JP2007235301A - Image data and evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide image data and a method for evaluating a device handling a moving video of extensive color gamut. <P>SOLUTION: A chrominance exceeding the range of a chrominance represented by a brightness signal and a color difference signal specified by ITU-R BT. 601 or BT. 709 is expressed. Image data consisting of a brightness signal and a color difference signal conforming to xvYCC regulation specified in IEC 61966-2-4 is recorded as chart data for evaluation in a recording medium 111. Evaluation chart data recorded in the recording medium 111 is processed and an evaluation object 121 is evaluated based on the results of processing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to image data and an evaluation method, and more particularly, to image data and an evaluation method that enable evaluation of, for example, a device that handles a moving image with a wide color gamut.

  For transmission of moving image data, for example, RGB (Red, Green, Blue) signals of three primary colors as image data are component signals (hereinafter referred to as YCC signals as appropriate) composed of luminance signals and color difference (chroma) signals. ) Is done.

  Conversion from RGB signal to YCC signal is ITU-R (International Telecommunication Union Radiocommunication sector) BT (Broadcasting service (Television)). 709 / SMPTE (Society of) Motion Picture & Television Engineers) 274M (hereinafter referred to as BT.709) is used to formulate SDTV (Standard Definition TV) videos such as NTSC (National Television System Committee). -R BT.601 (hereinafter referred to as BT.601).

  FIG. 1 shows an example of the configuration of an AV (Audio Visual) system that converts RGB signals into YCC signals and transmits moving image data as described above.

  In FIG. 1, the AV system includes a video camera 1 and a television receiver 2. In the AV system of FIG. 1, the video camera 1 captures a moving image, and image data of the moving image is transmitted to the television receiver 2 via the recording medium 11 or the network 12. The television receiver 2 displays an image (moving image) corresponding to the image data from the video camera 1.

  Note that the video camera 1 and the television receiver 2 perform processing compliant with, for example, the BT.709 standard of BT.601 and BT.709.

  FIG. 2 is a block diagram illustrating a configuration example of the video camera 1 of FIG.

  In FIG. 2, the video camera 1 includes an operation unit 21, a photographing unit 22, an A / D conversion unit 23, a primary color conversion unit 24, a color signal correction unit 25, a photoelectric conversion unit 26, a color signal conversion unit 27, an encoder 28, and a control. The unit 29, the recording unit 30, and the communication unit 31 are included.

  The operation unit 21 is operated when the user inputs various commands to the video camera 1 and supplies a signal indicating execution of processing instructed by the operation by the user to a necessary block. For example, the operation unit 21 supplies a signal related to image capturing to the image capturing unit 22. In addition, the operation unit 21 supplies the control unit 29 with a signal related to the output destination of the moving image data obtained by shooting by the shooting unit 22.

  The imaging unit 22 starts or stops the imaging process according to an instruction from the operation unit 21. The photographing unit 22 supplies image data obtained by photographing to an A / D (Analog / Digital) conversion unit 23. Here, the photographing unit 22 is composed of, for example, a CMOS (Complementary Metal Oxide Semiconductor) imager, a CCD (Charge Coupled Device), and the like, and R, G, B (Red, Green, Blue) color signals as image data. Output RGB signal consisting of.

The A / D conversion unit 23 A / D converts the color signal supplied from the photographing unit 22 and supplies it to the primary color conversion unit 24. Here, the color signals R, G, and B supplied from the A / D converter 23 to the primary color converter 24 are represented as R _org , G _org , and B _org , respectively.

The primary color conversion unit 24 converts the color signals R _org , G _org , and B _org supplied from the A / D conversion unit 23 into color signals R ₇₀₉ , G ₇₀₉ , and B ₇₀₉ based on the primary colors of BT.709, This is supplied to the color signal correction unit 25. That is, the primary color conversion unit 24 calculates the color signal R _org , G _org , B _org from the A / D conversion unit 23 by, for example, calculating Equation (1), and the color signal R based on the primary color of BT.709. Convert to ₇₀₉ , G ₇₀₉ , B ₇₀₉ .

  Note that the matrix of equation (1) varies depending on the primary color points of the photographing unit 22.

Color signal correction portion 25, the color signals supplied from the primary conversion unit _{24 R 709, G 709, B} 709 , and the color signals R ₇₀₉ value range of 0 to 1.0 defined by BT.709, G _709, Correct to B ₇₀₉ . That is, the color signal correcting part 25, for example, less than 0 color signals _{R 709, G 709, B 709} , corrected to 0 (clipping), greater than 1.0 color signals _{R 709, G 709, B 709} , The corrected color signals R ₇₀₉ , G ₇₀₉ , and B ₇₀₉ are supplied to the photoelectric conversion unit 26 after being corrected to 1.0. Here, it is assumed that 0 and 1.0 in the numerical range of 0 to 1.0 are the minimum value and the maximum value of the color signals R ₇₀₉ , G ₇₀₉ , and B ₇₀₉ compliant with BT.709, respectively.

The photoelectric conversion unit 26 converts the color signals R ₇₀₉ , G ₇₀₉ , and B ₇₀₉ supplied from the color signal correction unit 25 into γ (image signal for the image signal) according to the photoelectric conversion characteristics based on BT.709. The color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ corrected by the nonlinearity of light emission luminance) are converted and supplied to the color signal conversion unit 27.

That is, the photoelectric conversion unit 26 converts the color signals R ₇₀₉ , G ₇₀₉ , and B ₇₀₉ from the color signal correction unit 25 into color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ according to the equation (2), This is supplied to the color signal converter 27.

Here, the photoelectric conversion characteristics between the color signal R ₇₀₉ and the color signal R ′ ₇₀₉ are defined in the range from the minimum value to the maximum value of the color signal R ₇₀₉ compliant with BT.709, that is, from 0 to 1.0. ing. The same applies to the photoelectric conversion characteristics between the color signal G ₇₀₉ and the color signal G ′ ₇₀₉ and the photoelectric conversion characteristics between the color signal B ₇₀₉ and the color signal B ′ ₇₀₉ . Expression (2) is an expression for converting the color signal R ₇₀₉ into the color signal R ′ ₇₀₉ , but the other color signals G ₇₀₉ and B ₇₀₉ are similarly _processed. Converted to ₇₀₉ .

The color signal conversion unit 27 converts the color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ supplied from the photoelectric conversion unit 26 into a luminance signal Y ′ ₇₀₉ and a color difference signal in accordance with BT.709 according to Equation (3). cb _'709, Cr' is converted into YCC signals consisting of _709, further, the luminance signal Y _'709 and color difference signals Cb' _709, Cr _'709 expressed in 8 bits, supplied to the encoder 28.

  In addition, the matrix of Formula (3) is a matrix prescribed | regulated about the 1125/60/2: 1 signal format (Signal Format) in BT.709.

Here, according to BT.709, the luminance signal Y ′ ₇₀₉ obtained by calculating Expression (3) in the color signal conversion unit 27 is a value in a numerical range of 0 to 1.0. Further, the color difference signal Cb ′ ₇₀₉ and the color difference signal Cr ′ ₇₀₉ obtained by calculating the expression (3) in the color signal conversion unit 27 are values in a numerical range of −0.5 to 0.5, respectively.

Further, the color signal converter 27 calculates the luminance signal Y ′ ₇₀₉ in the numerical range of 0 to 1.0 obtained by calculating Expression (3) to 16 to 16 that is narrower than the integer range of 0 to 255 that can be expressed by 8 bits. An integer value in the range of 235 is assigned, and the luminance signal Y ′ ₇₀₉ that is the integer value is supplied to the encoder 28 as a luminance signal conforming to BT.709. Further, the color signal conversion unit 27 can represent the color difference signal Cb ′ ₇₀₉ and the color difference signal Cr ′ ₇₀₉ in the numerical range of −0.5 to 0.5 obtained by calculating Expression (3), each of which can be expressed by 8 bits. Is assigned to an integer value in the integer range of 16 to 240 that is narrower than the integer range of to 255, and the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ that are the integer values are supplied to the encoder 28 as color difference signals compliant with BT.709. To do.

The encoder 28 encodes the 8-bit luminance signal Y ′ ₇₀₉ and the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ supplied from the color signal converter 27 according to a predetermined format such as MPEG (Moving Picture Experts Group). Then, the encoded data obtained as a result is supplied to the control unit 29.

  The control unit 29 supplies the encoded data supplied from the encoder 28 to the recording unit 30 or the communication unit 31 in accordance with an instruction from the operation unit 21.

  The recording unit 30 records the encoded data supplied from the control unit 29 on the recording medium 11 in FIG. The communication unit 31 transmits the encoded data supplied from the control unit 29 via the network 12 in FIG.

  FIG. 3 is a block diagram showing a configuration example of the television receiver 2 of FIG.

  In FIG. 3, the television receiver 2 includes an image signal input unit 41, a luminance / color difference signal conversion unit 42, a specific γ characteristic correction unit 43, a D / A conversion unit 44, and a display mechanism 45.

The image signal input unit 41 receives encoded data reproduced from the recording medium 11 or transmitted from the network 12. Further, the image signal input unit 41 decodes the encoded data in accordance with a predetermined format such as MPEG, for example, and an 8-bit luminance signal Y ′ ₇₀₉ and color difference signal Cb compliant with BT.709 obtained by the decoding. _'709, Cr' the YCC signal consisting of _709, and supplies the luminance and color difference signal converter 42.

The luminance / color-difference signal converter 42 converts the luminance signal Y ′ ₇₀₉ and the color-difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ supplied from the image signal input unit 41 into color signals R compliant with BT.709 in accordance with Equation (4). It is converted into an RGB signal composed of ' ₇₀₉ , G' ₇₀₉ and B ' ₇₀₉ and supplied to the inherent γ characteristic correcting unit 43.

Here, the luminance signal Y ′ ₇₀₉ compliant with BT.709 supplied from the image signal input unit 41 to the luminance / color difference signal conversion unit 42 is an integer of 16 to 235 that can be expressed by 8 bits as described above. An integer value in the range. Further, the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ compliant with BT.709 supplied from the image signal input unit 41 to the luminance / color difference signal conversion unit 42 can be expressed by 8 bits as described above. An integer value in the range of 16 to 240.

The luminance / color difference signal conversion unit 42 sets the luminance signal Y ′ ₇₀₉ having an integer value in the range of 16 to 235 supplied to the luminance / color difference signal conversion unit 42 to a value expressed in a numerical range of 0 to 1.0. In addition, each of the color difference signals Cb ′ ₇₀₉ and Cr ′ _{709 having} an integer value in the integer range of 16 to 240 is represented by a numerical range of −0.5 to 0.5, and is represented by the numerical range of 0 to 1.0. The luminance signal Y ′ ₇₀₉ and the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ expressed in a numerical range of −0.5 to 0.5 are converted into color signals R ′ ₇₀₉ and G ′ _{709 in} the range of 0 to 1.0 according to the equation (4). , B ' ₇₀₉ .

When the γ characteristic of the television receiver 2 is different from the photoelectric conversion characteristic (γ characteristic) represented by the equation (2) of BT.709, the inherent γ characteristic correcting unit 43 is connected to the luminance / color difference signal converting unit 42. _'709 according to the inherent γ characteristics of the display mechanism television receiver 2 (CRT (Cathode Ray Tube), etc.), the color signals R' supplied color signals R _'709, G' _709, B _709, G ' ₇₀₉ , B' ₇₀₉ is converted and supplied to a D / A (Digital / Analog) converter 44.

