UI 144b, and a UI 144c shown in
A user operates the remote controller 20 as illustrated in the figure to select a desired display mode from “standard mode”, “dynamic mode”, and “movie mode”. Here, these modes are briefly described. The “dynamic mode” is a mode for performing a video process for vividly displaying the content (specifically, for increasing the saturation of each pixel) and a mode suitable for a case where the content corresponds to video of sports broadcast or live video of music. The “movie mode” is a mode for performing a video process so that the content is displayed with reduced. vividness (specifically, so that the saturation of each pixel is reduced) and suitable for a case where the content corresponds to movies or the like. The “standard mode” is a mode in which a video process according to the content is not performed in the television set 10b. Note that the display modes of the contents described here are mere examples, and the display mode of the contents is not limited to these examples.
When the remote control signal control unit 129 acquires a remote control signal denoting a display mode which is selected, the remote control signal control unit 129 changes the degree of change of the maximum luminance value MaxCLL (in other words, a value denoting a factor by which the maximum luminance value MaxCLL is multiplied) according to the remote control signal, which is acquired. Specifically, when receiving a remote control signal denoting that the “standard mode” is selected, the remote control signal control unit 129 outputs, to the luminance coefficient decision unit 123b, the correction instruction d4 that the degree of change of the maximum luminance value MaxCLL is multiplied by 1. Note that when the “standard mode” is selected, the maximum luminance value MaxCLL does not change, and therefore, the remote control signal control unit 129 may be configured not to output the correction instruction d4.
Alternatively, when acquiring a remote control signal denoting that the “dynamic mode” is selected, the remote control signal control unit 129 outputs, to the luminance coefficient decision unit 123b, the correction instruction d4 that the decree of chance of the maximum luminance value MaxCLL is multiplied by 1.5. This is because the dynamic mode is a mode for performing a video process for increasing the saturation of each pixel, and therefore, color noise is highly possibly emphasized. That is, since the maximum luminance value MaxCLL is multiplied by 1.5 as described above to increase the low luminance range (that is, a range in which correction of reducing the saturation is performed), selecting the “dynamic mode” enables color noise to be reduced in a pixel in which the occurrence of the color noise is concerned (in other words, a pixel newly included in the low luminance range due to the correction made to the maximum luminance value MaxCLL).
Alternatively, when acquiring a remote control signal denoting that the “movie mode” is selected, the remote control signal control unit 129 outputs, to the luminance coefficient decision unit 123b, the correction instruction d4 that the degree of change of the maximum luminance value MaxCLL is multiplied by 0.5. This is because the movie mode is a mode for performing a video process for reducing the saturation of each pixel, and therefore, if the low luminance range is not corrected, the saturation of a pixel which does not have to be subjected to noise reduction may also be reduced. That is, since the maximum luminance value MaxCLL is multiplied by 0.5 as described above to reduce the low luminance range (that is, a range in which correction of reducing the saturation is performed), excessive correction of contents can be prevented. Note that the degree of change of the maximum luminance value MaxCLL described here is a mere example and is not limited to this example.
The luminance coefficient decision unit 123, the luminance coefficient decision unit 123a, and the luminance coefficient decision unit 123b (when these are not necessary to be distinguished from one another, they are hereinafter referred to as luminance coefficient decision units 123) according to the above-described embodiments may correct the low luminance range decision coefficient B or the maximum luminance value MaxCLL in accordance with a content. Specifically, the luminance coefficient decision unit 123 acquires information (movie, sports broadcast, drama, etc.) denoting the kinds of a content from the broadcast signal control unit 121 and corrects the low luminance range decision coefficient B or the maximum luminance value MaxCLL in accordance with the information. For example, when the information is information denoting that the content is movie, the maximum luminance value MaxCLL is multiplied by 0.5. Alternatively, for example, when the information is information denoting that the content is sports broadcast, the maximum luminance value MaxCLL is multiplied by 1.5. Note that the luminance coefficient decision unit 123 may acquire the information denoting the kinds of the content from Electronic Program Guide (EPG).
