Source-adaptive video deinterlacer

1. A method of deinterlacing an interlaced video stream, comprising:

detecting whether groups of adjacent fields are derived from a common image frame source, wherein the detecting of adjacent fields that are derived from the common image frame source includes:

performing a correlation operation between field pairs, and

calculating a threshold value based on one or more factors, wherein the factors comprise a history of correlation operation values between field pairs, a minimum and maximum value in the history of correlation operation values, a minimum and maximum value for a range of correlation values, and detected scene transitions; and

merging field pairs of the interlaced video stream if the field pairs of the interlaced video stream are determined to be derived from the common image frame source.

2. The method recited in claim 1 , further comprising deinterlacing the interlaced video stream using motion adaptive deinterlacing if the field pairs of the interlaced video stream are determined not to be derived from the common image frame source.

3. The method recited in claim 1 , wherein performing a correlation operation between field pairs further comprises:

performing a difference operation between field pairs that are spaced one field apart.

4. The method recited in claim 3 , further comprising:

phase shifting field pairs to result in two spatially coincident calculated fields.

5. The method recited in claim 3 , further comprising:

performing a vertical low-pass filtering operation on each field of the field pairs to remove noise and aliasing artifacts.

6. The method recited in claim 1 , wherein performing a correlation operation between field pairs comprises:

performing a difference operation between field pairs that are spaced two fields apart.

7. The method recited in claim 1 , wherein adjacent fields that are derived from the common image frame source are further detected by:

determining whether a scene transition has occurred.

8. The method recited in claim l, wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

comparing a correlation value for a field pair with the threshold value, wherein a correlation value smaller than the threshold value indicates a field pair that is from a common source.

9. The method recited in claim 8 , wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

examining a history of comparison values obtained from comparing correlation values with the threshold value to determine if a repeating pattern exists in the interlaced video stream.

10. The method recited in claim 9 , wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

assigning a state value to a current field, wherein the state value is used to determine whether two fields can be properly merged.

11. The method recited in claim 9 , wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

acquiring a lock on the repeating pattern.

12. The method recited in claim 9 , wherein determining if a repeating pattern exists in the interlaced video stream comprises:

assigning a quality value to a field pair representing a level of similarity between correlation values of field pairs.

13. The method recited in claim 1 , wherein merging field pairs of the interlaced video stream further comprises:

determining how to construct the deinterlaced output frame from the sequence of fields.

14. The method recited in claim 13 , wherein motion adaptive deinterlacing is used if no repeating pattern exists.

15. A non-transitory computer-readable storage having stored thereon computer-executable instructions to deinterlace image signals, the computer-executable instructions comprising:

detecting whether groups of adjacent fields are derived from a common original image frame source, wherein the detection of adjacent fields that are derived from the common image frame source includes:

performing a correlation operation between field pairs, wherein performing a correlation operation between field pairs comprises:

performing a difference operation between field pairs that are spaced one field apart, and

phase shifting field pairs to result in two spatially coincident calculated fields, and

calculating a threshold value based on one or more factors, wherein the factors comprise a history of correlation operation values between field pairs, a minimum and maximum value in the history of correlation operation values, a minimum and maximum value for a range of correlation values, and detected scene transitions; and merging field pairs of the interlaced video stream if the field pairs of the interlaced video stream are determined to be derived from the common image frame source.

16. The non-transitory computer-readable storage of claim 15 , further comprising computer-executable instructions for:

deinterlacing the interlaced video stream using motion adaptive deinterlacing if the field pairs of the interlaced video stream are determined not to be derived from the common image frame source.

17. The non-transitory computer-readable storage of claim 15 , wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

comparing a correlation value for a field pair with the threshold value, wherein a correlation value smaller than the threshold value indicates a field pair that is from a common source.

18. The non-transitory computer-readable storage recited in claim 17 , wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

examining a history of comparison values obtained from comparing correlation values with the threshold value to determine if a repeating pattern exists in the interlaced video stream.

19. The non-transitory computer-readable storage recited in claim 18 , wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

assigning a state value to a current field, wherein the state value is used to determine whether two fields can be properly merged.

20. The non-transitory computer-readable storage recited in claim 18 , wherein determining if field pairs of the interlaced video stream are derived from the common image frame source further comprises:

acquiring a lock on the repeating pattern.