Video signal conversion device, video signal conversion table generation method, data and program having 3D lookup table structure

Abstract

To solve a problem in which the gradation in a highlight area becomes discontinuous when an SDR video signal is converted to an HDR video signal using an inverse tone mapping function.SOLUTION: An electrical / optical converter 11 of a video signal converter 1 performs electrical / optical conversion on an SDR video signal to obtain an SDR linear signal. An expander 12 expands luminance YSDR of the SDR linear signal to luminance YHDR using an inverse tone mapping function to obtain an HDR linear signal. A highlight area compressor 13 identifies a highlight area by HDR start luminance Yip and HDR maximum luminance Ymax specified by a user, and compresses the expanded luminance YHDR of the HDR linear signal to logarithmically increasing luminance YHDR,comp for the highlight area using a predetermined function. An optical / electrical converter 14 performs optical / electrical conversion on the HDR linear signal having the luminance YHDR,comp to obtain an HDR video signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a video signal conversion device that converts an HDR (High Dynamic Range) video signal into an SDR (Standard Dynamic Range) video signal, a method for generating a table for video signal conversion, data having the structure of a 3D look-up table, and a program.

Background Art

[0002] Conventionally, HDR programs are produced in consideration of the HDR reference white in order to suppress the brightness variation between programs. The HDR reference white in the case of using the HLG (Hybrid Log Gamma) method is 75% of the HLG video signal level (hereinafter referred to as "75% HLG").

[0003] In order to correctly represent camera images, graphics data, etc. produced by the SDR method as HLG video signals, direct mapping processing is required. Direct mapping multiplies the gain at which white adjusted at 100% of the SDR video signal level (hereinafter referred to as "100% SDR") corresponds to 75% HLG by the scene linear signal (SDR scene luminance) or display linear signal (SDR display luminance) of the SDR video signal, and converts it into an HLG video signal using the HLG opto-electronic transfer function.

[0004] On the other hand, in order to utilize program content produced as an HLG program for broadcasting as an SDR program, a technique for converting an HLG video signal into an SDR video signal has been reported (see, for example, Patent Document 1).

[0005] This Patent Document 1 describes a method of expressing the luminance represented by HLG in SDR by multiplying the HLG display luminance by a gain and compressing the luminance in the highlight region so that the video signal level of the facial muscles of an important person for constructing a video becomes appropriate. A function that performs luminance compression so as to fit the luminance of this HLG into the luminance of SDR is called a tone mapping function.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When comparing the process using the aforementioned tone mapping function with the process of the aforementioned direct mapping, the tone mapping function consists of a combination of a linear function and a logarithmic function, and the direct mapping consists of a linear function. Therefore, the two are not in an inverse function relationship.

[0008] The video signal of an HDR program may include an HDR video signal converted from an SDR video signal by direct mapping. In this case, when the HDR video signal of the HDR program is converted into an SDR video signal by a tone mapping function, the converted SDR video signal becomes a video signal different from the original SDR video signal.

[0009] Assume the premise of producing an SDR program by a conversion technique after producing an HDR program. Under this premise, when producing an SDR program by converting an HDR video signal into an SDR video signal, a tone mapping function that converts the HDR display luminance into the SDR display luminance is used for this conversion.

[0010] Therefore, when producing an HDR program by converting an SDR video signal into an HDR video signal, for this conversion, instead of direct mapping, it is desirable to use a function that arithmetically inverse-transforms the tone mapping function (hereinafter referred to as the "inverse tone mapping function").

[0011] However, when producing an HDR program by converting an SDR video signal into an HDR video signal, that is, when converting the SDR display luminance into HDR display luminance using the inverse tone mapping function, the greater the luminance compression by the tone mapping function, the greater the expansion of the SDR display luminance.

[0012] Then, when converting the HDR display luminance obtained by greatly expanding the SDR display luminance into an HDR video signal using the HDR opto-electronic transfer function, the continuity of the video signal level in the highlight region is lost, and the gradation becomes discontinuous.

[0013] Therefore, the present invention has been made to solve the above problems, and its object is to solve the problem that the gradation in the highlight region becomes discontinuous when converting an SDR video signal into an HDR video signal using an inverse tone mapping function, and to provide a video signal conversion device, a method for generating a table for video signal conversion, data having the structure of a 3D look-up table, and a program.

Means for Solving the Problems

[0014] To solve the above problems, the video signal conversion device according to claim 1 is a video signal conversion device that converts an SDR video signal into an HDR video signal, and includes an electro-optical conversion unit that converts the SDR video signal into an SDR linear signal by a predetermined electro-optical transfer function, and the luminance Y SDR of the SDR linear signal converted by the electro-optical conversion unit is expanded to obtain an HDR linear signal having the expanded luminance Y HDR and a luminance Y of the HDR linear signal obtained by the expansion unit HDRAmong them, the luminance of a predetermined highlight area is compressed, and the luminance Y after compression HDR,comp A highlight area compression unit that obtains an HDR linear signal having the above, and an optical / electrical conversion unit that converts the HDR linear signal obtained by the highlight area compression unit into the HDR video signal by a predetermined optical / electrical transfer function, characterized in that it is provided with.

[0015] In addition, the video signal conversion device according to claim 2 is a video signal conversion device that converts an SDR video signal into an HDR video signal, and includes an electrical / optical conversion unit that converts the SDR video signal into an SDR linear signal by a predetermined electrical / optical transfer function, and the luminance Y of the SDR linear signal converted by the electrical / optical conversion unit SDR While expanding, the luminance Y SDR is converted into luminance Y HDR so that the luminance to be expanded is compressed to a logarithmically increasing luminance for the highlight area, and an expansion compression unit that obtains an HDR linear signal having the luminance Y HDR and an optical / electrical conversion unit that converts the HDR linear signal obtained by the expansion compression unit into the HDR video signal by a predetermined optical / electrical transfer function, characterized in that it is provided with.

[0016] In addition, the video signal conversion device according to claim 3 is a video signal conversion device that converts an SDR video signal into an HDR video signal using a 3D look-up table, and includes a storage unit in which the 3D look-up table including the RGB values of a plurality of HDR video signals is stored, and the SDR video signal is input, and based on the RGB values of the input SDR video signal, a predetermined number of RGB values of HDR video signals are read from the 3D look-up table stored in the storage unit, and the RGB values of the predetermined number of HDR video signals are interpolated to obtain the HDR video signal corresponding to the input SDR video signal. A conversion unit, and in the 3D look-up table, the SDR video signal is converted into an SDR linear signal by a predetermined electrical / optical transfer function, and the luminance Y SDR is expanded, so that an HDR linear signal having the expanded luminance Y HDR is obtained, and the luminance Y of the HDR linear signal HDRBy compressing the luminance of a predetermined highlight area among them, the luminance Y after compression HDR,comp of the HDR linear signal is obtained, and the RGB values of the HDR video signal obtained by converting the HDR linear signal having the luminance Y HDR,comp by a predetermined optical / electrical transfer function, wherein the RGB values of the plurality of HDR video signals corresponding to the RGB values of the plurality of SDR video signals when the entire area of the SDR video signal is discretized at a predetermined interval are included.

