Extending image dynamic range

• US 9,264,681 B2
• Filed: 08/23/2011
• Issued: 02/16/2016
• Est. Priority Date: 08/25/2010
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Gish, Walter, Li, Zhen, Pian, Donald, Vogt, Christopher, Kim, Hyung-Suk, Ruhoff, David
• Primary Examiner(s): Perromat, Carlos
• Application Number:
  US13/818,288
• Publication Number:
  US 20130148029A1
• Time in Patent Office: 1,638 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 3/1423 controlling a plurality of local displays, e.g. CRT and flat panel display
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: H04N 9/12 Picture reproducers H04N9/11 takes precedence
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

Abstract

Enhancing image dynamic range is described. An input video signal that is represented in a first color space with a first color gamut, which is related to a first dynamic range, is converted to a video signal that is represented in a second color space with a second color gamut. The second color space is associated with a second dynamic range. At least two (e.g., three) color-related components of the converted video signal are mapped over the second dynamic range.

Claims

1. A method for processing a video signal, comprising the steps of:

(a) normalizing a first image, with which a scene is encoded in the video signal with a first luminance dynamic range, with a second image, with which the scene is renderable or displayable with a second luminance dynamic range;

wherein the second luminance dynamic range is greater than the first luminance dynamic range;

wherein the normalizing step comprises the steps of;

receiving the first image;

receiving the second image;

normalizing the first image with the second image to output a third image, a fourth image, and an invertible mapping function;

the third image having the second luminance dynamic range and the fourth image having the first luminance dynamic range;

the fourth image having a higher precision than the first image;

wherein the mapping function is losslessly invertible in relation to the first luminance dynamic range and color space and the second luminance dynamic range and color space; and

(b) subsequent to the normalizing step (a), converting an input video signal that is represented in a first color space with a first color gamut which is related to the first luminance dynamic range, the input video signal being provided by the fourth image, to a video signal that is represented in a second color space of a second color gamut, wherein the second color space is associated with the second luminance dynamic range, by mapping at least two color-related components of the converted video signal over the second luminance dynamic range using the invertible mapping function.

2. The method as recited in claim 1 wherein the second luminance dynamic range, on an intra-frame basis in relation the video signal, spans or approximates a range of intensity or color that is simultaneously perceivable by the human visual system.

3. The method as recited in claim 1 wherein the first luminance dynamic range spans or approximates a range of intensity or color that is capable of rendering with a low or standard dynamic range monitor or display or with a cathode ray tube (CRT) monitor or display.

4. The method as recited in claim 1 wherein the second color gamut is greater, broader or deeper than the first color gamut.

5. The method as recited in claim 1 wherein one or more of the first color space or the second color space comprises a RGB color space that has three color-related components, wherein the color-related components comprise a red color component, a green color component and a blue color component.

6. The method as recited in claim 5 wherein the mapping step comprises the step of mapping the three color-related components of the converted video signal over the second luminance dynamic range.

7. The method as recited in claim 1 wherein the mapping step comprises the step of performing a global tone mapping operation over the at least two color-related components of the converted input video signal.

8. The method as recited in claim 1, further comprising the step of preserving a saturation level associated with each of the at least two color-related components of the converted input video signal.

9. The method as recited in claim 8 wherein the saturation level preserving step comprises the step of mapping an intensity value associated with the input video signal over the second luminance dynamic range.

10. The method as recited in claim 9 wherein the intensity value is scaled according to a first gain setting.

11. The method as recited in claim 1 wherein the one or more of the converting step (b) comprises the step of concatenating one or more of:

a plurality of matrices;

a plurality of invertible non-linear mappings;

or

a plurality of invertible linear mappings.

12. The method as recited in claim 11 wherein:

a) one or more of;

the invertible non-linear mappings;

or

the invertible linear mappings, each comprise a tone mapping operation;

or

b) the plurality of matrices comprise a three by three array.

13. The method as recited in claim 11 wherein one or more of the invertible non-linear mapping or the linear mapping, upon inversion thereof, comprises an inverse tone mapping operation.

14. The method as recited in claim 13 wherein, prior to performing the mapping step, the method further comprises filtering one or more of the standard dynamic range (SDR) or low dynamic range (LDR) content versions, wherein the filtering of the standard dynamic range (SDR) or low dynamic range (LDR) content version comprises:

removing one or more contouring artifacts that are perceivable in one or more smooth regions of an image of the video content.

15. The method as recited in claim 1 wherein the converted video signal comprises a wide color gamut visual dynamic range (VDR) version of the content, wherein the input video signal comprises a low dynamic range (LDR) or standard dynamic range (SDR) version of the content that has a color gamut that is less than, narrower or shallower, in relation to the high precision or high bit depth or a wide color gamut of the visual dynamic range (VDR), and wherein the mapping step comprises estimating a wide color gamut standard dynamic range (SDR) or low dynamic range (LDR) version of the content.

16. The method as recited in claim 15 wherein the estimating step comprises generating an iterative series of estimations of the wide color gamut standard dynamic range (SDR) or low dynamic range (LDR) version of the content.

17. The method as recited in claim 15 wherein the generating step comprises recursively updating one or more of the wide color gamut standard dynamic range (SDR) or low dynamic range (LDR) version of the content or the mapping, wherein the mapping comprises an inter-layer mapping between the one or more of the wide color gamut visual dynamic range (VDR) version of the content or the standard dynamic range (SDR) or low dynamic range (LDR) version of the content, which that has the narrower color gamut in relation to the wide color gamut of the visual dynamic range (VDR), and the wide color gamut standard dynamic range (SDR) or low dynamic range (LDR) version of the content.

18. A video or computing apparatus, comprising:

at least one processor; and

a non-transitory computer readable storage medium that stores encoded instructions, which when executed with the processor, causes, controls, programs or configures the apparatus to perform, execute or control a method as recited in claim 1.

19. A non-transitory computer readable storage medium product, having stored thereon computer-executable instructions for executing a method with a processor in accordance with claim 1.