Management techniques for video playback

• US 8,766,902 B2
• Filed: 06/24/2008
• Issued: 07/01/2014
• Est. Priority Date: 12/21/2007
• 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:
  US12/145,348
• Publication Number:
  US 20090161020A1
• Time in Patent Office: 2,198 Days
• Field of Search: 345/102
• US Class Current: 345/102
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement
• 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 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/066 for control of contrast
• 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
• CPC Class Codes: H04N 21/44008 involving operations for analysing video streams, e.g. detecting features or characteristics in the video stream arrangements characterised by components specially adapted for monitoring, identification or recognition of video in broadcast systems H04H60/59
• CPC Class Codes: H04N 21/4402 involving reformatting operations of video signals for household redistribution, storage or real-time display details of conversion of video standards at pixel level H04N7/01; video transcoding H04N19/40; adapting incoming signals to the display format of the display terminal G09G5/005; media handling at the source in data packet switching networks H04L65/764
• CPC Class Codes: H04N 5/58 in dependence upon ambient light

Abstract

Embodiments of a system that includes one or more integrated circuits are described. During operation, the system may determine an intensity setting of the light source based on at least a portion of a video image, such as the portion of the transformed video image that includes spatially varying visual information in the video image. Moreover, the system may modify the video image so that a product of the intensity setting and a transmittance associated with the modified video image approximately equals a product of a previous intensity setting and a transmittance associated with the video image. For example, the modification may include scaling brightness values in the transformed video image. Next, the system may identify a region in the video image in which the scaling of the brightness values results in a visual artifact associated with reduced contrast. For example, the region may include a bright region surrounded by a darker region. Then, the system may reduce the scaling of the brightness values in the region to, at least partially, restore the contrast, thereby reducing the visual artifact. Additionally, the system may spatially filter the brightness values in the video image to reduce a spatial discontinuity between the brightness values of pixels within the region and the brightness values in a remainder of the video image.

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 a brightness metric of the video image data;

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

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

identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

reduce the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions to, at least partially, restore the contrast, thereby reducing the visual artifact.

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

3. The system of claim 1, wherein the scaling of the brightness values is determined on a pixel-by-pixel basis in the video image data.

4. The system of claim 1, wherein the one or more integrated circuits are further configured to spatially filter the brightness values in the video image data to reduce a spatial discontinuity between the brightness values of pixels within the one or more regions and the brightness values in a remainder of the video image data.

5. The system of claim 1, wherein each region of the one or more regions corresponds to pixels having brightness values exceeding a predetermined threshold;

and

wherein brightness values of pixels in the video image data surrounding each region are less than the predetermined threshold.

6. The system of claim 5, wherein each region of the one or more regions contains more than 3, 10, or 20 percent of the pixels in the video image data.

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 a light source to the display that is configured to display the visual representation of the video image data.

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

10. The system of claim 1, wherein the light source comprises a fluorescent lamp.

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

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

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

identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

restore contrast in the one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast by, at least partially, reducing the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions.

12. A system, comprising:

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

analysis logic electrically coupled to the extraction logic, the analysis logic configured to identify one or more regions in the video image data in which scaling of brightness of pixels results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

adjustment logic electrically coupled to the analysis logic and the extraction logic, the adjustment logic configured to determine an intensity setting of a light source based at least in part on the brightness metric, which illuminates a display that is configured to display a visual representation of the video image data, and to adjust a brightness of pixels in the video image data unless the pixels are in the one or more regions.

13. A method comprising:

receiving video image data;

calculating a brightness metric of the video image data;

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

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

identifying one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

reducing the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions to, at least partially, restore the contrast, thereby reducing the visual artifact.

14. A method for adjusting brightness of pixels, comprising:

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

scaling brightness values for the video image data based at least in part on the brightness metric;

identifying one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

restoring contrast in the one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast by, at least partially, reducing the scaling of the brightness values in the one or more regions.

15. A computer program product for use in conjunction with a computer system, the computer program product comprising a non-transitory computer-readable storage medium storing processor-executing instructions, the instructions comprising:

instructions a to receive video image data;

instructions to calculate a brightness metric associated with of the video image data;

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

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

instructions to identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

instructions to reduce the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions to, at least partially, restore the contrast, thereby reducing the visual artifact.

16. A system 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;

instructions to calculate a brightness metric of the video image data;

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

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

instructions to identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

instructions to reduce the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions to, at least partially, restore the contrast, thereby reducing the visual artifact.

17. A system comprising:

a processor;

a memory;

an instruction fetch unit within the processor configured to fetch;

instructions to receive video image data;

instructions to calculate a brightness metric of the video image data;

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

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

instructions to identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

instructions to reduce the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions to, at least partially, restore the contrast, thereby reducing the visual artifact; and

an execution unit within the processor configured to execute the instructions to receive the video image data, the instructions to calculate the brightness metric, the instructions to determine the intensity setting and scaling the brightness values, and the instructions to reduce the scaling of the brightness values in the one or more regions.

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

receive video image data;

calculate a brightness metric of the video image data;

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

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

identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

reduce the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions to, at least partially, restore the contrast, thereby reducing the visual artifact.

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

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

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

identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

restore contrast in the one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast by, at least partially, reducing the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions.

20. 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;

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

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

identify one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast, wherein each region of the one or more regions contains more than one percent of pixels in a frame of the video image and comprises less than an entirety of the video image data; and

restore contrast in one or more regions in the video image data in which the scaling of the brightness values results in a visual artifact associated with reduced contrast by, at least partially, reducing the scaling of the brightness values in the one or more regions without adjusting the video image data outside the regions.