[0017] Furthermore, the method for generating a table for video signal conversion according to claim 4 is a method for generating a 3D look-up table for converting an SDR video signal into an HDR video signal. The method includes: a first step of inputting an SDR video signal and converting it into an SDR linear signal by a predetermined electrical / optical transfer function; a second step of expanding the luminance Y SDR of the SDR linear signal converted in the first step to obtain an HDR linear signal having the expanded luminance Y HDR ; a third step of compressing the luminance of a predetermined highlight area among the luminance Y HDR of the HDR linear signal obtained in the second step to obtain an HDR linear signal having the compressed luminance Y HDR,comp ; a fourth step of converting the HDR linear signal having the luminance Y HDR,comp obtained in the third step into an HDR video signal by a predetermined optical / electrical transfer function; and a fifth step of generating the 3D look-up table including the RGB values of the HDR video signal converted in the fourth step corresponding to the RGB values of the SDR video signal input in the first step, wherein the RGB values of the plurality of HDR video signals corresponding to the RGB values of the plurality of SDR video signals when the entire area of the SDR video signal is discretized at a predetermined interval are included.

[0018] In addition, the data having the structure of the 3D look-up table according to claim 5 is data having the structure of the 3D look-up table used by a video signal conversion device that converts an SDR video signal into an HDR video signal. In this data, the SDR video signal is converted into an SDR linear signal by a predetermined electro-optical transfer function, and the luminance Y of the SDR linear signal SDR is stretched, so that an HDR linear signal having the stretched luminance Y HDR is obtained. The luminance Y of the HDR linear signal HDR is compressed in a predetermined highlight region, so that an HDR linear signal having the compressed luminance Y HDR,comp is obtained. The RGB values of the HDR video signal obtained by converting the HDR linear signal having the luminance Y HDR,comp into an HDR video signal by a predetermined opto-electrical transfer function include the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals when the entire region of the SDR video signal is discretized at a predetermined interval. The video signal conversion device inputs an SDR video signal to be converted, and reads out the RGB values of a predetermined number of HDR video signals from the 3D look-up table stored in the storage unit based on the RGB values of the input SDR video signal, and interpolates the RGB values of the predetermined number of HDR video signals to obtain an HDR video signal corresponding to the input SDR video signal. It is used for the process of obtaining, which is characterized by this.

[0019] Furthermore, the program according to claim 6 causes a computer to function as the video signal conversion device according to any one of claims 1 to 3, which is characterized by this.

Advantages of the Invention

[0020] As described above, according to the present invention, when converting an SDR video signal into an HDR video signal using an inverse tone mapping function, the problem that the gradation of the highlight region becomes discontinuous can be solved.

Brief Description of the Drawings

[0021]

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MODE FOR CARRYING OUT THE INVENTION

[0022] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. Example 1 is the luminance Y of the SDR linear signal obtained by electro-optical conversion of the SDR video signal SDR which is extended using an inverse tone mapping function, and the luminance Y of the HDR linear signal after extension for the highlight region HDR is compressed, and the compressed HDR linear signal is electro-optically converted to obtain an HDR video signal.

[0023] Also, in Example 2, the luminance Y of the SDR linear signal obtained by electro-optical conversion of the SDR video signal SDR is converted to the luminance Y of the HDR linear signal using a function that combines the extension process by the inverse tone mapping function of Example 1 and the compression process for the highlight region HDR and the HDR linear signal is electro-optically converted to obtain an HDR video signal.

[0024] Also, in Example 3, the SDR video signal is converted to an HDR video signal using a 3D look-up table T that includes the RGB values of a plurality of HDR video signals corresponding to the RGB values of the plurality of SDR video signals obtained according to Example 1 or Example 2. Hereinafter, Examples 1 to 3 will be described in detail.

[0025] 〔Example 1〕 First, Example 1 will be described. As described above, in Example 1, the luminance Y of the SDR linear signal obtained by electro-optical conversion of the SDR video signal SDR is extended using an inverse tone mapping function, and the luminance Y of the HDR linear signal after extension for the highlight region HDR is compressed, and the compressed HDR linear signal is electro-optically converted to obtain an HDR video signal.

[0026] FIG. 1 is a block diagram showing a configuration example of the video signal conversion apparatus of Example 1. This video signal conversion apparatus 1 includes an electro-optical conversion unit 11, an extension unit 12, a highlight region compression unit 13, and an electro-optic conversion unit 14.

[0027] The electrical / optical conversion unit 11 inputs an SDR video signal and obtains an SDR linear signal by performing electrical / optical conversion on the SDR video signal. Then, the electrical / optical conversion unit 11 outputs the SDR linear signal to the expansion unit 12.

[0028] The expansion unit 12 inputs an SDR linear signal (SDR linear signal having luminance Y SDR ) from the electrical / optical conversion unit 11, and uses a predetermined inverse tone mapping function to expand the luminance Y SDR of the SDR linear signal to luminance Y HDR to obtain an HDR linear signal.

[0029] As a result, the luminance Y SDR of the SDR linear signal is expanded by an inverse tone mapping function composed of a linear function and a non-linear function, and the luminance Y HDR of the HDR linear signal is obtained. The luminance Y SDR of the SDR linear signal is particularly greatly expanded by a non-linear function (the lower formula of Equation (1) showing the inverse tone mapping function described later) with reference to Equation (1) showing the inverse tone mapping function described later.

[0030] Then, the expansion unit 12 outputs an HDR linear signal having luminance Y HDR to the highlight area compression unit 13.

[0031] The highlight area compression unit 13 inputs an HDR linear signal having luminance Y HDR from the expansion unit 12, and inputs the HDR start luminance Y ip and the HDR maximum luminance Y max specified by the user.

[0032] The HDR start luminance Y ip represents the luminance at the start point d (see FIG. 4 described later) of the highlight area in the luminance Y HDR of the HDR linear signal. The HDR maximum luminance Y max represents the luminance at the end point e (see FIG. 4 described later) of the highlight area, that is, the maximum value in the luminance Y HDR of the HDR linear signal before highlight compression.

[0033] HDR start luminance Y ip and HDR maximum luminance Y max are used to identify the highlight area specified by the user. That is, the HDR start luminance Y ip from the HDR start luminance Y max to the HDR maximum luminance Y

[0034] For the highlight area specified by the user among the entire area of the HDR linear signal, the highlight area compressor 13 uses a predetermined function to compress the greatly expanded luminance Y HDR of the HDR linear signal into a logarithmically increasing luminance Y HDR,comp of the HDR linear signal.

[0035] As a result, the luminance Y HDR of the highlight area of the HDR linear signal is compressed to logarithmically increase or decrease according to a predetermined function, and the luminance Y HDR,comp of the HDR linear signal is obtained. That is, by using the inverse tone mapping function, the luminance Y HDR of the highlight area of the greatly expanded HDR linear signal is compressed into a logarithmically increasing luminance Y HDR,comp with a low degree of expansion. Therefore, it is possible to solve the problem that the continuity of the video signal level in the highlight area is lost and the gradation becomes discontinuous.

