Motion blur reduction for LCD video/graphics processors
The present invention relates to a method and a system of reducing motion blur in a liquid crystal cell. A basic idea of the invention is to process, in an LCD system, a luminance component (Y) of a picture frame to provide motion blur reduction, wherein overdrive is applied to the luminance component only. First, a luminance component related to a first picture frame is stored. Thereafter, a luminance component of a subsequent picture frame is acquired. To reduce motion blur in the LCD, a modified luminance component (Y′) is created based on a difference between the value of the luminance component of the subsequent frame and the value of the luminance component related to the first frame. Hence, based on the value of the difference in the luminance components, and color components (U, V) of the subsequent picture frame, a drive voltage is applied to the LC cell.
1. A method of reducing motion blur in a liquid crystal cell, the method comprising the steps of:
converting a previous picture frame from an RGB color space into a YUV color space;
storing a luminance component in the YUV color space related to the previous picture frame;
converting a current picture frame from an RGB color space into the YUV color space;
determining an overdrive factor based on a difference between a luminance component in the current picture frame in the YUV color space and the stored luminance component;
creating a modified luminance component by applying the overdrive factor only to the luminance component of the current picture frame in the YUV color space; and
converting the modified luminance component and color components of the current picture frame back into an RGB color space for display in the liquid crystal cell;
thereby increasing the transition speed from one luminance level to another.
2. The method according to claim 1 , wherein said creating the modified luminance component comprises assigning a value to the modified luminance component based on a function that relates to said difference.
3. The method according to claim 2 , wherein said creating the modified luminance component comprises assigning a value to the modified luminance component based on said difference multiplied by the overdrive factor.
4. The method according to claim 3 , wherein said creating the modified luminance component further comprises adding the value of the luminance component related to said previous picture frame.
5. The method according to claim 3 , wherein said creating modified luminance component further comprises adding the value of the luminance component of said current picture frame.
6. The method according to claim 3 , wherein the overdrive factor is a variable factor that depends on a magnitude of said difference.
7. The method according to claim 3 , wherein the overdrive factor is a variable factor that depends on a magnitude of a luminance component.
8. The method according to claim 6 , wherein the overdrive factor is obtained from a look-up table.
9. The method according to claim 2 , wherein the modified luminance component is created by assigning a value to the modified luminance component, which value is directly obtained from a predetermined look-up table.
10. The method according to claim 1 , wherein the luminance component of each picture frame is stored in a frame memory.
11. The method according to claim 10 , wherein motion blur reduction processing shares access to the frame memory with any other video processing that acquires a previous and a current luminance component.
12. The method according to claim 11 , wherein said any other video processing that acquires a previous and a current luminance component comprises temporal noise reduction processing.
13. The method according to claim 11 , wherein said any other video processing that acquires a previous and a current luminance component comprises motion detection processing.
14. The method according to claim 1 , further comprising the step of:
setting a threshold value for motion blur reduction, wherein a drive voltage is applied to the liquid crystal cell if the value of said difference exceeds the threshold value.
15. The method according to claim 1 , further comprising the step of:
setting a threshold value for temporal noise reduction wherein noise reduction is performed on said difference if a value of said difference is smaller than a temporal noise reduction threshold value.
16. The method according to claim 14 , wherein the threshold value for motion blur reduction is set equal to a threshold value for temporal noise reduction.
17. The method according to claim 1 , wherein the luminance component is stored with a resolution that is lower than a full panel resolution.
18. The method according to claim 1 , wherein the stored luminance component comprises a luminance component of the previous picture frame.
19. The method according to claim 1 , wherein the stored luminance component comprises a modified luminance component of the previous picture frame.
20. A computer program product comprising a non-transitory computer readable storage medium that stores computer-executable instructions that implement a method of reducing motion blur in a liquid crystal cell, the method comprising the steps of:
converting a previous picture frame from an RGB color space into a YUV color space;
storing a luminance component in the YUV color space related to the previous picture frame;
converting a current picture frame from an RGB color space into the YUV color space;
determining an overdrive factor based on a difference between a luminance component in the current picture frame in the YUV color space and the stored luminance component;
creating a modified luminance component by applying the overdrive factor only to the luminance component of the current picture frame in the YUV color space; and
converting the modified luminance component and color components of the current picture frame back into an RGB color space for display in the liquid crystal cell;
thereby increasing the transition speed from one luminance level to another.
21. A system for reducing motion blur in a liquid crystal cell, the system comprising:
means for converting a previous picture frame from an RGB color space into a YUV color space;
means for storing a luminance component in the YUV color space related to a the previous picture frame;
means for converting a current picture frame from an RGB color space into the YUV color space;
means for determining an overdrive factor based on a difference between a luminance component in said current picture frame in the YUV color space and the stored luminance component;
means for creating a modified luminance component by applying a drive factor only to the luminance component of the current picture frame in the YUV color space; and
converting the modified luminance component and color components of the current picture frame back into an RGB color space for display in the liquid crystal cell;
thereby increasing the transition speed from one luminance level to another.
22. The system according to claim 21 , said system being arranged in a scanning backlight system.