Moreover, the computation coefficient calculation unit 126 and the computation coefficient calculation unit 126b according to the above-described embodiments (when they are not necessary to be distinguished from each other, they are hereinafter referred to as computation coefficient calculation units 126) calculate the computation coefficient AT based on the luminance coefficient AY, the saturation coefficient AS, and the hue coefficient AH, but this should not be construed as limiting. Specifically, it is only required that the computation coefficient calculation units 126 determine the computation coefficient. AT based on at least the luminance coefficient AY. Note that when only the luminance coefficient. AY is used, the computation coefficient calculation unit 126 outputs as the computation coefficient AT, the luminance coefficient AY, which is acquired, to the saturation correction unit 127.
A control block (in particular, each component included in the control units 12, 12a, 12b) of the noise reduction apparatus 1, 1a, 1b may be realized by a logic circuit (hardware) formed in, for example, an integrated circuit (IC chip) or by software by using a Central Processing Unit (CPU).
In the latter case, the noise reduction apparatus 1, 1a, 1b includes, for example, a CPU configured to execute a command of a program serving as software which realizes various functions, Read Only Memory (ROM) or storage device (which is referred to as a “storage medium”) in which the program and various types of data are stored in a computer (or CPU)-readable manner, and Random Access Memory (RAM) into which the program is to be loaded. The computer (or the CPU) reads the program from the storage medium and executes the program to achieve the object of the present invention. As the storage medium, a “non-transitory tangible medium”, for example, a tape, disk, card, semiconductor memory, or programmable logic circuit may be used. Moreover, the program may be provided to the computer via any transmission medium (for example, a communication network or a broadcast wave) which can transmit the program. Note that the present invention can be realized in a form of a data signal which is realized by electronical transmission of the program and which is embedded in a carrier wave.
A display control device (noise reduction apparatus 1) according to a first aspect of the present invention includes a saturation changing unit (saturation correction unit 127) configured to reduce saturation of a pixel having luminance lower than luminance corresponding to a first value according to luminance of an image to be displayed while the luminance of the pixel is maintained.
This configuration reduces the saturation of a pixel whose luminance is lower than the first value. In other words, this configuration does not reduce the saturation of a pixel whose luminance is higher than or equal to the first value. Thus, the saturation in only a low luminance region of an image can be reduced. When the saturation of the pixel in the low luminance region is reduced, a difference between the color of the pixel and a color of a neighbor pixel becomes unnoticeable. Thus, color noise generated in the low luminance region in an image becomes unnoticeable
Thus, the color noise generated in the low luminance region in the image can be made unnoticeable. Consequently, color noise can be reduced. Moreover, with this configuration, the luminance of the pixel whose saturation is reduced is maintained, and therefore, color noise can be reduced without reducing the information amount of the image.
A display control apparatus according to a second aspect of the present invention referring to the first aspect further includes a maximum value specification unit (brightness distribution generation unit 122) configured, to specify a maximum value of the luminance of the image, wherein the first value may be a value that amounts to a prescribed ratio with respect to the maximum value.
With this configuration, the first value is the value that amounts to the prescribed ratio with respect to the maximum value of the luminance of the image. Thus, the value can be changed in accordance with the maximum value of the luminance of the image, and therefore, it is possible to configure an appropriate low luminance region in each image. Thus, it is possible to reduce color noise in only appropriate pixels in each image.
In a display control apparatus according to a third aspect of the present invention referring to the second aspect, the prescribed ratio may re small when the difference between the maximum value of the luminance of the image and a maximum value of luminance of a content including the image is large, the maximum value of the luminance of the content being pre-configured in the content, and the prescribed ratio may be large when the difference between the maximum value of the luminance of the image and the maximum value of the luminance of the content is small.
With this configuration, the prescribed ratio is small when a difference between the maximum value of the luminance of the image and a maximum value of luminance of a content is large, and the prescribed ratio is large when the difference between the maximum value of the luminance of the image and the maximum value of the luminance of the content is small. Thus, depending on whether an image as a target from which noise is to be reduced is an image of a dark scene in the content or an image of a bright scene in the content, a pixel which is a target from which noise is to be reduced (in other words saturation reduction target) can be changed. Thus, appropriate noise reduction can be performed in the image.
In a display control apparatus according to a fourth aspect of the present invention referring to the second or third aspect, the prescribed ratio may be changed in accordance with an. operation performed by a user.