[0036] Then, the highlight area compressor 13 outputs the HDR linear signal having the luminance Y HDR,comp to the optoelectronic conversion unit 14.

[0037] Note that the highlight area compressor 13 is configured to input the HDR start luminance Y ip and the HDR maximum luminance Y max specified by the user, but these data may be internally held as preset parameters.

[0038] The optoelectronic conversion unit 14 receives the luminance Y HDR,compAn HDR linear signal having [it] is input, and an HDR video signal is obtained by performing opto-electrical conversion on the HDR linear signal. Then, the opto-electrical conversion unit 14 outputs the HDR video signal.

[0039] FIG. 2 is a flowchart showing a processing example of the video signal conversion apparatus 1 of the first embodiment shown in FIG. 1.

[0040] The electro-optical conversion unit 11 inputs an SDR video signal (step S201), and converts the SDR video signal into an SDR linear signal using, for example, the SDR electro-optical transfer function (step S202).

[0041] The SDR linear signal can handle either the SDR scene luminance or the SDR display luminance. When the electro-optical conversion unit 11 converts the SDR video signal into an SDR linear signal having the SDR scene luminance, the inverse function of the SDR opto-electrical transfer function (OETF (Opto-Electroic Transfer Function)) that converts from the scene linear signal defined in Recommendation ITU-R BT.709 to the SDR video signal is used. -1 ) is used.

[0042] Also, when the electro-optical conversion unit 11 converts the SDR video signal into an SDR linear signal having the SDR display luminance, the SDR electro-optical transfer function (EOTF (Electro-Optical Transfer Function)) that converts from the SDR video signal defined in Recommendation ITU-R BT.1886 to the display linear signal is used.

[0043] The extension unit 12 uses a predetermined inverse tone mapping function to extend the luminance Y of the SDR linear signal SDR to the luminance Y HDR and converts it to obtain an HDR linear signal (step S203).

[0044] As the predetermined inverse tone mapping function, for example, a function that takes into account the color reproduction of highlights, the reference white level, and the skin level of a person described in the aforementioned Patent Document 1 is used as follows.

Number

[0045] Here, k 1 is the gain value considering the skin level, and is preset from the correspondence relationship between the skin level of the HDR video signal and the skin level of the SDR video signal.

[0046] k 2 is a correction value for making the slopes of the tangent lines of the linear signal (the upper formula of the formula (1)) and the exponential non - linear signal (the lower formula of the formula (1)) coincide at the inflection point a shown in FIG. 3 described later.

[0047] k 3 is, for example, when using the HLG method, a correction value for making a 109% SDR linear signal indicating a 109% SDR video signal level correspond to a 100% HLG linear signal indicating a 100% HLG video signal level, or a correction value for making a 100% SDR linear signal correspond to a 75% HLG linear signal.

[0048] k 4 is a correction value for making the values of the contact points of the linear signal (the upper formula of the formula (1)) and the exponential non - linear signal (the lower formula of the formula (1)) coincide.

[0049] Y SDR,ip is the luminance of the HDR linear signal (SDR knee - point luminance) at the inflection point of the inflection point a shown in FIG. 3 described later. Y HDR,ip is the luminance of the HDR linear signal (HDR knee - point luminance) corresponding to the SDR knee - point luminance Y SDR,ip at the inflection point of the inflection point a.

[0050] SDR knee - point luminance Y SDR,ip and HDR knee - point luminance Y HDR,ip and gain value k 1 and correction value k 2 , k 3 , k 4 are preset. For example, the gain value k1 = 0.6899, correction value k 2 = 14.6589, correction value k 3 = 0.8051, correction value k 4 = 99.1633, SDR knee point luminance Y SDR,ip = 75.1954, HDR knee point luminance Y HDR,ip = 108.9990.

[0051] Figure 3 shows the luminance Y of the SDR linear signal when using the inverse tone mapping function SDR and the luminance Y of the HDR linear signal HDR The horizontal axis represents the luminance Y of the SDR linear signal SDR which is the SDR display luminance [cd / m 2 , and the vertical axis represents the luminance Y of the HDR linear signal HDR which is the HDR display luminance [cd / m 2 .

[0052] When the SDR video signal is converted to a display linear signal with a peak luminance of 100 cd / m 2 , 100% SDR of the SDR display luminance is 100 cd / m 2 , and 109% SDR is approximately 123 cd / m 2 .

[0053] When the SDR display luminance is extended to the HDR display luminance using the inverse tone mapping function of the formula (1), the HDR display luminance corresponding to 100 cd / m 2 of 100% SDR is 203 cd / m 2 (refer to the 100% SDR point b). Also, the HDR display luminance corresponding to approximately 123 cd / m 2 of 109% SDR is approximately 643 cd / m 2 (refer to the 109% SDR point c).

[0054] Although not shown, when converting SDR display luminance to HDR display luminance using direct mapping, the SDR display luminance at the 10% video signal level between 100% SDR and 109% SDR is 23 cd / m 2 and the corresponding HDR display luminance ranges from 203 cd / m 2 to approximately 250 cd / m 2 with a difference of 47 cd / m 2 between them.

[0055] As shown in FIG. 3, when using the inverse tone mapping function, the SDR display luminance at the 10% video signal level between 100% SDR and 109% SDR is 23 cd / m 2 (23 = 123 - 100), and the corresponding HDR display luminance after luminance expansion is 440 cd / m 2 (440 = 643 - 203) (refer to the 100% SDR point b and 109% SDR point c). Also, if this is converted back to the HLG video signal when using the HLG method, it becomes the 18% video signal level between 75% HLG and 93% HLG.

[0056] In this way, due to the excessive expansion of the luminance in the highlight area originally represented by continuous SDR video signal levels, a phenomenon called banding may occur, where it is represented by discontinuous HDR video signal levels and causes discontinuity in gradation. To solve this problem, in the subsequent highlight area compression unit 13, the HDR display luminance in the highlight area is compressed.

[0057] In addition, when the color gamut of the SDR video signal is the standard color gamut defined by Recommendation ITU - R BT.709, the color gamut of the HDR video signal is the wide color gamut defined by Recommendation ITU - R BT.2100 and Recommendation ITU - R BT.2020, so the color gamuts of the two video signals are different. In this case, the expansion unit 12 performs a color gamut conversion to convert the standard color gamut of the SDR linear signal to a wide color gamut as a pre - processing of the expansion process of the above formula (1).

[0058] Returning to FIGS. 1 and 2, after step S203, the highlight area compression unit 13 inputs the HDR start luminance Y and the HDR maximum luminance Y specified by the user. Then, the highlight area compression unit 13 identifies the highlight area in the entire area of the HDR linear signal with luminance extended using the inverse tone mapping function of the formula (1) from these data. That is, the highlight area will be specified by the user. ip and the HDR maximum luminance Y max are input. Then, the highlight area compression unit 13 identifies the highlight area in the entire area of the HDR linear signal with luminance extended using the inverse tone mapping function of the formula (1) from these data. That is, the highlight area will be specified by the user.

