JP4887083B2 - Video signal processing circuit - Google Patents

Description

  The present invention relates to a video signal processing circuit mounted on a video input / output device using a digital signal, and in particular, by adjusting the image quality of a video by matrix operation for an input of a video signal composed of three primary color signals of red, green and blue. The present invention relates to a video signal processing circuit configured to output as a new video signal.

  For example, when viewing video content using a digital signal video input / output device such as a liquid crystal display or a video camera, there is a demand to improve the image quality by performing signal processing on the input video signal. As a technique for realizing such a requirement, a technique is known in which matrix calculation is performed on input signals R, G, and B, and the result is used as an output signal.

  In this matrix calculation, assuming that the color components of the input signal are R, G, and B, and the color components of the output signal are R ′, G ′, and B ′, respectively, the relationship between them is expressed as the following equation (1). Various image quality adjustments can be made according to the values of the coefficients a to i.

  For example, for the coefficient matrix of equation (1), when the matrix operation is performed with the non-diagonal terms b, c, d, f, g, h as α and the diagonal terms a, e, i as 1-2α. It is known that the calculation of the above expression (1) is equal to the calculation according to the expression (2), and the effect of improving the saturation and brightness is obtained without changing the hue. (See Non-Patent Document 1)

  The hue, saturation, and lightness referred to here are the values of H, S, and V in the HSV color system. The equation for obtaining the values of H, S, and V from R, G, and B is as the following equation (3). The definitions of Cr, Cg, and Cb in the formula (3) are as in the formula (4).

  Hereinafter, changes in hue, saturation, and brightness by the method of Non-Patent Document 1 will be described. In the following description, it is assumed that the values of the inputs R, G, B are in a magnitude relationship of R ≧ G ≧ B, but the relationship of R, G, B is an example and can be exchanged. It is.

  First, regarding the magnitude relationship between the outputs R ′, G ′, and B ′, the relationship of the equation (5) is derived from the definition of the equation (2).

  When α> 0, the right side of equation (5) is always greater than or equal to 0. Therefore, if R ≧ G ≧ B, the relationship R ′ ≧ G ′ ≧ B ′ is established. Therefore, the hue H of the input signal is always equal to the hue H ′ of the output signal. (See formula (6) below)

  Further, the saturation S of the input signal and the saturation S ′ of the output signal satisfy S ′ ≧ S. (See formulas (7) and (8) below)

  Further, the lightness V of the input signal and the lightness V ′ of the output signal satisfy V ′ ≧ V (see Expression (9)).

  From the above results, it can be confirmed that when the matrix calculation of the above equation (2) is performed using the coefficient α ≧ 0, the hue and the lightness are improved without changing the hue.

  However, in an actual video processing circuit, a value that can be expressed is not infinite and is limited to a certain range (for example, 0 to 255 in the case of 8 bits / color). Will be rounded.

  Therefore, in the case of the method of Non-Patent Document 1, when the value of the input signal is larger than a certain value, the same result is output and the gradation of the video is lost (see FIG. 2). As methods for solving this problem, methods such as Patent Document 1 and Patent Document 2 have been proposed.

  The technique described in Patent Literature 1 calculates a compression rate based on an overflowed output signal and a set reference value when any of the three primary color output signals overflows, and outputs all the output signals. Is converted at the above compression rate to be a final output signal.

  The technique described in Patent Literature 2 obtains a coefficient of calculation by a simple reduction function based on one of two kinds of color difference signals, and performs saturation enhancement using the coefficient.

Sung Hong, “Story / Color Image Processing”, CQ Publisher, April 15, 1999, p. 47-52 JP 2001-346222 A JP 2005-150907 A

  However, the embodiment of Patent Document 1 includes a first step for adjusting image quality and a second step for compressing values so that the output of the first step is within a predetermined range. Therefore, a complicated procedure and a large-scale circuit for realizing it are required.

  Further, in the technique of Patent Document 2 described above, output overflow is suppressed by simply reducing the coefficient. However, since the coefficient is reduced even for an input in which the output does not overflow, sufficient adjustment effect is achieved. There is a problem that cannot be obtained.

  For example, FIG. 3 is a graph of the input / output characteristics according to the technique of Patent Document 2, and it can be confirmed that the output is greatly reduced even for a UV input of 85 or less where overflow does not occur.

