Extending image dynamic range

Patent metadata

Field	Value
Publication number	US-10158835-B2
Application number	US-201615000782-A
Country	US
Kind code	B2
Filing date	Jan 19, 2016
Priority date	Aug 25, 2010
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

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.

First claim

What is claimed is:

1. A method to encode a video signal, the method comprising:
receiving an input video signal in a first content version in a first dynamic range and a second content version in a second dynamic range, wherein the first dynamic range is higher than the second dynamic range;
applying a normalization process to the first content version and the second content version to generate a third content version, a fourth content version, and an invertible mapping function between the third and the fourth content versions, wherein the third content version represents a modified version of the first content version and the fourth content version represents a modified content version of the second content version, wherein applying the normalization process comprises:
accessing a first image and a second image, wherein for a scene in the input video signal, the first image and the second image are corresponding representations of the scene in the first content version and the second content version;
initializing a third image in the third content version using the first image;
initializing a fourth image in the fourth content version using the second image;
generating an estimated invertible mapping function between the third image and the fourth image;
evaluating the accuracy of the invertible mapping function; and

if the evaluation step does not meet a certain criterion, modifying the mapping function and at least one of the third image and the fourth image; and

generating an output coded bit stream based on a coded representation of the fourth content version and the invertible mapping function.

2. The method of claim 1 wherein the first content version comprises a visual dynamic range (VDR) representation of the input signal and the second content version comprises a low dynamic range (LDR) representation of the input signal.

3. The method of claim 1 wherein the fourth content version has a higher precision bit depth than the second content version.

4. The method of claim 1 , wherein generating the output coded bit stream comprises coding the fourth content version and the invertible mapping function to generate a bit stream and related metadata compliant with the H.264 video coding standard.

5. The method of claim 1 wherein the third content version is visually indistinguishable from the first content version.

6. The method of claim one, wherein given a mapping function M[ ] and its inverse M −1 [ ]:
VDR′= M −1 [SDR′] and SDR′= M [VDR′],

wherein VDR′ denotes the third coded version of the input video signal and SDR′ denotes the fourth coded version of the input video signal.

7. The method of claim 1 , wherein the normalization process operates on at least two color components of the first image and the second image.

8. The method of claim 1 wherein the estimated invertible mapping function conforms to an S-shaped polynomial curve.

9. The method of claim 1 , further comprising:
in a decoder, receiving the output coded bit stream;
extracting the invertible mapping function and generating a decoded signal based on the coded representation of the fourth content version;
generating a fifth signal based on the decoded signal, wherein the fifth signal represents a decoded version of the input signal in the second dynamic range; and
generating a sixth signal based on the decoded signal and the invertible mapping function, wherein the sixth signal represents a decoded version of the input signal in the first dynamic range.

10. The method of claim 9 , wherein given a mapping function M[ ] and its inverse M −1 [ ]:
VDR′= M −1 [SDR′],

wherein VDR′ denotes the sixth signal and SDR′ denotes the decoded signal.

11. A system comprising an encoder and a decoder and means for performing any of the processing steps recited in claim 1 .

12. A non-transitory computer-readable storage medium having stored thereon computer-executable instructions for executing a method with a processor according to the method of claim 1 .

Assignees

• Dolby Laboratories Licensing Corp

Inventors

• Gish Walter
• Li Zhen
• Pian Donald
• Vogt Christopher J
• Kim Hyung-Suk
• Ruhoff David

Classifications

• H04N9/67 Primary

  for matrixing (camera processing pipelines for matrixing of colour signals H04N23/85) · CPC title

• G09G2320/0271

  Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping · CPC title

• G06F3/1423

  controlling a plurality of local displays, e.g. CRT and flat panel display · CPC title

• H04N9/68

  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) · CPC title

• G09G5/02

  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 title