CODING AND DECODING METHOD AND CORRESPONDING DEVICES

• US 20180249166A1
• Filed: 08/16/2016
• Published: 08/30/2018
• Est. Priority Date: 08/24/2015
• Status: Active Grant

• Current Assignee: InterDigital Madison Patent Holdings SAS (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: LELEANNEC, Fabrice, GALPIN, Franck, LASSERRE, Sebastien
• Granted Patent: US 11,070,830 B2
• Time in Patent Office: Days
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

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.

Claims

1-8. -8. (canceled)

9. A decoding method comprising:

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.

10. The method according to claim 9, wherein applying a dynamic expansion function on the color converted standard dynamic range luminance component L to obtain a high dynamic range luminance component Y is done as follows:

Y=g<sup>−

1</sup>(Ba,L))

where Ba is a modulation value and g<sup>−

1</sup>( ) is an inverse of a dynamic reduction function applied onto a linear-light high dynamic range luminance component on the encoder'"'"'s side.

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:

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 x_norm and a high dynamic range chrominance Z-component z_norm in the XYZ color space by applying a color conversion matrix on the squared intermediate components.

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 x_norm and the high dynamic range chrominance Z-component z_norm to obtain a high dynamic range picture in a RGB color space comprises:

multiplying a vector (x_norm, 1, z_norm)^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.

13. A decoder comprising a communication interface configured to access a bitstream produced by an encoder and at least one processor configured to:

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.

14. The decoder according to claim 13, wherein to apply a dynamic expansion function on the color converted standard dynamic range luminance component L to obtain a high dynamic range luminance component Y is done as follows:

Y=g<sup>−

1</sup>(Ba,L))

where Ba is a modulation value and g<sup>−

1</sup>( ) is an inverse of a dynamic reduction function applied onto a linear-light high dynamic range luminance component on the encoder'"'"'s side.

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:

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 x_norm and a high dynamic range chrominance Z-component z_norm, in the XYZ color space by applying a color conversion matrix on the squared intermediate components.

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 x_norm and the high dynamic range chrominance Z-component z_norm to obtain a high dynamic range picture in a RGB color space comprises:

multiplying a vector (x_norm, 1, z_norm)^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.

17. A non-transitory computer readable medium with instructions stored therein which, upon execution, instruct at least one processor to:

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.

18. The non-transitory computer readable medium according to claim 17, wherein to apply a dynamic expansion function on the color converted standard dynamic range luminance component L to obtain a high dynamic range luminance component Y is done as follows:

Y=g<sup>−

1</sup>(Ba,L))

where Ba is a modulation value and g<sup>−

1</sup>( ) is an inverse of a dynamic reduction function applied onto a linear-light high dynamic range luminance component on the encoder'"'"'s side.

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:

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 x_norm and a high dynamic range chrominance Z-component z_norm in the XYZ color space by applying a color conversion matrix on the squared intermediate components.

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 x_norm and the high dynamic range chrominance Z-component z_norm to obtain a high dynamic range picture in a RGB color space comprises:

multiplying a vector (x_norm, 1, z_norm)^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.