CODING AND DECODING METHOD AND CORRESPONDING DEVICES
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Abstract
A decoding method is disclosed that comprises: —decoding at least one luma component and two chroma components from a bitstream; —decoding color metadata, said metadata comprising at least one of: a syntax element representative of a color conversion type, a syntax element representative of an inverse transfer type and a syntax element representative of a color conversion matrix; —color converting the luma and/or chroma components responsive to said syntax element representative of a color conversion type; —applying an inverse transfer operation on the color converted luma and/or chroma to obtain a first, a second and a third component responsive to syntax element representative of an inverse transfer type; and —applying a color conversion matrix responsive to said syntax element representative of a color conversion matrix to obtain and RGB high dynamic range picture.
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Citations
20 Claims
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1-8. -8. (canceled)
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9. A decoding method comprising:
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decoding one standard dynamic range luminance component L′ and
two standard dynamic range chrominance components U′ and
V′
from a bitstream produced by an encoder;color converting the standard dynamic range luminance component L′
into L and the two decoded standard dynamic range chrominance components U′ and
V′
into Ur and Vr respectively as follows;
L=L′
+max(0,aU′
+bV′
), Ur=β
(L)*U′
, Vr=β
(L)*V′where a and b are constants and where β
(L) is a parameter that depends on L;applying a dynamic expansion function on the color converted standard dynamic range luminance component L to obtain a high dynamic range luminance component Y, wherein said dynamic expansion function is the inverse of a dynamic reduction function applied onto the high dynamic range luminance component on said encoder'"'"'s side; applying a color transfer operation on the color converted standard dynamic range chroma components Ur and Vr to obtain a high dynamic range chrominance X-component and a high dynamic range chrominance Z-component in a XYZ color space; applying a color conversion matrix on the high dynamic range luminance component Y, the high dynamic range chrominance X-component and the high dynamic range chrominance Z-component to obtain a high dynamic range picture in a RGB color space. - View Dependent Claims (10, 11, 12)
where Ba is a modulation value and g−
1( ) is an inverse of a dynamic reduction function applied onto a linear-light high dynamic range luminance component on the encoder'"'"'s side.
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11. The method according to claim 9, wherein applying a color transfer operation on the color converted standard dynamic range chroma components to obtain a high dynamic range chrominance X-component and a high dynamic range chrominance Z-component in a XYZ color space comprises:
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calculating T as a linear combination of Ur2,Vr2 and Ur*Vr; calculating S as √
{square root over (1−
T)} in the case where T≤
1 and setting S to 0 and dividing Ur and Vr by √
{square root over (T)} otherwise;calculating intermediate (R#,G#,B#) components in an RGB color space by applying a color conversion matrix on S, Ur, and Vr; calculating a high dynamic range chrominance X-component xnorm and a high dynamic range chrominance Z-component znorm in the XYZ color space by applying a color conversion matrix on the squared intermediate components.
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12. The method according to claim 9, wherein applying a color conversion matrix on the high dynamic range luminance component Y, the high dynamic range chrominance X-component xnorm and the high dynamic range chrominance Z-component znorm to obtain a high dynamic range picture in a RGB color space comprises:
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multiplying a vector (xnorm, 1, znorm)t by Y to obtain an intermediate vector; and multiplying the intermediate vector by a color conversion matrix used for mapping a XYZ signal into a RGB signal.
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13. A decoder comprising a communication interface configured to access a bitstream produced by an encoder and at least one processor configured to:
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decode one standard dynamic range luminance component L′ and
two standard dynamic range chrominance components U′ and
V′
from a bitstream;color convert the standard dynamic range luminance component L′
into L and the two decoded standard dynamic range chrominance components U′ and
V′
into Ur and Vr respectively as follows;
L=L′
+max(0,aU′
+bV′
), Ur=β
(L)*U′
, Vr=β
(L)*V′where a and b are constants and where β
(L) is a parameter that depends on L;apply a dynamic expansion function on the color converted standard dynamic range luminance component L to obtain a high dynamic range luminance component Y, wherein said dynamic expansion function is the inverse of a dynamic reduction function applied onto the high dynamic range luminance component on said encoder'"'"'s side; apply a color transfer operation on the color converted standard dynamic range chroma components Ur and Vr to obtain a high dynamic range chrominance X-component and a high dynamic range chrominance Z-component in a XYZ color space; apply a color conversion matrix on the high dynamic range luminance component Y, the high dynamic range chrominance X-component and the high dynamic range chrominance Z-component to obtain a high dynamic range picture in a RGB color space. - View Dependent Claims (14, 15, 16)
where Ba is a modulation value and g−
1( ) is an inverse of a dynamic reduction function applied onto a linear-light high dynamic range luminance component on the encoder'"'"'s side.