  If the γ characteristic of the display mechanism 45 of the television receiver 2 is the same as the photoelectric conversion characteristic of BT.709, the intrinsic γ characteristic correcting unit 43 is not necessary.

The D / A conversion unit 44 performs D / A conversion on the color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ supplied from the inherent γ characteristic correction unit 43 and supplies them to the display mechanism 45.

The display mechanism 45 is composed of, for example, a CRT and displays an image (moving image) based on the color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ supplied from the D / A conversion unit 44.

  Here, FIG. 4 shows positions on the chromaticity coordinates in the CIE (Commission Internationale de I'Eclariage) color system of the primary color and the reference white color in BT.709.

  In addition, Non-Patent Document 1 defines the color signal, luminance signal, and color difference signal compliant with BT.709 processed in the video camera 1 and the television receiver 2 described above.

In the video camera 1 of FIG. 2, as described above, the color signal conversion unit 27 converts the RGB signal composed of the color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ supplied from the photoelectric conversion unit 26 into an equation. According to (3), conversion is made into a YCC signal composed of a luminance signal Y ′ ₇₀₉ and color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ compliant with BT.709. In the television receiver 2 of FIG. 3, the luminance / color difference signal converting unit 42 receives the YCC signal composed of the luminance signal Y ′ ₇₀₉ and the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ supplied from the image signal input unit 41. According to the equation (4), the color signal is converted into an RGB signal composed of color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ compliant with BT.709.

When the color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ used in the calculation of Expression (3) are values in the numerical range of 0.0 to 1.0, such color signals R ′ ₇₀₉ and G ′ ₇₀₉ , B ′ ₇₀₉ are converted by calculating equation (3), the luminance signal Y ′ ₇₀₉ with a value in the range of 0 to 1.0 and the color difference signal Cb ′ _{709 with} a value in the range of −0.5 to 0.5 Cr ' ₇₀₉ can be obtained.

On the other hand, the luminance signal Y ′ ₇₀₉ having a value in the range of 0 to 1.0 and the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ having a value in the range of −0.5 to 0.5 are converted by calculating Equation (4). In this case, the color signals R ′ ₇₀₉ , G ′ ₇₀₉ , and B ′ ₇₀₉ obtained in this case may have values less than 0.0 or values exceeding 1.0.

  This is because the RGB signal and the YCC signal to be converted according to the equations (3) and (4) can express colors with a finer gradation than the YCC signal. This is because the YCC signal has a wider range of colors that can be expressed than the RGB signal.

Therefore, in BT.709, when a three-dimensional space with the luminance signal Y ′ ₇₀₉ and the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ as axes is considered, the luminance signal Y ′ ₇₀₉ has a numerical range of 0.0 to 1.0. The color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ are not used in a space (cubic space) in a numerical range of −0.5 to 0.5, that is, by conversion according to the expression (3). There is a point (Y ' ₇₀₉ , Cb' ₇₀₉ , Cr ' ₇₀₉ ) corresponding to a YCC signal that cannot be obtained, and a luminance signal Y' ₇₀₉ that can take a value in the numerical range of 0 to 1.0, and -0.5 to 0.5 It could not be said that the color difference signals Cb ′ ₇₀₉ and Cr ′ ₇₀₉ that can take values in the numerical range are effectively used.

  Therefore, the present applicant is able to express image data that can express colors with a wider color gamut than existing standards such as BT.709 and can be handled by devices that conform to existing standards. (For example, refer to Patent Document 1).

  In addition, the xvYCC standard for image data expressing colors in such a wide color gamut was approved as IEC61966-2-4 in December 2005 by the International Electrotechnical Commission (IEC) (see, for example, Non-Patent Document 2).

Japanese Unexamined Patent Publication No. 2006-033575 RECOMMENDATION ITU-R BT. 709-4 "Multimedia systems and equipment-Color measurement and management-Part 2-4: Color management-Extended-gamut YCC color space for video applications-xvYCC", 2006-01-17

  By the way, as a display mechanism 45 of the television receiver 2 (FIG. 3), a CRT has been mainstream, but in recent years, a plasma display or an LCD (Liquid Crystal Display) panel having a wider color reproduction range than the CRT has become mainstream. It has become.

  Furthermore, as described above, with the approval of the xvYCC standard, the momentum for widening the color gamut of images is increasing.

  For this reason, it is necessary to evaluate the performance of television receivers with a wide color reproduction range, such as plasma displays and LCD panels, as well as devices that handle video data of wide color gamut that conforms to the xvYCC standard. Has produced.

  The present invention has been made in view of such a situation, and makes it possible to evaluate a device or the like that handles a moving image with a wide color gamut.

  A first aspect of the present invention is moving image data used for evaluation of an evaluation object that handles moving images, and is expressed by a luminance signal and a color difference signal defined by ITU-R BT.601 or BT.709. This is image data composed of a luminance signal and a color difference signal compliant with the xvYCC standard defined in IEC 61966-2-4, which expresses chromaticity exceeding the range of chromaticity.

  The image data of the first aspect expresses chromaticity exceeding the range of chromaticity expressed by the luminance signal and the color difference signal defined by ITU-R BT.601 or BT.709. Used for evaluation of evaluation objects that handle image data consisting of luminance signals and color difference signals compliant with the xvYCC standard defined in 2-4.

  The image data can be recorded on a recording medium.

  A second aspect of the present invention is an evaluation method for evaluating an evaluation object that handles a moving image, and a chromaticity range expressed by a luminance signal and a color difference signal defined by ITU-R BT.601 or BT.709. Image data for evaluation consisting of a luminance signal and a color difference signal compliant with the xvYCC standard defined in IEC 61966-2-4, which expresses chromaticity exceeding JIS 61966-2-4, is processed by the evaluation object, and the evaluation object The evaluation method includes a step of evaluating the evaluation object based on the result of processing the image data for evaluation.

  In the evaluation method of the second aspect, the IEC 61966 expresses chromaticity exceeding the chromaticity range expressed by the luminance signal and the color difference signal defined by ITU-R BT.601 or BT.709. -2-4 Evaluation image data composed of luminance signals and color difference signals compliant with the xvYCC standard defined in 4-2-4 is processed by the evaluation object, and the evaluation object is a result of processing the evaluation image data Based on the above, the evaluation object is evaluated.

  According to the first and second aspects of the present invention, it is possible to evaluate a device or the like that handles a wide color gamut moving image.

  Embodiments of the present invention will be described below. Correspondences between the constituent elements of the present invention and the embodiments described in the specification or the drawings are exemplified as follows. This description is intended to confirm that the embodiments supporting the present invention are described in the specification or the drawings. Therefore, even if there is an embodiment which is described in the specification or the drawings but is not described here as an embodiment corresponding to the constituent elements of the present invention, that is not the case. It does not mean that the form does not correspond to the constituent requirements. Conversely, even if an embodiment is described here as corresponding to a configuration requirement, that means that the embodiment does not correspond to a configuration requirement other than the configuration requirement. It's not something to do.

The evaluation method of the second aspect of the present invention is:
In an evaluation method for evaluating an evaluation object that handles a video,
XvYCC standard specified in IEC 61966-2-4 that expresses chromaticity beyond the range of chromaticity expressed by the luminance signal and color difference signal specified by ITU-R BT.601 or BT.709 Image data for evaluation consisting of a luminance signal and a color difference signal conforming to the above are processed by the evaluation object (for example, step S11 in FIG. 17),
The evaluation object is evaluated based on the result of processing the image data for evaluation with the evaluation object (for example, step S12 in FIG. 17).
Includes steps.

  Hereinafter, an embodiment of the present invention will be described, but before that, a color space employed in the present embodiment will be described.

  FIG. 5 shows the relationship between the signal level of a standard signal that is an international standard and an integer value representing the signal level.

  First, in the sRGB standard, which is a color space standard defined by the IEC, 8 bits are used to represent each of R, G, and B color signals, and can be represented by 0 to 255. Since the signal level of 0 to 1.0 color signals R, G, and B is assigned to the value of 0, the color signals R, G, and B of 0 to 1.0 are expressed by 256 (= 255−0 + 1) gradations, respectively. Is done.

  Next, in the sYCC standard, which is a standard for the luminance signal and color difference signal of a still image, the luminance signal Y uses 8 bits to represent the luminance signal Y, as in the sRGB standard, thereby Since the signal level of the luminance signal Y of 0 to 1.0 is assigned to the value of 0 to 255 that can be expressed, the luminance signal Y of 0 to 1.0 is expressed by 256 (= 255−0 + 1) gradations. The

  For the color difference signals Cb and Cr, 8 bits are used to represent each signal, and the signal levels of the color difference signals Cb and Cr of -0.5 to 0.5 are added to the values of 0 to 255 that can be represented thereby. Therefore, the color difference signals Cb and Cr of −0.5 to 0.5 are expressed by 256 (= 255−0 + 1) gradations, respectively.

  Next, color signals, luminance signals, and color difference signals in BT.601, which is an SDTV standard, and BT.709, which is an HDTV standard, will be described.

  In BT.709, 8 bits are used to represent each color signal of R, G, and B, and an integer value in an integer range of 16 to 235 that is narrower than 0 to 255 that can be represented by Since the signal levels of 0 to 1.0 color signals R, G, and B are assigned, the 0 to 1.0 color signals R, G, and B are represented by 220 (= 235−16 + 1) gradations, respectively.

  In BT.709, 8 bits are used to represent the luminance signal Y, and the luminance signal of 0 to 1.0 is represented by an integer value in the range of 16 to 235 that is narrower than 0 to 255, which can be represented thereby. Since the Y signal level is assigned, the luminance signal Y of 0 to 1.0 is expressed by 220 (= 235−16 + 1) gradations.

  Further, in BT.709, 8 bits are used to represent each of the color difference signals Cb and Cr, and an integer value in an integer range of 16 to 240 narrower than 0 to 255 that can be represented thereby is represented by −0.5 to Since the signal levels of 0.5 color difference signals Cb and Cr are assigned, the color difference signals Cb and Cr of −0.5 to 0.5 are expressed by 225 (= 240−16 + 1) gradations, respectively.

  The BT.601 color signal, the luminance signal, and the color difference signal are also defined in the same manner as BT.709. In BT.709 and BT.601, 0 and 255 out of 0 to 255 represented by 8 bits representing a signal are not used.

  Next, the xvYCC standard will be described.

  The xvYCC standard is a predetermined standard for expressing a signal of each signal level by assigning it to an integer value in an integer range narrower than an integer range that can be expressed by a plurality of predetermined bits, for example, a color difference signal Cb in a range of -0.5 to 0.5. , BT.709 and BT601 standards that express Cr by assigning it to an integer of 16 to 240 narrower than 0 to 255 that can be represented by 8 bits.

  Specifically, in the xvYCC standard, the luminance signal Y is defined to be the same as, for example, BT.709. That is, in the xvYCC standard, for example, 8 bits are used to represent the luminance signal Y, and an integer value in the integer range of 16 to 235 that is narrower than 0 to 255 that can be represented thereby is represented by a luminance of 0 to 1.0. The signal level of signal Y is assigned. Therefore, in the xvYCC standard, as in BT.709, the luminance signal in the signal level range of 0 to 1.0 is expressed with 220 (= 235−16 + 1) gradations.

