JP6531591B2 - Video coding apparatus, video coding method, video coding program, video decoding apparatus, video decoding method, and video decoding program - Google Patents

Description

  The present invention relates to an encoding and decoding technique of an image obtained by converting a color space of a color space.

  A conventional general video system is an international standard BT. It is designed on the premise of displaying a color of 709 (sRGB (standard RGB)) standard. On the other hand, in order to improve the performance of recent devices, the color expression range (hereinafter referred to as "color gamut") tends to be expanded. For example, a liquid crystal display device using a liquid crystal panel using an LED with high color purity of luminescent color as a back light, a projector using a laser light source, and the like have a considerably wide color gamut as compared with the prior art.

  On the other hand, in response to this situation, a color space such as Adobe RGB (trademark) corresponding to a wide color gamut has been proposed and used from the viewpoint of standards. Furthermore, BT. In 2020, a color system having a larger color gamut is set.

  As a method of converting color data between systems having different color gamuts, Patent Document 1 and Patent Document 2 describe a method of displaying a signal acquired in a wide color gamut in a narrow color gamut. Further, as a method of widening the color gamut, there is a method described in Patent Document 3 by the present inventor.

Japanese Patent Application Laid-Open No. 2000-165692 JP 2002-359748 A JP, 2014-93617, A

  When an image produced in a wide color gamut is displayed as it is in a narrow color gamut display system, the displayed image is relatively saturated because the saturation of the primary colors that are the basis of the color system is higher than those of the narrow color gamut. It will be the way of seeing a dull shade of low degree. On the other hand, in the method described in Patent Document 1 and Patent Document 2 in which the image produced in the wide color gamut is adapted to the display system of the narrow color gamut, much of the color information will be rejected. . Although the method described in Patent Document 3 performs conversion from a narrow color gamut to a wide color gamut, since the original video does not have wide color gamut information, the overall saturation is to be improved. Although it is possible, it is not possible to reproduce the color information of a real scene correctly.

  The present invention has been made in view of these circumstances, and its object is to ensure compatibility and enable color gamut conversion so that color information of an image can be accurately displayed even on display systems with different color gamut color gamuts. Another object of the present invention is to provide a video encoding and decoding technique.

  In order to solve the above problems, a video encoding apparatus according to an aspect of the present invention converts an input video for a display system of a first color gamut into an output video for a display system of a second color gamut and codes the code. A video signal of a first color gamut, a video signal of a second color gamut, and the chromaticity of pixels of the video signal of the second color gamut, the first color , A video signal encoding unit for encoding the video signal of the second color gamut, and a separation processing unit for separating into the chroma expansion factor for restoring to the chromaticity of the pixel of the video signal of the area; A chroma enlargement magnification encoding unit that encodes the magnification ratio; and a bitstream integration unit that integrates the encoded video signal of the second color gamut and the encoded saturation enlargement magnification into a bitstream Including.

  Another aspect of the present invention is a video decoding apparatus. This apparatus is a video decoding apparatus for decoding an output video for a display system of a first color gamut from a bit stream in which an input video for a display system of a second color gamut is encoded, Color for restoring the bit stream of the video signal of the second color gamut and the chromaticity of the pixel of the video signal of the second color gamut to the chromaticity of the pixel of the video signal of the first color gamut A bit stream separation unit that separates the data into the data of the second enlargement ratio; a decoding unit that decodes the data of the video signal of the second color gamut; a decoding unit that decodes the data of the saturation enlargement ratio A high frequency component evaluation unit which evaluates the high frequency component of the decoded second color gamut video signal, and adjusts the saturation expansion ratio decoded according to the evaluation result of the high frequency component; , Based on the decoded second color gamut video signal and the adjusted saturation expansion factor. And a recovery processing unit that recovers the video signal of the first color gamut.

