Display Management for High Dynamic Range Video

Patent metadata

Field	Value
Publication number	US-2016005349-A1
Application number	US-201414767249-A
Country	US
Kind code	A1
Filing date	Feb 13, 2014
Priority date	Feb 21, 2013
Publication date	Jan 7, 2016
Grant date	—

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

I claim:

1 - 25 . (canceled)

26 . A method for the display management of images with a processor, the method comprising:
accessing an input image in a first color space with a first enhanced dynamic range (EDR); applying a color transformation step to the input image to determine a first output image ( 112 ) in a perceptually-corrected IPT color space (IPT-PQ), wherein the color transformation from the first color space to the IPT-PQ space is based at least in part in applying a non-linear perceptual quantizer (PQ) function to a function of the input image; applying a non-linear tone-mapping function to an intensity (I) component of the first output image to determine an intensity component of a first tone-mapped image with a second dynamic range, the second dynamic range being different than the first dynamic range; applying a detail preservation function 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; applying a saturation adjustment function to color (P, T) components of the second output image to generate color components of a second tone-mapped image, wherein the saturation adjustment function 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 applying a color gamut mapping function to the second tone-mapped image to generate a third output image.

27 . The method of claim 26 , wherein the first color space comprises the RGB color space and applying the color transformation step further comprises:
removing any non-linear encoding from the input signal to generate a liner RGB signal; converting the linear RGB signal into an LMS color signal; and applying the non-linear perceptual quantizer (PQ) function and a transformation matrix to the LMS color signal to generate an IPT-PQ color space signal.

28 . The method of claim 27 , 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 by applying the function
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.

29 . The method of claim 26 , wherein the non-linear tone-mapping function is expressed as a parameterized sigmoidal tone curve function, wherein parameters of the function are determined based on characteristics of a source display and a target display.

30 . The method of claim 29 wherein the characteristics of the source display comprise a minimum brightness value and a maximum brightness value for the source display.

31 . The method of claim 29 , wherein the characteristics of the target display comprise a minimum brightness value and a maximum brightness value for the target display.

32 . The method of claim 29 , wherein the characteristics of the source display are accessed through received source display metadata.

33 . The method of claim 29 , 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 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.

34 . The method of claim 33 , 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 the input signal.

35 . The method of claim 34 , 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).

36 . The method of claim 33 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.

37 . The method of claim 26 , wherein applying the sharpening function further comprises computing
I S =I n −F ( I n −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.

38 . The method of claim 37 wherein the kernel H comprises an 11×11 Gaussian filter with standard deviation equal to 2.

39 . The method of claim 37 wherein the kernel H comprises a low-pass filter.

40 . The method of claim 39 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.

41 . The method of claim 26 , wherein applying the saturation adjustment function comprises scaling color components of the first output signal by a scaling constant which is determined in response to intensity pixel values of the first output image and intensity pixel values of either the second output image or the first tone-mapped image.

42 . The method of claim 41 , wherein computing the scaling constant (S) comprises computing

S
=

I
S

*
CEDR

I
o

*
CMapped

where CEDR is variable determined as a linear function of the intensity (I o ) of the first output signal and CMapped is a variable determined as a linear function of the intensity (I S ) of the second output signal.

43 . The method of claim 29 wherein the tone curve parameters of the non-linear tone-mapping function are adjusted to boost the intensity of the luminance of the first tone-mapped image.

Assignees

• Dolby Lab Licensing Corp

Inventors

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

Classifications

• G06T5/20 Primary

  using local operators · CPC title

• G06T2207/10024

  Color image · CPC title

• G06T7/13

  Edge detection · CPC title

• G09G3/2003 Primary

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

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title