Dynamic backlight adaptation for video images with black bars

• US 8,576,256 B2
• Filed: 06/24/2008
• Issued: 11/05/2013
• 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.
• Primary Examiner(s): SHERMAN, STEPHEN G
• Application Number:
  US12/145,368
• Publication Number:
  US 20090002403A1
• Time in Patent Office: 1,960 Days
• Field of Search: 345/89, 345/102, 345/690, 345/211, 348/687, 348690-700, 348/571, 348/556
• US Class Current: 345/690
• 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 calculates a brightness metric associated with a video image. Then, the system identifies a subset of the video image based on the brightness metric, where the subset of the video image includes spatially varying visual information in the video image. Next, the system determines the intensity setting of the light source based on a first portion of the brightness metric associated with the subset of the video image, where the light source is configured to illuminate a display that is configured to display the video image.

Claims

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

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

analysis logic configured to analyze the brightness metric to identify a subset of the video image data, wherein the subset of the video image data comprises spatially varying visual information in the video image data;

intensity logic configured to determine an intensity setting of a light source based at least in part on a brightness setting of the light source and a first portion of the brightness metric of the subset of the video image data, wherein the light source is configured to illuminate a display that is configured to display a visual representation of the video image data; and

a low-pass filter configured to filter a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, and wherein, when filtering the change, the filter is configured to use a time constant from a plurality of time constants, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to the filter by the intensity logic.

2. The system of claim 1, comprising:

scaling logic, wherein the scaling logic is configured to scale video signals for the subset of the video image data using a mapping function that is generated from the first portion of the brightness metric, wherein the mapping function comprises a linear portion with a first slope in scaling values and a non-linear portion with a second slope in scaling values.

3. The system of claim 2,

wherein the scaling logic is configured to output modified video signals, wherein the modified video signals comprise the scaled video signals of the subset of the video image data.

4. The system of claim 3, wherein a distortion metric is associated with the mapping function.

5. The system of claim 4, wherein the intensity setting of the light source is based at least in part on the distortion metric.

6. The system of claim 3, wherein the scaling is based at least in part on a dynamic range of a mechanism that attenuates coupling of light from the light source to the display that is configured to display a visual representation of the video image data.

7. The system of claim 1, wherein the video image data comprises a frame of video.

8. The system of claim 1, wherein the subset of the video image data excludes a black bar, and wherein the black bar is associated with encoding of the video image data.

9. The system of claim 1, wherein the subset of the video image data excludes one or more lines, and wherein the one or more lines are associated with encoding of the video image.

10. The system of claim 9, wherein the one or more lines are identified based at least in part on a second portion of the brightness metric associated with the one or more lines.

11. The system of claim 10, wherein the brightness metric comprises a histogram of brightness values in the video image data,

wherein the second portion of the brightness metric comprises brightness values less than a first predetermined value, and

wherein the brightness values have a range of values less than a second predetermined value.

12. The system of claim 1, wherein the brightness metric comprises a histogram of brightness values in the video image data.

13. The system of claim 1, wherein the video image data comprises a sequence of video images, and wherein the intensity setting is determined on a image-by-image basis in the sequence of video images.

14. The system of claim 1, wherein the determined intensity setting of the light source reduces power consumption of the light source.

15. The system of claim 1, wherein the light source comprises a light emitting diode or a fluorescent lamp.

16. A non-transitory, non-transitory, computer-readable medium, having stored thereon:

instructions to calculate a brightness metric of video image data;

instructions to identify a subset of the video image data based at least in part on the brightness metric, wherein the subset of the video image data comprises spatially varying visual information in the video image data;

instructions to determine the intensity setting of the light source based at least in part on a first portion of the brightness metric of the subset of the video image data, wherein the light source is configured to illuminate a display that is configured to display a visual representation of the video image data; and

instructions to filter a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, wherein filtering the change comprises using a time constant from a plurality of time constants for the filtering, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to a filter from the determination of the intensity setting.

