Dynamic backlight adaptation with reduced flicker

• US 8,581,826 B2
• Filed: 06/24/2008
• Issued: 11/12/2013
• Est. Priority Date: 06/26/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Barnhoefer, Ulrich T., Yao, Wei H., Chen, Wei, Corlett, Barry J., Alessi, Victor E.
• Primary Examiner(s): SHERMAN, STEPHEN G
• Application Number:
  US12/145,388
• Publication Number:
  US 20090002311A1
• Time in Patent Office: 1,967 Days
• Field of Search: 348699-700, 348/687, 348/571, 348/556, 345/102, 345/690, 345/211, 345/698, 345/60, 345/76, 345/82, 345 87- 89, 345 98-100, 345/204, 382/168
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0232 Special driving of display border areas
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: Y10S 348/913 Letterbox, e.g. display 16:9 aspect ratio image on 4:3 screen

Abstract

Embodiments of a system that includes one or more integrated circuits are described. During operation, the system receives a video image, that when displayed, includes a picture portion and the non-picture portion, where the non-picture portion has a first brightness value. Then, the system scales the non-picture portion to have a second brightness value that is greater than the first brightness value to reduce user-perceived changes in the video image associated with backlighting of a display that displays the video image.

Claims

1. A system, comprising one or more integrated circuits, wherein the one or more integrated circuits include:

extraction logic configured to calculate a brightness metric associated with received video image data corresponding to at least one video image;

analysis logic configured to analyze the brightness metric to identify a first subset of the video image and a second subset of the video image, wherein the first subset of the video image includes spatially varying visual information in the video image and the second subset of the video image includes the remainder of the video image that does not include spatially varying visual information; and

adjustment logic configured to adjust a brightness of the second subset of the video image independent from the first subset, wherein a new brightness of the second subset of the video image is greater than a minimum brightness for a display that is configured to display a visual representation of the video image data, wherein the new brightness provides additional headroom to attenuate noise associated with displaying a portion of the visual representation that corresponds to the second subset of the video image.

2. The system of claim 1, wherein the video image includes a frame of video.

3. The system of claim 1, wherein the second subset of the video image includes one or more lines.

4. The system of claim 3, wherein the one or more lines are associated with encoding of the video image.

5. The system of claim 1, wherein the second subset of the video image includes a black bar.

6. The system of claim 1, wherein the brightness metric includes a histogram of brightness values in the video image.

7. The system of claim 6, wherein a portion of the brightness metric associated with the second subset of the video image has brightness values less than a first predetermined value and the brightness values have a range of values less than a second predetermined value.

8. The system of claim 1, wherein the adjustment of the brightness increases the brightness of the second subset of the video image by at least 1 candela per square meter.

9. The system of claim 1, wherein the adjustment of the brightness is based on a dynamic range of a mechanism that attenuates coupling of light from a light source to the display.

10. The system of claim 9, wherein the light source comprises a light emitting diode or a fluorescent lamp.

11. The system of claim 1, wherein a threshold value is used to identify the first and second subsets of the video image, wherein the threshold value associated with at least one subtitle in the video image data that overlaps at least a portion of the second subset of the video image.

12. The system of claim 11, wherein the analysis logic is configured to identify the subtitle and determine the threshold value.

13. The system of claim 11, comprising subtitle manipulation logic that is configured to blend the subtitle with an initial video image to produce the video image data.

14. The system of claim 13, wherein the subtitle manipulation logic is configured to dynamically generate the subtitle and associate the subtitle with the video image.

15. A method for adjusting a brightness of a subset of video image data corresponding to a video image, comprising:

calculating a brightness metric of the video image;

identifying a first subset of the video image and a second subset of the video image, wherein the identification of the first and second subsets is based on the brightness metric, and wherein the first subset of the video image includes spatially varying visual information in the video image and the second subset of the video image includes the remainder of the video image that does not include spatially varying visual information; and

adjusting a brightness of the second subset of the video image independent from the first subset, wherein a new brightness of the second subset of the video image is greater than a minimum brightness for a display that is configured to display a visual representation of the video image data, wherein the new brightness provides additional headroom to attenuate noise associated with displaying a portion of the visual representation that corresponds to the second subset of the video image.

16. The method of claim 15, wherein the second subset of the video image includes one or more lines.

17. The method of claim 16, wherein the one or more lines are associated with encoding of the video image.

18. The method of claim 16, wherein the one or more lines are included in a black bar.

19. A computer-program product for use in conjunction with a computer system, the computer-program product comprising a non-transitory computer-readable storage medium comprising:

instructions to receive video image data corresponding to a video image;

instructions to calculate a brightness metric of the video image;

instructions to calculate a first subset of the video image and a second subset of the video image, wherein the identification of the first and second subsets is based on the brightness metric, and wherein the first subset of the video image includes spatially varying visual information in the video image and the second subset of the video image includes the remainder of the video image that does not include spatially varying visual information; and

instructions to adjust a brightness of the second subset of the video image independent from the first subset, wherein a new brightness of the second subset of the video image is greater than a minimum brightness for a display that is configured to display a visual representation of the video image data, wherein the new brightness provides additional headroom to attenuate noise associated with displaying a portion of the visual representation that corresponds to the second subset of the video image.

