DYNAMIC BACKLIGHT ADAPTATION FOR VIDEO IMAGES WITH BLACK BARS

• US 20090002403A1
• Filed: 06/24/2008
• Published: 01/01/2009
• Est. Priority Date: 06/26/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Wei, Barnhoefer, Ulrich T., Corlett, Barry J., Yao, Wei H.
• Granted Patent: US 8,576,256 B2
• Time in Patent Office: Days
• 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 include:

an input interface configured to receive video signals associated with a video image and a brightness setting of a light source which is configured to illuminate a display that is configured to display the video image;

an extraction circuit electrically coupled to the input interface, the extraction circuit operative to calculate a brightness metric associated with the video image based on the received video signals;

an analysis circuit electrically coupled to the extraction circuit, the analysis circuit configured to analyze the brightness metric to identify a subset of the video image, wherein the subset of the video image includes spatially varying visual information in the video image;

an intensity circuit electrically coupled to the analysis circuit, the intensity circuit configured to determine an intensity setting of the light source based on the brightness setting and a first portion of the brightness metric associated with the subset of the video image; and

an output interface electrically coupled to the intensity circuit, the output interface configured to output the intensity setting of the light source.

2. The system of claim 1, wherein the one or more integrated circuits further include a scaling circuit electrically coupled to the input interface and the analysis circuit,

wherein the scaling circuit is configured to scale video signals associated with the subset of the video image based on a mapping function,

wherein the mapping function is based on the first portion of the brightness metric,

wherein the output interface is electrically coupled to the scaling circuit and is configured to output modified video signals, and

wherein the modified video signals include the scaled video signals associated with the subset of the video image.

3. The system of claim 2, wherein a distortion metric is associated with the mapping function.

4. The system of claim 3, wherein the intensity setting of the light source is based on the distortion metric.

5. The system of claim 2, wherein the scaling is based on a dynamic range of a mechanism that attenuates coupling of light from the light source to the display that is configured to display the video image.

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

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

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

9. The system of claim 8, wherein the one or more lines are identified based on a second portion of the brightness metric associated with the one or more lines.

10. The system of claim 9, wherein the brightness metric includes a histogram of brightness values in the video image,

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

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

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

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

13. The system of claim 12, wherein the one or more integrated circuits further include a filter electrically coupled to the intensity circuit and the output interface, wherein the filter is configured to filter a change in intensity settings between adjacent video images in the sequence of video images.

14. The system of claim 13, wherein the filter includes a low-pass filter.

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

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

17. A computer-program product for use in conjunction with a computer system, the computer-program product comprising a computer-readable storage medium and a computer-program mechanism embedded therein for determining an intensity setting of a light source, the computer-program mechanism comprising:

instructions for calculating a brightness metric associated with a video image;

instructions for identifying a subset of the video image based on the brightness metric, wherein the subset of the video image includes spatially varying visual information in the video image; and

instructions for determining the intensity setting of the light source based on a first portion of the brightness metric associated with the subset of the video image, wherein the light source is configured to illuminate a display that is configured to display the video image.

18. An integrated circuit, comprising:

an input interface configured to receive video signals associated with a video image and a brightness setting of a light source which is configured to illuminate a display that is configured to display the video image;

an extraction circuit electrically coupled to the input interface, the extraction circuit operative to calculate a brightness metric associated with the video image based on the received video signals;

an analysis circuit electrically coupled to the extraction circuit, the analysis circuit configured to analyze the brightness metric to identify a subset of the video image, wherein the subset of the video image includes spatially varying visual information in the video image;

an intensity circuit electrically coupled to the analysis circuit, the intensity circuit configured to determine an intensity setting of the light source based on the brightness setting and a first portion of the brightness metric associated with the subset of the video image; and

an output interface electrically coupled to the intensity circuit, the output interface configured to output the intensity setting of the light source.

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

calculate a brightness metric associated with a video image;

identify a subset of the video image based on the brightness metric, wherein the subset of the video image includes spatially varying visual information in the video image; and

determine the intensity setting of the light source based on a first portion of the brightness metric associated with the subset of the video image, wherein the light source is configured to illuminate a display that is configured to display the video image.

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

calculating a brightness metric associated with a video image;

identifying a subset of the video image based on the brightness metric, wherein the subset of the video image includes spatially varying visual information in the video image; and

determining the intensity setting of the light source based on a first portion of the brightness metric associated with the subset of the video image, wherein the light source is configured to illuminate a display that is configured to display the video image.

21. 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 configurable to be executed by the processor, the program module including;

instructions for calculating a histogram of brightness values associated with a video image;

instructions for identifying a picture portion of the video image based on the histogram; and

instructions for determining the intensity setting of the light source based on a portion of the histogram associated with the picture portion of the video image, wherein the light source is configured to illuminate a display that is configured to display the video image.

22. A computer system configured to execute instructions to determine an intensity setting of a light source, comprising:

a processor;

a memory;

an instruction fetch unit within the processor configured to fetch;

instructions for calculating a histogram of brightness values associated with a video image;

instructions for identifying a picture portion of the video image based on the histogram; and

instructions for determining the intensity setting of the light source based on a portion of the histogram associated with the picture portion of the video image, wherein the light source is configured to illuminate a display that is configured to display the video image; and

an execution unit within the processor configured to execute the instructions for calculating the histogram, the instructions for identifying the picture portion of the video image, and the instructions for determining the intensity setting of the light source.

23. A portable device, comprising:

a display;

a light source configured to output light based 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 video image; and

one or more integrated circuits, comprising;

an input interface configured to receive video signals associated with the video image and a brightness setting of the light source;

an extraction circuit electrically coupled to the input interface, the extraction circuit operative to calculate a brightness metric associated with the video image based on the received video signals;

an analysis circuit electrically coupled to the extraction circuit, the analysis circuit configured to analyze the brightness metric to identify a subset of the video image, and wherein the subset of the video image includes spatially varying visual information in the video image;

an intensity circuit electrically coupled to the analysis circuit, the intensity circuit configured to determine an intensity setting of the light source based on the brightness setting and a first portion of the brightness metric associated with the subset of the video image; and

an output interface electrically coupled to the intensity circuit, the output interface configured to output the intensity setting of the light source.

24. The portable device of claim 23, further comprising a scaling circuit electrically coupled to the input interface and the analysis circuit, wherein the scaling circuit is configured to scale video signals associated with the subset of the video image based on a mapping function,

wherein the mapping function is based on the first portion of the brightness metric,

wherein the output interface is electrically coupled to the scaling circuit and is configured to output modified video signals,

wherein the modified video signals include the scaled video signals associated with the subset of the video image, and

wherein the attenuation mechanism is configured to modulate the output light incident on the display based on the modified video signals.