Method of determining field dominance in a sequence of video frames

1. A method of determining field dominance in a sequence of video frames, the method comprising:

generating from a first video frame a top field and a bottom field;

interpolating the top and bottom fields to produce an interpolated top field frame and an interpolated bottom field frame respectively;

correlating each of the interpolated top field frame and interpolated bottom field frame with a second video frame occurring immediately previous to the first video frame in the sequence of video frames and with a third video frame occurring immediately subsequent to the first video frame in the sequence of video frames; and

determining from the outcome of the correlation the field dominance of the sequence of video frames.

2. The method of claim 1 wherein the interpolated top field frame is produced by averaging adjacent lines of the top field and the interpolated bottom field frame is produced by averaging adjacent lines of the bottom field.

3. The method of claim 2 , wherein when the correlation to the interpolated top field frame is greater with the subsequent frame than with the previous frame and the correlation to the interpolated bottom field is greater with previous frame than with the subsequent frame, then the field dominance is determined to be bottom field first.

4. The method of claim 2 , wherein prior to performing the determination step the method further comprises:

calculating a first difference value between correlation outcomes of the correlation of the interpolated top field frame to the previous frame and the correlation of the interpolated top field frame to the subsequent frame;

calculating a second difference value between the correlation outcomes of the correlation of the interpolated bottom field frame to the previous frame and the correlation of the interpolated bottom field frame to the subsequent frame; and

determining the field dominance only if the first and second difference values are greater than a predetermined threshold value.

5. The method of claim 2 , further comprising, subsequent to the correlation step, counting the number of pixels for which the difference in pixel value between a pixel in each of the interpolated top field frame and interpolated bottom field frame and a corresponding pixel in a first reference frame is less than the difference in pixel value between the pixel and a corresponding pixel in a second reference frame, wherein the number of pixels is counted for each of the interpolated top and bottom field frames when the first reference frame comprises the previous frame and the second reference frame comprises the subsequent frame and when the first reference frame comprises the subsequent frame and the second reference frame comprises the previous frame.

6. The method of claim 1 , wherein when the correlation to the interpolated top field frame is greater with the previous frame than with the subsequent frame and the correlation to the interpolated bottom field frame is greater with the subsequent frame than the previous frame, then the field dominance is determined to be top field first.

7. The method of claim 6 , wherein when the correlation to the interpolated top field frame is greater with the subsequent frame than with the previous frame and the correlation to the interpolated bottom field is greater with previous frame than with the subsequent frame, then the field dominance is determined to be bottom field first.

8. The method of claim 1 , wherein when the correlation to the interpolated top field frame is greater with the previous frame than with the subsequent frame and the correlation to the interpolated bottom field frame is greater with the subsequent frame than the previous frame, then the field dominance is determined to be top field first.

9. The method of claim 8 , wherein when the correlation to the interpolated top field frame is greater with the subsequent frame than with the previous frame and the correlation to the interpolated bottom field is greater with previous frame than with the subsequent frame, then the field dominance is determined to be bottom field first.

10. The method of claim 9 , wherein prior to performing the determination step the method further comprises:

calculating a first difference value between correlation outcomes of the correlation of the interpolated top field frame to the previous frame and the correlation of the interpolated top field frame to the subsequent frame;

calculating a second difference value between the correlation outcomes of the correlation of the interpolated bottom field frame to the previous frame and the correlation of the interpolated bottom field frame to the subsequent frame; and

determining the field dominance only if the first and second difference values are greater than a predetermined threshold value.

11. The method of claim 10 , wherein the threshold value is determined by calculating the first and second difference values for a known sequence of static frames.

12. The method of claim 11 further comprising, subsequent to the correlation step, counting the number of pixels for which the difference in pixel value between a pixel in each of the interpolated top field frame and interpolated bottom field frame and a corresponding pixel in a first reference frame is less than the difference in pixel value between the pixel and a corresponding pixel in a second reference frame, wherein the number of pixels is counted for each of the interpolated top and bottom field frames when the first reference frame comprises the previous frame and the second reference frame comprises the subsequent frame and when the first reference frame comprises the subsequent frame and the second reference frame comprises the previous frame.

13. The method of claim 9 , further comprising, subsequent to the correlation step, counting the number of pixels for which the difference in pixel value between a pixel in each of the interpolated top field frame and interpolated bottom field frame and a corresponding pixel in a first reference frame is less than the difference in pixel value between the pixel and a corresponding pixel in a second reference frame, wherein the number of pixels is counted for each of the interpolated top and bottom field frames when the first reference frame comprises the previous frame and the second reference frame comprises the subsequent frame and when the first reference frame comprises the subsequent frame and the second reference frame comprises the previous frame.

14. The method of claim 8 , wherein prior to performing the determination step the method further comprises:

calculating a first difference value between correlation outcomes of the correlation of the interpolated top field frame to the previous frame and the correlation of the interpolated top field frame to the subsequent frame;

calculating a second difference value between the correlation outcomes of the correlation of the interpolated bottom field frame to the previous frame and the correlation of the interpolated bottom field frame to the subsequent frame; and

determining the field dominance only if the first and second difference values are greater than a predetermined threshold value.

15. The method of claim 8 , further comprising, subsequent to the correlation step, counting the number of pixels for which the difference in pixel value between a pixel in each of the interpolated top field frame and interpolated bottom field frame and a corresponding pixel in a first reference frame is less than the difference in pixel value between the pixel and a corresponding pixel in a second reference frame, wherein the number of pixels is counted for each of the interpolated top and bottom field frames when the first reference frame comprises the previous frame and the second reference frame comprises the subsequent frame and when the first reference frame comprises the subsequent frame and the second reference frame comprises the previous frame.

16. The method of claim 1 , wherein when the correlation to the interpolated top field frame is greater with the subsequent frame than with the previous frame and the correlation to the interpolated bottom field is greater with previous frame than with the subsequent frame, then the field dominance is determined to be bottom field first.

17. The method of claim 1 , wherein prior to performing the determination step the method further comprises:

calculating a first difference value between correlation outcomes of the correlation of the interpolated top field frame to the previous frame and the correlation of the interpolated top field frame to the subsequent frame;

calculating a second difference value between the correlation outcomes of the correlation of the interpolated bottom field frame to the previous frame and the correlation of the interpolated bottom field frame to the subsequent frame; and

determining the field dominance only if the first and second difference values are greater than a predetermined threshold value.

18. The method of claim 17 , wherein the threshold value is determined by calculating the first and second difference values for a known sequence of static frames.

19. The method of claim 17 , further comprising, subsequent to the correlation step, counting the number of pixels for which the difference in pixel value between a pixel in each of the interpolated top field frame and interpolated bottom field frame and a corresponding pixel in a first reference frame is less than the difference in pixel value between the pixel and a corresponding pixel in a second reference frame, wherein the number of pixels is counted for each of the interpolated top and bottom field frames when the first reference frame comprises the previous frame and the second reference frame comprises the subsequent frame and when the first reference frame comprises the subsequent frame and the second reference frame comprises the previous frame.

20. The method of claim 1 , further comprising, subsequent to the correlation step, counting the number of pixels for which the difference in pixel value between a pixel in each of the interpolated top field frame and interpolated bottom field frame and a corresponding pixel in a first reference frame is less than the difference in pixel value between the pixel and a corresponding pixel in a second reference frame, wherein the number of pixels is counted for each of the interpolated top and bottom field frames when the first reference frame comprises the previous frame and the second reference frame comprises the subsequent frame and when the first reference frame comprises the subsequent frame and the second reference frame comprises the previous frame.