COLOR-ADJUSTMENT TECHNIQUE FOR VIDEO PLAYBACK

• US 20090002561A1
• Filed: 06/24/2008
• Published: 01/01/2009
• Est. Priority Date: 06/26/2007
• Status: Abandoned Application

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Wei, Barnhoefer, Ulrich T., Corlett, Barry J., Yao, Wei H.
• Application Number:
  US12/145,308
• Publication Number:
  US 20090002561A1
• Time in Patent Office: Days
• US Class Current: 348/655
• 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 video image. Then, the system jointly modifies brightness values of pixels in at least a portion of the video image and an intensity setting of a light source to maintain light output from a display while reducing power consumption by the light source, where the light source is configured to illuminate the display that is configured to display video images. Next, the system adjusts color content in the video image to correct for a dependence of a spectrum of the light source on the intensity setting.

Claims

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

receive a video image; and

determine an intensity setting of a light source based on at least a portion of the video image, the light source configured to illuminate a display that is configured to display video images;

modify brightness values of pixels in at least a portion of the video image to maintain a product of the intensity setting and a transmittance associated with the modified video image; and

adjust color content in the video image based on the intensity setting to maintain the color associated with the video image even as the spectrum associated with the light sources varies with the intensity setting.

2. The system of claim 1, wherein the modifying of the brightness of the pixels is performed on a pixel-by-pixel basis.

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

4. The system of claim 1, wherein the brightness is modified based on a histogram of brightness values in the video image.

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

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

7. The system of claim 1, wherein the color adjustment is based on a characteristic of the light source.

8. The system of claim 1, wherein the color adjustment maintains the color white.

9. The system of claim 8, wherein the color white is maintained to within approximately 100 K of a corresponding black-body temperature associated with the color of the video image prior to changes in the intensity setting.

10. The system of claim 1, wherein the color adjustment maintains a ratio of two color components in the video image and another ratio of two color components in the video image;

and

wherein color content of the video image is represented using three color components.

11. The system of claim 1, wherein the color adjustment is performed on a pixel-by-pixel basis.

12. The system of claim 1, wherein the color adjustment includes increasing a blue-color component in the video image when the intensity setting is reduced relative to a previous intensity setting and decreasing the blue-color component in the video image when the intensity setting is increased relative to the previous intensity setting.

13. The system of claim 1, wherein the color is adjusted so that a product of the color values associated with the video image and the spectrum results in an approximately unchanged grayscale for the video image.

14. The system of claim 1, wherein the one or more integrated circuits are further configured to transform the video image from an initial brightness domain to a linear brightness domain prior to determining the intensity setting, the linear brightness domain characterized by a range of brightness values corresponding to substantially equidistant adjacent radiant-power values in a displayed video image.

15. The system of claim 14, wherein the one or more integrated circuits are further configured to convert the video image, after the color content is adjusted, to another brightness domain characterized by the range of brightness values corresponding to non-equidistant adjacent radiant-power values in a displayed video image.

16. A system, comprising:

an input node configured to receive video signals associated with a video image;

an extraction circuit electrically coupled to the input interface, the extraction circuit operative to calculate a brightness metric associated with at least a portion of the video image based on the received video signals and operative to determine an intensity setting of a light source based on the brightness metric, the light source configured to illuminate a display that is configured to display video images;

an adjustment circuit electrically coupled to the extraction circuit, the adjustment circuit configured to modify a brightness of pixels in at least a portion of the video image based on the brightness metric to maintain a product of the intensity setting and a transmittance associated with the modified video image, and configured to adjust color content in the video image based on the intensity setting to maintain the color associated with the video image even as the spectrum associated with the light sources varies with the intensity setting; and

an output node electrically coupled to the adjustment circuit, the output node configured to output the video signals.

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

receive a video image; and

jointly modify brightness values of pixels in at least a portion of the video image and an intensity setting of a light source to maintain light output from a display while reducing power consumption by the light source, the light source configured to illuminate the display that is configured to display video images; and

adjust color content in the video image to correct for a dependence of a spectrum of the light source on the intensity setting.

18. A method for adjusting a video image, comprising:

receive a video image; and

determine an intensity setting of a light source based on at least a portion of the video image, the light source configured to illuminate a display that is configured to display video images;

modify brightness values of pixels in at least a portion of the video image to maintain a product of the intensity setting and a transmittance associated with the modified video image; and

adjust color content in the video image based on the intensity setting to maintain the color associated with the video image even as the spectrum associated with the light sources varies with the intensity setting.

19. A method for adjusting a video image, comprising:

receiving a video image; and

jointly modifying brightness values of pixels in at least a portion of the video image and an intensity setting of a light source to maintain light output from a display while reducing power consumption by the light source, the light source configured to illuminate the display that is configured to display video images; and

adjusting color content in the video image to correct for a dependence of a spectrum of the light source on the intensity setting.

20. 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 adjusting a video image, the computer-program mechanism comprising:

instructions for receiving a video image; and

instructions for jointly modifying brightness values of pixels in at least a portion of the video image and an intensity setting of a light source to maintain light output from a display while reducing power consumption by the light source, the light source configured to illuminate the display that is configured to display video images; and

instructions for adjusting color content in the video image to correct for a dependence of a spectrum of the light source on the intensity setting.

21. A computer system to scale a brightness of a portion of 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 for receiving a video image; and

instructions for jointly modifying brightness values of pixels in at least a portion of the video image and an intensity setting of a light source to maintain light output from a display while reducing power consumption by the light source, the light source configured to illuminate the display that is configured to display video images; and

instructions for adjusting color content in the video image to correct for a dependence of a spectrum of the light source on the intensity setting.

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

a processor;

a memory;

an instruction fetch unit within the processor configured to fetch;

instructions for receiving a video image; and

instructions for jointly modifying brightness values of pixels in at least a portion of the video image and an intensity setting of a light source to maintain light output from a display while reducing power consumption by the light source, the light source configured to illuminate the display that is configured to display video images; and

instructions for adjusting color content in the video image to correct for a dependence of a spectrum of the light source on the intensity setting; and

an execution unit within the processor configured to execute the instructions for receiving the video image, the instructions for jointly modifying the brightness values of the pixels and the intensity setting, and the instructions for adjusting the color content.

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

receive a video image; and

determine an intensity setting of a light source based on at least a portion of the video image, the light source configured to illuminate a display that is configured to display video images;

modify brightness values of pixels in at least a portion of the video image to maintain a product of the intensity setting and a transmittance associated with the modified video image; and

adjust color content in the video image based on the intensity setting to maintain the color associated with the video image even as the spectrum associated with the light sources varies with the intensity setting.

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

receive a video image; and

jointly modify brightness values of pixels in at least a portion of the video image and an intensity setting of a light source to maintain light output from a display while reducing power consumption by the light source, the light source configured to illuminate the display that is configured to display video images; and

adjust color content in the video image to correct for a dependence of a spectrum of the light source on the intensity setting.

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, the display configured to display a video image; and

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

receive the video image; and

determine an intensity setting of the light source based on at least a portion of the video image;

modify brightness values of pixels in at least a portion of the video image to maintain a product of the intensity setting and a transmittance associated with the modified video image; and

adjust color content in the video image based on the intensity setting to maintain the color associated with the video image even as the spectrum associated with the light sources varies with the intensity setting.