  Yet another aspect of the present invention is a video coding method. This method is a video encoding method for converting an input video for a display system of a first color gamut into an output video for a display system of a second color gamut and encoding the video data of the first color gamut Saturation for restoring the video signal to the chromaticity of the video signal of the second color gamut and the chromaticity of the pixel of the video signal of the second color gamut to the chromaticity of the pixel of the video signal of the first color gamut The steps of separating into an enlargement factor, encoding the video signal of the second color gamut, encoding the saturation enlargement factor, and the encoded video signal of the second color gamut And integrating the encoded saturation expansion factor into a bitstream.

  Yet another aspect of the present invention is a video decoding method. This method is a video decoding method for decoding an output video for the display system of the first color gamut from a bit stream in which the input video for the display system of the second color gamut is encoded, Color for restoring the bit stream of the video signal of the second color gamut and the chromaticity of the pixel of the video signal of the second color gamut to the chromaticity of the pixel of the video signal of the first color gamut Separating the data of the second color gamut image signal; decoding the data of the saturation expansion ratio; and Evaluating the high-frequency component of the video signal of two color gamuts, and adjusting the chroma expansion factor decoded according to the evaluation result of the high-frequency component; and the second color gamut decoded Of the first color gamut based on the adjusted video signal and the adjusted saturation magnification factor. And a step of recovering the signal.

  Note that arbitrary combinations of the above-described components, and conversions of the expression of the present invention among methods, apparatuses, systems, recording media, computer programs and the like are also effective as aspects of the present invention.

  According to the present invention, it is possible to encode and decode a color gamut converted image by ensuring compatibility so that color information of the image can be accurately displayed even in display systems having different color gamuts. .

It is a block diagram of the video coding apparatus concerning this Embodiment. It is a block diagram of the imaging | video decoding apparatus based on this Embodiment. It is a flowchart which shows the procedure of the moving image coding process by the video coding apparatus of FIG. It is a flowchart which shows the procedure of the moving image decoding process by the video decoding apparatus of FIG. FIG. 2 is a block diagram of a narrow color gamut signal / saturation enlargement magnification factor separation processing unit of FIG. 1; It is a block diagram of the wide color gamut recovery process part of FIG. It is a flowchart which shows the procedure of the isolation | separation processing by the narrow color gamut signal / saturation expansion magnification isolation | separation process part of FIG. It is a flowchart which shows the procedure of the recovery processing by the wide color gamut recovery process part of FIG.

  FIG. 1 is a block diagram of a video encoding apparatus 100 according to the present embodiment. FIG. 3 is a flowchart showing the procedure of the moving picture coding process by the video coding apparatus 100 of FIG. Hereinafter, the configuration and operation of the video encoding device 100 will be described with reference to these figures.

  The narrow color gamut signal / saturation expansion magnification separation processing unit 110 receives the wide color gamut RGB video signal, and separates the input wide color gamut RGB image into the narrow color gamut RGB image and the saturation expansion magnification α. A conversion process is performed (S10). Details of this conversion process will be described later.

  The narrow color gamut signal / saturation enlargement magnification factor separation processing unit 110 supplies the converted narrow color gamut RGB signal to the RGB-YPbPr conversion unit 120 in order to encode it by the moving image coding method such as MPEG, and the saturation expansion is performed. The scaling factor α is supplied to the saturation scaling factor encoding unit 140.

  The RGB-YPbPr conversion unit 120 converts RGB of the input image into Y color difference (S12). This conversion is based on a general color space conversion matrix, including decimation of color difference signals. The RGB-YPbPr converter 120 supplies the converted YPbPr signal to the video signal encoder 130.

  The video signal encoding unit 130 subjects the YPbPr signal to moving image encoding, and supplies the encoded image data to the bit stream integration unit 150 (S14). In the case of the MPEG method, techniques of discrete cosine transform (DCT) and motion prediction / motion compensation are used.

  The chroma enlargement magnification encoding unit 140 motion picture encodes the saturation enlargement magnification factor α, and supplies the encoded alpha data to the bitstream integration unit 150 (S16). Here, assuming coding with an alpha channel used in multi-level shape coding discussed in the MPEG4, the saturation enlargement ratio α is stored in the alpha channel, and moving image coding is performed.