[0059] The highlight area compression unit 13 compresses the extended luminance Y of the HDR linear signal to the luminance Y for the highlight area specified by the user using a predetermined function (step S204). HDR for the highlight area specified by the user using a predetermined function (step S204). HDR,comp to the luminance Y

[0060] As the predetermined function, for example, as in the following formula, for the highlight area, a function that compresses the luminance Y to the luminance Y such that the luminance Y increases logarithmically with respect to the increase in the greatly extended luminance Y is used. For the compression of the highlight area, it is necessary to continuously increase the luminance from the start point to the end point where luminance compression is performed, like the KNEE processing of the camera system. Therefore, it is formulated by a logarithmic function as shown in the following formula (2). HDR for the highlight area specified by the user using a predetermined function (step S204). HDR,comp such that the luminance Y HDR increases logarithmically with respect to the increase in the greatly extended luminance Y HDR,comp is used. For the compression of the highlight area, it is necessary to continuously increase the luminance from the start point to the end point where luminance compression is performed, like the KNEE processing of the camera system. Therefore, it is formulated by a logarithmic function as shown in the following formula (2).

Equation

[0061] Here, the coefficients c 1 , c 2 , c 3 are calculated by the following formula.

Equation

Equation

Equation

[0062] The specified function is the luminance Y extended by the inverse tone mapping function HDR that is directly set to the luminance Y HDR,comp (the upper formula of the formula (2)), and the luminance Y of the highlight area HDR that is compressed to the luminance Y HDR,comp (the lower formula of the formula (2)). Continuity needs to be ensured between these functions.

[0063] Therefore, the coefficient c 1 is derived by the formula (3) that matches the slopes of the signals, and the coefficient c 3 is derived by the formula (4) that matches the values of the signals. The coefficient c 2 is derived by obtaining the minimum value of the function f(c 2 ) of the formula (5).

[0064] For example, when the HDR start luminance Y ip = 203 cd / m 2 and the HDR maximum luminance Y max = 643 cd / m 2 are specified by the user, the coefficients c 1 = 13.2426, c 2 = 0.9348, c 3 = 239.3111 are derived.

[0065] Figure 4 is a diagram illustrating the case when the HDR start luminance Y HDR , Y HDR,comp and the HDR maximum luminance Y ip = 203 cd / m 2 and the HDR maximum luminance Y max = 643 cd / m 2 are specified by the user in the relationship between the luminance Y

[0066] before and after compressing the highlight area. The horizontal axis represents the HDR display luminance [cd / m HDR which is the luminance Y of the HDR linear signal before compressing the highlight area, and the vertical axis represents the luminance Y of the HDR linear signal after compressing the highlight area 2 HDR,comp ​The HDR display brightness [cd / m 2 is shown.

[0067] As shown in FIG. 4, when the user designates the HDR start brightness Y ip and the HDR maximum brightness Y max , the highlight area compression unit 13 identifies the highlight area from the start point d indicated by the HDR start brightness Y ip to the end point e indicated by the HDR maximum brightness Y max .

[0068] Then, as shown in the following formula of formula (2), the highlight area compression unit 13 compresses the brightness Y ip ≤Y HDR ≤Y max ) of the highlight area (Y HDR ) to the brightness Y HDR,comp .

[0069] Returning to FIGS. 1 and 2, after step S204, the opto / electrical conversion unit 14 converts the HDR linear signal into an HDR video signal using, for example, the opto / electrical transfer function of HDR (step S205). Then, the opto / electrical conversion unit 14 outputs the HDR video signal (step S206).

[0070] When the SDR video signal is converted into an SDR linear signal having the SDR scene brightness in step S202, the opto / electrical conversion unit 14 uses, in step S205, the opto / electrical transfer function (OETF (Opto-Electronic Transfer Function)) that converts the scene linear signal defined in Recommendation ITU-R BT.2100 into an HDR video signal.

[0071] Also, when the SDR video signal is converted into an SDR linear signal having SDR display luminance in step S202, the optical / electrical conversion unit 14, in step S205, uses the inverse function of the electro-optical transfer function (EOTF (Electro-Optical Transfer Function)) that converts the HDR video signal defined in Recommendation ITU-R BT.2100 into a display linear signal. -1 )

[0072] As described above, according to the video signal conversion device 1 of the first embodiment, the electro-optical conversion unit 11 obtains an SDR linear signal by electro-optically converting the SDR video signal. The expansion unit 12 uses a predetermined inverse tone mapping function to expand the luminance Y SDR of the SDR linear signal to luminance Y HDR to obtain an HDR linear signal.

[0073] The highlight area compression unit 13 identifies the highlight area based on the HDR start luminance Y ip and the HDR maximum luminance Y max specified by the user, and for the highlight area in the entire area of the HDR linear signal, uses a predetermined function to compress the expanded luminance Y HDR of the HDR linear signal to the logarithmically increasing luminance Y HDR,comp .

[0074] The optical / electrical conversion unit 14 obtains an HDR video signal by electro-optically converting the HDR linear signal having the luminance Y HDR,comp .

[0075] Thereby, when converting the SDR video signal into an HDR video signal using the inverse tone mapping function, since the luminance of the largely expanded highlight area is compressed, the problem that the continuity of the video signal level in the highlight area is lost and the gradation becomes discontinuous can be solved.

[0076] Also, assume a case where an HDR program is produced by converting an original SDR video signal into an HDR video signal, and an SDR program is produced by converting the HDR video signal of the HDR program into an SDR video signal using a tone mapping function.

[0077] In this case, when producing an HDR program, comparing the process of converting an SDR video signal into an HDR video signal by direct mapping with the process of converting an SDR video signal into an HDR video signal using the inverse tone mapping function in Example 1 and a predetermined function for compressing the highlight area, the latter can make the SDR video signal obtained by converting the HDR video signal closer to the original SDR video signal.

[0078] 〔Example 2〕 Next, Example 2 will be described. As described above, in Example 2, the luminance Y of the SDR linear signal obtained by electro-optical conversion of the SDR video signal SDR is converted into the luminance Y of the HDR linear signal using a function that combines the stretching process by the inverse tone mapping function in Example 1 and the compressing process for the highlight area, and the HDR linear signal is electro-optically converted to obtain an HDR video signal. HDR Figure 5 is a block diagram showing a configuration example of the video signal conversion device of Example 2. This video signal conversion device 2 includes an electro-optical conversion unit 21, an expansion compression unit 22, and an opto-electrical conversion unit 23.

[0079] The electro-optical conversion unit 21 inputs an SDR video signal and obtains an SDR linear signal by electro-optical conversion of the SDR video signal. Then, the electro-optical conversion unit 21 outputs the SDR linear signal to the expansion compression unit 22.

[0080] The expansion compression unit 22 inputs an SDR linear signal (SDR linear signal having luminance Y

[0081] from the electro-optical conversion unit 21) and also inputs the SDR start luminance Y SDR specified by the user. comp,ip

[0082] ​ SDR start luminance Y comp,ip is the luminance Y of the SDR linear signal SDR and indicates the luminance at the start point g of the highlight area (see FIG. 7 described later). The SDR start luminance Y comp,ip identifies the highlight area specified by the user. That is, the SDR start luminance Y comp,ip specified by the user to the luminance Y SDR of the SDR linear signal up to the maximum value is the highlight area.

