Adaptive coring for video peaking

• US 20050012866A1
• Filed: 05/20/2004
• Published: 01/20/2005
• Est. Priority Date: 05/21/2003
• Status: Active Grant

• Current Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Chiang, Patricia Wei Yin, Hui, Lucas Y.W.
• Granted Patent: US 7,176,983 B2
• Time in Patent Office: Days
• US Class Current: 348/625
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/003 Deblurring; Sharpening vibration or motion blur correction for cameras comprising an electronic image sensor H04N23/682
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/73 Deblurring; Sharpening
• CPC Class Codes: G06T 7/13 Edge detection
• CPC Class Codes: H04N 5/142 Edging; Contouring
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
• CPC Class Codes: H04N 9/77 Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase circuits for matrixing H04N9/67

Abstract

A processor for enhancing an input luminance signal including: a means for calculating a chroma edge value associated with the input luminance signal; a means for measuring a luminance gradient associated with the input luminance signal; a peaking filter for processing the input luminance signal; a gain adjustment circuit having a gain function that is adjustable relative to the calculated chroma edge value, the gain adjustment circuit being operable to adjust the magnitude of the output of the peaking filter wherein: in a first range of luminance gradients, the output is an attenuated version of the input; in a second range of luminance gradients the output is directly proportional to the input; in a third range of luminance gradients, the output is inversely proportional to the input; wherein said enhanced luminance signal is the sum of the input and output of the peaking filter.

Claims

1. A processor for enhancing an input luminance signal including:

a means for calculating a chroma edge value associated with the input luminance signal;

a means for measuring a luminance gradient associated with the input luminance signal;

a peaking filter that receives as an input the input luminance signal and is structured to process the input luminance signal to produce an output;

a gain adjustment circuit having a gain function that is adjustable relative to the calculated chroma edge value, the gain adjustment circuit being operable to adjust the magnitude of the output of the peaking filter wherein;

in a first range of luminance gradients, the output is an attenuated version of the input;

in a second range of luminance gradients the output is directly proportional to the input;

in a third range of luminance gradients, the output is inversely proportional to the input;

wherein said enhanced luminance signal is the sum of the input and output of the peaking filter.

2. A processor as claimed in claim 1 wherein the input luminance signal represents an inter-pixel array for display.

3. A processor as claimed in claim 2 wherein the luminance gradient corresponds to the difference between a maximum and a minimum pixel luminance within the inter-pixel array.

4. A processor as claimed in claim 2, including a means for measuring an average luminance of pixels within the inter-pixel array, wherein, the gain function of the gain adjustment circuit is adjustable relative to the measured average luminance.

5. A processor as claimed in claim 4 wherein the gain function of the gain adjustment circuit is adjustable relative to the measured average luminance, whereby the first range of luminance gradients attenuated by the gain function increases relative to a decrease in the measured average luminance.

6. A processor as claimed in claim 1 wherein the means for calculating the chroma edge value includes a means for calculating the sum of chroma gradients of a first and a second chroma signal associated with the input luminance signal.

7. A processor as claimed in claim 1 wherein the means for calculating the chroma edge value includes an edge detector.

8. A processor as claimed in claim 7 wherein the edge detector includes a pair of Sobel detectors.

9. A processor as claimed in claim 1 wherein the luminance gradients within the first range are smaller than the luminance gradients within the second range, and, the luminance gradients within the second range are smaller than the luminance gradients within the third range.

10. A processor as claimed in claim 1 wherein the gain function of the gain adjustment circuit is further adjustable such that, in a fourth range of luminance gradients, the output of the peaked filter is amplified by a constant value.

11. A processor as claimed in claim 10 wherein the luminance gradients within the fourth range of the luminance gradients are smaller than the luminance gradients within the third range, and, are larger than the luminance gradients within the second range.

12. A processor as claimed in claim 10 wherein the constant value is 1.0.

13. A processor as claimed in claim 1, including a means for measuring a noise value associated with the input luminance signal wherein, the gain function of the gain adjustment circuit is adjustable relative to the calculated noise value.

14. A processor as claimed in claim 13 wherein the means for measuring the noise value includes means for calculating the sum-of-absolute differences in luminance between adjacent pixels in the inter-pixel array.

15. A processor as claimed in claim 14 wherein absolute differences in luminance between adjacent pixels which are greater than, or equal to, a predetermined threshold value are not included in the calculation of the noise value.

16. A processor as claimed in claim 1 wherein the peaking filter includes a horizontal peaking filter for filtering a horizontal component of the input luminance signal.

17. A processor as claimed in claim 1 wherein the peaking filter includes a vertical peaking filter for filtering a vertical component of the input luminance signal.

18. A processor as claimed in claim 1 wherein the peaking filter includes a two-dimensional peaking filter a horizontal and a vertical component of the input luminance signal.