  The bitstream integration unit 150 integrates the encoded narrow color gamut image data and the encoded saturation expansion ratio, and outputs it as a bitstream (S18). As described above, in the case of a coding scheme having an alpha channel, it is integrated into a bitstream using that scheme.

  FIG. 2 is a block diagram of a video decoding apparatus 200 according to the present embodiment. FIG. 4 is a flow chart showing the procedure of moving picture decoding processing by the video decoding apparatus 200 of FIG. The configuration and operation of the video decoding apparatus 200 will be described below with reference to the functional block diagram of FIG. 2 and the flowchart of FIG.

  The bit stream separation unit 210 receives the bit stream encoded by the video encoding device 100, and separates the input bit stream into data of narrow color gamut RGB signals and data of the saturation expansion ratio α (S20). ). The bit stream separation unit 210 supplies the data of the narrow color gamut RGB signal to the video signal decoding unit 220, and supplies the data of the saturation enlargement ratio α to the saturation enlargement ratio decoding unit 230.

  The video signal decoding unit 220 decodes the data of the narrow color gamut RGB signal, and supplies the data of the decoded narrow color gamut RGB signal to the YPbPr-RGB conversion unit 240 and the high frequency component evaluation unit 250 (S22) . The chroma expansion factor decoding unit 230 decodes the data of the chroma expansion factor α, and supplies the decoded data of the chroma expansion factor α to the high frequency component evaluation section 250 (S26).

  The YPbPr-RGB conversion unit 240 converts the data (YPbPr signal) of the decoded narrow color gamut RGB signal from YPbPr to RGB, and restores the narrow color gamut RGB signal (S24). This conversion is based on a general color space conversion matrix, including interpolation of color difference signals. The YPbPr-RGB conversion unit 240 outputs the restored narrow color gamut RGB signal as it is, and supplies the restored narrow color gamut RGB signal to the wide color gamut recovery processing unit 260.

  The high-frequency component evaluation unit 250 receives data on the decoded narrow color gamut RGB signal (YPbPr signal) and data on the decoded saturation expansion ratio α, and generates data (YPbPr signal on the narrow color gamut RGB signal). It is determined whether or not there is a high frequency component for the luminance Y of) (S28). This determination is performed by comparing the sum of the absolute values of the difference between the brightness Y of the target pixel and the brightness of the adjacent eight pixels with a threshold. For example, when expressing a color in 8 bits, if the sum of the absolute values of the above differences is about 30 or more, it is determined that the high frequency component is present. When the luminance Y has a high frequency component (Y in S28), the saturation enlargement ratio α is set to 1 so that the color gamut expansion processing is not performed (S30). If there is no high frequency component in the luminance Y (N in S28), data of the saturation expansion factor α decoded for color gamut expansion processing is used (S32). In this case, the pixel value of the alpha channel is α = (A + 100) / 140 when A = α * 140-100 as described later.

  The wide color gamut recovery processing unit 260 receives the narrow color gamut RGB signal restored from the YPbPr-RGB conversion unit 240, and the saturation expansion magnification factor α set according to the presence or absence of the high frequency component from the high frequency component evaluation unit 250. The narrow color gamut RGB signal is converted into a wide color gamut based on the saturation enlargement ratio α to restore the wide color gamut RGB signal (S34). Details of the wide color gamut recovery processing will be described later.

  Here, the reason why the color gamut expansion processing is not performed when the image has high frequency components will be described. The data stored in the alpha channel is often lower in correlation between peripheral pixels and frames, especially in the outline portion, than at a general video signal, and at a rate similar to that of a general video signal. In the case of coding, there is a high probability that block noise, mosquito noise, aliasing and the like will occur. As described above, when the color gamut expansion processing is performed on the signal whose quality has deteriorated due to the high frequency component, an error is likely to be noticeable, so the color gamut expansion processing is suppressed for the pixels including the high frequency component. It was made to do.