[0083] The expansion / compression unit 22 performs a process combining the expansion unit 12 and the highlight area compression unit 13 shown in FIG. 1. Specifically, the expansion / compression unit 22 uses a predetermined function to expand the luminance Y SDR of the SDR linear signal and compress the luminance of the highlight area to a logarithmically increasing luminance by greatly expanding it, converting the luminance Y SDR to the luminance Y HDR .

[0084] As a result, the luminance Y SDR of the SDR linear signal is expanded to obtain the luminance Y HDR of the HDR linear signal, but for the highlight area, a luminance Y HDR with a low degree of expansion is obtained. Therefore, the problem that the continuity of the video signal level in the highlight area is lost and the gradation becomes discontinuous can be solved.

[0085] Then, the expansion / compression unit 22 outputs the HDR linear signal having the expanded / compressed luminance Y HDR to the optical / electrical conversion unit 23.

[0086] The optical / electrical conversion unit 23 inputs the HDR linear signal having the luminance Y HDR from the expansion / compression unit 22, performs optical / electrical conversion on the HDR linear signal to obtain an HDR video signal, and the optical / electrical conversion unit 23 outputs the HDR video signal.

[0087] FIG. 6 is a flowchart showing a processing example of the video signal conversion apparatus 2 according to the second embodiment shown in FIG. 5.

[0088] The electro-optical conversion unit 21 inputs an SDR video signal (step S601), and converts the SDR video signal into an SDR linear signal using, for example, the SDR electro-optical transfer function in the same manner as step S202 shown in FIG. 2 (step S602).

[0089] The expansion / compression unit 22 inputs the SDR start luminance Y comp,ip specified by the user. Then, the expansion / compression unit 22 uses a predetermined function to expand and compress the luminance Y SDR of the SDR linear signal to the luminance Y HDR and obtains an HDR linear signal by conversion (step S603).

[0090] The predetermined function expands the luminance Y SDR of the SDR linear signal, and compresses the luminance that increases logarithmically by a large amount in the highlight region to the luminance Y SDR to convert it to the luminance Y HDR . For example, the following formula is used for this function.

Equation

[0091] Here, the SDR knee point luminance Y SDR,ip , the HDR knee point luminance Y HDR,ip , the gain value k 1、 correction value k 2 , k 3 , k 4 and the coefficient c 1 , c 2 , c 3 are the same as those shown in the above formulas (1) and (2) and are assumed to be preset.

[0092] In the predetermined function shown in the above formula (6), the formula in the region where Y SDR < Y SDR,ip , and Y SDR,ip ≦ YSDR <Y comp,ip The formula for the region of <Y comp,ip ≤ Y SDR corresponds to the formula of the inverse tone mapping function shown in the above formula (1). Also, for the region of <Y SDR,ip ≤ Y SDR the formula of this region, and the formula of the lower formula of the predetermined function shown in the above formula (2) for the region of <Y ip ≤ Y HDR ≤ Y max is combined.

[0093] FIG. 7 is a diagram showing the relationship between the luminance Y SDR of the SDR linear signal and the luminance Y HDR of the HDR linear signal when using a function that combines the expansion process by the inverse tone mapping function and the compression process of the highlight region, and corresponds to FIG. 3.

[0094] The horizontal axis represents the luminance Y SDR of the SDR linear signal before conversion, which is the SDR display luminance [cd / m 2 , and the vertical axis represents the luminance Y HDR of the HDR linear signal after conversion, which is the HDR display luminance [cd / m 2 .

[0095] In the region from the origin to the inflection point f as shown in the formula for the region of <Y SDR < Y SDR,ip in the formula (6) by the expansion / compression unit 22, the luminance Y SDR is expanded to the luminance Y HDR according to the linear function in the inverse tone mapping function shown in the upper formula of the formula (1).

[0096] Also, in the region from the inflection point f to the start point g as shown in the formula for the region of <Y SDR,ip ≤ Y SDR < Y comp,ip in the formula (6) by the expansion / compression unit 22, the luminance Y SDRis the luminance Y HDR is stretched to

[0097] Furthermore, by the stretching / compression unit 22, Y in the formula (6) comp,ip ≦Y SDR In the highlight region which is the region where the value is equal to or greater than the start point g, as shown in the formula of the region, it is converted to increase logarithmically.

[0098] Returning to FIGS. 5 and 6, after step S603, the photo / electric conversion unit 23 converts the HDR linear signal into an HDR video signal (step S604) using, for example, the photo / electric transfer function of HDR in the same manner as step S205 shown in FIG. 2. Then, the photo / electric conversion unit 23 outputs the HDR video signal (step S605).

[0099] As described above, according to the video signal conversion apparatus 2 of the second embodiment, the electro-optical conversion unit 21 obtains the SDR linear signal by electro-optical converting the SDR video signal. The stretching / compression unit 22 stretches the luminance Y of the SDR linear signal using a predetermined function, and compresses the luminance, which is greatly stretched in the highlight region, into a logarithmically increasing luminance, thereby converting the luminance Y SDR to the luminance Y SDR to the luminance Y HDR to convert it.

[0100] The photo / electric conversion unit 23 obtains the HDR video signal by photo / electric converting the HDR linear signal having the luminance Y HDR .

[0101] Thereby, by using a predetermined function, the SDR video signal is converted into the HDR video signal so that the luminance, which is greatly stretched in the highlight region, is compressed into a logarithmically increasing luminance. Therefore, similar to the first embodiment, it is possible to solve the problem that the continuity of the video signal level in the highlight region is lost and the gradation becomes discontinuous.

[0102] Also, assume a case where an HDR program is produced by converting an original SDR video signal into an HDR video signal, and an SDR program is produced by converting the HDR video signal of the HDR program into an SDR video signal using a tone mapping function.

[0103] In this case, when producing an HDR program, comparing the process of converting the SDR video signal into an HDR video signal by direct mapping with the process of converting the SDR video signal into an HDR video signal using the predetermined function in Example 2, the latter can bring the SDR video signal obtained by converting the HDR video signal closer to the original SDR video signal.

[0104] 〔Another Example of Example 1〕 Next, another example of Example 1 will be described. In addition to the process of Example 1 described above, another example of Example 1 further associates the input SDR video signal with the HDR video signal into which the SDR video signal is converted, and generates a 3D look-up table T including the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals.

[0105] FIG. 8 is a block diagram showing a configuration example of a video signal conversion apparatus in another example of Example 1. This video signal conversion apparatus 1' includes an electric / optical conversion unit 11, an extension unit 12, a highlight area compression unit 13, an optical / electric conversion unit 14, a table generation unit 15, and a storage unit 16.

[0106] Comparing the video signal conversion apparatus 1 of Example 1 shown in FIG. 1 with the video signal conversion apparatus 1' in another example of Example 1 shown in FIG. 8, the video signal conversion apparatuses 1 and 1' are common in that they include an electric / optical conversion unit 11, an extension unit 12, a highlight area compression unit 13, and an optical / electric conversion unit 14.