  Further, in the xvYCC standard, for example, 8 bits are used to represent each of the color difference signals Cb and Cr, and an integer value in an integer range of 16 to 240 narrower than 0 to 255, which can be represented by it, Signal levels of color difference signals Cb and Cr of -0.5 to 0.5 are assigned. This is the same as BT.709.

  However, in the xvYCC standard, the integer range to which the signal levels of the color difference signals Cb and Cr are assigned is extended to an integer range of 1 to 254 including the integer range of 16 to 240 to which the signal level is assigned in BT.709. ing. That is, in the xvYCC standard, as in BT.709, the color difference signals Cb and Cr in the signal level range of −0.5 to 0.5 are assigned to the integer range of 16 to 240 225 (= 240−16 + 1) gradations, respectively. The signal levels are also assigned to the integer range of 1 to 15 and the integer range of 241 to 254 in the same manner as the assignment of the signal level to the integer range of 16 to 240.

  As a result, in the xvYCC standard, a signal level of −0.57 to 0.56 is assigned to an integer range of 1 to 254. Therefore, in the xvYCC standard, the color difference signals Cb and Cr in the signal level range of −0.57 to 0.56 are expressed by dividing them into 254 (= 254−1 + 1) gradations.

  As described above, the xvYCC standard can handle the color difference signals Cb and Cr having a signal level in the range of −0.57 to 0.56 including −0.5 to 0.5 which is the signal level of the color difference signals Cb and Cr of BT.709. .

  Therefore, according to the xvYCC standard, a color having a wider color gamut than the color that can be expressed by BT.709 can be expressed.

  Further, the luminance signal Y of the xvYCC standard is the same as the luminance signal Y of BT.709, and the color difference signals Cb and Cr of the xvYCC standard are assigned to an integer range of 16 to 240, from −0.5 to 0.5. The signal level is the same as the color difference signals Cb and Cr of BT.709. Therefore, the luminance signal Y and the color difference signals Cb and Cr of the xvYCC standard can be handled as long as the device conforms to BT.709. For example, an image is displayed in a color range that can be expressed by BT.709. be able to.

  In the xvYCC standard, the color difference signals Cb and Cr can take a signal level in the range of -0.57 to 0.56 which is wider than the range of -0.5 to 0.5 that the color difference signals Cb and Cr of BT.709 can take. When the standard luminance signal Y and the color signals Cb, Cr are converted into the color signals R, G, B, the signal levels of the color signals R, G, B are all in a range wider than 0 to 1.0. Value, that is, a value less than 0 (negative value) or a value greater than 1. Here, 0 is the minimum value of the color signals R, G, and B compliant with BT.709, and 1 is the maximum value of the color signals R, G, and B compliant with BT.709. .

  The xvYCC standard can handle color signals R, G, and B that are negative or greater than 1, such color signals R, G, and B, luminance signal Y in the range of 0 to 1.0, and- Mutual conversion between color difference signals Cb and Cr in the range of 0.57 to 0.56 is performed.

  By the way, for example, when an image is taken and the color signals R, G, and B of the image are converted to the luminance signal Y and the color difference signals Cb and Cr of the xvYCC standard, the luminance signal Y and the color difference of the xvYCC standard are processed. In order to be able to handle signals Cb and Cr with a device compliant with BT.709, color signals R, G, and B converted to luminance signal Y and color difference signals Cb and Cr of BT.709 are converted into BT. It is necessary to convert (γ (gamma) correction) into color signals R, G, and B according to the photoelectric conversion characteristics of the display mechanism 709.

  On the other hand, in BT.709, photoelectric conversion characteristics are defined for the range of 0 to 1.0 that the color signals R, G, B can take, but for negative values and values exceeding 1.0, photoelectric conversion characteristics are defined. Is not defined.

  Since the color signals R, G, and B converted to the luminance signal Y and the color difference signals Cb and Cr of the xvYCC standard can take negative values and values exceeding 1.0 as described above, such negative values. In other words, there is a problem as to what photoelectric conversion characteristics the color signals R, G, and B having values exceeding 1.0 are converted.

  Therefore, in the xvYCC standard, for example, the photoelectric conversion characteristics stipulated in BT.709 are applied as it is even in a region exceeding 1.0, and when the input is negative, it is extended point-symmetrically with respect to the origin. The photoelectric conversion characteristics obtained by the above are adopted.

  That is, FIG. 6 shows the photoelectric conversion characteristics adopted in the xvYCC standard.

  The photoelectric conversion characteristics of the xvYCC standard shown in FIG. 6 are the same as the photoelectric conversion characteristics in BT.709 when the input signals (color signals R, G, B) are in the range of 0 to 1.0.

  That is, the range of the input signal from 0 to 1.0 in the photoelectric conversion characteristics of the xvYCC standard in FIG. 6 is expressed in the same manner as in the equation (2) as defined in BT.709.

  Further, in the photoelectric conversion characteristics of the xvYCC standard in FIG. 6, the range where the input signal exceeds 1.0 is an extension of the range of 0.018 to 1.0 in Equation (2). Further, in the photoelectric conversion characteristic of the xvYCC standard in FIG. 6, the range where the input signal is negative is obtained by extending the photoelectric conversion characteristic of Expression (2) symmetrically with respect to the origin.

  Therefore, the photoelectric conversion characteristic of the xvYCC standard in FIG. 6 is expressed by Expression (5).

In equation (5), the color signal R before conversion according to the photoelectric conversion characteristics is indicated as R _ex709, and the color signal R after conversion according to the photoelectric conversion characteristics is indicated as R ′ _ex709 . Similarly to the color signal R, the color signals G and B are also converted according to the equation (5).

  Next, colors that can be expressed by the xvYCC standard as described above will be described.

  FIG. 7 is a diagram illustrating the relationship between the color space covered by BT.709 and the color space of the 768 colors of the high saturation color target called Munsell Color Cascade and the color space of the sRGB standard.

  In FIG. 7 (the same applies to FIGS. 8 and 9 described later), the color signals R, G, B are converted according to the photoelectric conversion characteristics, and the converted color signals R, G, B are converted into the luminance signal Y. In addition, the luminance signal Y and the color difference signals Cb and Cr when converted into the color difference signals Cb and Cr represent a color space for the three axes. In FIG. 7, in order to indicate that the luminance signal Y and the color difference signals Cb, Cr correspond to the color signals R, G, B that have been converted according to the photoelectric conversion characteristics, the luminance signal Y and the color difference signal are shown. Cb and Cr are shown as a luminance signal Y ′ and color difference signals Cb ′ and Cr ′, respectively.

  In FIG. 7, the ● mark indicates the 768 colors of the Munsell color cascade, and the range of the parallelepiped surrounded by the lattice shape indicates the color expressed by the color signal of the BT.709 standard. Further, in FIG. 7, a range surrounded by a rectangular parallelepiped indicates a range covered by the luminance signal and color difference signal of BT.709.

  The luminance signal and color difference signal of BT.709 cover the color space of the sRGB standard, but there are parts that cannot be covered for 768 colors of the Munsell color cascade.

  FIG. 8 shows the relationship between the luminance signal of the xvYCC standard, the color space based on the color difference signal, the 768 colors of the Munsell color cascade, the color space based on the color signal of the BT.709 standard, and the color space based on the luminance signal of the BT.709 standard and the color difference signal. FIG.

  In FIG. 8, as in FIG. 7, the ● mark indicates the 768 colors of the Munsell color cascade, and the range surrounded by the parallelepiped indicates the color expressed by the color signal of the BT.709 standard. Furthermore, of the two rectangular parallelepipeds, the range enclosed by the inner rectangular parallelepiped shows the range covered by the luminance and color difference signals of BT.709, and the range enclosed by the outer rectangular parallelepiped is the xvYCC standard The range covered by the luminance signal and the color difference signal is shown.

  FIG. 9 is a projection view in the Cb ′ direction of FIG.

  In FIG. 9, as in FIG. 7, the ● mark indicates 768 colors of the Munsell color cascade, and the range of the parallelogram indicates the color represented by the color signal of the BT.709 standard. In addition, of the two rectangles, the range enclosed by the inner rectangle indicates the range covered by the luminance and color difference signals of BT.709, and the range enclosed by the outer rectangle is the xvYCC standard. The range covered by the luminance signal and the color difference signal is shown.

  As shown in FIGS. 8 and 9, the xvYCC standard completely covers the color space of the 768 colors of the Munsell color cascade and the color signal of the BT.709 standard.

  Here, the coverage for the surface area of 768 colors in the Munsell color cascade is 55% in the color space of the color signal of BT.709, whereas it is 100% in the color space of the luminance signal and color difference signal of the xvYCC standard. is there. Also, the coverage ratio for the volume of the uniform color space (L * a * b *) is 61% in the color space of the color signal of BT.709, whereas the color space of the luminance signal and color difference signal of the xvYCC standard Then it is 100%.

  As described above, according to the xvYCC standard, a wide color space can be covered and a color in a wide color gamut can be expressed.

  Next, FIG. 10 shows a configuration example of an embodiment of an AV system corresponding to the above-described xvYCC standard.

  The AV system shown in FIG. 10 includes a video camera 60 and a television receiver 70. In the AV system, an image signal captured by the video camera 60 is supplied to the television receiver 70 via the recording medium 11 or the network 12, and is captured by the video camera 60 in the television receiver 70. The displayed image is displayed.

  FIG. 11 is a block diagram illustrating a configuration example of an embodiment of the video camera 60 of FIG. In FIG. 11, the same parts as those in the video camera 1 shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The video camera 60 includes an operation unit 21, a photographing unit 61, an A / D conversion unit 23, a primary color conversion unit 62, a photoelectric conversion unit 63, a color signal conversion unit 64, a correction unit 64A, an encoder 28, a control unit 29, and a recording unit 30. The communication unit 31 is configured.

  The imaging unit 61 starts or stops the imaging process according to an instruction from the operation unit 21. Further, the photographing unit 61 supplies an image signal of the photographed image to the A / D conversion unit 23. Here, the photographing unit 61 is configured by, for example, a CMOS imager, a CCD, or the like, and outputs R, G, and B color signals as image signals. It should be noted that the primary color point of the CMOS imager or CCD that is the photographing unit 61 should be in a position of a wider color gamut than the primary color point of BT.709 in order to transmit color information of a wide color gamut.

The A / D converter 23 performs A / D conversion on the color signals R, G, and B supplied from the photographing unit 61 and supplies the signals to the primary color converter 62. Here, the color signals R, G, and B supplied from the A / D converter 23 to the primary color converter 62 are represented as R _ex , G _ex , and B _ex , respectively.

The primary color conversion unit 62 converts the color signals R _ex , G _ex , B _ex supplied from the A / D conversion unit 23 into color signals R _ex709 , G _ex709 , B _ex709 based on the primary colors of BT.709, This is supplied to the photoelectric conversion unit 63. That is, the primary color conversion unit 62 calculates the color signal R _ex , G _ex , B _ex from the A / D conversion unit 23 and calculates the color signal R based on the primary color of BT.709 by calculating Equation (6), for example. _{Convert to ex709} , _Gex709 , _Bex709 . The primary color of BT.709 is as shown in FIG.