  The present invention has been made in view of such a situation, and an image configured to adjust and output image quality by matrix calculation with respect to an input of a video signal composed of three primary color signals of red, green, and blue. A video signal processing circuit, wherein the output after the calculation does not exceed a predetermined range, and the value of the coefficient used for the calculation is automatically adjusted so that a good adjustment effect is obtained. It aims to be realized.

  In order to solve the above problems, a video signal processing circuit according to the present invention includes a matrix arithmetic circuit for performing a matrix operation on an input of a video signal composed of three primary color signals of red, green and blue, and the matrix arithmetic circuit. A video signal processing circuit configured to adjust the image quality of the video by the matrix arithmetic circuit and to output a new video signal, wherein the video signal processing circuit comprises: The coefficient is automatically adjusted so that the output value does not exceed a predetermined range.

  The automatic adjustment of the coefficient may be performed by including a coefficient calculation unit and a control unit for obtaining an appropriate coefficient in accordance with the input of the video signal in the coefficient calculation unit.

The coefficient calculation unit may further include one or more control parameter inputs, and may be configured to finely adjust a control unit for obtaining a coefficient according to the control parameter.
The control means for obtaining the coefficient includes means for obtaining a maximum value among the color signals constituting the input video signal, and reduces the coefficient in proportion to the maximum value of the color signal. It may be based on such control.

  The control means for obtaining the coefficient is further provided with means for obtaining a difference between the maximum value and the minimum value of the color signal, and controlling the coefficient so as to decrease in proportion to the difference. May be.

  A plurality of the coefficient calculation units may be provided corresponding to the types of control means for obtaining the coefficients, and in that case, an optimal one of the plurality of coefficients respectively calculated from the plurality of coefficient calculation units. A coefficient selecting unit for selecting one of the coefficients, and further comprising control means for determining an optimum coefficient in the coefficient selecting unit.

  In the coefficient selection unit, the control means for determining the optimum coefficient may be based on using a minimum one of the plurality of coefficients.

  In the coefficient selection unit, the control means for determining the optimum coefficient may be based on using a product in which the product of the plurality of coefficients and the weighting variable is minimized.

  In the coefficient selection unit, the control means for determining the optimum coefficient includes means for holding the coefficient adopted in the previous process, and the difference between the coefficient used in the previous process and the coefficient calculated from the coefficient calculation part. And a unit that detects the difference between the coefficients.

  In the coefficient selection unit, the control means for determining the optimum coefficient may be based on using a product in which the product of the difference between the coefficients and the weighting variable is minimized.

  In the coefficient selection unit, the control means for determining the optimum coefficient is by referring to a look-up table that associates the maximum value of the color signal and the output of which coefficient selection unit is adopted. May be.

  According to the present invention, it is possible to reduce an output overflow of image quality adjustment by matrix calculation and obtain a good adjustment effect.

  In the video signal processing circuit configured to improve the saturation by matrix calculation for the input of the video signal (RGB), the inventor sets the coefficient value used for the calculation so as to suppress output overflow. I thought about adjusting automatically. Below, it explains including how to adjust.

In the present specification, the matrix calculation refers to a matrix calculation represented by Expression ( 2 ).

  Embodiments of a preferred video signal processing circuit of the present invention will be described below in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same elements throughout the following description and all the drawings.

[First Embodiment]
FIG. 4 is a functional block diagram showing a configuration example of the video signal processing circuit according to the first embodiment of the present invention. In FIG. 4, the video signal processing circuit 10 inputs video signals R, G, and B of three primary colors and outputs video signals R ′, G ′, and B ′ of three primary colors. The video signal processing circuit 10 includes a maximum value detector 31 that detects the largest one of the R, G, and B signals, a coefficient calculation unit 301, a matrix operation circuit 20 that performs the matrix operation of the above equation (1), including.

  The coefficient calculation unit 301 has a function of performing calculation based on a control unit that decreases the coefficient α in proportion to the maximum values of R, G, and B. Hereinafter, the control means is referred to as first coefficient calculation means.

