Methods and apparatus for motion-based video tonal stabilization

Patent metadata

Field	Value
Publication number	US-2017374334-A1
Application number	US-201615543350-A
Country	US
Kind code	A1
Filing date	Jan 15, 2016
Priority date	Jan 15, 2015
Publication date	Dec 28, 2017
Grant date	—

Abstract

One general aspect for motion-based video tonal stabilization uses a keyframe and motion estimation techniques to determine the level of spatial correspondence between input images and the keyframe. When the level of spatial correspondence is high, tonal stabilization is performed through regression and power law tonal transformation to minimize the color differences between images caused by automatic camera parameters without a priori knowledge of the camera model. Tonal error accumulation is reduced by using long-term tonal propagation.

First claim

1 - 8 . (canceled)

9 . A method for correcting color and/or brightness instabilities of a sequence of images, said method comprising correcting color and/or brightness instabilities of at least one first image of said sequence according to a reference image, said reference image being determined between images of said sequence according to a number of motion based correspondences between said first image and said reference image.

10 . The method of claim 9 , wherein said reference image is a reference image previously used for correcting a second image of said sequence when said number of motion based correspondences is less than a first value.

11 . The method of claim 10 , wherein said second image is the last previously corrected image of said sequence.

12 . The method of claim 9 , wherein said reference image is different from another reference image previously used for correcting a third image of said sequence when said number of motion based correspondences is greater than a second value.

13 . The method of claim 12 , wherein said reference image is the last previously corrected image of said sequence.

14 . The method of claim 9 , wherein said method comprises determining said number of motion based correspondences, said determining comprising:
performing motion estimation between said first image and said reference image; warping said first image to align with said reference image; and discarding values higher than a third value on a difference map regarding said aligned first and reference images.

15 . The method of claim 14 , wherein correcting color and/or brightness instabilities comprises:
generating pairs of spatially corresponding points between said image and said reference image based on said difference map; and performing, on said first image, a transformation based on a color mapping regression over said pairs of spatially corresponding points.

16 . The method of claim 15 , wherein said transformation comprises a power law tonal transformation.

17 . The method of claim 15 , wherein said transformation uses a six-parameters color transformation model.

18 . An apparatus adapted for correcting color and/or brightness instabilities of a sequence of images, said apparatus comprising a processing circuitry adapted for correcting color and/or brightness instabilities of at least one first image of said sequence according to a reference image, said reference image being determined between images of said sequence according to a number of motion based correspondences between said first image and said reference image.

19 . The apparatus of claim 18 , wherein said reference image is a reference image previously used for correcting a second image of said sequence when said number of motion based correspondences is less than a first value.

20 . The apparatus of 19 , wherein said second image is the last previously corrected image of said sequence.

21 . The apparatus of claim 18 , wherein said reference image is a reference image different from previously used for correcting a third image of said sequence when said number of motion based correspondences is greater than a second value.

22 . The apparatus of claim 18 , wherein said apparatus comprises a motion estimator adapted to determine said number of motion based correspondences.

23 . The apparatus of claim 18 , wherein said processing circuitry is adapted for determining said number of motion based correspondences, said determining comprising:
performing motion estimation between said first image and said reference image; warping said first image to align with said reference image; and discarding values higher than a third value on a difference map of said aligned first and reference images.

24 . The apparatus of claim 18 , wherein said apparatus comprises an image processor adapted to align said first image and said reference image.

25 . The apparatus of claim 24 , wherein said apparatus comprises a comparator adapted to operate on said difference map to discard values higher than said third value.

26 . The apparatus of claim 18 , wherein correcting color and/or brightness instabilities comprises:
generating pairs of spatially corresponding points between said image and said reference image based on said difference map; and performing, on said first image, a transformation based on a color mapping regression over said pairs of spatially corresponding points.

27 . A computer readable storage medium having stored thereon computer program comprising program code instructions for executing a method for correcting color and/or brightness instabilities of a sequence of images, said method comprising correcting color and/or brightness instabilities of at least one first image of said sequence according to a reference image, said reference image being determined between images of said sequence according to a number of motion based correspondences between said first image and said reference image.

28 . A non-transitory computer readable program storage product comprising program code instructions for executing, when said program is executed by a computer, the method according to claim 9 .

Assignees

• Thomson Licensing

Inventors

• Frigo Oriel
• Sabater Neus
• Hellier Pierre
• Delon Julie

Classifications

• H04N5/145 Primary

  Movement estimation (for video coding H04N19/51) · CPC title

• H04N23/73

  by influencing the exposure time · CPC title

• H04N23/6811

  based on the image signal · CPC title

• H04N23/81

  for suppressing or minimising disturbance in the image signal generation · CPC title

• H04N23/76

  by influencing the image signals · CPC title