Dynamic range compression method

Patent metadata

Field	Value
Publication number	US-11138703-B2
Application number	US-201816958935-A
Country	US
Kind code	B2
Filing date	Dec 21, 2018
Priority date	Dec 29, 2017
Publication date	Oct 5, 2021
Grant date	Oct 5, 2021

Abstract

Disclosed is a method for processing a video stream including a set of images liable to contain a transition effect, the method including the following steps: detecting a fade-type transition effect within the set of images of the video stream and, where appropriate, calculating minimum and maximum brightnesses LMIN and LMAX for each image of the set of images containing the fade; estimating minimum and maximum brightnesses EMIN and EMAX for all of the images not containing the detected transition effect; determining minimum and maximum brightnesses SMIN and SMAX for a standard dynamic range; calculating minimum and maximum brightnesses TMIN and TMAX depending on the minimum and maximum brightnesses LMIN, LMAX, EMIN, EMAX, SMIN and SMAX calculated and determined beforehand; transmitting the calculated minimum and maximum brightnesses TMIN and TMAX with a view to dynamic range compression.

First claim

The invention claimed is:

1. A method, implemented by computing means, for processing a video stream comprising a set of images, the method comprising:
detecting a fade-type transition effect within the set of images of the video stream to obtain a first subset of images containing the fade-type transition effect;
calculating minimum and maximum brightnesses L MIN and L MAX for each image of the first subset of images containing the fade-type transition effect;
estimating minimum and maximum brightnesses E MIN and E MAX for a second subset of images not containing the detected fade-type transition effect;
determining minimum and maximum brightnesses S MIN and S MAX for a standard dynamic range;
calculating minimum and maximum brightnesses T MIN and T MAX depending on the minimum and maximum brightnesses L MIN , L MAX , E MIN , E MAX , S MIN and S MAX calculated and determined beforehand; and
transmitting the calculated minimum and maximum brightnesses T MIN and T MAX for dynamic range compression.

2. The method according to claim 1 , wherein the estimating the minimum and maximum brightnesses E MIN and E MAX for all of the images is followed by storing these brightnesses E MIN and E MAX in a circular buffer of parametrizable size.

3. The method according to claim 1 , wherein in a case where the fade-type transition effect is not detected within the set of images of the video stream, the method further comprises:
transmitting the calculated minimum and maximum brightnesses L MIN and L MAX for dynamic range compression.

4. The method according to claim 3 , further comprising: storing the calculated minimum and maximum brightnesses L MIN and L MAX in a circular buffer of parametrizable size.

5. The method according to claim 1 , wherein the calculation of the minimum and maximum brightnesses T MIN and T MAX is expressed in the following manner:
T MIN =S MIN +( L MIN −min( E MIN ,L MIN ))*( S MAX −S MIN )/(min(E MAX ,L MAX )−min( E MIN ,L MIN )) and

T MAX =S MIN +( L MAX −min( E MIN ,L MIN ))*( S MAX −S MIN )/(min(E MAX ,L MAX )−min( E MIN ,L MIN )).

6. The method according to claim 1 , wherein the calculation of the minimum and maximum brightnesses T MIN and T MAX is performed in the logarithmic domain.

7. The method according to claim 1 , wherein the estimated brightnesses E MIN and E MAX are transmitted for dynamic range compression.

8. The method according to claim 1 , wherein the minimum and maximum brightnesses E MIN and E MAX are multiplied by inversely proportional safety factors f and 1/f, respectively.

9. A device for processing a video stream comprising a set of images, the device comprising:
a processor configured to perform the following operations:
detecting a fade-type transition effect within the set of images of the video stream to obtain a first subset of images containing the fade-type transition effect;
calculating minimum and maximum brightnesses L MIN and L MAX for each image of the first subset of images containing the detected fade-type transition effect;
estimating minimum and maximum brightnesses E MIN and E MAX for a second subset of images not containing the detected fade-type transition effect;
calculating minimum and maximum brightnesses S MIN and S MAX for a standard dynamic range;
calculating minimum and maximum brightnesses T MIN and T MAX depending on the minimum and maximum brightnesses L MIN , L MAX , E MIN , E MAX , S MIN and S MAX calculated and determined beforehand;
determining a target dynamic range for a local tone mapping operation depending on the calculated minimum and maximum brightnesses T MIN and T MAX ; and
transmitting the calculated minimum and maximum brightnesses T MIN and T MAX for dynamic range compression.