  FIG. 1 is a functional block diagram showing a detailed configuration example of the matrix arithmetic circuit 20 included in the video signal processing circuit according to the present embodiment. In FIG. 1, a matrix calculation circuit 20 includes a subtractor 21 that calculates a color difference signal, a multiplier 22 that multiplies the color difference signal by a coefficient α, and an addition that adds the color difference signal multiplied by the coefficient α and an input signal. Container 23.

  First, the operation of the matrix operation circuit 20 will be described. The R signal input to the matrix operation circuit 20 is input to the subtractor 21 and the color difference signals (RG) and (RB) are output. The color difference signals are input to a multiplier 22 and multiplied by a coefficient α. The color difference signal multiplied by this coefficient is input to the adder 23, added to the original input signal R, and output as R '. The same processing is performed on the inputs G and B. With the above operation, it is possible to obtain a calculation result similar to the above equation (2).

  Next, the operation of the video signal processing circuit in FIG. 4 will be described. In the following description, calculation is performed on the assumption that the lower limit that can be expressed for R, G, and B is 0, the upper limit is also 1, and an arbitrary real value between the upper limit and the lower limit can be taken. However, in an actual circuit, processing can be simplified by processing with discrete values approximated with appropriate accuracy. In the subsequent input / output characteristic graphs, signal values are approximated by 8-bit integers, and the results are shown when the lower limit is set to 0 and the upper limit is set to 255.

  In FIG. 4, input signals R, G, B are input to the maximum value detector 31, and the maximum value MAX is output. The coefficient calculation unit 301 having the first coefficient calculation means performs a calculation based on the following equation (10) for the maximum value MAX, and outputs a coefficient α.

The matrix calculation circuit 20 performs the above-described matrix calculation using the coefficient α calculated by the coefficient calculation unit 301, and outputs R ′, G ′, and B ′.
Regarding the values of R ′, G ′, and B ′, it is known from the above formula (5) that if R ≧ G ≧ B, the relationship of R ′ ≧ G ′ ≧ B ′ is established. G ′ and B ′ do not exceed 1 unless R ′ is greater than 1. In the equation (10), the coefficient α decreases as R increases, and when R = 1, α = 0 and R ′ = R. Therefore, R ′ does not exceed 1 (see FIG. 5). reference). That is, the input / output characteristic graph including FIG. 5 shows the result when approximating 0 to 1 in the real number calculation with 0 to 255 of the 8-bit integer, and the calculation does not exceed “1”. The description corresponds to “does not exceed 255” on the graph.

  With the above operation, in the video signal processing circuit according to the present embodiment, it is possible to obtain a video output with amplified saturation while suppressing an overflow of matrix operation output.

[Second Embodiment]
FIG. 6 is a functional block diagram showing a configuration example of the video signal processing circuit according to the second embodiment of the present invention. In FIG. 6, the video signal processing circuit 10 includes an input unit for a control parameter P <b> 11 that allows the user to set an arbitrary value greater than 0 in the coefficient calculation unit 301 in the first embodiment. Further, the first coefficient calculating means replaces the calculation represented by the following formula (11) from the formula (10).

  In the above equation (11), the coefficient α increases as the control parameter P11 increases. In any case, however, since it converges to α = 0 when MAX = 1, as shown in FIG. 7, R′G′B 'Saturation can be suppressed. According to the present embodiment, it is possible to arbitrarily set the degree of saturation enhancement within a range in which the output does not overflow based on the above operation.

[Third Embodiment]
FIG. 8 is a functional block diagram showing a configuration example of the video signal processing circuit according to the third embodiment of the present invention. In FIG. 8, the video signal processing circuit 10 uses the coefficient calculation unit 301 of the second embodiment as a first coefficient calculation unit, and the output thereof is α1. Further, the second coefficient calculation unit includes a second coefficient calculation unit 302 including an input unit for a control parameter P21 that allows the user to set an arbitrary value larger than 0, and an output thereof is α2. In addition, a coefficient selection unit 40 that inputs α1 and α2 and outputs one value is provided.

  The second coefficient calculation unit 302 includes control means for controlling to output a constant value regardless of the values of R, G, and B. Hereinafter, this control means is referred to as a second coefficient calculation unit. The value output by the second coefficient calculation unit 302 can be changed by the control parameter P21, and the calculation formula is represented by (12).

