Color transient improvement unit and method to reduce blurring at color transients in video images

1. A method of improving color transients of an image having a plurality of pixels, the method comprising:

defining a color transient detection window around a current pixel;

calculating one or more transient characterization values for the color transient detection window with a transient characterization unit, wherein the transient characterization values correspond to a likelihood of a color transition occurring in the color transient detection window; and

generating an improved U chrominance value and an improved V chrominance value for the current pixel;

wherein the calculating one or more transient characterization values for the color transient detection window further comprises:

calculating an average U chrominance value for each column of the color transient detection window to form a plurality of average U chrominance values;

calculating an average V chrominance value for each column of the color transient detection window to form a plurality of average V chrominance values;

calculating a first U transient characterization value corresponding to a degree that the plurality of average U chrominance values is monotonically increasing; and

calculating a first V transient characterization value corresponding to a degree that the plurality of average V chrominance values is monotonically increasing.

2. The method of claim 1 , wherein the color transient detection window includes 3 lines of 7 pixels centered around the current pixel.

3. The method of claim 1 , wherein calculating one or more transient characterization values for the color transient detection window further comprises:

calculating a second U transient characterization value corresponding to a degree that the plurality of average U chrominance values is monotonically decreasing; and

calculating a second V transient characterization value corresponding to a degree that the plurality of average V chrominance values is monotonically decreasing.

4. The method of claim 3 , wherein the first U transient characterization value is an average U chrominance increment sum, the second U transient characterization value is an average U chrominance decrement sum, the first V transient characterization value is an average V chrominance increment sum, and the second V transient characterization value is an average V chrominance decrement sum.

5. The method of claim 3 , wherein calculating one or more transient characterization values for the color transient detection window further comprises determining that a color transient exits in the color transient detection window when the first U transient characterization value and the first V transient characterization value are greater than a chrominance color improvement threshold.

6. The method of claim 5 , wherein calculating one or more transient characterization values for the color transient detection window further comprises determining that a color transient exits in the color transient detection window when the first U transient characterization value and the second V transient characterization value are greater than the chrominance color improvement threshold.

7. The method of claim 6 , wherein calculating one or more transient characterization values for the color transient detection window further comprises determining that a color transient exits in the color transient detection window when the second U transient characterization value and the first V transient characterization value are greater than the chrominance color improvement threshold.

8. The method of claim 7 , wherein calculating one or more transient characterization values for the color transient detection window further comprises determining that a color transient exits in the color transient detection window when the second U transient characterization value and the second V transient characterization value are greater than the chrominance color improvement threshold.

9. The method of claim 8 , wherein generating an improved U chrominance value and an improved V chrominance value for the current pixel comprises:

defining a U chrominance proxy for the U chrominance value of the current pixel;

defining a V chrominance proxy for the V chrominance value of the current pixel;

calculating an average left side U chrominance value;

calculating an average right side U chrominance value;

calculating an average left side V chrominance value;

calculating an average right side V chrominance value;

setting the improved U chrominance value and the improved V chrominance value equal to the average left side U chrominance value and the average left side V chrominance value, respectively, when a color transient exists in the color transient detection window, the U chrominance proxy is closer to the average left side U chrominance value than to the average right side U chrominance value, and the V chrominance proxy is closer to the average left side V chrominance value than to the average right side V chrominance value; and

setting the improved U chrominance value and the improved V chrominance value equal to the average right side U chrominance value and the average right side V chrominance value, respectively, when a color transient exists in the color transient detection window, the U chrominance proxy is closer to the average right side U chrominance value than to the average left side U chrominance value, and the V chrominance proxy is closer to the average right side V chrominance value than to the average left side V chrominance value.

10. The method of claim 9 , wherein the U chrominance proxy is equal to the average U chrominance value containing the current pixel and the V chrominance proxy is equal to the average V chrominance value containing the current pixel.

11. The method of claim 9 , wherein the U chrominance proxy is equal to the U chrominance value of the current pixel and the V chrominance proxy is equal to the V chrominance value of the current pixel.

12. The method of claim 9 , wherein

the average left side U chrominance value is equal to an average of U chrominance values from pixels in the color transient detection window to the left of the current pixel; and

the average right side U chrominance value is equal to an average of U chrominance values from pixels in the color transient detection window to the right of the current pixel.

13. The method of claim 9 , wherein

the average left side V chrominance value is equal to an average of V chrominance values from pixels in the color transient detection window to the left of the current pixel; and

the average right side V chrominance value is equal to an average of V chrominance values from pixels in the color transient detection window to the right of the current pixel.

