Technique for adjusting a backlight during a brightness discontinuity

• US 8,648,781 B2
• Filed: 06/24/2008
• Issued: 02/11/2014
• Est. Priority Date: 06/26/2007
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Barnhoefer, Ulrich T., Yao, Wei H., Chen, Wei
• Primary Examiner(s): BOYD, JONATHAN A
• Application Number:
  US12/145,266
• Publication Number:
  US 20090002564A1
• Time in Patent Office: 2,058 Days
• Field of Search: 345/102, 345/89
• US Class Current: 345/89
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2310/0232 Special driving of display border areas
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0646 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 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• 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

Abstract

Embodiments of a system that includes one or more integrated circuits are described. During operation, the system receives a sequence of video images, and calculates brightness metrics associated with the video images in the sequence of video images. Then, the system determines an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scales brightness values of a given video image in the sequence of video images based on a given brightness metric associated with the given video image. Next, the system changes the intensity setting and scaling the brightness values when there is a discontinuity in the brightness metrics between two adjacent video images in the sequence of video images.

Claims

1. A system, comprising one or more integrated circuits, wherein the one or more integrated circuits are configured to:

receive video image data;

calculate brightness metrics of the video image data;

determine an intensity setting of a light source that illuminates a display that is configured to display a visual representation of video image data, wherein the determination is based at least in part on a first or second brightness metric, or both, of the brightness metrics of the video image data;

scale brightness values of the video image data based at least in part on the first or second brightness metric, or both, of the video image data;

change the intensity setting and scale the brightness values when there is a discontinuity between the first brightness metric and the second brightness metric of the brightness metrics of the video data, wherein the first and second brightness metrics correspond to two adjacent video images in the video image data, respectively; and

apply a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in the video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a predetermined value unless the discontinuity between the first and second brightness metrics is greater than the predetermined value, in which case the temporal filter is turned off when the discontinuity is greater than the predetermined value.

2. The system of claim 1, wherein the first and second brightness metrics each comprise respective histograms of brightness values in the video image data.

3. The system of claim 1, wherein the discontinuity comprises a change in a maximum brightness value that exceeds the value.

4. The system of claim 1, wherein a rate of change of the portion corresponds to a size of the discontinuity between the first and second brightness metrics.

5. The system of claim 1, wherein the determined intensity setting of the light source for the video image data is configured to reduce power consumption of the light source.

6. The system of claim 1, wherein the scaling of the brightness values is determined on a pixel-by-pixel basis.

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

8. The system of claim 1, wherein the brightness values are scaled 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 a visual representation of the video image data.

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

10. A system, comprising one or more integrated circuits, wherein the one or more integrated circuits are configured to:

identify a discontinuity between a first brightness metric and a second brightness metric of video image data, wherein the video image comprises adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric;

determine a change in an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on the first or second brightness metric of the video image data;

scale brightness values of the video image data corresponding to the second video image based at least in part on the second brightness metric; and

apply the change in the intensity setting and scale the brightness values, wherein applying the change in the intensity setting and scaling the brightness values comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in the video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity between the first and second brightness metrics is greater than the certain value, in which case the temporal filter is turned off when the discontinuity is greater than the certain value.

11. A system, comprising:

extraction logic configured to calculate brightness metrics of video image data;

analysis logic electrically coupled to the extraction logic, the analysis logic configured to analyze the brightness metrics to identify a discontinuity between a first brightness metric and a second brightness metric of the brightness metrics of the video image data, wherein the video image data comprises adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric; and

adjustment logic electrically coupled to the analysis logic, the adjustment logic configured to adjust a brightness of the video image data corresponding to the second video image and to determine an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein adjusting a brightness of video image data corresponding to the second video image and determining an intensity setting of a light source comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness on an image-by-image basis in the video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.

12. A method for adjusting a brightness of a video image, comprising:

identifying a discontinuity between a first brightness metric and a second brightness metric of video image data comprising adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric;

determining a change in an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on the first or second brightness metric, or both, of the video image data;

scaling brightness values of the video image data corresponding to the second video image based at least on the second brightness metric of the video image data; and

applying the change in the intensity setting and the scaling of the brightness values, wherein applying the change in the intensity setting and scaling the brightness values comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in the video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.