  The coefficient selection unit 40 includes a minimum value detector 41 inside, and outputs the smaller value of α1 and α2. When P11 and P21 are set to arbitrary values under the condition of P11> P21, α1 (broken line in FIG. 9) is large in the range where the value of MAX is small, that is, in the low brightness region, so α2 (FIG. (9 dotted line) becomes smaller and emphasis is performed with a constant coefficient. On the other hand, in a range where the value of MAX is larger than a certain level, that is, in a region with high brightness, α1 is small, so the coefficient is small in proportion to the value of MAX. With the above operation, in this embodiment, a certain percentage of emphasis is performed in the low lightness region, and the coefficient is suppressed small in the high lightness region where the output may exceed the upper limit, thereby suppressing output overflow. It becomes possible to do.

[Fourth Embodiment]
FIG. 10 is a functional block diagram showing a configuration example of a video signal processing circuit according to the fourth embodiment of the present invention. In FIG. 10, the video signal processing circuit 10 includes a minimum value detector 32 and a subtractor 33 in addition to the circuit according to the third embodiment. The minimum value detector 32 receives R, G and B signals and outputs a minimum value MIN among them. The subtractor 33 calculates the difference between the outputs MAX and MIN of the maximum value detector 31 and outputs the difference with respect to the input of the first coefficient calculation unit 301. The calculation in the first coefficient calculation unit included in the first coefficient calculation unit 301 is replaced with the calculation represented by the following expression (13) from the expression (11).

  In equation (13), α1 increases as the difference between MAX and MIN decreases, and according to the present embodiment, the enhancement in the range with low saturation is performed while suppressing the enhancement in the range with high brightness. It becomes possible.

[Fifth Embodiment]
FIG. 11 is a functional block diagram showing a configuration example of a video signal processing circuit according to the fifth embodiment of the present invention. In FIG. 11, the video signal processing circuit 10 further includes, as the third coefficient calculation unit in the fourth embodiment, a control parameter P31 that allows the user to set an arbitrary value greater than 0, and an arbitrary value. Is provided with a coefficient calculation unit 303 having a P32 input unit, and its output is α3. The coefficient selection unit 40 receives α1, α2, and α3, and outputs the minimum value among them.

The third coefficient calculation unit 303 includes control means for performing control to increase the coefficient α3 in proportion to the maximum values of R, G, and B. Hereinafter, this control means is referred to as third coefficient calculation means.
The third coefficient calculation unit 303 provided with the third coefficient calculation means performs a calculation based on the following equation (14) for the maximum value MAX, and outputs a coefficient α3.

  When the value is set to an arbitrary value under the above-described conditions, α3 (the one-dot chain line in FIG. 12) is the smallest and the coefficient is kept small in the low lightness region. In the region where the brightness is intermediate, α2 (broken line in FIG. 12) becomes the smallest, and emphasis is performed with a constant coefficient. In the high lightness region, α1 (dotted line in FIG. 12) is the smallest, so the coefficient is small in proportion to the value of MAX.

  With the above operation, according to the present embodiment, the low brightness area does not change much, and the high brightness area has higher brightness, so that the contrast of the entire video can be improved.

[Sixth Embodiment]
FIG. 13 is a functional block diagram showing a configuration example of a video signal processing circuit according to the sixth embodiment of the present invention. In FIG. 13, the video signal processing circuit 10 includes n coefficient calculation units (where n is an arbitrary natural number) including the second coefficient calculation unit, inputs the control parameters P21 and P22, and an adder 34. Prepare. In addition, the coefficient selection unit 40 includes, for example, a lookup table 42 that associates the maximum value MAX of the input signal with the value of α to be used.

  A plurality of provided coefficient calculation units 302 perform calculations based on the following formula (15), respectively, and store α1 to αn in the lookup table 42.

  The coefficient selection unit 40 refers to the lookup table 42 based on the MAX value, selects one of α1 to αn, and selects the value. The look-up table 42 is set so that α2, α2,... Αn are sequentially used as MAX increases.

  With the above configuration, in the present embodiment, the coefficient α is small in the low lightness region, and the coefficient α is small in the high lightness region where the output may exceed the upper limit. 14).