14. The method of claim 1 , wherein generating an improved U chrominance value and an improved V chrominance value for the current pixel comprises:

defining a U chrominance proxy for the U chrominance value of the current pixel;

defining a V chrominance proxy for the V chrominance value of the current pixel;

calculating an average left side U chrominance value;

calculating an average right side U chrominance value;

calculating an average left side V chrominance value;

calculating an average right side V chrominance value;

setting the improved U chrominance value and the improved V chrominance value equal to the left side average U chrominance value and the left side average V chrominance value, respectively, when a color transient exists in the color transient detection window, the U chrominance proxy is closer td the left side average U chrominance value than to the right side average U chrominance value, and the V chrominance proxy is closer to the left side average V chrominance value than to the right side average V chrominance value; and

setting the improved U chrominance value and the improved V chrominance value equal to the right side average U chrominance value and the right side average V chrominance value, respectively, when a color transient exists in the color transient detection window, the U chrominance proxy is closer to the right side average U chrominance value than to the left side average U chrominance value, and the V chrominance proxy is closer to the right side average V chrominance value than to the left side average V chrominance value.

15. The method of claim 14 , wherein

the left side average U chrominance value is equal to an average of U chrominance values from pixels in the color transient detection window to the left of the current pixel; and

the right side average U chrominance value is equal to an average of U chrominance values from pixels in the color transient detection window to the right of the current pixel.

16. The method of claim 14 , wherein

the left side average V chrominance value is equal to an average of V chrominance values from pixels in the color transient detection window to the left of the current pixel; and

the right side average V chrominance value is equal to an average of V chrominance values from pixels in the color transient detection window to the right of the current pixel.

17. A color transient improvement unit for improving color transients of an image having a plurality of pixels comprising:

a transient characterization unit configured to calculate one or more transient characterization values for a color transient detection window containing a current pixel;

a transient threshold unit coupled to the transient characterization unit and configured to determine whether a color transient exists in the color transient detection window by comparing the transient characterization values to a chrominance color improvement threshold;

a transient correction unit coupled to the transient threshold unit and configured to generate an improved U chrominance value and an improved V chrominance value for the current pixel; and

a line averaging unit coupled to the transient characterization unit and configured to calculate an average U chrominance value and an average V chrominance value for each column of the color transient detection window to form a plurality of average U chrominance values and a plurality of V chrominance values.

wherein the transient characterization unit is configured to calculate a first U transient characterization value corresponding to a degree that the plurality of average U chrominance values is monotonically increasing and to calculate a first V transient characterization value corresponding to a degree that the plurality of average V chrominance values is monotonically increasing.

18. The color transient improvement unit of claim 17 , wherein the transient characterization unit is configured to calculate a second U transient characterization value corresponding to a degree that the plurality of average U chrominance values is monotonically decreasing and to calculate a second V transient characterization value corresponding to a degree that the plurality of average V chrominance values is monotonically decreasing.

19. The color transient improvement unit of claim 17 further comprising an averaging unit configured to calculating a left side average U chrominance value, a right side average U chrominance value, a left side average V chrominance value, and a right side average V chrominance value.

20. The color transient improvement unit of claim 19 , wherein the transient correction unit is configured to set the improved U chrominance value and the improved V chrominance value equal to the left side average U chrominance value and the left side average V chrominance value, respectively, when a color transient exists in the color transient detection window, a U chrominance proxy is closer to the left side average U chrominance value than to the right side average U chrominance value, and a V chrominance proxy is closer to the left side average V chrominance value than to the right side average V chrominance value.

21. The color transient improvement unit of claim 20 , wherein the transient correction unit configured to set the improved U chrominance value and the improved V chrominance value equal to the right side average U chrominance value and the right side average V chrominance value, respectively, when a color transient exists in the color transient detection window, the U chrominance proxy is closer to the right side average U chrominance value than to the left side average U chrominance value, and the V chrominance proxy is closer to the right side average V chrominance value than to the left side average V chrominance value.

22. The color transient improvement unit of claim 20 , wherein the U chrominance proxy is equal to the average U chrominance value containing the current pixel and the V chrominance proxy is equal to the average V chrominance value containing the current pixel.

23. The color transient improvement unit of claim 20 , wherein

the left side average U chrominance value is equal to an average of U chrominance values from pixels in the color transient detection window to the left of the current pixel; and

the right side average U chrominance value is equal to an average of U chrominance values from pixels in the color transient detection window to the right of the current pixel.

24. The color transient improvement unit of claim 20 , wherein

the left side average V chrominance value is equal to an average of V chrominance values from pixels in the color transient detection window to the left of the current pixel; and

the right side average V chrominance value is equal to an average of V chrominance values from pixels in the color transient detection window to the right of the current pixel.