  FIG. 5 is a block diagram of the narrow color gamut signal / saturation enlargement magnification factor separation processing unit 110 of FIG. FIG. 7 is a flow chart showing the procedure of separation processing by the narrow color gamut signal / saturation enlargement magnification factor separation processing unit 110 of FIG. The configuration and operation of the narrow color gamut signal / saturation enlargement magnification factor separation processing unit 110 will be described below with reference to these drawings.

  The narrow color gamut color system lightness / saturation / hue calculation unit 10 previously calculates the lightness / saturation / hue of the outer circumference of the narrow color gamut for the lightness L * to 0 to 100, and A process is performed to generate saturation as a function of lightness and hue (S40). This function can be configured as a look-up table (LUT) in which the saturation of the outer periphery of the narrow color gamut is associated with lightness and hue. Specifically, it calculates as follows.

In the narrow color gamut side, here, BT. A triangle with a color gamut of point R (0.640, 0.330), point G (0.300, 0.500), point B (0.150, 0.060) on the CIE xy chromaticity diagram of 709 First, the equation of a straight line is determined for each side, and division is further performed, for example, about 1000 divisions, chromaticity a * and b * are derived for xy coordinates of each point, and hue h is determined. About Y, it derives by the below-mentioned formulas (14) and (17), and others are computed by the following formulas (1), (2), (3), (5)-(8).
z = 1-x-y (1)
X = x * y / Y (2)
Z = z * y / Y (3)
L * = 116f (Y / Yn) -16 (4)
a * = 500 [f (X / Xn) -f (Y / Yn)] (5)
b * = 200 [f (Y / Yn) -f (Z / Zn)] (6)
f (t) = t ^ (1/3) (t> (6/29) ^ 3 = 0.008856) (7)
f (t) = [(29/3) ^ 3t + 16] / 116 (other cases) (8)
However, under the D65 light source, Xn = 95.045, Yn = 100, Zn = 108.892

About the 1000 points of data obtained above,
h '= atan (b * / a *) (9)
The phase, that is, the hue h ′ is calculated and the frequency-converted one is used as the hue h, and the lightness L * and the chromaticity a * and b * when the hue h is closest to the integer are incorporated into the array. By circling the entire side, a look-up table of lightness L * and chromaticity a * and b * of lightness 0 to 100 and hue 0 ° to 360 ° can be obtained. Here, a tan means reverse tangent.

  The color space conversion unit 12 receives an input of the wide color gamut RGB image (S42). For example, BT. A wide color gamut RGB image equivalent to the 2020 color gamut is input. The color space conversion unit 12 converts the input video of the RGB color space into a video of the L * a * b * color space, and calculates the lightness and chromaticity of each pixel. The color space conversion unit 12 includes an RGB-linear RGB conversion unit, a linear RGB-CIE XYZ conversion unit, and a CIE XYZ-L * a * b * conversion unit, and converts RGB to linear RGB, linear RGB to CIE XYZ, Convert color space of wide gamut RGB image from CIE XYZ to L * a * b *. Hereinafter, it is assumed that processing is performed in pixel units in raster scan.

  The RGB-linear RGB conversion unit converts the color space from RGB to linear RGB with respect to the input image by general normalization and inverse gamma conversion (S44).

The linear RGB-CIE XYZ conversion unit is, for example, a BT. In the case of 2020, conversion of the following equation is performed (S46).
X = 100 * (0.6370 * R + 0.1446 * G + 0.1689 * B) (10)
Y = 100 * (0.2627 * R + 0.6780 * G + 0.0593 * B) (11)
Z = 100 * (0.0000 * R + 0.0281 * G + 1.0610 * B) (12)

  The CIE XYZ-L * a * b * conversion unit calculates the lightness L * and the chromaticity a * and b * using the above-mentioned equations (4) to (8) (S48).

