Method and apparatus for controlling display refresh

• US 20060146056A1
• Filed: 12/30/2004
• Published: 07/06/2006
• Est. Priority Date: 12/30/2004
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Wyatt, David A.
• Granted Patent: US 7,692,642 B2
• Time in Patent Office: Days
• US Class Current: 345/501
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04

Abstract

An approach for dynamic refresh rate control. For one aspect, a policy, such as a power, performance, quality or other policy, for example, is accessed. A refresh rate may then be dynamically selected in response to detected display content activity and policy preferences for displays that are regularly refreshed. Alternatively, if the display is one of a bi-stable, a self-refreshing display or another type of display that is refreshed irregularly, whether or not to refresh the display may be determined based on detected content activity.

Claims

1. A method comprising:

accessing a policy; and

if a display is regularly refreshed, dynamically selecting a refresh rate in response to detected display content activity and a preference indicated by the policy, and

if the display is one of a bi-stable and a self-refreshing display, determining whether to refresh the display based on detected display content activity and a preference indicated by the policy.

2. The method of claim 1 further comprising

detecting display content activity,

if the display is regularly refreshed,

if the detected display content activity exceeds a first threshold, indicating a change to a higher refresh rate, and

if the detected display content activity drops below a second threshold, indicating a change to a lower refresh rate.

3. The method of claim 1 further comprising

detecting display content activity,

if the display is one of a bi-stable and a self-refreshing display,

if the detected display content activity exceeds a first threshold and a display is one of a bi-stable and a self-refreshing display, indicating that the display is to be refreshed, and

if the detected display content activity drops below a second threshold and the display is one of a bi-stable and a self-refreshing display, indicating that the display is not to be refreshed.

4. The method of claim 2 wherein detecting display content activity includes

comparing contents of at least some display scanlines of a first frame with contents of corresponding scanlines of a second frame.

5. The method of claim 4 wherein

comparing contents of at least some display scanlines of the first frame with contents of corresponding scanlines of the second frame includes

computing a hash of the at least some display scanlines of the first frame and corresponding scanlines of the second frame, and

comparing the hashes of the at least some display scanlines of the first frame with hashes of the corresponding scanlines of the second frame.

6. The method of claim 5 wherein detecting display content activity further comprises

maintaining a count of a number of scanlines for which a difference is detected,

determining whether the count exceeds a third threshold,

indicating a novel frame if the count exceeds the third threshold, and

wherein determining whether the detected display content activity exceeds the first threshold includes determining a number of novel frames over a first time period.

7. The method of claim 2 further comprising

if a change in refresh rate is indicated, coordinating the change in refresh rate to occur such at a time such that visually disturbing artifacts are substantially avoided.

8. The method of claim 2 wherein detecting display content activity includes

computing a hash of a first area of display contents for a first frame;

computing a hash of a corresponding area of display contents for a second frame; and

comparing the computed hashes to determine whether the amount of difference between the first and second frames is above a third threshold.

9. The method of claim 2 wherein detecting display content activity includes

indicating a novel frame if one of

a number of areas being rendered exceeds a third threshold,

a size of an area being rendered exceeds a fourth threshold, and

a number of rendering operations in an area exceeds a fifth threshold, and

determining that the display content activity exceeds the first threshold if a number of novel frames over a time interval exceeds the first threshold.

10. The method of claim 2 further comprising

determining a number of transitions between each refresh state, a refresh state including a specific refresh rate and mode,

computing a weight associated with each refresh state based on a proportional time spent in the refresh state, and

if a rate of transitions between refresh states exceeds a third threshold value, delaying a transition from a refresh state associated with a highest weight until the state of transitions drops below a fourth threshold.

11. An apparatus comprising:

a display content activity detection module to detect display content activity, and

a dynamic refresh rate control module to access a policy and to determine whether to dynamically adjust a refresh rate of a display based on detected display content activity and a preference indicated by the policy.

12. The apparatus of claim 11 wherein

if the detected display content activity exceeds a first threshold, the dynamic refresh rate control module is to indicate a change to a higher refresh rate, and

if the detected display content activity drops below a second threshold, the dynamic refresh rate control module is to indicate a change to a lower refresh rate.

13. The apparatus of claim 12 wherein

the display content activity detection module is to compare contents of at least some display scanlines of a first frame with contents of corresponding scanlines of a second frame.

14. The apparatus of claim 13 wherein

comparing contents of at least some display scanlines of the first frame with contents of corresponding scanlines of the second frame includes

computing a hash of the at least some display scanlines of the first frame and corresponding scanlines of the second frame, and

comparing the hashes of the at least some display scanlines of the first frame with hashes of the corresponding scanlines of the second frame.

15. The apparatus of claim 14 wherein the display content activity detection module is further to

maintain a count of a number of scanlines for which a difference is detected,

determine whether the count exceeds a third threshold,

indicate a novel frame if the count exceeds the third threshold, and

wherein determining whether the detected display content activity exceeds the first threshold includes determining a number of novel frames over a first time period.

16. The apparatus of claim 12 wherein

if a change in refresh rate is indicated, the dynamic refresh rate control module is further to co-ordinate the change in refresh rate to occur at a time such that visually disturbing artifacts are substantially avoided.

17. The apparatus of claim 12 wherein the display content activity module is to

indicate a novel frame if one of

a number of areas being rendered exceeds a third threshold,

a size of an area being rendered exceeds a fourth threshold, and

a number of rendering operations in an area exceeds a fifth threshold, and

determine that the display content activity exceeds the first threshold if a number of novel frames over a time interval exceeds the first threshold.

