Method and system for detection and enhancement of video images

• US 8,395,708 B2
• Filed: 07/21/2010
• Issued: 03/12/2013
• Est. Priority Date: 07/21/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Lee, Louie, Lachine, Vladimir, Smith, Greg
• Primary Examiner(s): Natnael, Paulos M
• Application Number:
  US12/840,973
• Publication Number:
  US 20110019096A1
• Time in Patent Office: 965 Days
• Field of Search: 348/625, 348/618, 348606-607, 348/558, 348/699, 348/700, 348/673, 348/674, 348/678, 348/687, 348/441, 348/448, 382/274, 382/254, 382/173, 382/167, 382/275, 375/240.01, 375/240.02
• US Class Current: 348/625
• CPC Class Codes: G06T 2207/30168 Image quality inspection
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: H04N 5/205 for correcting amplitude versus frequency characteristic
• CPC Class Codes: H04N 5/208 for compensating for attenuation of high frequency components, e.g. crispening, aperture distortion correction
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
• CPC Class Codes: H04N 7/0145 the interpolation being class adaptive, i.e. it uses the information of class which is determined for a pixel based upon certain characteristics of the neighbouring pixels
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

A method and a system for adaptive image enhancement are provided for measuring the image quality of a pixel region in a frame, performing an image classification based on the image quality measurement, and enhancing image quality by applying operations according to image classification of the region. Also provided is a method as above including the steps of dividing a frame into P pixel regions; and for each one of the pixel regions measuring the image quality; assigning an image quality class; and enhancing the image. Also provided is a system for adaptive image enhancement including a circuit to measure the image quality of a pixel region in a frame in a source video image; a circuit to perform an image classification of the region based on the image quality measurement; and a circuit to enhance the image quality of the region in the source video image a by applying operations based on the image classification of the frame.

Claims

1. A method for adaptive image enhancement, comprising:

measuring an image quality of a pixel region in a frame in a source video;

performing an image classification of the pixel region based on the measured image quality; and

enhancing the image quality of the pixel region by applying operations based on the image classification of the pixel region;

wherein measuring the image quality of the pixel region comprises;

performing a spectral decomposition of the pixel region into one or more spectral bands;

measuring and evaluating a histogram of the spectral bands of the pixel region;

assigning an image quality class to the pixel region; and

adjusting parameters of one or more image enhancement steps selected from the group consisting of a noise reduction step, a signal transition improvement step, an adaptive scaling step, a detail enhancement step, and a contrast enhancement step.

2. The method of claim 1, wherein the pixel region is coextensive with the frame.

3. The method of claim 1, wherein the pixel region is selected from the frame, as any sub-frame contained within the frame, wherein a sub-frame can be any size from a single pixel within the frame to the frame itself.

4. The method of claim 1, wherein performing a spectral decomposition of the pixel region further comprises:

filtering with M spectral band filters for coverage of N spectral bands, where N is a number equal to or greater than 1, and M is equal to or less than N;

segmenting the frame into M sub-frames for filtering by the M spectral band filters;

changing the parameters and measurement histograms of the M spectral band filters for each of the N spectral bands to filter a next image frame until all N spectral bands have been measured;

shifting the spectral band filters sequentially over the sub-frames until each filter has sequenced through all sub-frames in the frame; and

accumulating the histogram of each spectral band for a plurality of frames.

5. The method of claim 1, wherein measuring and evaluating the histogram of the spectral bands comprises using a band measurement threshold power and the band measurement threshold power being selected from a group consisting of a ratio of absolute power level to filter noise power and a quantization-induced band power from the spectral band histogram.

6. The method of claim 1, wherein assigning an image quality class comprises using a classification threshold.

7. The method of claim 6 wherein the classification threshold is an absolute spectral band power in one or more spectral bands.

8. The method of claim 6, wherein the classification threshold is a relative ratio of spectral band power to weighted power of one or more spectral bands, and wherein the classification threshold is independent of brightness and contrast.

9. The method of claim 1, wherein performing a spectral decomposition of the pixel region further comprises decomposition of one or more of Y, Cr, and Cb image components in a YCrCb color space.

10. The method of claim 1, wherein performing a spectral decomposition of the pixel region comprises decomposition of one or more components of H, S, and I image components in a HSI color space.

11. The method of claim 1 wherein enhancing the image quality of the pixel region comprises performing a noise reduction step having a noise reduction level, wherein the noise reduction level has reduced strength for high resolution content, and has increased strength for low resolution content.

13. The method of claim 1 wherein assigning an image quality class to the pixel region provides greater sensitivity to low contrast and local content, thereby enabling local image enhancement.

14. The method of claim 1, further wherein assigning an image quality class to the pixel region comprises assigning an image quality selected from a group consisting of:

a flat pixel region, a detailed pixel region, and an edge area pixel region.

15. The method of claim 1, further wherein assigning an image quality class to the pixel region comprises assigning an image quality class selected from a group consisting of:

wide bandwidth, medium bandwidth, and low bandwidth per color component.