The color signals R _ex709 , G _ex709 , and B _ex709 obtained by the primary color conversion in the primary color conversion unit 62 are obtained when the primary color point of the photographing unit 61 is different from the primary color point of BT.709 (the operation unit 61 has a wide color gamut). Color signals R, G, and B) can be negative values or values exceeding 1.

The photoelectric conversion unit 63 converts the color signals R _ex709 , G _ex709 , and B _ex709 supplied from the primary color conversion unit 62 into color signals R ′ _ex709 , G ′ _ex709 , and B ′ _ex709 according to the photoelectric conversion characteristics of the xvYCC standard. And supplied to the color signal converter 64.

That is, the photoelectric conversion unit 63 converts the color signals R _ex709 , G _ex709 , and B _ex709 from the primary color conversion unit 62 into the color signals R ′ _ex709 , G ′ _ex709 , and B ′ _ex709 according to Expression (5), and the color signal This is supplied to the conversion unit 64.

Here, Expression (5) is an expression for converting the color signal R _ex709 into the color signal R ′ _ex709 , but the color signals G _ex709 and B _ex709 are also similar to the color signal R ₇₀₉ of Expression (5), respectively. The color signals are converted into G ′ _ex709 and B ′ _ex709 .

Note that in the photoelectric conversion unit 63, 0 of the color signals R _ex709, G _ex709, B and _{ex 709,} the color signal is obtained by converting in accordance with the photoelectric conversion characteristics of the xvYCC standard _{R 'ex709, G' ex709,} B 'ex709 The range from 1.0 to 1.0 is the same as the BT.709 standard.

The color signal conversion unit 64 converts the color signals R ′ _ex709 , G ′ _ex709 and B ′ _ex709 supplied from the photoelectric conversion unit 63 into the luminance signal Y ′ _ex709 and the color difference signals Cb ′ _ex709 and Cr ′ according to Expression (7). _Convert to _ex709 . Further, the signal conversion unit 64 includes a correction unit 64A, and the correction unit 64A corrects the luminance signal _Y′ex709 to a luminance signal in a numerical value range of 0 to 1.0 defined by the xvYCC standard, and outputs a color difference signal. Cb ′ _ex709 and Cr ′ _ex709 are corrected to color difference signals in a numerical range of −0.57 to 0.56 defined by the xvYCC standard, and supplied to the encoder 28.

That is, the color signal conversion unit 64 corrects, for example, the luminance signal Y ′ _ex709 smaller than 0 to 0 and the luminance signal Y ′ _ex709 larger than 1.0 to 1.0 in the correction unit 64A. Further, it corrected to -0.57 smaller color difference signals Cb _'ex709, Cr' _ex709 to -0.57, and corrects 0.56 greater than the color difference signals Cb _'ex709, Cr' _ex709 to 0.56, the luminance signal Y after the correction _{'ex 709 Is} assigned to an integer value in the integer range of 16 to 235 that is narrower than the integer range of 0 to 255 that can be expressed by 8 bits, and the luminance signal Y ′ _ex709 that is the integer value is assigned as the luminance signal in conformity with the xvYCC standard by the encoder 28. Further, the corrected color difference signals Cb ′ _ex709 and Cr ′ _ex709 are respectively assigned to integer values in the integer range from 1 to 254 that are narrower than the integer range from 0 to 255 that can be expressed in 8 bits, The color difference signal Cb ′ _ex709 and the color difference signal Cr ′ _ex709 which are numerical values are supplied to the encoder 28 as color difference signals compliant with the xvYCC standard.

  Thereafter, the control unit 29, the recording unit 30, and the communication unit 31 perform the same processing as that of the video camera 1 of FIG.

  Next, FIG. 12 is a block diagram showing a configuration example of an embodiment of the television receiver 70 of FIG. In FIG. 12, the same parts as those in the television receiver 2 shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  In FIG. 12, a television receiver 70 includes an image signal input unit 41, a luminance / color difference signal conversion unit 71, an inverse photoelectric conversion unit 72, a primary color conversion unit 73, a color signal correction unit 74, an inherent γ characteristic correction unit 75, D The / A conversion unit 44 and the display mechanism 76 are included.

The luminance / color difference signal converting unit 71 uses the luminance signal Y ′ _ex709 and the color difference signals Cb ′ _ex709 and Cr ′ _ex709 supplied from the image signal input unit 41 in accordance with the photoelectric conversion characteristics of the xvYCC standard in accordance with Expression (8). The color signals R ′ _ex709 , G ′ _ex709 , and B ′ _ex709 are converted and _supplied to the inverse photoelectric conversion unit 72.

That is, the luminance / color-difference signal converting unit 71 sets the luminance signal _Y′ex709 having an integer value in the integer range of 16 to 235 that can be expressed in 8 bits as a value expressed in the numerical range of 0 to 1.0, and 8 Each of the integer value color difference signals Cb ′ _ex709 and Cr ′ _ex709 in the integer range of 1 to 254 that can be expressed in bits is a value expressed in the numerical range of −0.57 to 0.56, and in the numerical range of 0 to 1.0 'and _{ex 709,} the color difference signal Cb is represented by a numerical range of -0.57 to 0.56' luminance signal Y expressed 'the _{ex 709,} according to equation (8), the color signals _{R' ex709, Cr ex709, G} 'ex709, B' _Convert to _ex709 .

The inverse photoelectric conversion unit 72 converts the color signals R ′ _ex709 , G ′ _ex709 and B ′ _ex709 supplied from the luminance / color difference signal conversion unit 71 according to photoelectric conversion characteristics of the xvYCC standard. That is, inverse photoelectric conversion unit 72, the color signal _{R 'ex709, G' ex709,} B 'ex709 supplied from the luminance and color difference signal converter 71, in accordance with Equation (9), the color signals R _ex709, G _ex709, B _Ex709 is converted and supplied to the primary color conversion unit 73.

The inverse photoelectric conversion unit 72 performs the operation on the color signals R ′ _ex709 , G ′ _ex709 , and B ′ _ex709 supplied from the luminance / color difference signal conversion unit 71 by the photoelectric conversion unit 63 of the video camera 60 (FIG. 11). By performing the reverse process, the color signals R ′ _ex709 , G ′ _ex709 and B ′ _ex709 supplied from the luminance / color difference signal conversion unit 71 are converted by the photoelectric conversion unit 63 of the video camera 60. _{Return to the} previous color signals R _ex709 , G _ex709 , and B _ex709 .

Equation (9) is an equation for converting the color signal R ′ _ex709 into the color signal R _ex709 , but the color signals G ′ _ex709 and B ′ _ex709 are also the same as the color signal R ′ _ex709 in Equation (9), respectively. Similarly, the color signals G _ex709 and B _ex709 are converted.

The primary color conversion unit 73 converts the color signals R _ex709 , G _ex709 , and B _ex709 supplied from the inverse photoelectric conversion unit 72 into color signals R _tv , G _tv , B _tv based on the primary colors of the display mechanism 76, and performs color conversion. The signal is supplied to the signal correction unit 74. That is, the primary color conversion unit 73 calculates the equation (10), for example, to convert the color signals R _ex709 , G _ex709 , and B _ex709 from the inverse photoelectric conversion unit 72 into color signals R _tv based on the primary colors of the display mechanism 76. , G _tv , B _tv .

The color signal correction unit 74 corrects a color signal that cannot be displayed in the display mechanism 76 out of the color signals R _rv , G _tv , and B _tv supplied from the primary color conversion unit 73, and the inherent γ This is supplied to the characteristic correction unit 75. That is, the color signal correction unit 74 includes, for example, the signal levels of the color signals R _tv , G _tv , and B _tv supplied from the primary color conversion unit 73 in the signal level range of the color signals that can be displayed on the display mechanism 76. If not, the color signals R _tv , G _tv , and B _tv are corrected to color signals in the range of signal levels of the color signals that can be displayed by the display mechanism 76.

For example, in the correction processing performed by the color signal correction unit 74, if the color signals R _tv , G _tv , B _tv supplied from the primary color conversion unit 73 are negative values, the color signals R _tv , G _tv , Adjust B _tv to 0.

In the correction processing performed by the color signal correction unit 74, if the color signals R _tv , G _tv , B _tv supplied from the primary color conversion unit 73 are color signals that cannot be displayed on the display mechanism 76, The color signals R _tv , G _tv , and B _tv may be corrected to the color signals in the color gamut that can be displayed by the display mechanism 76 that minimize the color difference from the color signals R _tv , G _tv , and B _tv. It is also possible to correct to a color signal whose saturation is lowered while maintaining the luminance.

The inherent γ characteristic correcting unit 75 corrects the inherent γ characteristics of the display mechanism 76 of the television receiver 70 with _respect to the color signals R _tv , G _tv , and B _tv supplied from the color signal correcting unit 74. The color signals are converted into 76 color signals R ′ _tv , G ′ _tv , and B ′ _tv , and supplied to the D / A converter 44.

The D / A conversion unit 44 performs D / A conversion on the color signals R ′ _tv , G ′ _tv , and B ′ _tv supplied from the inherent γ characteristic correction unit 75 and supplies them to the display mechanism 76.

The display mechanism 76 is composed of, for example, a CRT or LCD, and displays an image based on the color signals R ′ _tv , G ′ _tv , B ′ _tv supplied from the D / A conversion unit 44. The display mechanism 76 corresponds to the xvYCC standard, and can express (display) a color having a wide color gamut compared to the display mechanism 45 of FIG.

  Next, with reference to FIG. 13, the flow of signals until an image taken by the video camera 60 is displayed on the television receiver 70 will be schematically described. The arrows in FIG. 13 represent processing (such as signal conversion processing).

  Processes 81 to 83 are processes performed by the video camera 60, and processes 91 to 94 are processes performed by the television receiver 70.

First, an image photographed by the photographing unit 61 of the video camera 60 is passed through the D / A conversion unit 23 as color signals R _ex , G _ex , B _ex based on the primary colors of the photographing unit 61 (FIG. 11). Supplied to the primary color conversion unit 62 and converted into color signals R _ex709 , G _ex709 , and B _ex709 based on the primary colors of BT.709 (processing 81).

Thereafter, the color signals R _ex709 , G _ex709 , and B _ex709 are converted into color signals R ′ _ex709 , G ′ _ex709 , and B ′ _ex709 according to the photoelectric conversion characteristics of the xvYCC standard by the photoelectric conversion unit 63 (processing 82). Further, the color signals R ′ _ex709 , G ′ _ex709 and B ′ _ex709 are converted into the luminance signal Y ′ _ex709 and the color difference signals Cb ′ _ex709 and Cr ′ _ex709 compliant with the xvYCC standard by the color signal conversion unit 62 ( Process 83) After being encoded by the encoder 28, the encoded data is recorded or transmitted via the network 12.

Meanwhile, the television receiver 70, decodes the encoded data obtained by the video camera 60, the resulting, the luminance signal Y _{'ex 709} and color difference signals Cb' _ex709, Cr _'ex709 that conforms to xvYCC standard, luminance The color difference signal conversion unit 71 converts the color signals to R ′ _ex709 , G ′ _ex709 , and B ′ _ex709 according to the photoelectric conversion characteristics of the xvYCC standard (processing 91). That is, the process of _returning the luminance signal Y ′ _ex709 and the color difference signals Cb ′ _ex709 and Cr ′ _ex709 to the color signals R ′ _ex709 , G ′ _ex709 and B ′ _ex709 obtained by the process performed by the photoelectric conversion unit 63 of the video camera 60. I do.