[0107] In contrast, the video signal conversion apparatus 1' is different from the video signal conversion apparatus 1 in that, in addition to the configuration of the video signal conversion apparatus 1, it further includes a table generation unit 15 and a storage unit 16. In FIG. 8, the same parts as those in FIG. 1 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0108] The table generation unit 15 inputs the SDR video signal input by the video signal conversion device 1', and inputs the HDR video signal corresponding to the SDR video signal from the optical / electrical conversion unit 14. The HDR video signal input from the optical / electrical conversion unit 14 is a signal obtained by converting the SDR video signal through the processing of the electrical / optical conversion unit 11, the expansion unit 12, the highlight area compression unit 13, and the optical / electrical conversion unit 14.

[0109] The table generation unit 15 associates the RGB values (R value, G value, and B value) of the input SDR video signal with the RGB values of the input HDR video signal. By performing such processing on each signal in the entire area that the input SDR video signal can take, the RGB values of each signal in the entire area of the SDR video signal and the RGB values of the corresponding HDR video signal are obtained.

[0110] The table generation unit 15 constitutes a plurality of sets of data in which each of the RGB values of a plurality of SDR video signals when the entire area of the SDR video signal is discretized at a predetermined interval and the RGB values of the corresponding HDR video signal are paired. Then, the table generation unit 15 generates a 3D look-up table T composed of a plurality of sets of data in which the RGB values of the SDR video signal and the RGB values of the HDR video signal correspond, and stores the 3D look-up table T in the storage unit 16.

[0111] FIG. 9 is a diagram showing an example of the data structure of the 3D look-up table T, and shows an example in the case of a 10-bit color space.

[0112] The RGB values (0, 0, 0), (0, 0, 15), ···, (1023, 1023, 1023) of the SDR video signal are the RGB values of a plurality of SDR video signals when the entire area of the SDR video signal is discretized at a predetermined interval to form a lattice point data group.

[0113] This 3D look-up table T is composed of a plurality of sets of data, taking the RGB values (0, 0, 0) of the SDR video signal and the RGB values of the HDR video signal as a set of data, the RGB values (0, 0, 15) of the SDR video signal and the RGB values of the HDR video signal as a set of data, ···, and the RGB values (1023, 1023, 1023) of the SDR video signal and the RGB values of the HDR video signal as a set of data.

[0114] In this way, after the processing (steps S201 to S206) by the electro-optical conversion unit 11, the expansion unit 12, the highlight area compression unit 13, and the opto-electrical conversion unit 14 shown in FIG. 2, the table generation unit 15 generates the 3D look-up table T and stores it in the storage unit 16.

[0115] Thus, by using the 3D look-up table T stored in the storage unit 16, as shown in the third embodiment of FIG. 11 described later, the SDR video signal to be converted can be converted into an HDR video signal.

[0116] As described above, according to the video signal conversion device 1' in another example of the first embodiment, similar to the video signal conversion device 1 of the first embodiment, the problem that the continuity of the video signal level in the highlight area is lost and the gradation becomes discontinuous can be solved.

[0117] Note that the table generation unit 15 generates a 3D look-up table T composed of a plurality of sets of data in which the RGB values of the SDR video signal and the RGB values of the HDR video signal correspond, and stores it in the storage unit 16.

[0118] On the other hand, the table generation unit 15 may generate a 3D look-up table T composed only of the RGB values of a plurality of HDR video signals from among a plurality of sets of data in which the RGB values of the SDR video signal and the RGB values of the HDR video signal correspond, and store it in the storage unit 16. That is, the table generation unit 15 generates a 3D look-up table T composed only of the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals.

[0119] In this case, the 3D look-up table T in the example shown in FIG. 9 is composed of the RGB values of the HDR video signal corresponding to the RGB values (0, 0, 0) of the SDR video signal, the RGB values of the HDR video signal corresponding to the RGB values (0, 0, 15) of the SDR video signal, ···, and the RGB values of the HDR video signal corresponding to the RGB values (1023, 1023, 1023) of the SDR video signal.

[0120] [Another Example of Example 2] Next, another example of Example 2 will be described. In addition to the processing of Example 2 described above, another example of Example 2 further associates the input SDR video signal with the HDR video signal obtained by converting the SDR video signal, and generates a 3D look-up table T including the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals.

[0121] FIG. 10 is a block diagram showing a configuration example of a video signal conversion device in another example of Example 2. This video signal conversion device 2' includes an electric / optical conversion unit 21, an extension / compression unit 22, an optical / electric conversion unit 23, a table generation unit 24, and a storage unit 25.

[0122] Comparing the video signal conversion device 2 of Example 2 shown in FIG. 5 with the video signal conversion device 2' in another example of Example 2 shown in FIG. 10, the video signal conversion devices 2 and 2' are common in that they include an electric / optical conversion unit 21, an extension / compression unit 22, and an optical / electric conversion unit 23.

[0123] On the other hand, the video signal conversion device 2' is different from the video signal conversion device 2 in that, in addition to the configuration of the video signal conversion device 2, it further includes a table generation unit 24 and a storage unit 25. In FIG. 10, the same parts as those in FIG. 5 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0124] Similar to the table generation unit 15 shown in FIG. 8, the table generation unit 24 generates a 3D look-up table T composed of a plurality of sets of data in which the RGB values of the SDR video signal and the RGB values of the HDR video signal correspond to each other, and stores this in the storage unit 25. Since the table generation unit 24 and the storage unit 25 are the same as the table generation unit 15 and the storage unit 16 shown in FIG. 8, detailed description thereof will be omitted.

[0125] In this way, after the processing (steps S601 to S605) by the electric / optical conversion unit 21, the extension / compression unit 22, and the optical / electric conversion unit 23 shown in FIG. 6, the table generation unit 24 generates the 3D look-up table T and stores this in the storage unit 25.

[0126] Thereby, by using the 3D look-up table T stored in the storage unit 25, as shown in Example 3 of FIG. 11 described later, the SDR video signal to be converted can be converted into an HDR video signal.

[0127] As described above, according to the video signal conversion device 2' in another example of Example 2, similar to the video signal conversion device 2 of Example 2, it is possible to solve the problem that the continuity of the video signal level in the highlight region is lost and the gradation becomes discontinuous.

[0128] Note that, similar to the table generation unit 15 shown in FIG. 8, the table generation unit 24 may generate a 3D look-up table T composed only of the RGB values of a plurality of HDR video signals from among a plurality of sets of data in which the RGB values of the SDR video signal and the RGB values of the HDR video signal correspond to each other, and store this in the storage unit 25. That is, the table generation unit 24 generates a 3D look-up table T composed only of the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals.

[0129] 〔Example 3〕 Next, Example 3 will be described. As described above, Example 3 converts an SDR video signal into an HDR video signal using the 3D look-up table T generated by another example of Example 1 or another example of Example 2.