  With the above operation, output overflow can be suppressed only by a simple combination of circuit components without using a particularly complicated arithmetic circuit.

[Seventh Embodiment]
FIG. 15 is a functional block diagram showing a configuration example of the video signal processing circuit according to the seventh embodiment of the present invention.

  In FIG. 15, the video signal processing circuit 10 includes a comparator 44 instead of the minimum value detector 41 of the fifth embodiment, and further includes a coefficient storage unit 43. The coefficient storage unit 43 has a function of storing the coefficient used in the previous process as αpre, and the comparator 44 calculates the difference between α1, α2, α3, and αpre, and the absolute value of the difference is the smallest. A function of outputting the coefficient value as α is provided.

  Since the video signal processing circuit 10 is configured to sequentially process and output adjacent pixels, the configuration described above prevents a coefficient value used between pixels from changing abruptly. Therefore, an image with a more natural gradation can be obtained.

  In the above-described embodiment, the specific combination of the coefficient calculation unit and the coefficient selection unit has been described. However, the combination of the coefficient calculation unit and the coefficient selection unit is not limited to these, and may be any combination. Also good.

  Also, the number of coefficient calculation units has been described only for a specific number, but it goes without saying that an arbitrary number of coefficient calculation units may be provided.

[Eighth Embodiment]
Hereinafter, embodiments relating to a mobile phone terminal using the video signal processing circuit of the present invention will be described.

  First, the TV phone function of the mobile phone terminal will be described with reference to FIG. FIG. 16 is a schematic diagram showing an outline of a system including a mobile phone terminal having a TV phone function. In FIG. 16, the mobile phone terminal 50 </ b> A of the user A modulates the video data captured by the imaging device 59 provided in the mobile phone terminal A into a radio signal, and the nearest base station from the antenna 51 of the mobile phone terminal A To 71A. This video data is transmitted from the base station 71A to the mobile phone terminal 50B of the user B who is the communication partner of the mobile phone terminal 50A via the telephone line network 70 and the base station 71B nearest to the user B. The mobile phone terminal 50B of the user B can display the received video data on the display device (LCD) 56 of the mobile phone terminal 50B. The above-described communication is performed between the mobile phone terminals A and B in real time with each other, thereby realizing a TV phone function.

  Next, the configuration of the mobile phone terminal according to the present embodiment will be described with reference to FIG. FIG. 17 is a functional block diagram showing a configuration example of the mobile phone terminal according to the present embodiment.

  In FIG. 17, the mobile phone terminal 50 includes a video signal processing circuit 10, an antenna 51, a wireless control unit 52, a received data processing unit 53, a video signal generation unit 54, a display control unit 55, and a display device 56. An input device 57, a control unit 58, an imaging device 59, an imaging control unit 60, and a transmission data processing unit 61. An example of the display device 56 is a liquid crystal display. An example of the input device 57 is an operation key string.

  The control unit 58 is mainly composed of a microprocessor, and is connected to the other units described above, and functions to control these operations and exchange of data between the units by a program stored in a memory (not shown). It has functions that make it possible. Examples of the imaging device 59 include a CCD camera and a CMOS camera.

  First, an outline of the transmission process will be described. The imaging control unit 60 controls the imaging device 59 and acquires a video signal. The transmission data processing unit 61 performs processing such as compression on the video signal, generates transmission data, and sends it to the wireless control unit 52. The radio control unit 52 modulates transmission data and sends out transmission radio waves via the antenna 51.

  Next, the reception process will be described. The radio control unit 52 demodulates the received radio wave received by the antenna 51 and sends it to the data processing unit 53 as received data. The data processing unit 53 extracts video data from the received data and sends the extracted video data to the video signal generation unit 54. The video signal generation unit 54 decodes the video data and sends it to the video signal processing circuit 10 as an RGB video signal.

  The video signal processing circuit 10 adjusts the saturation of the video and outputs the output signal to the display control unit 56 based on the RGB input signal and the parameter input from the control unit 58 by any of the above-described embodiments. To send.

  The parameter input may be configured so that the user can adjust the value to a desired value by operating the input device 57.

  The display control unit 56 drives the display device 56 based on the input video signal and displays the video.