18. The apparatus of claim 12 wherein the dynamic refresh rate control module is further to

determine a number of transitions between each refresh rate,

compute a weight associated with each refresh rate based on a proportional time spent at the refresh rate, and

if a rate of transitions between refresh rates exceeds a third threshold value, delay a transition from a refresh rate associated with a highest weight until the rate of transitions drops below a fourth threshold.

19. A system comprising:

a bus to communicate information;

a display coupled to the bus to display graphics content;

an antenna coupled to the bus to enable wireless communications;

a processor coupled to the bus to process instructions;

a graphics control module coupled to the bus to provide graphics and display control;

a display content activity detection module to detect display content activity; and

a refresh control module to access a policy associated with the system, the refresh control module to determine one of a refresh rate for the display and whether to refresh the display based on detected display content activity and a preference for one of quality, performance and power savings indicated by the policy.

20. The system of claim 19 further comprising a machine-accessible storage medium, the machine-accessible storage medium to store at least one of the display content activity detection module and the refresh control module.

21. The system of claim 19 wherein

if the display is regularly refreshed,

if the detected display content activity exceeds a first threshold, the refresh control module is to indicate a change to a higher refresh rate, and

if the detected display content activity drops below a second threshold, the refresh control module is to indicate a change to a lower refresh rate.

22. The system of claim 19 wherein

if the display is one of a bi-stable and a self-refreshing display,

if the detected display content activity exceeds a first threshold and a display is one of a bi-stable and a self-refreshing display, the refresh control module is to indicate that the display is to be refreshed, and

if the detected display content activity drops below a second threshold and the display is one of a bi-stable and a self-refreshing display, the refresh control module is to indicate that the display is not to be refreshed.

23. The system of claim 21 wherein the display content activity detection module is to

compare contents of at least some display scanlines of a first frame with contents of corresponding scanlines of a second frame.

24. The system of claim 23 wherein

comparing contents of at least some display scanlines of the first frame with contents of corresponding scanlines of the second frame includes

computing a hash of the at least some display scanlines of the first frame and corresponding scanlines of the second frame, and

comparing the hashes of the at least some display scanlines of the first frame with hashes of the corresponding scanlines of the second frame.

25. The system of claim 24 wherein detecting display content activity further comprises

maintaining a count of a number of scanlines for which a difference is detected,

determining whether the count exceeds a third threshold,

indicating a novel frame if the count exceeds the third threshold, and

wherein determining whether the detected display content activity exceeds the first threshold includes determining a number of novel frames over a first time period.

26. The system of claim 21 wherein the display content activity detection module is to

indicate a novel frame if one of

a number of areas being rendered exceeds a third threshold,

a size of an area being rendered exceeds a fourth threshold, and

a number of rendering operations in an area exceeds a fifth threshold, and

determine that the display content activity exceeds the first threshold if a number of novel frames over a time interval exceeds the first threshold.

27. A machine-accessible medium storing information that, when accessed by a machine, causes the machine to

access a policy;

and

if a display is regularly refreshed, dynamically select a refresh rate in response to detected display content activity and a preference indicated by the policy, and

if the display is one of a bi-stable and a self-refreshing display, determine whether to refresh the display based on detected display content activity and a preference indicated by the policy.

28. The machine-accessible medium of claim 27 further storing information that, when accessed by a machine, causes the machine to

detect display content activity,

if the display is regularly refreshed,

if the detected display content activity exceeds a first threshold, indicate a change to a higher refresh rate, and

if the detected display content activity drops below a second threshold, indicate a change to a lower refresh rate.

29. The machine-accessible medium of claim 27 further storing information that, when accessed by a machine, causes the machine to

detect display content activity,

if the display is one of a bi-stable and a self-refreshing display,

if the detected display content activity exceeds a first threshold and a display is one of a bi-stable and a self-refreshing display, indicate that the display is to be refreshed, and

if the detected display content activity drops below a second threshold and the display is one of a bi-stable and a self-refreshing display, indicate that the display is not to be refreshed.

30. The machine-accessible medium of claim 28 wherein detecting display content activity includes

comparing contents of at least some display scanlines of a first frame with contents of corresponding scanlines of a second frame.

31. The machine-accessible medium of claim 30 wherein

comparing contents of at least some display scanlines of the first frame with contents of corresponding scanlines of the second frame includes

computing a hash of the at least some display scanlines of the first frame and corresponding scanlines of the second frame, and

comparing the hashes of the at least some display scanlines of the first frame with hashes of the corresponding scanlines of the second frame.

32. The machine-accessible medium of claim 31 wherein detecting display content activity further comprises

maintaining a count of a number of scanlines for which a difference is detected,

determining whether the count exceeds a third threshold,

indicating a novel frame if the count exceeds the third threshold, and

wherein determining whether the detected display content activity exceeds the first threshold includes determining a number of novel frames over a first time period.

33. The machine-accessible medium of claim 28 wherein detecting display content activity includes

indicating a novel frame if one of

a number of areas being rendered exceeds a third threshold,

a size of an area being rendered exceeds a fourth threshold, and

a number of rendering operations in an area exceeds a fifth threshold, and

determining that the display content activity exceeds the first threshold if a number of novel frames over a time interval exceeds the first threshold.