[0130] FIG. 11 is a block diagram showing a configuration example of the video signal conversion device according to the third embodiment. This video signal conversion device 3 includes a conversion unit 31 and a storage unit 32. It is assumed that the storage unit 32 stores the 3D look-up table T generated by the video signal conversion device 1' shown in FIG. 8 or the video signal conversion device 2' shown in FIG. 10. That is, the storage unit 32 stores the same 3D look-up table T as the 3D look-up table T stored in the storage unit 16 shown in FIG. 8 or the storage unit 25 shown in FIG. 10.

[0131] The conversion unit 31 inputs an SDR video signal, and based on the RGB values of the SDR video signal, reads out the RGB values of a predetermined number of HDR video signals from the 3D look-up table T stored in the storage unit 32.

[0132] The conversion unit 31 obtains the RGB values of the HDR video signal corresponding to the RGB values of the SDR video signal by interpolating the RGB values of a predetermined number of HDR video signals, and outputs the HDR video signal.

[0133] FIG. 12 is a flowchart showing a processing example of the video signal conversion device 3 according to the third embodiment shown in FIG. 11.

[0134] The conversion unit 31 inputs an SDR video signal (step S1201), specifies the RGB values of a predetermined number of SDR video signals based on the RGB values of the input SDR video signal, and reads out the RGB values of a predetermined number of HDR video signals corresponding to the RGB values of the predetermined number of SDR video signals from the 3D look-up table T stored in the storage unit 32 (step S1202).

[0135] For example, the conversion unit 31 specifies the lattice point data of the eight nearest points around the RGB values of the input SDR video signal as a base point in the three-dimensional space of the RGB axis, and reads out the RGB values of the eight points of the HDR video signal corresponding to the RGB values of the eight points of the SDR video signal, which are the lattice point data of the eight points, from the numerical data described in the 3D look-up table T shown in FIG. 9.

[0136] The conversion unit 31 obtains the RGB values of the HDR video signal corresponding to the input SDR video signal by interpolating the RGB values of a predetermined number of HDR video signals using the RGB values of the input SDR video signal, the RGB values of a predetermined number of SDR video signals, and the RGB values of a predetermined number of HDR video signals corresponding to the RGB values of the predetermined number of SDR video signals (step S1203). Then, the conversion unit 31 outputs the HDR video signal (step S1204).

[0137] In the above example, since the RGB values of the input SDR video signal are located inside the 8-point lattice point data, the conversion unit 31 uses this 8-point lattice point data to calculate the RGB values of the converted HDR video signal by interpolation processing using the 8-point RGB values of the HDR video signal.

[0138] FIG. 13 is a diagram for explaining an interpolation processing example (step S1203) of the conversion unit 31. In the 3D look-up table T shown in FIG. 9, when the entire region of the SDR video signal is discretized at a predetermined interval to form a lattice point data group, let each of the RGB values of a plurality of SDR video signals be x, and the RGB values of the HDR video signal corresponding to the RGB values of the SDR video signal be y. Also, assume that there is a relationship of y = g(x) between x and y. g is a function that converts the RGB value x of the SDR video signal into the RGB value y of the HDR video signal.

[0139] A case of converting the SDR video signal at the position of point P into an HDR video signal in the three-dimensional space of the RGB axes shown in FIG. 13 will be described. Assume that, among all the samples of the RGB values of the SDR video signal stored in the 3D look-up table T by the conversion unit 31, n = 8 samples of lattice point data are specified in ascending order of the distance from the RGB value x of the input SDR video signal.

[0140] The RGB values of the SDR video signal in the 8 specified samples are x 1 , x 2 , ···, x 8 and the RGB values of the HDR video signal corresponding to these are y 1 = g(x1 ), y 2 = g(x 2 ), ···, y 8 = g(x 8 ) is.

[0141] And, by the conversion unit 31, the RGB value y of the HDR video signal 1 = g(x 1 ), y 2 = g(x 2 ), ···, y 8 = g(x 8 ) is interpolated, and the RGB value y = g(x) of the HDR video signal corresponding to the RGB value x of the input SDR video signal is obtained.

[0142] As described above, according to the video signal conversion device 3 of the third embodiment, the conversion unit 31 reads a predetermined number of RGB values of the HDR video signal from the 3D look-up table T based on the RGB values of the SDR video signal, and interpolates the predetermined number of RGB values of the HDR video signal, thereby obtaining the RGB value of the HDR video signal corresponding to the SDR video signal and outputting the HDR video signal.

[0143] The 3D look-up table T is a table including the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals obtained by other examples of the first embodiment or other examples of the second embodiment.

[0144] In the 3D look-up table T, for the highlight region, the RGB values of the HDR video signal obtained so that the greatly extended luminance is compressed to the logarithmically increasing luminance are stored. Therefore, similar to the first and second embodiments, when converting the SDR video signal into the HDR video signal, the problem that the continuity of the video signal level in the highlight region is lost and the gradation becomes discontinuous can be solved.

[0145] Also, assume a case where an HDR program is produced by converting the original SDR video signal into an HDR video signal, and an SDR program is produced by converting the HDR video signal of the HDR program into an SDR video signal using a tone mapping function.

[0146] In this case, when producing an HDR program, comparing the process of converting an SDR video signal into an HDR video signal by direct mapping with the process of converting an SDR video signal into an HDR video signal using the 3D look-up table T in the third embodiment, the latter can make the SDR video signal obtained by converting the HDR video signal closer to the original SDR video signal.

[0147] As mentioned above, the present invention has been described by way of Examples 1-3, other examples of Example 1, and other examples of Example 2. However, the present invention is not limited to the above-described Example 1 and the like, and various modifications can be made without departing from the technical idea thereof.

[0148] For example, HDR video signals include not only video signals in the HLG format but also video signals in the PQ (Perceptual Quantization) format.

[0149] Also, in the video signal conversion device 1 of Example 1 shown in FIG. 1, the highlight area compression unit 13 inputs the HDR start luminance Y ip and the HDR maximum luminance Y max , and compresses the luminance Y of the greatly extended HDR linear signal for the highlight area between the HDR start luminance Y ip and the HDR maximum luminance Y max HDR into a logarithmically increasing luminance Y HDR,comp .

[0150] On the other hand, the highlight area compression unit 13 may be configured to input the HDR start luminance Y ip and the HDR intermediate luminance Y cor . The HDR intermediate luminance Y cor is the intermediate luminance in the highlight area between the HDR start luminance Y ip and the maximum luminance (HDR maximum luminance Y max ip ), and Y ip <Y cor ≦Y max .

[0151] In this case, the highlight area compression unit 13 compresses the luminance Y of the greatly expanded HDR linear signal for the highlight area between the HDR start luminance Y ip and the HDR intermediate luminance Y cor to the maximum luminance, and for the area between the HDR start luminance Y ip and the HDR intermediate luminance Y cor , it compresses the luminance Y of the greatly expanded HDR linear signal to the logarithmically increasing luminance Y HDR in the first form. Also, for the area between the HDR intermediate luminance Y HDR,comp and the maximum luminance, the highlight area compression unit 13 compresses the luminance Y of the greatly expanded HDR linear signal to the logarithmically increasing luminance Y cor in the second form. HDR HDR,comp HDR

[0152] FIG. 14 is a diagram for explaining the case where the user designates the HDR start luminance Y HDR , Y HDR,comp = 60 cd / m ip and the HDR intermediate luminance Y 2 = 203 cd / m cor when compressing the highlight area and the relationship between the luminance Y 2 of the HDR linear signal before and after that.

