Method and System for Motion Compensated Noise Reduction
The present invention is directed to a method and system for improved motion compensated noise reduction. The system uses a temporal noise reduction filter to remove noise from the current input field and pass it through a de-interlacer to produce a noise reduced full output frame. The temporal noise reduction filter reduces noise in the present field by blending it with a predicted (motion compensated) field determined from the immediately preceding full output frame. In accordance with the invention where the current input field is for time or sequence n, the motion compensated field can be determined from the output frame corresponding to time or sequence n−1. In addition, the motion compensated field can be predicted using motion estimation and motion compensation using the current input field and the previous output frame. By using the previous de-interlaced frame which includes the information for both field polarities, the vertical resolution of the motion estimation process can be improved.
1 . A system for motion compensated noise reduction of an input signal, the input signal comprising a plurality of input fields, the system comprising:
a motion estimation and motion compensation module adapted to produce a motion compensated field corresponding to an input field as a function of the input field corresponding to a first field position and a de-interlaced frame corresponding to a previous field position; and
a noise reduction filter adapted to produce a noise reduced output field as a function of the input field and the motion compensated field.
2 . A system according to claim 1 wherein the input field is the current field corresponding to the current field position.
3 . A system according to claim 1 wherein the de-interlaced frame corresponds to the field position immediately preceding the field position of the input field.
4 . The system according to claim 1 further comprising:
a de-interlacer adapted to produce a noise reduced de-interlaced output frame as a function of the noise reduced output field.
5 . The system according to claim 4 wherein said noise reduced de-interlaced output frame is fed back to said motion estimation and motion compensation module for use in generating a motion compensated field corresponding to a subsequent field position.
6 . The system according to claim 1 wherein the noise reduction filter is a temporal noise reduction filter.
7 . The system according to claim 1 wherein the noise reduction filter removes random noise from the input signal.
8 . The system according to claim 1 wherein the noise reduction filter removes noise by blending the input field corresponding to the first field position and the motion compensated field corresponding to the input field.
9 . The system according to claim 8 wherein the noise reduction filter uses a blending coefficient equal to 1.
10 . A method for motion compensated noise reduction of an input signal, the input signal comprising a plurality of input fields, the method comprising:
producing a motion compensated field corresponding to an input field as a function of the input field corresponding to a first field position and a de-interlaced frame corresponding to a previous field position; and
applying a noise reduction filter to produce a noise reduced output field corresponding to the first field position as a function of the input field and the motion compensated field corresponding to the current field position; and
outputting the noise reduced output field for use in storing or displaying a video signal.
11 . The method according to claim 10 wherein the input field is the current field corresponding to the current field position.
12 . The method according to claim 10 wherein the de-interlaced frame corresponds to the field position immediately preceding the field position of the input field.
13 . The method according to claim 10 further comprising:
de-interlacing the noise reduced output field to produce a noise reduced de-interlaced output frame.
14 . The method according to claim 13 wherein said noise reduced de-interlaced output frame is used for generating a motion compensated field corresponding to a subsequent field position.
15 . The method according to claim 10 wherein the noise reduction filter is a temporal noise reduction filter.
16 . The method according to claim 10 wherein the noise reduction filter removes random noise from the input signal.
17 . The method according to claim 10 wherein the noise reduction filter removes noise by blending the input field corresponding to the first field position and the motion compensated field corresponding to the input field.
18 . The method according to claim 17 wherein the noise reduction filter uses a blending coefficient equal to 1.
19 . A video signal processing device comprising:
a motion estimation and motion compensation module adapted to produce a motion compensated field corresponding to an input field as a function of the input field and a de-interlaced frame, the de-interlaced frame corresponding to a field position prior to a field position of the input field;
a noise reduction filter adapted to produce a noise reduced output field as a function of the input field and the motion compensated field; and
a de-interlacer adapted to produce a noise reduced de-interlaced output frame as a function of the noise reduced output field.
20 . A method for noise reduction of an input field, the method comprising:
generating a motion compensated frame as a function of the input field and a noise reduced frame;
applying the input field to a temporal noise reduction filter to reduce the noise in the input field as a function of the motion compensated frame to produce a noise reduced output field; and
applying the noise reduced output field to a deinterlacer for generating a noise reduced frame as a function of the noise reduced output field and feeding said noise reduced frame back for use in generating a motion compensated frame corresponding to a subsequent field position.