Noise reduction in frame transmitted video signals

A method for reducing noise in frames of video information comprising:

• making available a number of frames including a reference frame in which noise is to be reduced;
• deriving a MAD.sub.o value for each of a plurality of blocks of pixels in said reference frame with respect to corresponding blocks in at least one other frame, said MAD.sub.o value representing a mean absolute difference between the pixels in the block in the reference frame and the respective pixels in the block in the other frame;
• for each of the blocks in a reference frame having a MAD.sub.o greater than a predetermined threshold value A, deriving a MAD.sub.min value, representing a minimum mean absolute difference value between the block in the reference frame and a plurality of blocks selected from the other frame wherein the MAD.sub.min value defines a matching block in the other frame;
• averaging the blocks of the reference frame with corresponding blocks of the other frame when,
• the value of their MAD.sub.o is less than said predetermined threshold value A, or
• the ratio of the MAD.sub.o and MAD.sub.min values for the block from the reference frame is less than a predetermined threshold value B;
• and
• averaging the blocks of the reference frame with the respective matching blocks in at least one other frame when,
• the value of MAD.sub.o for the block from the reference frame is greater than the predetermined threshold value A and the ratio of MAD.sub.o to MAD.sub.min is for the block in the reference frame is greater than the predetermined threshold value B.

A method for reducing noise in video signals transmitted in sequential frames comprising:

• making available a number of frames including a reference frame in which noise is to be reduced;
• sequentially addressing blocks in said reference frame;
• holding blocks in said reference frame for averaging;
• determining a value of MAD.sub.o for each of the blocks in said reference frame, said value of MAD.sub.o representing the mean absolute difference between pixels in the block in the reference frame and pixels in a corresponding block in the other frame;
• holding the corresponding blocks in the other frame for averaging with the blocks in the reference frame for which the value of the MAD.sub.o value is greater than a predetermined threshold value A;
• finding matching blocks in said at least one other frame for blocks in said reference frame for each block in the reference frame for which the MAD.sub.o value is greater than the predetermined threshold value A;
• providing the mean absolute difference values between the blocks in the reference frame and the respective matching blocks in the other frame as respective MAD.sub.min values for said matching blocks;
• holding said matching blocks for averaging with the respective blocks from the reference frame if the ratio of their respective MAD.sub.min values to their respective MAD.sub.o values is greater than the predetermined threshold value, B;
• and
• averaging the blocks held for averaging.