20. A method for scaling a brightness of a non-picture portion of a video image, comprising:

receiving video image data corresponding to a video image, wherein the video image comprises a picture portion and the non-picture portion, the non-picture portion having a first brightness value; and

scaling the non-picture portion independent of the picture portion to have a second brightness value that is greater than the first brightness value and a minimum brightness for a display configured to display a visual representation of the video image data to reduce user-perceived changes in the visual representation associated with backlighting of the display by providing additional headroom to attenuate noise.

21. A computer system to scale a brightness of a non-picture portion of video image data corresponding to a video image, comprising:

a processor;

memory;

a program module, wherein the program module is stored in the memory and configurable to be executed by the processor, the program module including;

instructions to receive video image data corresponding to a video image, wherein the video image comprises a picture portion and the non-picture portion, the non-picture portion having a first brightness value; and

instructions to scale the non-picture portion independent of the picture portion to have a second brightness value that is greater than the first brightness value and a minimum brightness for a display configured to display a visual representation of the video image data to reduce user-perceived changes in the visual representation associated with backlighting of a display that displays a visual representation of the video image data by providing additional headroom to attenuate noise.

22. A computer system configured to scale a brightness of a non-picture portion of a video image, comprising:

a processor;

a memory;

an instruction fetch unit within the processor configured to fetch;

instructions to receive video image data corresponding to a video image that comprises a picture portion and the non-picture portion, the non-picture portion having a first brightness value; and

instructions to scale the non-picture portion independent from the picture portion to have a second brightness value that is greater than the first brightness value and a minimum brightness of a display configured to display a visual representation of the video image data to reduce user-perceived changes in the visual representation associated with backlighting of the display by providing additional headroom to attenuate noise; and

an execution unit within the processor configured to execute the instructions to receive and instructions to scale.

23. An integrated circuit, comprising one or more sub-circuits, wherein the one or more sub-circuits are configured to:

calculate a brightness metric of video image data corresponding to a video image;

identify a first subset of the video image and a second subset of the video image, wherein the identification of the first and second subsets is based on the brightness metric, and wherein the first subset of the video image includes spatially varying visual information in the video image and the second subset of the video image includes the remainder of the video image that does not include spatially varying visual information; and

adjust a brightness of the second subset of the video image independent of the first subset, wherein a new brightness of the second subset of the video image is greater than a minimum brightness for a display that is configured to display a visual representation of the video image data, wherein the new brightness provides additional headroom to attenuate noise associated with displaying a portion of the visual representation that corresponds to the second subset of the video image.

24. An integrated circuit, comprising:

extraction logic configured to calculate a brightness metric of video image data corresponding to at least one video image;

analysis logic configured to analyze the brightness metric to identify a first subset of a video image of the at least one video image and a second subset of the video image, wherein the first subset of the video image includes spatially varying visual information in the video image and the second subset of the video image includes the remainder of the video image that does not include spatially varying visual information; and

adjustment logic configured to adjust a brightness of the second subset of the video image independent of the first subset, wherein a new brightness of the second subset of the video image is greater than a minimum brightness for a display that is configured to display a visual representation of the video image data, wherein the new brightness provides additional headroom to attenuate noise associated with displaying a portion of the visual representation that corresponds to the second subset of the video image.

25. A portable device, comprising:

a display;

a light source configured to output light;

an attenuation mechanism configured to modulate the output light incident on the display, wherein the display is configured to display a visual representation of video image data corresponding to at least one video image; and

one or more integrated circuits, comprising;

extraction logic configured to calculate a brightness metric the video image data;

analysis logic configured to analyze the brightness metric to identify a first subset of the video image and a second subset of the video image, wherein the first subset of the video image includes spatially varying visual information in the video image and the second subset of the video image includes the remainder of the video image that does not include spatially varying visual information; and

adjustment logic configured to adjust a brightness of the second subset of the video image independent of the first subset, wherein a new brightness of the second subset of the video image is greater than a minimum brightness for the display, wherein the new brightness provides additional headroom for the attenuation mechanism to attenuate noise associated with displaying a portion of the visual representation that corresponds to the second subset of the video image on the display.

26. The portable device of claim 25, wherein the second subset of the video image includes one or more lines.

27. The portable device of claim 26, wherein the one or more lines are associated with encoding of the video image.

28. The portable device of claim 25, wherein the second subset of the video image includes a black bar.