Display Management for High Dynamic Range Video

Patent metadata

Field	Value
Publication number	US-2016005153-A1
Application number	US-201514755755-A
Country	US
Kind code	A1
Filing date	Jun 30, 2015
Priority date	Jul 3, 2014
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-quantized (PQ) color space. A non-linear mapping function generates a tone-mapped intensity image in response to the characteristics of the source and target display and a measure of the intensity of the PQ image. After a detail-preservation step which may generate a filtered tone-mapped intensity image, an image-adaptive intensity and saturation adjustment step generates an intensity adjustment factor and a saturation adjustment factor as functions of the measure of intensity and saturation of the PQ image, which together with the filtered tone-mapped intensity image are used to generate the output image. Examples of the functions to compute the intensity and saturation adjustment factors are provided.

First claim

What is claimed is:

1 . A method for the display management of images with a processor, the method comprising:
accessing an input image ( 102 ) in a first color space with a first dynamic range; applying a color transformation step ( 110 ) to the input image to determine a first output image ( 112 ) in a perceptually-quantized (PQ) color space, wherein the color transformation from the first color space to the PQ color space is based at least in part in applying a non-linear perceptual quantizer function to a function of the input image; generating an intensity component ( 324 ) of the first output image ( 112 ); in response to characteristics of a target display, applying a non-linear tone-mapping function ( 320 ) to the intensity (I O ) component of the first output image ( 112 ) to determine a tone-mapped intensity image ( 322 ) for the target display; applying a detail preservation function ( 125 ) to generate a filtered tone-mapped intensity image ( 127 ) in response to the intensity component ( 324 ) of the first output image and the tone-mapped intensity image ( 322 ); generating an intensity adjustment factor (CM) in response to a saturation metric (S) of the first output image; generating a saturation adjustment factor (SM) in response to a function of the intensity component of the first output image ( 324 ); and generating a second output image ( 132 ) in response to the intensity adjustment factor (CM), the saturation adjustment factor (SM), and the filtered tone-mapped intensity image, wherein the second output image has a different dynamic range than the input image.

2 . The method of claim 1 , wherein applying the color transformation step ( 110 ) further comprises:
converting ( 215 ) the input image to the RGB color space to generate an RGB image ( 217 ); removing any non-linear encoding ( 220 ) from the RGB image ( 217 ) to generate a linear RGB image ( 222 ); converting the linear RGB image ( 222 ) into an LMS color image ( 227 ); and applying the non-linear perceptual quantizer (PQ) function to the LMS color image to generate the first output image ( 112 ).

3 . The method of claim 1 , wherein the non-linear tone-mapping function ( 320 ) 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.

4 . The method of claim 3 wherein the characteristics of the source display comprise a minimum brightness value and a maximum brightness value for the source display.

5 . The method of claim 3 , wherein the characteristics of the target display comprise a minimum brightness value and a maximum brightness value for the target display.

6 . The method of claim 3 , wherein the characteristics of the source display are accessed through received source display metadata ( 104 ).

7 . The method of claim 3 , 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.

8 . The method of claim 7 , 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 image ( 102 ).

9 . The method of claim 8 , wherein the gray-value characteristics of the input image ( 102 ) are accessed through content metadata ( 106 ) and comprise a minimum luminance value (Crush), a maximum luminance value (Clip), and an average mid-tone luminance value (Mid).

10 . 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.

11 . The method of claim 1 , wherein applying the detail preservation function further comprises computing:
D=I o −I m , B=F ( D, H ), I mf =I O −B−f E ( D, B ),
where F(D,H) denotes applying to image D a filter with kernel H, I o denotes intensity pixel values of the first output image ( 112 ), I m denotes the tone-mapped intensity image, I mf denotes the filtered tone-mapped intensity image, and f E (D, B) is a function of the D and B values.

12 . The method of claim 11 , wherein, given
E =max(0, min(1, abs ( D−B )* W MSE +(1− W MS ))),
f E ( D, B )= E *( D−B ),
where W MSE and W MS are weighting factors.

13 . The method of claim 11 wherein the kernel H comprises a 5×11 Gaussian filter with standard deviation equal to 2.

14 . The method of claim 11 wherein the kernel H comprises a low-pass filter.

15 . The method of claim 1 , wherein generating the intensity component for a pixel of the first output image, wherein the pixel comprises two or more color components, comprises:
computing a first weighted average of the two or more color components of the pixel; computing the maximum of the two or more color components of the pixel; and computing a second weighted average of the maximum and the first weighted average.

16 . The method of claim 1 , wherein generating the second output image ( 132 ) comprises computing:
S=V IL−I O , V OL =SM*S+I mf −CM,
where, V IL denotes the first output image, I O denotes the intensity component of the first output image, V OL denotes the second output image, CM denotes the intensity adjustment factor, SM denotes the saturation adjustment factor, and I mf denotes the filtered tone-mapped intensity image.

17 . The method of claim 15 , wherein
CM=f c ( S ),
wherein f c ( ) denotes a function of saturation with a quadratic input-output characteristic.

18 . The method of claim 17 , wherein for an input S
f c ( S )=((Σ i ( abs ( Si ))* W c ) 2 )* W TM ,

wherein W C and W TM denote weighting factors and S, denotes a color component of the S value.

19 . The method of claim 16 , wherein for an intensity input I O

SM
=

f
s



Assignees

• Dolby Lab Licensing Corp

Inventors

• Atkins Robin
• Hulyalkar Samir N

Classifications

• 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

• H04N9/67

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

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• G06K9/52

  Physics · mapped topic

• G09G5/10

  Intensity circuits · CPC title