Method and apparatus to synchronize backlight intensity changes with image luminance changes
An approach for coordinating backlight intensity and image luminance changes. For one aspect, in response to determining that a display-related event has occurred during a vertical frame period indicating a subsequent change associated with at least one of a backlight intensity and a frame buffer palette is to be undertaken, an interrupt is enabled. During subsequent interrupt processing, associated changes to the backlight intensity and the frame buffer palette are applied in a coordinated manner. For a specific implementation, an approach is provided for a graphics controller driver to synchronize response to changes in display backlight, color-space controls, and in the luminance of images, wherein said changes can come from different sources, occur at a different rates, and have different latencies, for the purpose of applying graphics settings responses such that those effects occur at a visually co-incident interval so as to substantially minimize discordant visual artifacts.
1. A method comprising:
determining that a display-related event has occurred during a vertical frame period by determining whether an average image intensity has changed, whether a backlight setting has changed, and whether a gamma look-up table has changed;
setting a histogram dirty flag in response to detecting a change in average image intensity, setting a backlight dirty flag in response to a request to adjust a backlight setting, and setting a gamma dirty flag in response to a request to change a gamma look-up table;
in response to determining that the display-related event has occurred during a vertical frame period indicating that an associated change to at least one of a backlight intensity and an image luminance are to be undertaken, enabling an interrupt; and
during subsequent interrupt processing, applying corresponding changes to the backlight intensity and the image luminance in a coordinated manner by initiating changes to the backlight intensity and, after a delay based on an amount of time it takes for the backlight intensity to reach a target level, applying changes to the image luminance.
2. The method of claim 1 wherein applying changes to the backlight intensity and the image luminance in a coordinated manner includes
applying a backlight intensity change, and
decrementing a delay counter based on a predetermined delay to determine when to apply a change to the image luminance.
3. The method of claim 1 wherein
setting a histogram dirty flag in response to detecting the change in average image intensity includes setting the histogram dirty flag only if the detected change is larger than or equal to a predetermined trigger point.
4. A method comprising:
enabling an interrupt if one or more of an average image intensity, a backlight setting, or a gamma look-up table has changed during a vertical frame period;
setting a histogram dirty flag in response to detecting a change in average image intensity larger than or equal to a threshold change, setting a backlight dirty flag in response to receiving a request to change the backlight intensity, and setting a gamma dirty flag in response to receiving a request to change the image luminance; and
in response to the interrupt, applying associated changes to a backlight intensity and an image luminance in a coordinated manner by initiating changes to the backlight intensity and, after a delay based on an amount of time it takes for the backlight intensity to reach a target level, applying changes to the image luminance.
5. The method of claim 4 further comprising
receiving a request to change at least one of the backlight intensity and the image luminance from at least one of an input device, an operating system, a software module and an application program.
6. The method of claim 4 wherein
detecting a change in average image intensity larger than or equal to a threshold change includes comparing an average image intensity of a current frame to an average image intensity of a previous frame.
7. The method of claim 6 further comprising
computing a histogram for each frame, and
determining an average image intensity for each frame based on the respective histogram.
8. The method of claim 4 wherein applying associated changes to the backlight intensity and the image luminance in a coordinated manner includes
applying the change to the backlight intensity, and
applying the change to the image luminance after a delay such that the change to the image luminance and the change to the backlight intensity take effect at substantially a same time.
9. The method of claim 8 further comprising
initiating a delay count, and
wherein applying the change to the image luminance occurs in response to completion of the delay count.
10. An article comprising a non-transitory computer-accessible medium storing a plurality of instructions that in response to being executed by a processor, cause the processor to:
determine that a display-related event has occurred during a vertical frame period by determining whether an average image intensity has changed, whether a backlight setting has changed, and whether a gamma look-up table has changed;
set a histogram dirty flag in response to detecting a change in average image intensity, set a backlight dirty flag in response to a request to adjust a backlight setting, and set a gamma dirty flag in response to a request to change a gamma look-up table;
in response to determining that the display-related event has occurred during a vertical frame period indicating that an associated change to at least one of a backlight intensity and an image luminance are to be undertaken, enable an interrupt; and
during subsequent interrupt processing, apply corresponding changes to the backlight intensity and the image luminance in a coordinated manner by initiating changes to the backlight intensity and, after a delay based on an amount of time it takes for the backlight intensity to reach a target level, applying changes to the image luminance.
11. The article of claim 10 wherein applying changes to the backlight intensity and the image luminance in a coordinated manner includes
applying a backlight intensity change, and
decrementing a delay counter based on a predetermined delay to determine when to apply a change to the image luminance.
12. The article of claim 10 , wherein
setting a histogram dirty flag in response to detecting the change in average image intensity includes setting the histogram dirty flag only if the detected change is larger than or equal to a predetermined trigger point.