Thereafter, the color signals R ′ _ex709 , G ′ _ex709 , and B ′ _ex709 are color signals based on the primary colors of BT.709 obtained by the inverse photoelectric conversion unit 72 in the process performed by the primary color conversion unit 63 of the video camera 60. Conversion into R _ex709 , G _ex709 , and B _ex709 (processing 92).

Then, the color signals R _ex709 , G _ex709 , and B _ex709 are converted into color signals R _tv , G _tv , and B _tv based on the primary colors of the display mechanism 76 (FIG. 12) by the primary color conversion unit 73 (process 93). .

The color signals R _tv , G _tv , B _tv are converted into color signals R ′ _tv , G ′ _tv , B ′ _tv in accordance with the specific γ characteristics of the television receiver 70 by the specific γ characteristic correction unit 75 ( Processing 94), an image is displayed on the basis of the color signals R ′ _tv , G ′ _tv , B ′ _tv .

  As described above, in the video camera 60 and the television receiver 70, by adopting the xvYCC standard in which effective values (signal widths) of the color difference signals Cb and Cr are expanded from BT.709, BT.709 Wide color gamut colors that cannot be expressed can be reproduced.

  The luminance signal Y of the image taken by the video camera 60 conforms to BT.709, and the color difference signals Cb and Cr also conform to BT.709 in the range of −0.5 to 0.5. Therefore, when the luminance signal Y and the color difference signals Cb and Cr are processed by a television receiver compliant with BT.709, an image can be displayed in the color gamut of BT.709.

  Here, in the xvYCC standard, the luminance signal Y compliant with BT.601 and the color difference signals Cb and Cr compliant with BT.601 in the range of −0.5 to 0.5 can also be adopted. In this case, it is possible to reproduce a color having a wide color gamut that cannot be expressed by BT.601. Further, in this case, the luminance signal Y conforms to BT.601, and the color difference signals Cb and Cr also conform to BT.601 in the range of −0.5 to 0.5. When the color difference signals Cb and Cr are processed by a television receiver compliant with BT.601, an image can be displayed in the BT.601 color gamut.

However, when the luminance signal Y compliant with BT.601 and the color difference signals Cb, Cr compliant with BT.601 in the range of −0.5 to 0.5 are used, the color signals R ′ _ex601 , G ′ _ex601 , B ′ _{ex601 Is} converted into a YCC signal consisting of the luminance signal Y ′ _ex601 and the color difference signals Cb ′ _ex601 and Cr ′ _ex601 using the following equation (11) instead of equation (7): Conversion needs to be done.

  Each of the primary color conversion unit 62 and the color signal conversion unit 64 of the video camera 60 is realized by a circuit that performs a 3 × 3 matrix operation, and the photoelectric conversion unit 63 is a one-dimensional LUT (Look Up Table) or the like. Can be realized. Further, all of the primary color conversion unit 62, the photoelectric conversion unit 63, and the color signal conversion unit 64 can be realized by a single three-dimensional LUT.

  Further, each of the luminance / color difference signal conversion unit 71 and the primary color conversion unit 73 of the television receiver 70 is realized by a circuit that performs a 3 × 3 matrix operation, and the inverse photoelectric conversion unit 72 and the inherent γ characteristic correction unit 75 Each can be realized by a one-dimensional LUT or the like. Furthermore, all of the luminance / color difference signal conversion unit 71, the inverse photoelectric conversion unit 72, the primary color conversion unit 73, and the intrinsic γ characteristic correction unit 75 can be realized by a single three-dimensional LUT.

  Next, a method for evaluating the performance of an apparatus that handles image data of the xvYCC standard, such as the video camera 60 of FIG. 10 and the television receiver 70 of FIG. 11, will be described.

  Here, hereinafter, the color difference signal expressed as an analog value will be described as Pb and Pr, and the color difference signal expressed as a digital value (integer value) will be described as Cb and Cr.

  FIG. 14 shows a configuration example of an embodiment of an evaluation system for evaluating an evaluation object such as an apparatus that handles image data of the xvYCC standard.

  The evaluation system of FIG. 14 can be broadly divided into an evaluation chart data generation side and an evaluation side.

  In FIG. 14, the evaluation chart data generation side includes a chart data generation unit 101, a resizing unit 102, a recorder 103, and an output unit 104, and is used for evaluation of an evaluation target that handles image data of the xvYCC standard. Is generated for the evaluation chart data.

  That is, the chart data generation unit 101 generates chart data including a luminance signal Y ′ in the xvYCC standard and color difference signals Cb ′ and Cr ′ from a tristimulus value having a wide color gamut, for example, XYZ of color stimulus data. .

  Specifically, the chart data generation unit 101 converts, for example, an XYZ signal into an RGB signal based on the primary color of BT.709 based on the RGB primary color point defined by BT.709, and further converts the RGB signal into the RGB signal. In accordance with the photoelectric conversion characteristic represented by the equation (5), the signals are converted into R ′, G ′, B ′ signals (color signals R ′, G ′, B ′). Then, the chart data generation unit 101 converts the R ′, G ′, and B ′ signals into an analog luminance signal Y ′ and color difference signals Pb ′ and Pr ′ according to Equation (7), and further The analog luminance signal Y ′ and the color difference signals Pb ′ and Pr ′ are converted into an HDTV by converting, for example, 8-bit digital luminance signal Y ′ and color difference signals Cb ′ and Cr ′ in accordance with the xvYCC standard. The chart data used for the evaluation of the corresponding evaluation object is supplied to the resizing unit 102.

  Alternatively, the chart data generation unit 101 converts the R ′, G ′, and B ′ signals into the analog luminance signal Y ′ and the color difference signals Pb ′ and Pr ′ according to the equation (11), and further, the analog data Converts luminance signal Y 'and color difference signals Pb' and Pr 'into 8-bit digital value luminance signal Y' and color difference signals Cb 'and Cr', for example, in compliance with the xvYCC standard to support SDTV The chart data used for the evaluation of the evaluation target is supplied to the resizing unit 102.

  The resizing unit 102 resizes (changes) the size of the image displayed by the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ from the chart data generation unit 101 to a size for HDTV or SDTV as necessary. Then, the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ corresponding to the HDTV or SDTV size image are obtained as evaluation chart data.

  Here, the evaluation chart data obtained as described above expresses chromaticity exceeding the range of chromaticity expressed by the luminance signal and the color difference signal defined by BT.601 or BT.709. It consists of a luminance signal Y ′ and color difference signals Cb ′ and Cr ′ compliant with the xvYCC standard defined in IEC 61966-2-4.

  The resizing unit 102 converts the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ as the above-described evaluation chart data into a format that can be read by the subsequent recorder 103 and transfers the converted signal to the recorder 103.

  The recorder 103 is, for example, a disk recorder that can record and reproduce a component signal of a series called UDR of Measurement Technology Laboratory, Inc., and a luminance signal Y that is chart data for evaluation from the resizing unit 102 'And color difference signals Cb' and Cr 'are recorded on the built-in HD (Hard Disk). Further, the recorder 103 reproduces the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ as evaluation chart data from the built-in HD, and supplies them to the output unit 104.

  The output unit 104 is, for example, an output unit such as an HD-SDI (Signal Digital Interface) unit, an SDI unit, or an analog component unit, and a luminance signal Y ′ and color difference signals Cb ′, which are chart data for evaluation from the recorder 103, Send Cr 'in various signal formats.

  The chart data for evaluation sent out by the output unit 104 can be distributed via a network such as the Internet, for example. Further, the evaluation chart data sent out by the output unit 104 can be recorded on the recording medium 111 and distributed. If the evaluation chart data is HDTV data, the recording medium 111 can be, for example, a HDCAM (R) or HDCAM-SR tape, a disk-shaped recording medium, a semiconductor memory, or the like. . Further, if the evaluation chart data is SDTV data, as the recording medium 111, for example, a DV (Digital Video) or Betacam tape, a disk-shaped recording medium, a semiconductor memory, or the like can be employed.

  In FIG. 14, the evaluation side includes an evaluation object 121 and an evaluation unit 122, receives the provision of the recording medium 111 from the evaluation chart data generation side, and uses the evaluation chart data recorded on the recording medium 111. Then, the evaluation object 121 is evaluated.

  That is, the evaluation object 121 is an apparatus or other device that handles image data compliant with the xvYCC standard, and processes the evaluation chart data recorded on the recording medium 111. Here, examples of the evaluation target 121 include a display device that displays an image corresponding to image data, an editing device that edits image data, a codec that encodes and decodes image data, and image data. There are storage for storage, a transmission device or transmission medium for transmitting image data, a recording / reproducing device for recording and reproducing image data on a recording medium, a reproducing device for reproducing image data from a recording medium, and the like.

  The evaluation unit 122 evaluates the evaluation target 121 based on the result of processing the evaluation chart data by the evaluation target 121 and outputs the evaluation result.

  That is, when the evaluation target 121 is, for example, a display device, the evaluation target 121 performs a necessary process on the evaluation chart data and displays a corresponding image. In this case, the evaluation unit 122 evaluates the evaluation target 121 based on an image corresponding to data obtained by processing the chart data for evaluation with the display device as the evaluation target 121.

  Specifically, the evaluation unit 122 includes, for example, a chromaticity meter, measures the chromaticity of an image displayed by the display device as the evaluation target 121 with the chromaticity meter, and the measured value and the recording medium 111. Is compared with the evaluation chart data recorded in the above, the error of the measured value with respect to the evaluation chart data is obtained, and the error is output as the evaluation result of the evaluation object 121.

  In addition, the evaluation of the evaluation target 121 can be performed by visually confirming an image displayed on the display device as the evaluation target 121 by a person (evaluator) who wants to evaluate the evaluation target 121.

  Next, FIG. 15 shows a configuration example of another embodiment of an evaluation system for evaluating an evaluation object such as a device that handles image data of the xvYCC standard.

  In the figure, portions corresponding to those in the evaluation system of FIG. 14 are denoted by the same reference numerals, and description thereof will be omitted below as appropriate.

  The evaluation system of FIG. 15 differs from the evaluation system of FIG. 14 in that a waveform monitor 131 and an image monitor 132 are provided on the evaluation side instead of the evaluation unit 122.

  In the evaluation system of FIG. 15, evaluation chart data recorded on the recording medium 111 is processed in the evaluation object 121, and data obtained as a result of the processing is supplied to one or both of the waveform monitor 131 and the image monitor 132. Is done.

  The waveform monitor 131 displays a waveform of data from the evaluation target 121, and the image monitor 132 displays an image corresponding to the data from the evaluation target 121.

  The evaluator visually confirms the waveform displayed on the waveform monitor 131 and the image displayed on the image monitor 132, and evaluates the evaluation target 121.

  Next, a method for evaluating the evaluation object 121 using the evaluation system of FIGS. 14 and 15 will be described with reference to the flowcharts of FIGS.

  First, the process on the evaluation chart data generation side of the evaluation system (FIGS. 14 and 15) will be described with reference to the flowchart of FIG.