17. An integrated circuit, comprising:

extraction logic configured to calculate a brightness metric of video image data based at least in part on received video signals;

analysis logic configured to analyze the brightness metric to identify a subset of the video image data, wherein the subset of the video image data comprises spatially varying visual information in the video image data;

intensity logic configured to determine an intensity setting of a light source based at least in part on a brightness setting and a first portion of the brightness metric of the subset of the video image data, wherein the light source is configured to illuminate a display that is configured to display a visual representation of the video image data; and

a low-pass filter, wherein the filter is configured to filter a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, and wherein, when filtering the change, the filter is configured to use a time constant from a plurality of time constants, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to the filter by the intensity logic.

18. 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;

identify a subset of the video image data based at least in part on the brightness metric, wherein the subset of the video image data comprises spatially varying visual information in the video image data;

determine the intensity setting of the light source based at least in part on a first portion of the brightness metric of the subset of the video image data, wherein the light source is configured to illuminate a display that is configured to display a visual representation of the video image data; and

filter a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, wherein filtering the change comprises using a time constant from a plurality of time constants for the filtering, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to a filter from the determination of the intensity setting.

19. A method for determining an intensity of a light source, comprising:

calculating a brightness metric video image data;

identifying a subset of the video image data based at least in part on the brightness metric, wherein the subset of the video image data comprises spatially varying visual information in the video image data;

determining the intensity setting of the light source based at least in part on a first portion of the brightness metric of the subset of the video image data, wherein the light source is configured to illuminate a display that is configured to display a visual representation of the video image data; and

filtering a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, wherein filtering the change comprises using a time constant from a plurality of time constants for the filtering, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to a filter from the determination of the intensity setting.

20. A computer system to determine an intensity setting of a light source, comprising:

a processor;

memory;

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

instructions to calculate a histogram of brightness values of video image data;

instructions to identify a picture portion of the video image data based at least in part on the histogram;

instructions to determine the intensity setting of the light source based at least in part on a portion of the histogram of the picture portion of the video image data, wherein the light source is configured to illuminate a display that is configured to display a visual representation of the video image data; and

instructions to determine a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, wherein filtering the change comprises using a time constant from a plurality of time constants for the filtering, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to a filter from the determination of the intensity setting.

21. A computer system comprising:

a processor;

a memory;

an instruction fetch unit within the processor configured to fetch;

instructions to calculate a histogram of brightness values of video image data;

instructions to identify a picture portion of the video image data based at least in part on the histogram; and

instructions to determine the intensity setting of the light source based at least in part on a portion of the histogram of the picture portion of the video image data, wherein the light source is configured to illuminate a display that is configured to display the video image data; and

instructions to filter a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, wherein filtering the change comprises using a time constant from a plurality of time constants for the filtering, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to a filter from the determination of the intensity setting;

an execution unit within the processor configured to execute the instructions to calculate the histogram, the instructions to identify the picture portion of the video image data, and the instructions to determine the intensity setting of the light source.

22. A portable device, comprising:

a display;

a light source configured to output light based at least in part on an intensity setting;

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; and

one or more integrated circuits, comprising;

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

logic configured to analyze the brightness metric to identify a subset of the video image data, and wherein the subset of the video image data comprises spatially varying visual information in the video image data;

intensity logic configured to determine an intensity setting of the light source based at least in part on the brightness setting and a first portion of the brightness metric of the subset of the video image data; and

a low-pass filter, wherein the filter is configured to filter a change in the intensity setting between adjacent video images in the video image data to limit changes in the intensity setting from image to image, and wherein, when filtering the change, the filter is configured to use a time constant from a plurality of time constants, each time constant corresponding to a range of magnitudes of a change in the intensity setting input to the filter by the intensity logic.

23. The portable device of claim 22, comprising:

scaling logic electrically coupled to the analysis logic, wherein the scaling logic is configured to scale video signals for the subset of the video image data using a mapping function that is generated from the first portion of the brightness metric, wherein the mapping function comprises a linear portion with a first slope in scaling values and a non-linear portion with a second slope in scaling values, wherein the scaling logic is configured to output modified video signals, wherein the modified video signals comprise the scaled video signals of the subset of the video image data, and wherein the attenuation mechanism is configured to modulate the output light incident on the display based at least in part on the modified video signals.