19. A processor as claimed in claim 1 wherein the output of the gain adjustment circuit may be amplified by a user-defined gain value.

20. A processor for enhancing an input luminance signal, including:

a means for calculating a noise value associated with the input luminance signal;

a means for measuring a luminance gradient associated with the input luminance signal;

a peaking filter that receives as an input the input luminance signal and is structured to process the input luminance signal to produce an output;

a gain adjustment circuit having a gain function that is adjustable relative to the calculated noise value, the gain adjustment circuit being operable to adjust the magnitude of the output of the peaking filter wherein;

in a first range of luminance gradients, the output is an attenuated version of the input;

in a second range of luminance gradients the output is directly proportional to the input;

in a third range of luminance gradients, the output is inversely proportional to the input;

wherein said enhanced luminance signal is the sum of the input and output of the peaking filter.

21. A processor as claimed in claim 20 wherein the input luminance signal represents an inter-pixel array for display.

22. A processor as claimed in claim 21 wherein the means for calculating the noise value includes a means for measuring a sum-of-absolute differences in luminances between pixels in the inter-pixel array.

23. A processor as claimed in claim 21 wherein absolute differences in luminance between pixels which are equal to, or greater than, a predetermined threshold are excluded from the calculation of the noise value.

24. A processor as claimed in claim 21 wherein the luminance gradient corresponds to the difference between a maximum and a minimum pixel luminance within the inter-pixel array.

25. A processor as claimed in claim 21, including a means for measuring an average luminance of pixels within the inter-pixel array, wherein, the gain function of the gain adjustment circuit is adjustable relative to the measured average luminance.

26. A processor as claimed in claim 25 wherein the first range of luminance gradients attenuated by the gain function increases relative to a decrease in the measured average luminance.

27. A processor as claimed in claim 20, including a means for measuring a chroma edge value associated with the input luminance signal, wherein, the gain function of the gain adjustment circuit is adjustable relative to the calculated chroma edge value.

28. A processor as claimed in claim 27 wherein the means for calculating the chroma edge value includes a means for measuring the sum of gradients of a first and a second chroma signal associated with the input luminance signal.

29. A processor as claimed in claim 20 wherein the means for calculating the chroma edge value includes an edge detector.

30. A processor as claimed in claim 29 wherein the edge detector includes a pair of Sobel detectors.

31. A processor as claimed in claim 20 wherein the luminance gradients within the first range are smaller than the luminance gradients within the second range, and, the luminance gradients within the second range are smaller than the luminance gradients within the third range.

32. A processor as claimed in claim 20 wherein the gain function of the gain adjustment circuit is further adjustable such that, in a fourth range of luminance gradients, the output of the peaked filter is amplified by a constant amplitude.

33. A processor as claimed in claim 32 wherein the constant value is 1.0.

34. A processor as claimed in claim 20 wherein the peaking filter includes a horizontal peaking filter for filtering a horizontal component of the input luminance signal.

35. A processor as claimed in claim 20 wherein the peaking filter includes a vertical peaking filter for filtering a vertical component of the input luminance signal.

36. A processor as claimed in claim 20 wherein the peaking filter includes a two-dimensional peaking filter for filtering a horizontal and a vertical component of the input luminance signal.

37. A processor as claimed in claim 20 wherein the output of the gain adjustment circuit may be amplified by a user-defined gain value.

38. A method of enhancing an input luminance signal including the steps of:

calculating a chroma edge value associated with the input luminance signal;

measuring a luminance gradient associated with the input luminance signal;

filtering the input luminance signal with a peaking filter;

adjusting a gain function of a gain adjustment circuit relative to the calculated chroma edge value, the gain adjustment circuit being operable to adjust the magnitude of an output of the peaking filter wherein;

in a first range of luminance gradients, the output is an attenuated version of an input of the peaking filter;

in a second range of luminance gradients the output is directly proportional to the input;

in a third range of luminance gradients, the output is inversely proportional to the input;

wherein said enhanced luminance signal is the sum of the input and output of the peaking filter.

39. A method as claimed in claim 38 wherein the input luminance signal represents an inter-pixel array for display.

40. A method as claimed in claim 39 wherein the luminance gradient corresponds to the difference between a maximum and a minimum pixel luminance within the inter-pixel array.

41. A method as claimed in claim 39, including the step of measuring an average luminance of pixels within the inter-pixel array, wherein, the gain function of the gain adjustment circuit is adjustable relative to the measured average luminance.

42. A method as claimed in claim 51 wherein the gain function of the gain adjustment circuit is adjustable relative to the measured average luminance, whereby the first range of luminance gradients attenuated by the gain function increases relative to a decrease in the measured average luminance.

43. A method as claimed in claim 38 wherein the step of calculating the chroma edge value includes calculating the sum of chroma gradients of a first and a second chroma signal associated with the input luminance signal.

44. A method as claimed in claim 38 wherein the step of calculating the chroma edge value includes using an edge detector.