  On the evaluation chart data generation side, in step S1, evaluation chart data is generated and recorded in the recording medium 111, and the process ends.

  That is, on the evaluation chart data generation side, the chart data generation unit 101 generates the analog luminance signal Y ′ and the color difference signals Pb ′ and Pr ′ as described above. Further, the chart data generation unit 101 converts the analog value luminance signal Y ′ and the color difference signals Pb ′ and Pr ′ into digital value luminance signals Y ′ and color difference signals Cb ′ and Cr ′ compliant with the xvYCC standard, The data is supplied to the resizing unit 102 as chart data used for the evaluation of the evaluation target 121 corresponding to HDTV or SDTV.

  Then, the resizing unit 102 resizes the digital value luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ compliant with the xvYCC standard from the chart data generation unit 101, and the size of the resulting HDTV or SDTV is obtained. A luminance signal Y ′ and color difference signals Cb ′ and Cr ′ corresponding to the image are obtained as evaluation chart data.

  The evaluation chart data obtained by the resizing unit 102 as described above is recorded in the built-in HD by the recorder 103. In the recorder 103, the evaluation chart data recorded in the built-in HD is reproduced as necessary, and is recorded on the recording medium 111 via the output unit 104, for example. The recording medium 111 on which the evaluation chart data is recorded is distributed for a fee or free of charge as necessary.

  Next, processing on the evaluation side of the evaluation system (FIGS. 14 and 15) will be described with reference to the flowchart of FIG.

  In step S <b> 11, the evaluation target 121 processes the evaluation chart data recorded on the recording medium 111.

  In step S <b> 12, the evaluation unit 122 or the evaluator evaluates the evaluation target 121 based on the result of processing the evaluation chart data on the evaluation target 121.

  Next, FIG. 18 illustrates a configuration example of the chart data generation unit 101 of FIGS. 14 and 15.

  The chart data generation unit 101 includes an acquisition unit 161, a primary color conversion unit 162, a photoelectric conversion unit 163, and a color signal conversion unit 164. The color signal conversion unit 164 includes a correction unit 164A.

  Then, the chart data generation unit 101 expresses chromaticity exceeding the chromaticity range expressed by the luminance signal and the color difference signal defined by BT.601 or BT.709, according to IEC 61966-2-4 Image data composed of a luminance signal and a color difference signal compliant with the prescribed xvYCC standard is generated as chart data.

  That is, the acquisition unit 161 acquires XYZ signals, RGB signals, and other color signals to be subjected to primary color conversion by the primary color conversion unit 162 in the subsequent stage, and supplies the acquired color signals to the primary color conversion unit 162.

  Here, in the chart data generation unit 101, for example, based on a color chart including chromaticity exceeding the chromaticity range expressed by the luminance signal and the color difference signal defined by BT.601 or BT.709. The chart data composed of the luminance signal and the color difference signal compliant with the xvYCC standard can be generated.

  In this case, the acquisition unit 161 includes, for example, a photoelectric conversion element for capturing an image such as a CCD or a CMOS sensor, and is expressed by a luminance signal and a color difference signal defined by BT.601 or BT.709. A color chart that includes chromaticity that exceeds the chromaticity range is photographed, and as a result, colors that exceed the chromaticity range expressed by the luminance signal and color difference signal specified in BT.601 or BT.709. Get the color signal of degree.

  As a color chart including chromaticity exceeding the range of chromaticity expressed by the luminance signal and chrominance signal specified in BT.601 or BT.709, for example, Macbeth Color Checker of Gretagma Kubes A color chart called (R), a color chart in which a color with higher saturation is added to the color chart, or the like can be adopted.

  Further, the acquisition unit 161 has a chromaticity exceeding the range of chromaticity expressed by the luminance signal and the color difference signal defined by BT.601 or BT.709 based on the object color of the object other than the color chart. It is possible to acquire a color signal.

  That is, when the acquisition unit 161 includes, for example, a chromaticity meter that measures chromaticity, the chromaticity meter expresses the luminance signal and the color difference signal defined by BT.601 or BT.709. Measure the chromaticity of a color chart created using a highly saturated colorant with a chromaticity that exceeds the chromaticity range, and use the measurement results to determine the chromaticity specified in BT.601 or BT.709. A color signal having a chromaticity exceeding the range of chromaticity expressed by the luminance signal and the color difference signal can be generated.

  In addition, when the acquisition unit 161 includes, for example, a chromaticity meter that measures chromaticity, the luminance signal and the color difference signal defined by BT.601 or BT.709 are based on the light source color instead of the object color. It is possible to acquire a color signal having a chromaticity exceeding the range of chromaticity expressed by.

  That is, in the acquisition unit 161, in the chromaticity meter, for example, transmitted object light or light source having a chromaticity exceeding the range of chromaticity expressed by the luminance signal and the color difference signal defined by BT.601 or BT.709. Measure the chromaticity of the image, and use the measurement result to generate a color signal with a chromaticity that exceeds the chromaticity range expressed by the luminance signal and color difference signal specified by BT.601 or BT.709. be able to.

  In addition, the acquisition unit 161 generates a color signal representing a color corresponding to the coordinates based on one or more coordinates on a chromaticity diagram of a predetermined color space such as a standard color space or a uniform color space. By doing so, the color (chromaticity) corresponding to the predetermined coordinates on the chromaticity diagram of the predetermined color space, and the color expressed by the luminance signal and color difference signal specified by BT.601 or BT.709 A color signal with a chromaticity exceeding the range of degrees can be acquired.

  In addition, the color (chromaticity) corresponding to the predetermined coordinates on the chromaticity diagram of the predetermined color space, and the chromaticity represented by the luminance signal and the color difference signal defined by BT.601 or BT.709. The color signal having a chromaticity exceeding the range includes, for example, a color corresponding to a predetermined coordinate on a chromaticity diagram in a predetermined color space, and a luminance defined by ITU-R BT.601 or BT.709. It is also possible to generate the image based on an image having a chromaticity exceeding the range of chromaticity expressed by the signal and the color difference signal, that is, for example, by photographing the image.

  Furthermore, in the acquisition unit 161, for example, when the operator operates an operation unit (not shown), the chromaticity range expressed by the luminance signal and the color difference signal specified by BT.601 or BT.709 is exceeded. By receiving the value input as the color signal value of the specified chromaticity, the color of the chromaticity that exceeds the range of chromaticity expressed by the luminance signal and color difference signal specified by BT.601 or BT.709 A signal can be acquired.

  As described above, the acquisition unit 161 acquires a color signal having a chromaticity exceeding the range of chromaticity expressed by the luminance signal and the color difference signal defined by BT.601 or BT.709, and a primary color conversion unit. 162.

  Then, the primary color conversion unit 162, the photoelectric conversion unit 163, and the color signal conversion unit 164 perform the same processing as the primary color conversion unit 62, the photoelectric conversion unit 63, and the color signal conversion unit 64 in FIG. From the color signal having a chromaticity exceeding the range of chromaticity expressed by the luminance signal and the color difference signal specified by BT.601 or BT.709, acquired by the unit 161, the signal is transmitted from BT.601 or BT.709. Expresses chromaticity beyond the range of chromaticity expressed by the specified luminance signal and color difference signal, and conforms to the xvYCC standard, for example, 8-bit digital value luminance signal Y ′ and color difference signal Cb ′, Image data composed of Cr ′ is generated as chart data.

  The luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ generated as described above are supplied from the chart data generation unit 101 to the resizing unit 102. Then, in the resizing unit 102, as described above, the image sizes corresponding to the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ from the chart data generating unit 101 are resized as necessary.

  As the resizing unit 102, for example, software for image processing called “PhotoShop®” of Adobe can be adopted. Here, FIG. 19 shows a table displaying images corresponding to the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ of 8-bit digital values compliant with the xvYCC standard by PhotoShop® (a computer executing the same). An example is shown. That is, FIG. 19 shows an image obtained by inputting the luminance signal Y ′ to the R channel of PhotoShop® and inputting the color difference signals Cb ′ and Cr ′ to the G and B channels, respectively.

  Next, a specific example of the evaluation chart data will be described.

  Note that, here, the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ as the evaluation chart data are both represented by 8 bits, but the luminance signal Y ′ and the color difference as the evaluation chart data are both represented. The number of bits of the signals Cb ′ and Cr ′ is not limited to 8 bits.

  Here, when the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ compliant with the xvYCC standard are each expressed by n bits of 8 bits or more, the integer range that can be expressed by the n bits is used. The signal level is assigned as follows.

That is, for the luminance signal Y ′, for example, as described above, when the luminance signal Y ′ is represented by 8 bits, 16 to 235 out of 0 to 255 that can be represented by the 8 bits. The signal level of the luminance signal Y ′ from 0 to 1.0 is assigned to an integer value in the integer range. If the luminance signal Y ′ is expressed by n bits larger than 8 bits, it should be expressed by the n bits. In the integer range corresponding to 16 to 235 when the luminance signal Y ′ is expressed by 8 bits, the luminance signal Y ′ in the numerical range of 0 to 1.0 in the integer range 0 to 2 ⁿ −1 Signal levels are assigned.

Also for the color difference signal Cb ′ (the same applies to the color difference signal Cr ′), when the color difference signal Cb ′ in the integer range 0 to 2 ⁿ −1 that can be represented by n bits is represented by 8 bits. The signal level of the color difference signal Pb ′ in the numerical range of −0.57 to 0.56 is assigned to the integer range corresponding to 1 to 254.

  Here, the minimum and maximum signal levels of the color difference signals Pb ′ and Pr ′ of BT.709 and BT.601 are −0.5 and +0.5, respectively, and the signals of the color difference signals Pb ′ and Pr ′ of the xvYCC standard The minimum and maximum levels are -0.57 to 0.56, respectively. Therefore, the color difference signals Pb 'and Pr' of the xvYCC standard are -0.57 to -0.5 (exactly -0.57 or more and less than -0.5) that the color difference signals Pb 'and Pr' of BT.709 and BT.601 cannot take. The signal level can be between 0.5 and 0.56 (greater than 0.5 and less than 0.56).

When the color difference signal Cb of xvYCC standard 'is represented by n bits of 8 bits or more, -0.57 to -0.5 signal level is assigned to the 2 ^n-8 or 15 × 2 ^n-8 an integer ranging , 0.5 to 0.56 is assigned to an integer range from 241 × 2 ^{n−8 to} 255 × 2 ⁿ⁻⁸ −1.

The color difference signals Cb ′ and Cr ′ as the evaluation chart data used for the evaluation of the evaluation object 121 (FIGS. 14 and 15) handling a moving image with a wide color gamut are assigned to a signal level of −0.57 to −0.5 2 ^n. An integer value in the integer range between ^{-8 and} 15 x 2 ^{n-8 and} an integer in the integer range between 241 x 2 ^{n-8 and} 255 x 2 ^n-8 -1 assigned to a signal level between 0.5 and 0.56 It is desirable to include at least one or both of the numerical values.

  FIG. 20 shows an image of a color chart displayed according to the first example of the evaluation chart data.

  In FIG. 20, the luminance signal Y ′ is 16 (8-bit conversion value) in the 5 × 5 small square in the left part. In FIG. 20, in the left 5 × 5 small square, the color difference signal Cb ′ is 1,16,128,240,254 (8-bit conversion value) in order from the left to the right, and the color difference signal Cr ′ is From the top to the bottom, the numbers are 1,16,128,240,254 (8-bit converted values) in this order.