The hue / saturation calculation unit 14 calculates the hue h and saturation C * frequency-converted from the chromaticity a * and b * finally derived by the color space conversion unit 12 (S50). The hue h is calculated according to the above equation (9), and is determined by frequency conversion. The saturation C * is calculated by the length of a vector whose components are the chromaticity a * and b * as in the following equation.
C * = sqrt (a * ^ 2 + b * ^ 2) (13)

  The saturation comparison unit 16 compares the pixel saturation of the video signal determined above with the pixel and the lightness of the video signal on the LUT generated by the narrow color gamut color system lightness / saturation / hue calculation unit 10 The saturation having the same hue is obtained (S52), and the saturation Ca of the pixel of the video signal is compared with the saturation Cb on the LUT (S54).

As described below, when the saturation Ca of the video signal is larger than the saturation Cb of the LUT, the saturation expansion magnification determining unit 18 sets the ratio of the saturation expansion α to the saturation Ca of the video signal and the saturation Cb of the LUT In the other case, α is set to 1 (S58).
if (Ca> Cb) α = Ca / Cb;
else α = 1.0;

  The chroma expansion factor determination unit 18 outputs the chroma expansion factor α determined as described above and supplies the chroma expansion factor α to the chromaticity division part 20.

  The significance of the saturation enlargement factor determination unit 18 determining the saturation enlargement factor α in this manner will be described. If Ca> Cb, the color gamut of the input video signal exceeds the narrow color gamut, so the color gamut reduction processing is performed as described later, and if not, the input video signal is a signal within the narrow color gamut Since it is a level, it is used without reducing the color gamut. The data of the saturation expansion magnification α is narrow color gamut color system BT. 709, wide color gamut color system is BT. In the case of 2020, the upper limit is generally about 2.4, and the lower limit is 1.0 without enlargement. Therefore, the value of A = α * 140-100 is 8 bits in the 32-bit bitmap. It should be stored in the alpha channel.

  The chromaticity division unit 20 reduces the color gamut of the input image by dividing the chromaticity a * and b * by the saturation expansion ratio α (S60).

  The color space inverse conversion unit 22 performs a conversion reverse to the color space conversion of the color space conversion unit 12 on the image for which the color gamut reduction processing has been performed according to the saturation expansion ratio α by the chromaticity division unit 20. To generate and output a narrow color gamut RGB image. The color space inverse conversion unit 22 inversely converts an image in the L * a * b * color space into an image in the original RGB color space. The color space conversion unit 12 includes an L * a * b * -CIE XYZ conversion unit, a CIE XYZ-linear RGB conversion unit, and a linear RGB-RGB conversion unit, and L * a * b * to CIE XYZ, CIE XYZ To linear RGB, and from linear RGB to RGB, the color space of the image subjected to color gamut reduction processing is converted.

The L * a * b * -CIE XYZ conversion unit converts the color space from L * a * b * to CIE XYZ conversion according to Equations (14) to (19) (S62).
Y = fy ^ 3 * Yn (fy> 6/29), Y = (3/29) ^ 3 (116fy-16) Yn (fy <6/29) (14)
X = fx ^ 3 * Xn (fx> 6/29), X = (3/29) ^ 3 (116fx-16) Xn (fx <6/29) (15)
Z = fz ^ 3 * Zn (fz> 6/29), Z = (3/29) ^ 3 (116fz-16) Zn (fz <6/29) (16)
fy = (L * + 16) / 116 (17)
fx = fy + (a * / 500) (18)
fz = fy− (b * / 200) (19)
However, under the D65 light source, Xn = 95.045, Yn = 100, Zn = 108.892

The CIE XYZ-linear RGB conversion unit is, for example, a BT. When outputting as a signal of 709, the color space is converted from CIE XYZ to linear RGB according to the following equation (S64).
R = 0.01 * (3.2410 * X-1.5374 * Y-0.4986 * Z) (20)
G = 0.01 * (-0.9692 * X + 1.8760 * Y + 0.0416 * Z) (21)
B = 0.01 * (0.0556 * X-0.2040 * Y + 1.0570 * Z) (22)

  The linear RGB-RGB conversion unit converts the color space from linear RGB to RGB by general gamma conversion and constant multiplication (for example, 255 for 8 bits) (S66).