13. A method for adjusting a brightness of a video image, comprising:

receiving video image data;

calculating brightness metrics of the video image data;

determining an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on a first or a second brightness metric, or both, of the brightness metrics of the video image data;

scaling brightness values of video image data based at least on the first or second brightness metric, or both, of the brightness metrics of the video image data;

changing the intensity setting and scaling the brightness values when there is a discontinuity between the first brightness metric and the second brightness metric of the brightness metrics corresponding to two adjacent video images in the video image data, respectively; and

applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in the video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.

14. A computer-program product comprising:

instructions to identify a discontinuity between a first brightness metric and a second brightness metric of video image data, wherein the video image data comprises adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric;

instructions to determine a change in an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on the first or second brightness metric, or both, of the video image data;

instructions to scale brightness values of the video image data corresponding to the second video image based at least in part on the second brightness metric; and

instructions to apply the change in the intensity setting and to scale the brightness values, wherein applying the change in the intensity setting and scaling the brightness values comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.

15. A computer system to scale a brightness of video image data, 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 identify a discontinuity between a first brightness metric and a second brightness metric of video image data, wherein the video image data comprises adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric;

instructions to determine a change in an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on the first or second brightness metric, or both, of the video image data;

instructions to scale brightness values of the video image data corresponding to the second video image based at least in part on the second brightness metric; and

instructions to apply the change in the intensity setting and the scaling of the brightness values, wherein applying the change in the intensity setting and scaling the brightness values comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.

16. A computer system configured to scale a brightness of video image data, comprising:

a processor;

a memory;

an instruction fetch unit within the processor configured to fetch;

instructions to identify a discontinuity between a first brightness metric and a second brightness metric of video image data, wherein the video image data comprises adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric;

instructions to determine a change in an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on the first or second brightness metric, or both, of the video image data;

instructions to scale brightness values of the video image data corresponding to the second video image based at least in part on the second brightness metric; and

instructions to apply the change in the intensity setting and the scaling of the brightness values, wherein applying the change in the intensity setting and scaling the brightness values comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value; and

an execution unit within the processor configured to execute the instructions to identify the discontinuity, the instructions to determine the change in the intensity setting and for scaling of the brightness values, and the instructions for applying the intensity setting and the scaling of the brightness values.

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

receive video image data;

calculate brightness metrics of the video image data;

determine an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on a first or second brightness metric, or both, of the brightness metrics of the video image data;

scale brightness values of the video image data based at least in part on the brightness metric of the video image data;

change the intensity setting and scale the brightness values when there is a discontinuity between the first brightness metric and the second brightness metric of the brightness metrics in the video image data, wherein the first and second brightness metrics correspond to two adjacent video images in the video image data, respectively; and

applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.

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

identify a discontinuity between a first brightness metric and a second brightness metric in video image data, wherein the video image data comprises adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric;

determine a change in an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on the first or second brightness metric, or both, of the video image data;

scale brightness values of the video image data corresponding to the second video image based at least in part on the second brightness metric; and

apply the change in the intensity setting and scale the brightness values, wherein applying the change in the intensity setting and scaling the brightness values comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.

19. 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, the display configured to display a visual representation of video image data; and

one or more integrated circuits, wherein the one or more integrated circuits are configured to;

identify a discontinuity a first brightness metric and a second brightness metric of the video image data, wherein the video image data comprises adjacent video images, and wherein the adjacent video images comprise a first video image corresponding to the first brightness metric and a second video image corresponding to the second brightness metric;

determine a change in an intensity setting of a light source that illuminates a display that is configured to display a visual representation of the video image data, wherein the determination is based at least in part on the first or second brightness metric, or both, of the video image data;

scale brightness values of the video image data corresponding to the second video image based at least in part on the second brightness metric; and

apply the change in the intensity setting and scale the brightness values, wherein applying the change in the intensity setting and scaling the brightness values comprises applying a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on an image-by-image basis in video image data using a temporal filter when an initial difference between the first and second brightness metrics is less than a certain value unless the discontinuity exceeds a certain value, in which case the temporal filter is turned off when the discontinuity exceeds the certain value.