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15. The decoder according to claim 13, wherein to apply a color transfer operation on the color converted standard dynamic range chroma components to obtain a high dynamic range chrominance X-component and a high dynamic range chrominance Z-component in a XYZ color space comprises:
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calculating T as a linear combination of Ur2,Vr2 and Ur*Vr; calculating S as √
{square root over (1−
T)} in the case where T≤
1 and setting S to 0 and dividing Ur and Vr by √
{square root over (T)} otherwise;calculating intermediate (R#,G#,B#) components in an RGB color space by applying a color conversion matrix on S, Ur, and Vr; calculating a high dynamic range chrominance X-component xnorm and a high dynamic range chrominance Z-component znorm, in the XYZ color space by applying a color conversion matrix on the squared intermediate components.
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16. The decoder according to claim 13, wherein to apply a color conversion matrix on the high dynamic range luminance component Y, the high dynamic range chrominance X-component xnorm and the high dynamic range chrominance Z-component znorm to obtain a high dynamic range picture in a RGB color space comprises:
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multiplying a vector (xnorm, 1, znorm)t by Y to obtain an intermediate vector; and multiplying the intermediate vector by a color conversion matrix used for mapping a XYZ signal into a RGB signal.
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17. A non-transitory computer readable medium with instructions stored therein which, upon execution, instruct at least one processor to:
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decode one standard dynamic range luminance component L′ and
two standard dynamic range chrominance components U′ and
V′
from a bitstream produced by an encoder;color convert the standard dynamic range luminance component L′
into L and the two decoded standard dynamic range chrominance components U′ and
V′
into Ur and Vr respectively as follows;
L=L′
+max(0,aU′
+bV′
), Ur=β
(L)*U′
, Vr=β
(L)*V′where a and b are constants and where β
(L) is a parameter that depends on L;apply a dynamic expansion function on the color converted standard dynamic range luminance component L to obtain a high dynamic range luminance component Y, wherein said dynamic expansion function is the inverse of a dynamic reduction function applied onto the high dynamic range luminance component on said encoder'"'"'s side; apply a color transfer operation on the color converted standard dynamic range chroma components Ur and Vr to obtain a high dynamic range chrominance X-component and a high dynamic range chrominance Z-component in a XYZ color space; apply a color conversion matrix on the high dynamic range luminance component Y, the high dynamic range chrominance X-component and the high dynamic range chrominance Z-component to obtain a high dynamic range picture in a RGB color space. - View Dependent Claims (18, 19, 20)
where Ba is a modulation value and g−
1( ) is an inverse of a dynamic reduction function applied onto a linear-light high dynamic range luminance component on the encoder'"'"'s side.
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19. The non-transitory computer readable medium according to claim 17, wherein to apply a color transfer operation on the color converted standard dynamic range chroma components to obtain a high dynamic range chrominance X-component and a high dynamic range chrominance Z-component in a XYZ color space comprises:
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calculating T (421) as a linear combination of Ur2,Vr2 and Ur*Vr; calculating (423) S as √
{square root over (1−
T)} in the case where T≤
1 and setting (424) S to 0 and dividing Ur and Vr by √
{square root over (T)} otherwise;calculating (425) intermediate (R#,G#,B#) components in an RGB color space by applying a color conversion matrix on S, Ur, and Vr; calculating (5200) a high dynamic range chrominance X-component xnorm and a high dynamic range chrominance Z-component znorm in the XYZ color space by applying a color conversion matrix on the squared intermediate components.
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20. The non-transitory computer readable medium according to claim 17, wherein to apply a color conversion matrix on the high dynamic range luminance component Y, the high dynamic range chrominance X-component xnorm and the high dynamic range chrominance Z-component znorm to obtain a high dynamic range picture in a RGB color space comprises:
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multiplying a vector (xnorm, 1, znorm)t by Y to obtain an intermediate vector; and multiplying the intermediate vector by a color conversion matrix used for mapping a XYZ signal into a RGB signal.
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Specification