With this configuration, the prescribed ratio is changed in accordance with the operation performed by a user. Therefore, a pixel as a target from which noise is to be reduced (in other words saturation reduction target) can be changed in accordance with the operation performed by a user. Thus, a pixel as a target from which noise is to be reduced can be desirable for a user.
In a display control apparatus according to a fifth aspect of the present invention referring to the fourth aspect, a user interface for changing the prescribed ratio may be displayed on a display apparatus.
With this configuration, a user interface for changing the prescribed ratio is displayed on the display apparatus. Therefore, a user can check the modification of the prescribed ratio. Thus, it is possible to realize a display control device easily usable by a user.
In a display control apparatus according to a sixth aspect of the present invention referring to any one of the first to fifth aspects, the saturation changing unit may reduce saturation of a pixel to 0, the pixel having luminance included within a range of 0 to a second value, the second value being a value according to the luminance of the image and being a smaller value than the first value, and the saturation changing unit may reduce the extent of reduction of saturation of a pixel having luminance included within a range of the second value to the first value as the luminance increases.
With this configuration, the saturation of the pixel having luminance included within a range of 0 to the second value is reduced to 0, and thus, color noise in a further low luminance region (in other words, a region in which color noise is more noticeable) of the low luminance region can accordingly be reduced. Moreover, the extent of reduction of saturation of pixel having luminance included within a range of the second value to the first value is reduced as the luminance increases. Therefore, between pixels with small luminance differences, in particular between pixels whose luminance corresponds to a value around the second value, a precipitous change of saturation can be reduced.
In a display control apparatus according to a seventh aspect of the present invention referring to any one of the first to sixth aspects, the saturation changing unit may increase an extent of reduction of saturation for a pixel whose hue is closer to blue.
The color noise is noise which is more noticeable with hue closer to blue. Here, with this configuration, the extent of reduction of saturation is increased for a pixel whose hue is closer to blue. Thus, color noise which is more noticeable can be made more unnoticeable, and thus, it is possible to realize a more effective color noise reduction.
In a display control apparatus according to an eighth aspect of the present invention referring to any one of the first to seventh aspects, the saturation changing unit may increase an extent of reduction of saturation for a pixel having higher saturation.
With this configuration, the extent of reduction of saturation is increased for a pixel having higher saturation, and therefore, the saturation of the pixel which is closer to the original color (in other words, color noise is more noticeable) can be more reduced. Thus, it is possible to realize a more effective color noise reduction.
A display apparatus (television set 10) according to a ninth aspect of the present invention may include the display control device according to any one of the first to eighth aspects.
With this configuration, it is possible to realize a display apparatus which enables color noise in a low luminance region of an image to be reduced without reducing the information amount of the image.
A television receiver (television set 10) according to a tenth aspect of the present invention may include the display control device according to any one of the first to eighth aspects.
With this configuration, it is possible to realize a television receiver which enables color noise in a low luminance region of an image to be reduced without reducing the information amount of the image.
A control method of a display control device according to an eleventh aspect of the present invention includes a saturation changing step (step S8) of reducing saturation of a pixel having luminance lower than luminance corresponding to a first value according to luminance of an image to be displayed while the luminance of the pixel is maintained.
This configuration provides an effect similar to that provided by the display control device according to the first aspect.
The display control device according to each aspect of the present invention may be realized by a computer. In this case, the scope of the present invention includes a control program of the display control device which causes a computer to operate as each component (software element) included in the display control device to realize the display control device by the computer, and a computer-readable recording medium which stores the control program.
The present invention is not limited to the embodiments described above. Various modifications may be made within the scope of the claims. Embodiments obtained by accordingly combining the techniques disclosed in different embodiments are also within the technical scope of the present invention. Moreover, combining technical means disclosed in the embodiments can provide new technical feature.
1 NOISE REDUCTION APPARATUS (DISPLAY CONTROL DEVICE)
10 TELEVISION SET (DISPLAY APPARATUS, TELEVISION RECEIVER)
122 BRIGHTNESS DISTRIBUTION GENERATION UNIT (MAXIMUM VALUE SPECIFICATION UNIT)
127 SATURATION CORRECTION UNIT (SATURATION CHANGING UNIT)
S8 SATURATION CHANGING STEP
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-056094 | Mar 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/005422 | 2/15/2017 | WO | 00 |
