Display management for high dynamic range video

Patent metadata

Field	Value
Publication number	US-10540920-B2
Application number	US-201414767249-A
Country	US
Kind code	B2
Filing date	Feb 13, 2014
Priority date	Feb 21, 2013
Publication date	Jan 21, 2020
Grant date	Jan 21, 2020

Abstract

A display management processor receives an input image with enhanced dynamic range to be displayed on a target display which has a different dynamic range than a reference display. The input image is first transformed into a perceptually-corrected IPT color space. A non-linear mapping function generates a first tone-mapped signal by mapping the intensity of the input signal from the reference dynamic range into the target dynamic range. The intensity (I) component of the first tone-mapped signal is sharpened to preserve details, and the saturation of the color (P and T) components is adjusted to generate a second tone-mapped output image. A color gamut mapping function is applied to the second tone-mapped output image to generate an image suitable for display onto the target display. The display management pipeline may also be adapted to adjust the intensity and color components of the displayed image according to specially defined display modes.

First claim

What is claimed is:

1. A method for the display management of images with one or more computer processors, the method comprising:
accessing an input image in a first color space with a first enhanced dynamic range (EDR) of a source display device;
performing a color transformation operation on the input image to generate a first output image ( 112 ) in a perceptually-corrected IPT color space (IPT-PQ), wherein the color transformation operation transforming the input image from the first color space to the IPT-PQ space is based at least in part on applying non-linear perceptual quantization (PQ) to the input image;
performing a non-linear tone-mapping operation on an intensity (I) component of the first output image to generate an intensity component of a first tone-mapped image with a second dynamic range of a target display device, the second dynamic range of the target display device being different than the first dynamic range of the source display device;
performing a detail preservation operation to generate an intensity component of a second output image in response to the intensity components of the first output image and the first tone-mapped image;
performing a saturation adjustment operation on color (P, T) components of the second output image to generate color components of a second tone-mapped image, wherein the saturation adjustment operation is determined by the intensity component of the first output image and the intensity component of either the second output image or the first tone-mapped image; and
performing a color gamut mapping operation on the second tone-mapped image to generate a third output image;
causing a display mapped image generated from the third output image to be rendered on the target display device;
wherein performing the detail preservation operation further comprises computing
I S =I o −F (( I o −I m ), H ),

where F(I,H) denotes applying to an image I a filter with kernel H, I o denotes intensity pixel values of the first output image, I m denotes intensity pixel values of the first tone-mapped output image, and I s denotes intensity pixel values of the second output image.

2. The method of claim 1 , wherein the first color space comprises the RGB color space and performing the color transformation operation further comprises:
removing any non-linear encoding from an input signal to generate a linear RGB signal;
converting the linear RGB signal into an LMS color signal; and
performing the non-linear PQ operation and a transformation operation based on a transformation matrix on the LMS color signal to generate an IPT-PQ color space signal.

3. The method of claim 2 , further comprising adjusting the intensity (I) of the IPT-PQ color signal to generate an adjusted IPT-PQ signal, wherein the adjusting step is performed at least in part based on an intensity adjustment function as follows:
I′ i =I i +d*CH i

where d is a constant, and given I i , P i , and T i values of a pixel of the IPT-PQ color signal, CH i =√{square root over (P i 2 +T i 2 )} and I′ i denotes an intensity value of the adjusted IPT-PQ signal.

4. The method of claim 1 , wherein the non-linear tone-mapping operation is based at least in part on a non-linear tone-mapping function expressed as a parameterized sigmoidal tone curve function, wherein parameters of the non-linear tone-mapping function are determined based on characteristics of a source display and a target display.

5. The method of claim 4 wherein the characteristics of the source display comprise a minimum brightness value and a maximum brightness value for the source display.

6. The method of claim 4 , wherein the characteristics of the target display comprise a minimum brightness value and a maximum brightness value for the target display.

7. The method of claim 4 , wherein the characteristics of the source display are accessed through received source display metadata.

8. The method of claim 4 , wherein the sigmoidal tone function is expressed as

I
m

=

(

C
1

+

C
2

⁢

I
o
n

1
+

C
3

⁢

I
o
n

)

Rolloff

wherein n is an exponential power parameter; C 1 , C 2 , C 3 , and Rolloff are constants defining the parameters of the tone-mapping function, and for an input I o , I m is a corresponding output value.

9. The method of claim 8 , wherein the C 1 , C 2 , and C 3 constants are determined at least in part based on one or more gray-value characteristics of an input signal.

10. The method of claim 9 , wherein the gray-value characteristics of the input signal are accessed through content metadata and comprise a minimum luminance value (Crush), a maximum luminance value (Clip), and an average mid-tone luminance value (Mid).

11. The method of claim 8 wherein the C 1 , C 2 , and C 3 constants are determined at least in part based on one or more intermediate tone curve adjustment parameters.

12. The method of claim 4 wherein the parameters of the non-linear tone-mapping function are adjusted to boost the intensity of the luminance of the first tone-mapped image.

13. The method of claim 12 wherein boosting the intensity of the luminance further comprises:
computing a first set of intermediate adjustment tone curve parameters to determine a mapping range of the non-linear tone-mapping function with no luminance boosting;
scaling the first set of intermediate adjustment tone curve parameters in response to a set of desired intermediate adjustment tone curve parameters;
determining the parameters of the non-linear tone- mapping function based on a second set of intermediate adjustment tone curve parameters;
applying the non-linear tone-mapping function to the intensity of the first output signal to determine an intermediate tone-mapped signal; and
adjusting the intensity of the intermediate tone-mapped signal to determine the first tone-mapped signal.

14. The method of claim 1 wherein the kernel H comprises an 11×11 Gaussian filter with standard deviation equal to 2.

15. The method of claim 1 wherein the kernel H comprises a low-pass filter.

16. The method of claim 15 further comprising:
applying an edge detection filter to the I o −I m signal to derive an edge output image; and
generating the I s signal in response to both the output of the low-pass filter and the edge output image.

17. The method of claim 1 , wherein perfo

Assignees

• Dolby Laboratories Licensing Corp

Inventors

• Atkins Robin
• Kunkel Timo
• Beier Thaddeus
• Chen Tao

Classifications

• G09G2340/06

  Colour space transformation · CPC title

• G06T7/13

  Edge detection · CPC title

• G06T5/20 Primary

  using local operators · CPC title

• G06T2207/10024

  Color image · CPC title

• G09G3/2003 Primary

  Display of colours (specific for liquid crystal displays G09G3/3607) · CPC title