16. The method of claim 1, further wherein assigning an image quality class to selected portions of the pixel region comprises selecting an image quality class from the group consisting of:

high detail, medium detail, and low detail.

17. The method of claim 1, further wherein assigning an image quality class to the pixel region comprises selecting an image quality class from the group consisting of:

high detail, medium detail, and low detail.

12. The method of claim wherein performing an image classification of the pixel region frame is implemented on a microprocessor executing software previously stored.

18. A method for adaptive image enhancement, comprising:

measuring an image quality of a pixel region in a frame in a source video;

performing an image classification of the pixel region based on the measured image quality; and

enhancing the image quality of the pixel region by applying operations based on the image classification of the pixel region;

wherein measuring the image quality of the pixel region comprises;

collecting a luminance histogram of a Y component in a YCrCb color space or an I component in a HSI color space of the pixel region;

assigning a brightness class and a contrast class to the pixel region; and

adjusting a gain and an offset of image color components based on the luminance histogram.

19. A method for adaptive image enhancement, comprising:

measuring an image quality of a pixel region in a frame in a source video;

performing an image classification of the pixel region based on the measured image quality; and

enhancing the image quality of the pixel region by applying operations based on the image classification of the pixel region;

wherein measuring the image quality of the pixel region comprises;

collecting a luminance histogram of an I component in a HSI color space of the pixel region

assigning a brightness class and a contrast class to the pixel region; and

adjusting a gain and an offset of image color components according to the brightness class and the contrast class.

20. A method for adaptive image enhancement, comprising:

measuring an image quality of a pixel region in a frame in a source video;

performing an image classification of the pixel region based on the measured image quality; and

enhancing the image quality of the pixel region by applying operations based on the image classification of the pixel region;

wherein measuring the image quality of the pixel region further comprises;

measuring inactive borders of the frame in the source video image;

assigning an inactive region of the frame in the source video image for alternate image enhancing.

21. The method of claim 20 further wherein the alternate image enhancing step comprises a step selected from the group consisting of a noise reduction step, a signal transition improvement step, a detail enhancement step, and an adaptive scaling step.

22. The method of claim 20 wherein enhancing the image quality of the pixel region comprises a noise reduction step having a noise reduction level;

further wherein the noise reduction level is increased in the inactive region, and otherwise adaptive to image classification.

23. The method of claim 20 wherein enhancing the image quality of the pixel region comprises a signal transition improvement step and a detail enhancement step, whereby enhancements are reduced in the inactive region and otherwise adaptive to image classification.

24. The method of claim 20 wherein enhancing the image quality of the pixel region comprises an adaptive scaling step, whereby the scaler bandwidth is reduced in the inactive region to reduce noise and a scale factor is adjusted to optimize displayed area for an active image.

25. The method of claim 20 further wherein enhancing the image quality of the pixel region comprises a contrast enhancement step, whereby a luminance measurement and a brightness and a contrast enhancement is disabled in the inactive region.

26. A method for adaptive image enhancement, comprising:

dividing a frame in a source video image into P pixel regions, where P is a number greater than 1 and as large as a total number of pixels in an output display; and

for each one of the P pixel regions the method further comprising;

measuring an image quality of the pixel region;

assigning an image quality class to selected portions of the pixel region; and

enhancing each of the pixel regions in a frame of a source video image according to their image quality class;

wherein measuring the image quality class of the pixel region comprises;

having the pixel region in the source video image limited by borders;

using a box detector stage to evaluate the borders of the pixel region;

performing a spectral decomposition of the pixel region;

evaluating a histogram of a luminance component in the pixel region; and

measuring the image quality of the pixel region based on the spectral decomposition and the luminance histogram.

27. A system for adaptive image enhancement, comprising:

a circuit to measure an image quality of a region of a frame in a source video image;

a circuit to perform an image classification of the region based on the measured image quality; and

a circuit to enhance the image quality of the region by applying operations based on the image classification of the region;

wherein the circuit to measure the image quality of the region comprises;

a box detection circuit to evaluate borders of the region;

a circuit to perform a spectral measurement of the region;

a circuit to evaluate a luminance histogram of the region;

a circuit to measure the image quality of the region based on the spectral measurement and the luminance histogram; and

a circuit for assigning image classifications to selected portions of the region.

28. A system for adaptive image enhancement, comprising:

a circuit to measure an image quality of a region of a frame in a source video image;

a circuit to perform an image classification of the region based on the measured image quality; and

a circuit to enhance the image quality of the region by applying operations based on the image classification;

a circuit to perform noise reduction to the region, according to the image classification;

a circuit to perform signal transition improvement to the noise reduced region, according to the image classification;

a circuit to perform adaptive scaling to the signal transition improved region, according to the image classification and box borders evaluated by a box detection circuit;

a circuit to perform detail enhancement to the adaptively scaled region, according to the image classification; and

a circuit to perform contrast enhancement to the detail enhanced region.