  The narrow color gamut signal / saturation enlargement magnification factor separation processing unit 110 outputs the signal whose color space has been inversely converted by the color space inverse conversion unit 22 as a narrow color gamut RGB image, and the saturation expansion used in the reduction processing. The magnification factor α is output (S68).

  FIG. 6 is a block diagram of the wide color gamut recovery processing unit 260 of FIG. FIG. 8 is a flowchart showing the procedure of recovery processing by the wide color gamut recovery processing unit 260 of FIG. Hereinafter, the configuration and operation of the wide color gamut recovery processing unit 260 will be described with reference to these drawings.

  The color space conversion unit 30 receives an input of the narrow color gamut RGB image (S70). Since the signal generated by the video encoding device 100 is input, here, BT. An image equivalent to the 709 color gamut is input. The color space conversion unit 30 includes an RGB-linear RGB conversion unit, a linear RGB-CIE XYZ conversion unit, and a CIE XYZ-L * a * b * conversion unit, and converts RGB to linear RGB, linear RGB to CIE XYZ, Convert the color space of narrow color gamut RGB image from CIE XYZ to L * a * b *. In the following, it is assumed that processing is performed pixel by pixel in raster scan.

  The chromaticity multiplication unit 32 receives an input of the saturation expansion ratio α (S72). In accordance with the specification of the coding scheme by the video coding apparatus 100, here, alpha channel data A of a 32-bit bitmap is input, and the result obtained by (A + 100) / 140 is taken as the saturation enlargement ratio α.

  The RGB-linear RGB conversion unit converts the color space from RGB to linear RGB with respect to the input image by general normalization and inverse gamma conversion (S74).

The linear RGB-CIE XYZ conversion unit is, for example, a BT. In the case of 709, the following conversion is performed (S76).
X = 100 * (0.4124 * R + 0.3576 * G + 0.1805 * B) (23)
Y = 100 * (0.2126 * R + 0.7152 * G + 0.0722 * B) (24)
Z = 100 * (0.0193 * R + 0.1192 * G + 0.9505 * B) (25)

  The CIE XYZ-L * a * b * conversion unit calculates the lightness L * and the chromaticity a * and b * using the above-mentioned equations (4) to (8) (S78).

  The chromaticity multiplication unit 32 performs expansion of the color gamut of the input image by multiplying the chromaticity a * and b * finally derived by the color space conversion unit 30 by the saturation expansion ratio α (S80) .

  The color space inverse conversion unit 34 performs a conversion reverse to the color space conversion of the color space conversion unit 30 on the image on which the color space expansion processing has been performed according to the saturation enlargement ratio α by the color space conversion unit 30. To generate and output a wide color gamut RGB image. The color space inverse conversion unit 34 includes an L * a * b * -CIE XYZ conversion unit, a CIE XYZ-linear RGB conversion unit, and a linear RGB-RGB conversion unit, and L * a * b * to CIE XYZ, CIE Converts the color space of an image that has been subjected to gamut expansion processing from XYZ to linear RGB, and from linear RGB to RGB.

  The L * a * b * -CIE XYZ conversion unit converts the color space from L * a * b * to CIE XYZ conversion according to Equations (14) to (19) (S82).

The CIE XYZ-linear RGB conversion unit is, for example, a BT. When outputting as a signal of 2020, the color space is converted from CIE XYZ to linear RGB according to the following equation (S84).
R = 0.01 * (1.7167 * X-0.3557 * Y-0.2534 * Z) (26)
G = 0.01 * (-0.6667 * X + 1.6165 * Y + 0.0158 * Z) (27)
B = 0.01 * (0.0176 * X-0.0428 * Y + 0.9421 * Z) (28)

  The linear RGB-RGB conversion unit converts the color space from linear RGB to RGB (S86) by general gamma conversion and constant multiplication (for example, 255 for 8 bits).

  The wide color gamut recovery processing unit 260 outputs the signal whose color space is inversely converted by the color space inverse conversion unit 34 as a wide color gamut RGB image (S88).

