Temporal filtering based on motion detection between temporally non-adjacent pictures
A method for temporal filtering based on motion detection between non-adjacent pictures. The method may compute a motion score by motion detection between a target area in a target picture and a first area in a non-adjacent one of a plurality of reference pictures; and temporal filter the target area with a second area in an adjacent one of the reference pictures based on the motion score to generate a filtered area in a filtered picture. At least one of (i) the motion score and (ii) the generation of the filtered area may be controlled by one or more gain settings in a circuit.
1. A method for temporal filtering based on motion detection between non-adjacent pictures comprising the steps of:
computing a motion score by motion detection between a target area in a target picture and a temporally non-adjacent first area in a non-adjacent one of a plurality of reference pictures;
generating a temporal filter strength based on the motion score, wherein said temporal filter strength is determined based upon said motion score and a blending function that is nonlinear over a range of values of said motion score; and
temporal filtering said target area with a second area in an adjacent one of said reference pictures based on said temporal filter strength to generate a filtered area in a filtered picture, wherein said target area, said first area, and said second area are spatially co-located and at least one of (i) said motion score and (ii) said generation of said filtered area is controlled by one or more gain settings in a circuit.
2. The method according to claim 1 , further comprising the step of:
computing an additional motion score by motion detection between said target area and a third area in an additional one of said reference pictures, wherein said additional reference picture is non-adjacent to said target picture.
3. The method according to claim 2 , further comprising the step of:
computing a combined motion score as a combination of said motion score and said additional motion score, wherein said temporal filter strength is based on said combined motion score and said blending function.
4. The method according to claim 3 , wherein said combined motion score is read from a lookup table indexed by said motion score and said additional motion score.
5. The method according to claim 1 , further comprising the step of:
computing an additional motion score by motion detection between said target area and said second area, wherein said generation of said filtered area is further based on said additional motion score.
6. The method according to claim 5 , further comprising the step of:
computing a combined motion score as a combination of said motion score and another motion score based on a third area in another one of said reference pictures, wherein said other reference picture is non-adjacent to said target picture.
7. The method according to claim 1 , further comprising the steps of:
generating a maximum motion score by selecting a maximum value between said motion score and another motion score, wherein said other motion score is independent of said target picture; and
transforming said maximum motion score to generate a combined motion score, wherein said temporal filter strength is based on said combined motion score and said blending function.
8. The method according to claim 1 , further comprising the steps of:
determining a maximum score among (i) said motion score and (ii) one or more additional motion scores computed between two or more co-located areas in two or more of said reference pictures; and
combining said maximum score and said motion score to generate a combined motion score, wherein said temporal filter strength is based on said combined motion score and said blending function.
9. The method according to claim 1 , wherein the steps are performed in a digital camera.
10. The method according to claim 1 , further comprising the step of:
motion compensating said non-adjacent reference picture prior to said motion detection with said target area.
11. An apparatus comprising:
an interface configured to receive a sequence of pictures; and
a circuit configured to (i) compute a motion score by motion detection between a target area in a target picture and a first area in a non-adjacent one of a plurality of reference pictures, (ii) generate a temporal filter strength based on the motion score, wherein said temporal filter strength is determined based upon said motion score and a blending function that is nonlinear over a range of values of said motion score, and (iii) temporal filter said target area with a second area in an adjacent one of said reference pictures based on said temporal filter strength to generate a filtered area in a filtered picture, wherein said target area, said first area, and said second area are spatially co-located and at least one of (i) said motion score and (ii) said generation of said filtered area is controlled by one or more gain settings.
12. The apparatus according to claim 11 , wherein (i) said circuit is further configured to compute an additional motion score by motion detection between said target area and a third area in an additional one of said reference pictures and (ii) said additional reference picture is non-adjacent to said target picture.
13. The apparatus according to claim 12 , wherein (i) said circuit is further configured to compute a combined motion score as a combination of said motion score and said additional motion score and (ii) said temporal filter strength is based on said combined motion score and said blending function.
14. The apparatus according to claim 13 , wherein said combined motion score is read from a lookup table indexed by said motion score and said additional motion score.
15. The apparatus according to claim 11 , wherein (i) said circuit is further configured to compute an additional motion score by motion detection between said target area and said second area and (ii) said generation of said filtered area is further based on said additional motion score.
16. The apparatus according to claim 15 , wherein (i) said circuit is further configured to compute a combined motion score as a combination of said motion score and another motion score based on a third area in another one of said reference pictures and (ii) said other reference picture is non-adjacent to said target picture.
17. The apparatus according to claim 11 , wherein (i) said circuit is further configured to (a) generate a maximum motion score by selecting a maximum value between said motion score and another motion score, (b) said other motion score is independent of said target picture and (c) transform said maximum motion score to generate a combined motion score and (ii) said temporal filter strength is based on said combined motion score and said blending function.
18. The apparatus according to claim 11 , wherein (i) said circuit is further configured to (a) determine a maximum score among said motion score and one or more additional motion scores computed between two or more co-located areas in two or more of said reference pictures and (b) combine said maximum score and said motion score to generate a combined motion score and (ii) said temporal filter strength is based on said combined motion score and said blending function.
19. The apparatus according to claim 11 , wherein said interface and said circuit are part of a digital camera.
20. The apparatus according to claim 11 , wherein said non-adjacent reference picture is motion compensated prior to said motion detection with said target area.