  With the above configuration, it is possible to obtain a more vivid image in the TV phone communication. Further, since the video signal processing circuit 10 does not require an external memory or the like for temporarily storing video during processing, an increase in the size and cost of components can be minimized. Further, since the video signal is not accumulated and the input signal is immediately processed and output, the display is not delayed by the processing, which is suitable for the video signal processing of a TV phone that requires real-time characteristics.

  In the above-described embodiment, the video of the TV phone has been described, but in addition to this, it is possible to obtain a more vivid video by performing the same processing on any video content such as TV, e-mail, Web, camera shooting, etc. It is.

  Further, the type of terminal is not limited to the mobile phone terminal as described above, but can be similarly used as a video display technique of a video display device such as a liquid crystal television, a PDA, or a personal computer.

  The present invention is applicable to a video signal processing circuit. Further, it can be used for an LCD display device using a video signal processing circuit, a liquid crystal television using the same, a personal computer, a mobile phone, and the like.

It is a block diagram which shows the structure of the matrix arithmetic circuit included in this invention. 10 is a graph showing input / output characteristics for saturation enhancement according to Non-Patent Document 1. 10 is a graph showing input / output characteristics for saturation enhancement according to Patent Document 2. It is a block diagram which shows the structure of the video signal processing circuit of 1st Embodiment of this invention. It is a graph which shows the input / output characteristic of the saturation emphasis by 1st Embodiment of this invention. It is a block diagram which shows the structure of the video signal processing circuit of 2nd Embodiment of this invention. It is a graph which shows the input / output characteristic of the saturation emphasis by 2nd Embodiment of this invention. It is a block diagram which shows the structure of the video signal processing circuit of 3rd Embodiment of this invention. It is a graph which shows the input / output characteristic of the saturation emphasis by 3rd Embodiment of this invention. It is a block diagram which shows the structure of the video signal processing circuit of 4th Embodiment of this invention. It is a block diagram which shows the structure of the video signal processing circuit of 5th Embodiment of this invention. It is a graph which shows the input / output characteristic of the saturation emphasis by 5th Embodiment of this invention. It is a block diagram which shows the structure of the video signal processing circuit of 6th Embodiment of this invention. It is a graph which shows the input / output characteristic of the saturation emphasis by 6th Embodiment of this invention. It is a block diagram which shows the structure of the video signal processing circuit of 7th Embodiment of this invention. It is a schematic diagram which shows the outline | summary of the video telephone function of a mobile telephone. It is a block diagram which shows the structural example of the mobile telephone terminal by the 8th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Video signal processing circuit 20 Matrix arithmetic circuit 21 Subtractor 22 Multiplier 23 Adder 301 1st coefficient calculation part 302 2nd coefficient calculation part 303 3rd coefficient calculation part 30X X coefficient calculation part (X is arbitrary Natural number)
31 Maximum value detector 32 Minimum value detector 33 Subtractor 34 Adder 35 Subtractor 40 Coefficient selection unit 41 Minimum value detector 42 Look-up table 43 Coefficient storage unit 44 Comparator 50 Mobile phone terminal 51 Antenna 52 Radio control unit 53 Reception data processing unit 54 Video signal generation unit 55 Display control unit 56 Display device 57 Input device 58 Control unit 59 Imaging device 60 Imaging control unit 61 Transmission data processing unit 70 Telephone network 71 Base station R, G, B Input of three primary colors Signal R ′, G ′, B ′ Output signal of three primary colors MAX Maximum value of input signal MIN Minimum value of input signal α Coefficient α1 of matrix calculation Coefficient α2 calculated by first coefficient calculation unit Second coefficient calculation unit The coefficient α3 calculated by the coefficient αX calculated by the third coefficient calculation unit The coefficient calculated by the Xth coefficient calculation unit (X is an arbitrary natural number)
αpre Coefficient P11 used in the previous processing P11 First control parameter P12 given to the first coefficient calculation unit Second control parameter P1k given to the first coefficient calculation unit Second control parameter P1k given to the first coefficient calculation unit 2 control parameters (k is an arbitrary natural number)
P21 First control parameter given to the second coefficient calculation unit P22 Second control parameter given to the second coefficient calculation unit P2m Second control parameter given to the first coefficient calculation unit (m is an arbitrary natural number)
P31 First control parameter to be given to the third coefficient calculation unit P32 Second control parameter to be given to the third coefficient calculation unit PX1 First control parameter to be given to the Xth coefficient calculation unit (X is an arbitrary natural number)
PX2 Second control parameter given to the Xth coefficient calculation unit (X is an arbitrary natural number)
PXn The nth control parameter (X and n are arbitrary natural numbers) given to the Xth coefficient calculation unit