  As described above, according to the present embodiment, the wide color gamut video signal is converted into the narrow color gamut video and the signal format of the saturation expansion magnification, and the wide color gamut in the narrow color gamut display system is encoded. It is possible to realize compatibility with a narrow color gamut display system by outputting a narrow color gamut image including color information of the low range video signal. Further, if a video file of this signal format is used, in a wide color gamut display system, it is possible to return to a wide color gamut video by multiplying the chromaticity of the narrow color gamut video by the saturation expansion ratio.

  Further, in the decoding process, a wide color gamut video signal can be reproduced while avoiding a coding error by controlling a saturation expansion ratio to be multiplied by the chromaticity according to the high frequency band of the video signal.

  The present invention has been described above based on the embodiments. It is understood by those skilled in the art that the embodiment is an exemplification, and that various modifications can be made to the combination of each component and each processing process, and such a modification is also within the scope of the present invention. .

  Although the saturation enlargement factor α is stored in the alpha channel in the above description, the saturation enlargement factor α may be stored in the lower bits of the video signal. For example, by continuously transmitting frame images according to 48-bit Tiff (each RGB color is 16 bits), BT. When transmitting a moving image according to the 2020 standard, the upper limit is 12 bits for each color according to the standard for each of the RGB image information, so the lower four bits for each color have a total of 12 bits. If 8 bits of these bits are used to store the saturation expansion factor α, it is possible to transmit the image by storing the saturation expansion factor α in the lower bits of the high definition multi-bit moving image. Alternatively, as another method, the saturation enlargement factor α may be stored in a file separate from the video and provided as auxiliary information.

  In the above description, the case of converting from the wide color gamut to the narrow color gamut has been described, but the conversion of the color gamut is not necessarily limited to the conversion from the wide area to the narrow area of the color area. The present embodiment can be applied to arbitrary color gamut conversion as long as reduction and enlargement processing of the color gamut is required when converting from the first color gamut to the second color gamut.

  The functional configuration of each device described in the embodiment can be realized by cooperation of hardware resources and software resources, or only hardware resources. Processors, ROMs, RAMs, and other LSIs can be used as hardware resources. Programs such as operating systems and applications can be used as software resources.

  10 narrow color gamut color system lightness / saturation / hue calculation unit, 12 color space conversion unit, 14 hue / saturation calculation unit, 16 saturation comparison unit, 18 saturation enlargement ratio determination unit, 20 chromaticity division unit, 22 color space inverse conversion unit, 30 color space conversion unit, 32 chromaticity multiplication unit, 34 color space inverse conversion unit, 100 video encoding device, 110 narrow color gamut signal / saturation enlargement magnification factor separation processing unit, 120 RGB-YPbPr Conversion unit, 130 video signal encoding unit, 140 saturation expansion ratio encoding unit, 150 bit stream integration unit, 200 video decoding apparatus, 210 bit stream separation unit, 220 video signal decoding unit, 230 saturation expansion ratio decoding The conversion unit, 240 YPbPr-RGB conversion unit, 250 high-frequency component evaluation unit, 260 wide gamut recovery processing unit.

Claims (9)