[0153] The horizontal axis indicates the HDR display luminance [cd / m HDR which is the luminance Y of the HDR linear signal before compressing the highlight area, and the vertical axis indicates the HDR display luminance [cd / m 2 which is the luminance Y of the HDR linear signal after compressing the highlight area. HDR,comp 2 ip

[0154] For the area between the HDR start luminance Y ip and the HDR intermediate luminance Y cor , since the exponentially increasing part is compressed to increase logarithmically, as a result, it has a linearly increasing form. Also, for the area between the HDR intermediate luminance Y cor and the maximum luminance, it has a logarithmically increasing form.​​

[0155]

[0156]

[0157]

[0158]

[0159]

[0160]

Industrial Applicability

[0161] The video signal conversion device 1 and the like according to Embodiment 1 of the present invention are expected to be used in a wide range of fields such as imaging devices, video signal conversion devices, video monitoring devices, and editing devices.

Explanation of Reference Numerals

[0162] 1, 1’, 2, 2’, 3 Video signal conversion device 11, 21 Electrical / optical conversion unit 12 Expansion unit 13 Highlight area compression unit 14, 23 Optical / electrical conversion unit 15, 24 Table generation unit 16, 25, 32 Storage unit 22 Expansion and compression unit 31 Conversion unit T 3D look-up table Y SDR SDR linear signal Y HDR , Y HDR,comp HDR linear signal Y ip HDR start luminance Y max HDR maximum luminance Y SDR,ip SDR knee point luminance Y HDR,ip HDR knee point luminance Y comp,ip SDR start luminance Y cor HDR intermediate luminance a, f Inflection point b 100% SDR point c 109% SDR point d, g Start point e End point c 1 , c 2 , c 3 Coefficient

Claims

1. In a video signal conversion device that converts an SDR video signal into an HDR video signal, an electro-optical conversion unit that converts the SDR video signal into an SDR linear signal using a predetermined electro-optical transfer function; The luminance Y of the SDR linear signal converted by the electric / optical conversion unit SDR is expanded, and an expansion unit that obtains an HDR linear signal having the expanded luminance Y HDR is provided, The luminance Y of the HDR linear signal obtained by the stretching unit HDR Among them, compress the luminance of a predetermined highlight area, and the luminance Y after compression HDR,comp A highlight area compression unit that obtains an HDR linear signal having an opto-electrical conversion unit that converts the HDR linear signal obtained by the highlight region compression unit into the HDR video signal using a predetermined opto-electrical transfer function; A video signal conversion device characterized by comprising:

2. In a video signal conversion device that converts an SDR video signal into an HDR video signal, an electro-optical conversion unit that converts the SDR video signal into an SDR linear signal using a predetermined electro-optical transfer function; The luminance Y of the SDR linear signal converted by the electric / optical conversion unit SDR While stretching the luminance Y, for the highlight region, compress the stretched luminance to a logarithmically increasing luminance, SDR Convert the luminance Y HDR To luminance Y HDR An expansion / compression unit that obtains an HDR linear signal having the luminance Y an opto-electrical conversion unit that converts the HDR linear signal obtained by the stretching and compression unit into the HDR video signal using a predetermined opto-electrical transfer function; A video signal conversion device characterized by comprising:

3. In a video signal conversion device that converts an SDR video signal into an HDR video signal using a 3D look-up table, a storage unit that stores the 3D look-up table including the RGB values of a plurality of HDR video signals; a conversion unit that inputs the SDR video signal, reads out the RGB values of a predetermined number of HDR video signals from the 3D look-up table stored in the storage unit based on the RGB values of the input SDR video signal, and interpolates the RGB values of the predetermined number of HDR video signals to obtain the HDR video signal corresponding to the input SDR video signal, In the 3D look-up table, The SDR video signal is converted into an SDR linear signal according to a predetermined electrical / optical transfer function, and the luminance Y of the SDR linear signal SDR is expanded, so that an HDR linear signal having an expanded luminance Y HDR is obtained. The luminance of a predetermined highlight region among the luminance Y HDR of the HDR linear signal is compressed, so that an HDR linear signal having a compressed luminance Y HDR,comp is obtained. The RGB values of the HDR video signal obtained by converting the HDR linear signal having the luminance Y HDR,comp into an HDR video signal according to a predetermined optical / electrical transfer function the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals when the entire region of the SDR video signal is discretized at a predetermined interval are included. A video signal conversion device characterized by this.

4. In a video signal conversion table generation method for generating a 3D look-up table for converting an SDR video signal into an HDR video signal, a first step of inputting an SDR video signal and converting it into an SDR linear signal using a predetermined electro-optical transfer function; The luminance Y of the SDR linear signal converted by the first step SDR is expanded, and a second step of obtaining an HDR linear signal having the expanded luminance Y HDR is performed. The luminance Y of the HDR linear signal obtained by the second step HDR is compressed for the luminance of a predetermined highlight area among them, and a third step of obtaining an HDR linear signal having the compressed luminance Y HDR,comp is performed. The luminance Y obtained in the third step HDR,comp A fourth step of converting the HDR linear signal having the luminance Y into an HDR video signal by a predetermined optical / electrical transfer function; the RGB values of the HDR video signal converted by the fourth step corresponding to the RGB values of the SDR video signal input in the first step, a fifth step of generating the 3D look-up table including the RGB values of a plurality of HDR video signals corresponding to the RGB values of a plurality of SDR video signals when the entire region of the SDR video signal is discretized at a predetermined interval. A method for generating a video signal conversion table, characterized by having **Claim 5** In data having the structure of a 3D look-up table used by a video signal conversion device that converts an SDR video signal into an HDR video signal, The SDR video signal is converted into an SDR linear signal by a predetermined electrical / optical transfer function, and the luminance Y of the SDR linear signal SDR is expanded, so that an HDR linear signal having the expanded luminance Y HDR is obtained. The luminance of a predetermined highlight region among the luminance Y HDR of the HDR linear signal is compressed, so that an HDR linear signal having the compressed luminance Y HDR,comp is obtained. The RGB values of the HDR video signal obtained by converting the HDR linear signal having the luminance Y HDR,comp into an HDR video signal by a predetermined optical / electrical transfer function including RGB values of a plurality of HDR video signals corresponding to RGB values of a plurality of SDR video signals when the entire area of the SDR video signal is discretized at a predetermined interval, the video signal conversion device inputs an SDR video signal to be converted, and based on the RGB values of the input SDR video signal, reads RGB values of a predetermined number of HDR video signals from the 3D look-up table stored in the storage unit, and interpolates the RGB values of the predetermined number of HDR video signals, and is used for a process of obtaining an HDR video signal corresponding to the input SDR video signal. Data having the structure of a 3D look-up table, characterized by the above. **Claim 6** A program for causing a computer to function as the video signal conversion device according to any one of claims 1 to 3.

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