45. A method as claimed in claim 44 wherein the edge detector includes a pair of Sobel detectors.

46. A method as claimed in claim 38 wherein the luminance gradients within the first range are smaller than the luminance gradients within the second range, and, the luminance gradients within the second range are smaller than the luminance gradients within the third range.

47. A method as claimed in claim 38 wherein the gain adjustment circuit is further adjustable such that, in a fourth range of luminance gradients, the output of the peaked filter is amplified by a constant value.

48. A method as claimed in claim 47 wherein luminance gradients within the fourth range of luminance gradients are smaller than luminance gradients within the third range, and, are larger than the luminance gradients within the second range.

49. A method as claimed in claim 47 wherein the constant value is 1.0.

50. A method as claimed in claim 38 including the step of measuring a noise value associated with the input luminance signal wherein, the gain function is adjustable relative to the calculated noise value.

51. A method as claimed in claim 50 wherein the step of measuring the noise value includes calculating the sum-of-absolute differences in luminance between adjacent pixels in the inter-pixel array.

52. A method as claimed in claim 51 wherein absolute differences in luminance between adjacent pixels which are equal to, or greater than, a predetermined threshold value are excluded from the calculation of the noise value.

53. A method as claimed in claim 38 wherein the peaking filter includes a horizontal peaking filter for filtering a horizontal component of the input luminance signal.

54. A method as claimed in claim 38 wherein the peaking filter includes a vertical peaking filter for filtering a vertical component of the input luminance signal.

55. A method as claimed in claim 38 wherein the peaking filter includes a two-dimensional peaking filter for filtering a horizontal and a vertical component of the input luminance signal.

56. A method as claimed in claim 38 wherein the output of the gain adjustment circuit may be amplified by a user-defined gain value.

57. A method of enhancing an input luminance signal, including the steps of:

calculating a noise value associated with the input luminance signal;

measuring a luminance gradient associated with the input luminance signal;

filtering the input luminance signal with a peaking filter to produce an output;

adjusting a gain function of a gain adjustment circuit relative to the calculated noise value, the gain adjustment circuit being operable to adjust the magnitude of the output of the peaking filter wherein;

in a first range of luminance gradients, the output is an attenuated version of the input;

in a second range of luminance gradients the output is directly proportional to the input;

in a third range of luminance gradients, the output is inversely proportional to the input;

wherein said enhanced luminance signal is the sum of the input and output of the peaking filter.

58. A method as claimed in claim 57 wherein the input luminance signal represents an inter-pixel array for display.

59. A method as claimed in claim 58 wherein the step of calculating the noise value includes measuring a sum-of-absolute differences in luminances between pixels in the inter-pixel array.

60. A method as claimed in claim 58 wherein absolute differences in luminance between pixels which fall below a predetermined threshold are excluded from the calculation of the noise value.

61. A method as claimed in claim 58 including the step of measuring an average luminance of pixels within the inter-pixel array, wherein, the gain function of the gain adjustment circuit is adjustable relative to the measured average luminance.

62. A method as claimed in claim 61 wherein, the first range of luminance gradients attenuated by the gain function increases relative to a decrease in the measured average luminance.

63. A method as claimed in claim 57 including the step of calculating a chroma edge value associated with the input luminance signal, wherein, the gain function of the gain adjustment circuit is adjustable relative to the calculated chroma edge value

64. A method as claimed in claim 63 wherein the step of calculating the chroma edge value includes calculating the sum of gradients of a first and a second chroma signal associated with the input luminance signal.

65. A method as claimed in claim 57 wherein the step of calculating the chroma edge value includes using an edge detector.

66. A method as claimed in claim 65 wherein the edge detector includes a pair of Sobel detectors.

67. A method as claimed in claim 57 wherein the luminance gradient corresponds to the difference between a maximum and a minimum pixel luminance within the inter-pixel array.

68. A method as claimed in claim 57 wherein the luminance gradients within the first range are smaller than the luminance gradients within the second range, and, the luminance gradients within the second range are smaller than the luminance gradients within the third range.

69. A method as claimed in claim 57 wherein the gain function of the gain adjustment circuit is further adjustable such that, in a fourth range of luminance gradients, the output of the peaked filter is amplified by a constant amplitude.

70. A method as claimed in claim 69 wherein the constant value is 1.0.

71. A method as claimed in claim 57 wherein the peaking filter includes a horizontal peaking filter for filtering a horizontal component of the input luminance signal.

72. A method as claimed in claim 57 wherein the peaking filter includes a vertical peaking filter for filtering a vertical component of the input luminance signal.

73. A processor as claimed in claim 57 wherein the peaking filter includes a two-dimensional peaking filter for filtering a vertical and a horizontal component of the input luminance signal.

74. A method as claimed in claim 57 wherein the output of the gain adjustment circuit may be amplified by a user-defined gain value.