A video encoding apparatus for converting an input video for a display system of a first color gamut into an output video for a display system of a second color gamut and encoding the video.
The video signal of the first color gamut is the video signal of the second color gamut, and the chromaticity of the pixel of the video signal of the second color gamut is the chromaticity of the pixel of the video signal of the first color gamut A separation processing unit for separating into a saturation enlargement factor for restoration;
A video signal encoding unit that encodes the video signal of the second color range;
A saturation enlargement factor encoding unit that encodes the saturation enlargement factor;
A video coding apparatus comprising: a bitstream integration unit that integrates the encoded video signal of the second color gamut and the encoded saturation expansion ratio into a bitstream.   The video encoding apparatus according to claim 1, wherein the chroma enlargement magnification encoding unit stores the chroma enlargement magnification in an alpha channel and encodes the alpha channel.   The video encoding apparatus according to claim 1, wherein the chroma enlargement magnification encoding unit stores the chroma enlargement magnification in lower bits of an image and encodes the chroma enlargement magnification. A video decoding apparatus for decoding an output video for a display system of a first color gamut from a bitstream in which an input video for a display system of a second color gamut is encoded,
In order to restore the input bit stream to the video signal data of the second color gamut and the chromaticity of the pixels of the video signal of the second color gamut to the chromaticity of the pixels of the video signal of the first color gamut A bit stream separation unit that separates the data into data of saturation expansion factors of
A video signal decoding unit that decodes data of the video signal of the second color gamut;
A saturation expansion factor decoding unit that decodes the data of the saturation expansion factor;
A high frequency component evaluation unit that evaluates high frequency components of the video signal of the second color gamut that has been decoded, and adjusts the saturation expansion ratio that is decoded according to the evaluation result of the high frequency components;
And a recovery processing unit configured to recover the video signal of the first color gamut based on the video signal of the second color gamut decoded and the adjusted saturation expansion factor. Device.   The high frequency component evaluation unit sets the saturation enlargement ratio to 1 when the high frequency component of the video signal of the second color gamut exceeds a predetermined threshold, and in the other cases, the decoded saturation 5. The video decoding apparatus according to claim 4, wherein an enlargement factor is used. A video encoding method for converting an input video for a display system of a first color gamut into an output video for a display system of a second color gamut and encoding the video.
The video signal of the first color gamut is the video signal of the second color gamut, and the chromaticity of the pixel of the video signal of the second color gamut is the chromaticity of the pixel of the video signal of the first color gamut Separating into a saturation expansion factor for restoration;
Encoding the video signal of the second color gamut;
Encoding the saturation expansion factor;
And c. Integrating the encoded video signal of the second color gamut and the encoded saturation expansion factor into a bit stream. A video encoding program for converting an input video for a display system of a first color gamut into an output video for a display system of a second color gamut and encoding the video.
The video signal of the first color gamut is the video signal of the second color gamut, and the chromaticity of the pixel of the video signal of the second color gamut is the chromaticity of the pixel of the video signal of the first color gamut Separating into a saturation expansion factor for restoration;
Encoding the video signal of the second color gamut;
Encoding the saturation expansion factor;
A computer-readable storage medium storing a video encoding program comprising: causing a computer to execute the step of integrating the encoded video signal of the second color gamut and the encoded saturation expansion ratio into a bit stream. A video decoding method for decoding an output video for a display system of a first color gamut from a bit stream in which an input video for a display system of a second color gamut is encoded,
In order to restore the input bit stream to the video signal data of the second color gamut and the chromaticity of the pixels of the video signal of the second color gamut to the chromaticity of the pixels of the video signal of the first color gamut Separating into data of saturation expansion factors of
Decoding data of the video signal of the second color gamut;
Decoding the data of the saturation expansion factor;
Evaluating a high frequency component of the video signal of the second color gamut that has been decoded, and adjusting the saturation enlargement ratio decoded according to the evaluation result of the high frequency component;
And v. Recovering the video signal of the first color gamut based on the video signal of the second color gamut and the adjusted saturation expansion factor. . A video decoding program for decoding an output video for a display system of a first color gamut from a bitstream in which an input video for a display system of a second color gamut is encoded,
In order to restore the input bit stream to the video signal data of the second color gamut and the chromaticity of the pixels of the video signal of the second color gamut to the chromaticity of the pixels of the video signal of the first color gamut Separating into data of saturation expansion factors of
Decoding data of the video signal of the second color gamut;
Decoding the data of the saturation expansion factor;
Evaluating a high frequency component of the video signal of the second color gamut that has been decoded, and adjusting the saturation enlargement ratio decoded according to the evaluation result of the high frequency component;
Recovering the video signal of the first color gamut based on the decoded video signal of the second color gamut and the adjusted chroma expansion factor. Decryption program.

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