  Further, in FIG. 20, the luminance signal Y ′ is 16 (8-bit converted value) in the large square in the right part. In FIG. 20, in the large square in the right part, the color difference signal Cb ′ is continuously from left to right and the color difference signal Cr ′ is continuously from 1 to 254 (8-bit conversion value) from top to bottom. It has changed.

  21 is a waveform diagram showing a waveform displayed by inputting the evaluation chart data of the color chart of FIG. 20 to the waveform monitor, that is, a waveform of the evaluation chart data of the color chart of FIG.

  Here, a waveform monitor called WFM700M manufactured by Tektronix was used as the waveform monitor.

  In the waveform diagram of FIG. 21 (the same applies to other waveform diagrams described later), the leftmost scale 700 corresponds to the integer value of 240 of the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′, and the leftmost scale. 0 (midpoint between 100 and -100) corresponds to 16 integer values of the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′. Furthermore, in the waveform diagram, when the waveform diagram is divided into approximately three equal parts in the horizontal direction and divided into three regions, the waveform in the first region from the left indicates the waveform of the luminance signal Y ′. The waveform in the second area from the left indicates the waveform of the color difference signal Cb ′, and the waveform in the third area from the left (first area from the right) indicates the waveform of the color difference signal Cr ′.

  The evaluation chart data as shown in FIG. 20 can be generated for luminance signals Y ′ having various integer values.

  That is, FIG. 22 shows an image of a color chart displayed by the second example of the evaluation chart data.

  The evaluation chart data in FIG. 22 is the same as the evaluation chart data in FIG. 20 except that the luminance signal Y ′ is not 254 (equivalent 8-bit value) but 254.

  Here, FIG. 23 shows a waveform of the chart data for evaluation of the color chart of FIG.

  By adopting integer values at appropriate intervals in the range of 1 to 254 as the value of the luminance signal Y ′, and generating the chart data for evaluation as shown in FIG. 20 and FIG. Evaluation object 121 can be evaluated.

  FIG. 24 shows an image of a color chart displayed by the third example of the evaluation chart data.

  The left side of FIG. 24 shows a signal solid composed of the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ on the three-dimensional coordinate system having the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ as axes. Taken along the Y′-Cb ′ plane (the plane defined by the axis of the luminance signal Y ′ and the axis of the color difference signal Cb ′) (the plane of Cr ′ = 0) (Y′−Cb 'Cross section). Further, the right side of FIG. 24 includes the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ on a three-dimensional coordinate system having the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ as axes. A cross section (Y ′) that is visible when the signal solid is cut along a Y′−Cr ′ plane (a plane defined by the axis of the luminance signal Y ′ and the axis of the color difference signal Cr ′) (the plane of Cb ′ = 0) -Cr 'cross section).

  In the color chart image of FIG. 24, sRGB boundary lines are displayed together with the left Y′-Cb ′ section and the right Y′-Cr ′ section.

  Here, FIG. 25 shows a waveform of the chart data for evaluation of the color chart of FIG.

  The evaluation chart data shown in FIGS. 20 to 25 evaluate, for example, whether or not the evaluation target 121 normally passes the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ of the xvYCC standard. Can be used for

  FIGS. 26 to 30 show fourth to eighth examples of evaluation chart data for displaying images of chromaticity diagrams in various color spaces.

  26 shows evaluation chart data for displaying an image of an xy chromaticity diagram in the CIE1931 standard color space, and FIG. 27 shows evaluation chart data for displaying an image of a u'v 'chromaticity diagram in the CIE1976UCS space. FIG. 28 shows the chart data for evaluation displaying the image of the L * a * b * chromaticity diagram in the CIE1976 L * a * b * color space.

  The left side of FIGS. 26 to 28 is a chromaticity diagram in a case where the color signals corresponding to the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ are limited to values within the range of the spectral locus (spectral locus). The right side of FIGS. 26 to 28 shows the luminance signal corresponding to the color signal even if the color signal corresponding to the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ is outside the range of the spectral locus. If Y ′ and color difference signals Cb ′ and Cr ′ are values in a range allowed by the xvYCC standard, the chromaticity diagram is obtained when the color signals are not limited.

  In the evaluation chart data of FIGS. 26 to 28, the luminance Y value is a constant value, but various numerical values are adopted as the luminance Y value to generate the evaluation chart data of FIGS. This makes it possible to evaluate the evaluation object 121 for various values of luminance. As the luminance Y value, for example, a value at intervals of 0.1 is employed from 1.5 to 0.1, and for 0.1 or less, for example, 0.05, 0.03, 0.01, 0.005, 0.001 can be employed. However, the luminance Y value employed in generating the evaluation chart data of FIGS. 26 to 28 is not limited to this.

  FIG. 29 and FIG. 30 show the chart data for evaluation that displays the color of the maximum luminance permitted by the xvYCC standard for the chromaticity coordinates in the spectral locus on the CIE1931 standard color space.

  In FIG. 29, a color within the range of the spectral locus is displayed in the center portion, and a color rectangle on a plurality of points (coordinates) on the spectral locus is displayed around the range of the spectral locus. Thus, in the evaluation of the evaluation target 121, it is possible to easily check the color.

  In FIG. 30, a color within the range of the spectral locus is displayed on the left side, and a plurality of red rectangles are displayed on the right side.

  That is, in FIG. 30, on the right side, red rectangles whose luminance decreases at the same chromaticity are arranged from top to bottom, and red rectangles whose luminance increases at the same luminance and equal hue from the left. Lined up to the right.

  By evaluating the evaluation object 121 using the evaluation chart data of FIG. 30, it is possible to perform detailed evaluation regarding red.

  In addition, as the chart data for evaluation as shown in FIG. 30, not the red rectangles arranged on the right side, but the green, blue, cyan, magenta, yellow, and other color rectangles are generated. be able to. In this case, detailed evaluation can be performed for various colors.

  In addition to the xy chromaticity diagram, the evaluation chart data in which rectangles of specific colors are arranged as shown in FIG. 30 can be generated for specific colors in the L * a * b * space.

  FIG. 31 shows an image of a color chart displayed according to the ninth example of the evaluation chart data.

  Fig. 31 shows 24 colors (2A to 5F) of a color chart called Macbeth Color Checker (R) of Greta Kumak Beth Co., Ltd., and 16 colors with higher saturation than the 24 colors (first line and G, This is a color chart of a total of 40 colors to which (column H) is added.

  The evaluation chart data as shown in FIG. 31 actually exists as a commercially available color chart (for example, Macbeth Color Checker (R) manufactured by Gretagma Kubes) or an original wide color gamut color chart created by itself. It can be generated by measuring the chromaticity of a color chart (actual color chart). The evaluation of the evaluation target 121 using the evaluation chart data is performed by displaying an image (color chart image) corresponding to data obtained by processing the evaluation chart data on the evaluation target 121, for example. It can be performed by comparing with the color of the actual color chart, or by measuring and comparing the chromaticity between the image of the displayed color chart and the actual color chart.

  FIG. 32 shows an image of a color chart displayed by the tenth example of the evaluation chart data.

  In FIG. 32, for the three primary colors of red (R), blue (B), and green (G), the maximum and minimum values allowed by the color signal in the xvYCC standard, and the range from the maximum value to the minimum value The colors corresponding to each of the one or more values are arranged.

  According to the evaluation chart data as described above, for example, a waveform of Tektronix, Inc. for the evaluation target 121 such as a storage for storing image data compliant with the xvYCC standard, a transmission medium for transmitting image data, or other devices. Analyzing the signal using a device that can read the signal (data) digitally, such as a monitor “WFM700M”, the signal (image data compliant with the xvYCC standard) can be evaluated normally. And so on (without distortion).

  That is, for example, when the waveform of the chart data for evaluation in FIG. 20 is displayed on the waveform monitor, it is as shown in FIG.

  Therefore, the waveform of the data obtained by processing the evaluation chart data in the evaluation target 121 (for example, the evaluation chart data that has passed through the evaluation target 121) is displayed on the waveform monitor, and the waveform is the waveform shown in FIG. By comparing, it is possible to evaluate the performance of the evaluation target 121 such as whether or not image data compliant with the xvYCC standard is normally processed (treated) in the evaluation target 121.

  Further, when the evaluation target 121 is, for example, an editing apparatus that performs nonlinear editing, the waveform before editing of the evaluation chart data is compared with the waveform after editing, so that before editing and after editing. It is possible to confirm at a glance whether image data compliant with the xvYCC standard is properly stored.

  Further, when the evaluation target 121 is, for example, an MPEG codec, the waveform before encoding of the evaluation chart data is compared with the waveform after encoding and further decoding, thereby comparing the waveform before encoding. Thus, it is possible to confirm at a glance whether or not image data compliant with the xvYCC standard is properly stored after decoding.

  Here, FIG. 33 shows the QuickTime (R) format data obtained by converting the evaluation chart data shown in FIG. 20 into QuickTime (R) format data using software for nonlinear editing executed on a computer. It is a wave form diagram which shows the waveform of data.

  The waveform of the evaluation chart data in FIG. 21 is compared with the waveform in FIG. 33 to convert the evaluation chart data in FIG. 20 into data in the QuickTime (R) format, thereby changing the waveform. You can investigate what to do.

  Further, for example, according to the chart data for evaluation in FIG. 24, the sRGB boundary line is displayed together with the Y′-Cb ′ section and the Y′-Cr ′ section, and therefore the evaluation target 121 conforms to the xvYCC standard. In addition to confirming whether image data passes normally, visually confirm whether the color at the time of display of the image corresponding to the image data conforming to the xvYCC standard that passed the evaluation target 121 is not unnatural. Can do.

  Furthermore, when the evaluation target 121 is a display device, an image corresponding to the image data compliant with the xvYCC standard is intuitively displayed by displaying an image corresponding to the evaluation chart data in FIG. Judgment can be made as to whether it is displayed properly.

  When the evaluation target 121 is a display device, when there is a color that cannot be displayed by the evaluation target 121 among the colors that can be expressed by the luminance signal Y ′ and the color difference signals Cr ′ and Cb ′ of the xvYCC standard. In addition, it is possible to easily confirm how signals corresponding to such colors are processed in the evaluation object 121 by using the evaluation chart data.

  Further, when the evaluation target 121 is a display device, a color with high luminance can be displayed on the evaluation target 121, but is expressed by a luminance signal Y ′ and color difference signals Cr ′ and Cb ′ of the xvYCC standard. There are times when you can't. It is possible to easily confirm how signals corresponding to such colors are processed in the evaluation object 121 by using the evaluation chart data.

  In addition, according to the evaluation chart data in FIGS. 26 to 28, it is confirmed whether or not a hue shift or a luminance change is caused by processing image data compliant with the xvYCC standard in the evaluation target 121. be able to.

  Further, according to the chart data for evaluation in FIGS. 26 to 28, as described above, on the left side, the color signals corresponding to the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ are within the spectral locus range. A chromaticity diagram is displayed when the value is limited, and the color signal corresponding to the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ is displayed on the right side even if the color signal is outside the spectral locus range. If the luminance signal Y ′ and the color difference signals Cb ′ and Cr ′ corresponding to the signal are within the range permitted by the xvYCC standard, a chromaticity diagram when the color signal is not limited is displayed, and therefore the evaluation target 121 Can be evaluated separately for the actual color range and the out-of-range color range.