10. The device according to claim 9 , wherein the estimating the minimum and maximum brightnesses E MIN and E MAX for all of the second subset of images is followed by storing these brightnesses E MIN and E MAX in a circular buffer of parametrizable size.

11. The device according to claim 9 , wherein the processor is further configured to perform the following operations: in a case where a fade-type transition effect is not detected within the set of images of the video stream, transmitting the calculated minimum and maximum brightnesses L MIN and L MAX for dynamic range compression.

12. The device according to claim 9 , wherein the calculating the minimum and maximum brightnesses L MIN and L MAX is followed by storing these brightnesses L MIN and L MAX in a circular buffer of parametrizable size.

13. The device according to claim 9 , wherein the calculation of the minimum and maximum brightnesses T MIN and T MAX is expressed in the following manner:
T MIN =S MIN +( L MIN −min( E MIN ,L MIN ))*( S MAX −S MIN )/(min(E MAX ,L MAX )−min( E MIN ,L MIN )) and

T MAX =S MIN +( L MAX −min( E MIN ,L MIN ))*( S MAX −S MIN )/(min(E MAX ,L MAX )−min( E MIN ,L MIN )).

14. The device according to claim 9 , wherein the calculation of the minimum and maximum brightnesses T MIN and T MAX is performed in the logarithmic domain.

15. The device according to claim 9 , wherein the estimated brightnesses E MIN and E MAX are transmitted for dynamic range compression.

16. The device according to claim 9 , wherein the minimum and maximum brightnesses E MIN and E MAX are multiplied by inversely proportional safety factors f and 1/f, respectively.

17. A non-transitory computer-readable medium encoded with executable instructions which, when executed, causes an apparatus comprising a processor operatively coupled with a memory, to perform a method for processing a video stream comprising a set of images, the method comprising:
detecting a fade-type transition effect within the set of images of the video stream to obtain a first subset of images containing the fade-type transition effect;
calculating minimum and maximum brightnesses L MIN and L MAX for each image of the first subset of images containing the fade-type transition effect;
estimating minimum and maximum brightnesses E MIN and E MAX for a second subset of images not containing the detected fade-type transition effect;
determining minimum and maximum brightnesses S MIN and S MAX for a standard dynamic range;
calculating minimum and maximum brightnesses T MIN and T MAX depending on the minimum and maximum brightnesses L MIN , L MAX , E MIN , E MAX , S MIN and S MAX calculated and determined beforehand; and
transmitting the calculated minimum and maximum brightnesses T MIN and T MAX for dynamic range compression.

18. The non-transitory computer-readable medium according to claim 17 , wherein the estimating the minimum and maximum brightnesses E MIN and E MAX for all of the images is followed by storing these brightnesses E MIN and E MAX in a circular buffer of parametrizable size.

19. The non-transitory computer-readable medium according to claim 17 , wherein the processor is further configured to perform the following operations: in a case where a fade-type transition effect is not detected within the set of images of the video stream, transmitting the calculated minimum and maximum brightnesses L MIN and L MAX for dynamic range compression.

20. The non-transitory computer-readable medium according to claim 17 , wherein the calculating the minimum and maximum brightnesses L MIN and L MAX is fo

Assignees

• Ateme

Inventors

• Guionnet Thomas

Classifications

• G06T5/50

  using two or more images, e.g. averaging or subtraction · CPC title

• G06T2207/10016

  Video; Image sequence · CPC title

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• G06T2207/20008

  Globally adaptive · CPC title

• G06T5/009 Primary

  Physics · mapped topic