HDR tone mapping methods with scene adaptive parameterized tone map function
A method includes receiving a quantized video having a first maximum luminance level or brightness associated with a mastering display with which the quantized video was mastered. The method also includes de-quantizing the quantized video in order to generate a de-quantized video. The method further includes applying a scene-adaptive tone mapping function to the de-quantized video in order to generate a tone mapped video. In addition, the method includes displaying the tone mapped video on a target display. The tone mapped video has a second maximum luminance level or brightness associated with the target display, and the second maximum luminance level or brightness is less than the first maximum luminance level or brightness.
1. A method comprising:
receiving a quantized video having a first maximum luminance level or brightness associated with a mastering display with which the quantized video was mastered;
de-quantizing the quantized video in order to generate a de-quantized video;
applying a scene-adaptive tone mapping function to the de-quantized video in order to generate a tone mapped video, wherein applying the scene-adaptive tone mapping function comprises:
determining a distribution of luminance values of one or more image frames based on multiple bins, each bin corresponding to a range of luminance values, the distribution comprising multiple distribution ratio values, each distribution ratio value associated with a different one of the bins and involving the luminance values within the associated bin; and
determining multiple control points of the scene-adaptive tone mapping function based on the distribution of luminance values, each control point associated with a different one of the distribution ratio values; and
displaying the tone mapped video on a target display;
wherein the tone mapped video has a second maximum luminance level or brightness associated with the target display, the second maximum luminance level or brightness less than the first maximum luminance level or brightness.
2. The method of claim 1 , further comprising:
obtaining metadata associated with the quantized video, the metadata identifying the first maximum luminance level or brightness.
3. The method of claim 1 , wherein:
the scene-adaptive tone mapping function is associated with a Bezier curve; and
a number of the control points is associated with an order of the Bezier curve.
4. The method of claim 1 , wherein each of the distribution ratio values is determined by:
r
i
=
H
i
∑
k
=
1
N
-
1
H
k
,
where r represents the distribution of luminance values and H represents the bins.
5. The method of claim 1 , wherein the tone mapping function is expressed by:
y
=
∑
k
=
0
N
(
N
k
)
x
k
(
1
-
x
)
N
-
k
P
k
,
where N represents an order of a Bezier curve, x represents an input value for a pixel, P represents a control point, and y represents an output value for the pixel.
6. The method of claim 1 , further comprising:
displaying a user interface configured to receive at least one user input, the at least one user input defining the control points of the tone mapping function.
7. The method of claim 6 , wherein:
the at least one user input comprises coordinates to adjust a specified one of the control points of the tone mapping function; and
the method further comprises adjusting the tone mapping function based on the coordinates of the specified control point.
8. An apparatus comprising:
at least one processing device configured to:
receive a quantized video having a first maximum luminance level or brightness associated with a mastering display with which the quantized video was mastered;
de-quantize the quantized video in order to generate a de-quantized video;
apply a scene-adaptive tone mapping function to the de-quantized video in order to generate a tone mapped video, wherein, to apply the scene-adaptive tone mapping function, the at least one processing device is configured to:
determine a distribution of luminance values of one or more image frames based on multiple bins, each bin corresponding to a range of luminance values, the distribution comprising multiple distribution ratio values, each distribution ratio value associated with a different one of the bins and involving the luminance values within the associated bin; and
determine multiple control points of the scene-adaptive tone mapping function based on the distribution of luminance values, each control point associated with a different one of the distribution ratio values; and
initiate display of the tone mapped video on a target display;
wherein the tone mapped video has a second maximum luminance level or brightness associated with the target display, the second maximum luminance level or brightness less than the first maximum luminance level or brightness.
9. The apparatus of claim 8 , wherein the at least one processing device is further configured to obtain metadata associated with the quantized video, the metadata identifying the first maximum luminance level or brightness.
10. The apparatus of claim 8 , wherein:
the scene-adaptive tone mapping function is associated with a Bezier curve; and
a number of the control points is associated with an order of the Bezier curve.
11. The apparatus of claim 8 , wherein each of the distribution ratio values is determined by:
r
i
=
H
i
∑
k
=
1
N
-
1
H
k
,
where r represents the distribution of luminance values and H represents the bins.
12. The apparatus of claim 8 , wherein the tone mapping function is expressed by:
y
=
∑
k
=
0
N
(
N
k
)
x
k
(
1
-
x
)
N
-
k
P
k
,
where N represents an order of a Bezier curve, x represents an input value for a pixel, P represents a control point, and y represents an output value for the pixel.
13. The apparatus of claim 8 , wherein:
the at least one processing device is further configured to initiate display of a user interface; and
the user interface is configured to receive at least one user input defining the control points of the tone mapping function.
14. The apparatus of claim 13 , wherein:
the at least one user input comprises coordinates to adjust a specified one of the control points of the tone mapping function; and
the at least one processing device is further configured to adjust the tone mapping function based on the coordinates of the specified control point.
15. A non-transitory computer readable medium comprising program code that when executed causes at least one processor to:
receive a quantized video having a first maximum luminance level or brightness associated with a mastering display with which the quantized video was mastered;
de-quantize the quantized video in order to generate a de-quantized video;
apply a scene-adaptive tone mapping function to the de-quantized video in order to generate a tone mapped video, wherein the program code that when executed causes the at least one processor to apply the scene-adaptive tone mapping function comprises program code that when executed causes the at least one processor to:
determine a distribution of luminance values of one or more image frames based on multiple bins, each bin corresponding to a range of luminance values, the distribution comprising multiple distribution ratio values, each distribution ratio value associated with a different one of the bins and involving the luminance values within the associated bin; and
determine multiple control points of the scene-adaptive tone mapping function based on the distribution of luminance values, each control point associated with a different one of the distribution ratio values; and
initiate display of the tone mapped video on a target display;
wherein the tone mapped video has a second maximum luminance level or brightness associated with the target display, the second maximum luminance level or brightness less than the first maximum luminance level or brightness.
16. The non-transitory computer readable medium of claim 15 , further comprising program code that when executed causes the at least one processor to obtain metadata associated with the quantized video, the metadata identifying the first maximum luminance level or brightness.
17. The non-transitory computer readable medium of claim 15 , wherein:
the scene-adaptive tone mapping function is associated with a Bezier curve; and
a number of the control points is associated with an order of the Bezier curve.
18. The non-transitory computer readable medium of claim 15 , wherein each of the distribution ratio values is determined by:
r
i
=
H
i
∑
k
=
1
N
-
1
H
k
,
where r represents the distribution of luminance values and H represents the bins.
19. The non-transitory computer readable medium of claim 15 , wherein the tone mapping function is expressed by:
y
=
∑
k
=
0
N
(
N
k
)
x
k
(
1
-
x
)
N
-
k
P
k
,
where N represents an order of a Bezier curve, x represents an input value for a pixel, P represents a control point, and y represents an output value for the pixel.
20. The non-transitory computer readable medium of claim 15 , further comprising program code that when executed causes the at least one processor to:
initiate display of a user interface that is configured to receive at least one user input, the at least one user input comprising coordinates to adjust a specified one of the control points of the tone mapping function; and
adjust the tone mapping function based on the coordinates of the specified control point.