  Further, for example, according to the chart data for evaluation in FIG. 27 and FIG. 28 in which chromaticity diagrams in a uniform color space such as L * a * b * chromaticity diagrams and u′v ′ chromaticity diagrams are displayed, The hue saturation can be confirmed.

  Furthermore, according to the chart data for evaluation in FIG. 29, the display of the color in the spectral locus can be visually confirmed by the color in the range of the spectral locus in the central portion, and the peripheral portion on the spectral locus is visually confirmed. The color of the color on the spectral locus can be confirmed by the color rectangles on the dots.

  In addition, according to the evaluation chart data of FIG. 30, it is possible to perform a detailed evaluation regarding a specific color such as red, and in particular, check for deviations in brightness and hue by, for example, the arrangement of red rectangles on the right side.

  Further, since the evaluation chart data in FIG. 31 is created from the actual color material, it is possible to compare the colors by comparing or measuring the color with the actual color material (color chart).

  For example, when the color signal of R, G, and B is larger than 0, red, green, and blue colors with brightness corresponding to the value of the color signal are displayed. If the value is less than or equal to 0, the luminance is 0 (none), so black is originally displayed. However, depending on the display device, even if there is no luminance signal, if there is a color difference signal, a bright display may be displayed instead of displaying black. According to the evaluation chart data of FIG. 32, when the evaluation target 121 is a display device, it is possible to confirm what kind of display is performed on the display device, including the display as described above.

  As described above, by using the evaluation chart data, various signals can be evaluated, reproduced, checked for passage, and image display can be evaluated.

  Next, the series of processes described above can be performed by hardware or software. When a series of processing is performed by software, a program constituting the software is installed in a general-purpose computer or the like.

  Therefore, FIG. 34 shows a configuration example of an embodiment of a computer in which a program for executing the above-described series of processing is installed.

  The program can be recorded in advance in a hard disk 205 or ROM 203 as a recording medium built in the computer.

  Alternatively, the program is stored temporarily on a removable recording medium 211 such as a flexible disk, a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto Optical) disk, a DVD (Digital Versatile Disc), a magnetic disk, or a semiconductor memory. It can be stored permanently (recorded). Such a removable recording medium 211 can be provided as so-called package software.

  The program is installed on the computer from the removable recording medium 211 as described above, or transferred from the download site to the computer wirelessly via a digital satellite broadcasting artificial satellite, LAN (Local Area Network), The program can be transferred to a computer via a network such as the Internet. The computer can receive the program transferred in this way by the communication unit 208 and install it in the built-in hard disk 205.

  The computer includes a CPU (Central Processing Unit) 202. An input / output interface 210 is connected to the CPU 202 via the bus 201, and the CPU 202 operates the input unit 207 including a keyboard, a mouse, a microphone, and the like by the user via the input / output interface 210. When a command is input as a result of this, the program stored in a ROM (Read Only Memory) 203 is executed accordingly. Alternatively, the CPU 202 also receives a program stored in the hard disk 205, a program transferred from a satellite or a network, received by the communication unit 208 and installed in the hard disk 205, or a removable recording medium 211 attached to the drive 209. The program read and installed in the hard disk 205 is loaded into a RAM (Random Access Memory) 204 and executed. Thereby, the CPU 202 performs processing according to the above-described flowchart or processing performed by the configuration of the above-described block diagram. Then, the CPU 202 outputs the processing result from the output unit 206 configured with an LCD (Liquid Crystal Display), a speaker, or the like, for example, via the input / output interface 210, or from the communication unit 208 as necessary. Transmission, and further recording on the hard disk 205 is performed.

  Here, in this specification, the processing steps for describing a program for causing a computer to perform various types of processing do not necessarily have to be processed in time series according to the order described in the flowchart, but in parallel or individually. This includes processing to be executed (for example, parallel processing or processing by an object).

  Further, the program may be processed by a single computer, or may be processed in a distributed manner by a plurality of computers. Furthermore, the program may be transferred to a remote computer and executed.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a block diagram which shows the structure of an example of the conventional AV system. It is a block diagram which shows the structural example of the video camera 1 of FIG. It is a block diagram which shows the structural example of the television receiver 2 of FIG. It is a figure which shows the primary color and reference | standard white in ITU-R BT.709. It is a figure which shows the relationship between the signal level of the signal of each standard, and the integer value expressing the signal level. It is a figure which shows the photoelectric conversion characteristic employ | adopted by xvYCC standard. It is a figure showing the relationship between the color space which ITU-R BT.709 covers and the 768 colors of the Munsell color cascade and the color space of the sRGB standard. This figure shows the relationship between the xvYCC standard luminance signal, color space by color difference signal, 768 colors of Munsell color cascade, color space by color signal of BT.709 standard, and color space by luminance signal of BT.709 standard, color difference signal is there. FIG. 9 is a projection view in the Cb ′ direction of FIG. 8. 1 is a block diagram illustrating a configuration example of an embodiment of an AV system compliant with the xvYCC standard. It is a block diagram which shows the structural example of the video camera 60 of FIG. It is a block diagram which shows the structural example of the television receiver 70 of FIG. It is a figure which shows the flow of the signal in the process with the video camera 60 of FIG. 11, and the television receiver 70 of FIG. It is a block diagram which shows the structural example of one Embodiment of the evaluation system which evaluates evaluation objects, such as an apparatus which handles the image data of xvYCC specification. FIG. 10 is a block diagram illustrating a configuration example of another embodiment of an evaluation system that evaluates an evaluation target such as an apparatus that handles image data of the xvYCC standard. It is a flowchart explaining the process by the side of the chart data generation for evaluation of an evaluation system. It is a flowchart explaining the process by the side of evaluation of an evaluation system. 3 is a block diagram illustrating a configuration example of a chart data generation unit 101. FIG. It is a figure which shows the example of a display of the image corresponding to the luminance signal Y 'of 8-bit digital value based on xvYCC standard, and color difference signal Cb', Cr '. It is a figure which shows the image displayed by the 1st example of the chart data for evaluation. It is a wave form diagram which shows the waveform of the 1st example of the chart data for evaluation. It is a figure which shows the image displayed by the 2nd example of the chart data for evaluation. It is a wave form diagram which shows the waveform of the 2nd example of the chart data for evaluation. It is a figure which shows the image displayed by the 3rd example of the chart data for evaluation. It is a wave form diagram which shows the waveform of the 3rd example of the chart data for evaluation. It is a figure which shows the image displayed by the 4th example of the chart data for evaluation. It is a figure which shows the image displayed by the 5th example of the chart data for evaluation. It is a figure which shows the image displayed by the 6th example of the chart data for evaluation. It is a figure which shows the image displayed by the 7th example of the chart data for evaluation. It is a figure which shows the image displayed by the 8th example of the chart data for evaluation. It is a figure which shows the image displayed by the 9th example of the chart data for evaluation. It is a figure which shows the image displayed by the 10th example of the chart data for evaluation. It is a wave form diagram which shows the waveform of the chart data for evaluation converted into QuickTime (R) format. It is a block diagram which shows the hardware structural example of a computer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Video camera, 2 Television receiver, 11 Recording medium, 12 Network, 21 Operation part, 22 Shooting part, 23 A / D conversion part, 24 Primary color conversion part, 25 Color signal correction part, 26 Photoelectric conversion part, 27 colors Signal conversion unit, 28 encoder, 29 control unit, 30 recording unit, 31 communication unit, 41 image signal input unit, 42
Luminance / color difference signal conversion unit, 43 intrinsic γ characteristic correction unit, 44 D / A conversion unit, 45 display mechanism, 60 video camera, 61 shooting unit, 62 primary color conversion unit, 63 photoelectric conversion unit, 64 color signal conversion unit, 64A Correction unit, 70 television receiver, 71 luminance / color difference signal conversion unit, 72 inverse photoelectric conversion unit, 73 primary color conversion unit, 74 color signal correction unit, 75 intrinsic γ characteristic correction unit, 76 display mechanism, 101 chart data generation unit , 102 Resizing unit, 103 recorder, 104 output unit, 111 recording medium, 121 evaluation target, 122 evaluation unit, 131 waveform monitor, 132 image monitor, 161 acquisition unit, 162 primary color conversion unit, 163 photoelectric conversion unit, 164 color signal conversion Section, 164A correction section, 201 bus, 202 CPU, 203 ROM, 204 RAM, 205 hard disk, 20 Output unit, 207 input unit, 208 communication unit, 209 drive, 210 input-output interface, 211 removable recording medium

Claims (9)

In the image data of the video used for the evaluation of the evaluation target that handles the video,
XvYCC standard specified in IEC 61966-2-4 that expresses chromaticity beyond the range of chromaticity expressed by the luminance signal and color difference signal specified by ITU-R BT.601 or BT.709 Image data consisting of luminance signal and color difference signal conforming to Including the color corresponding to the predetermined coordinates on the chromaticity diagram of the predetermined color space, it exceeds the chromaticity range expressed by the luminance signal and color difference signal specified by ITU-R BT.601 or BT.709. The image data according to claim 1, wherein the image data includes a luminance signal and a color difference signal compliant with the xvYCC standard that expresses the chromaticity. Compliant with the xvYCC standard generated based on the color chart including chromaticity exceeding the range of chromaticity expressed by the luminance signal and color difference signal specified by ITU-R BT.601 or BT.709 The image data according to claim 1, wherein the image data comprises a luminance signal and a color difference signal. A color chart created using a highly saturated color material with a chromaticity exceeding the range of chromaticity expressed by the luminance signal and color difference signal specified by ITU-R BT.601 or BT.709. The image data according to claim 1, comprising a luminance signal and a color difference signal compliant with the xvYCC standard, which measure chromaticity and express the chromaticity. Measure chromaticity of transmitted object light or light source with chromaticity exceeding the range of chromaticity expressed by luminance signal and color difference signal specified by ITU-R BT.601 or BT.709, and calculate the chromaticity The image data according to claim 1, wherein the image data includes a luminance signal and a color difference signal compliant with the xvYCC standard. The color difference signal according to the xvYCC standard, when expressed by n bits of 8 bits or more, the color difference signal, a value in the range of 2 ^n-8 or 15 × 2 ^n-8 or less, 241 × 2 ⁿ The image data according to claim 1, comprising at least one or both of a value within a range of ^{−8 to} 255 × 2 ⁿ⁻⁸ −1. In an evaluation method for evaluating an evaluation object that handles a video,
XvYCC standard specified in IEC 61966-2-4 that expresses chromaticity beyond the range of chromaticity expressed by the luminance signal and color difference signal specified by ITU-R BT.601 or BT.709 Image data for evaluation consisting of a luminance signal and a color difference signal compliant with the above-mentioned evaluation object,
An evaluation method including a step of evaluating the evaluation object based on a result of processing the image data for evaluation on the evaluation object. The evaluation method according to claim 7, wherein the evaluation object is evaluated based on a waveform of data obtained by processing the image data for evaluation with the evaluation object. The evaluation method according to claim 7, wherein the evaluation object is evaluated based on an image corresponding to data obtained by processing the image data for evaluation with the evaluation object.

Images