Claims (9)

A video signal processing circuit that adjusts input of a video signal composed of R, G, and B primary color signals and outputs a signal composed of R ′, G ′, and B ′,
A maximum value detection unit for detecting a maximum signal value MAX among the signals of the three primary colors constituting one pixel of the input video signal;
An input unit that receives an input of a control parameter P11 (where 0 <P11 ≦ 1) of the following equation 17 ,
A calculation unit for performing the calculation of the following equation 16;
A first coefficient calculation unit for obtaining the coefficient α of the following expression 16 by the following expression 17;
A video signal processing circuit comprising:

A minimum value detecting unit for detecting a minimum signal value MIN among the three primary colors constituting one pixel of the input video signal;
The input unit receives an input of a control parameter P12 of the following formula 18,
2. The video signal processing circuit according to claim 1, wherein the first coefficient calculation unit obtains the coefficient α by the following Expression 18.

A second coefficient calculation unit that calculates the coefficient α2 using the following equation 19,
A coefficient selection unit that selects any one of the coefficient α and the coefficient α2 calculated by the first coefficient calculation unit as a coefficient α used by the calculation unit;
With
The input unit receives an input of a control parameter P21 of the following equation 19 ,
3. The video signal processing circuit according to claim 1 , wherein the coefficient selection unit selects a minimum one of the coefficients as the coefficient α of the expression 16 .

A third coefficient calculation unit that calculates the coefficient α3 using the following equation 20,
The input unit receives input of control parameters P31 and P32 of the following equation 20,
The coefficient selection unit selects the smallest one of the coefficient α, the coefficient α2, and the coefficient α3 calculated by the first coefficient calculation unit as the coefficient α used by the calculation unit. The video signal processing circuit according to claim 3.

A second coefficient calculation unit that calculates the coefficient α2 using the following equation 19,
A coefficient selection unit that selects any one of the coefficient α and the coefficient α2 calculated by the first coefficient calculation unit as a coefficient α used by the calculation unit;
A storage unit that holds the coefficients adopted in the previous process;
Means for detecting a difference between the coefficient held in the storage unit and each coefficient;
With
The input unit receives an input of a control parameter P21 of the following equation 19 ,
The video signal processing circuit according to claim 1 , wherein the coefficient selection unit selects a coefficient having the smallest difference as the coefficient α used by the calculation unit .

A third coefficient calculation unit that calculates the coefficient α3 using the following equation 20,
The input unit receives input of control parameters P31 and P32 of the following equation 20,
The coefficient selection unit selects the coefficient having the smallest difference among the coefficient α, the coefficient α2, and the coefficient α3 calculated by the first coefficient calculation unit as the coefficient α used by the calculation unit. 6. The video signal processing circuit according to claim 5 , wherein

A video signal processing circuit that adjusts image quality by matrix operation and outputs a video signal composed of three primary color signals of red, green, and blue,
A plurality of coefficient calculation units for obtaining coefficients used in the calculation so as to suppress an overflow of the output of the matrix calculation, with the video signal as an input;
A coefficient selection unit that selects an optimum coefficient for reproduction of gradation among the plurality of coefficients respectively calculated from the plurality of coefficient calculation units;
Means for determining the optimum coefficient;
A storage unit that holds the coefficients adopted in the previous process;
Means for detecting a difference between the coefficient employed in the previous process and the coefficient calculated by the coefficient calculation unit;
A video signal processing circuit characterized in that the means for determining an optimum coefficient for reproduction of gradation uses a coefficient having the smallest difference between the coefficients. Video display apparatus having a video signal processing circuit according to any one of claims 1 to 7. An imaging device, a display device, and a video signal processing circuit according to any one of claims 1 to 7 , wherein a video signal captured by the imaging device is processed by the video signal processing circuit, An image display device characterized by being displayed on a display device.

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