1. A method of noise filtering of a digital video sequence, the method comprising: receiving a frame of the digital video sequence and a reference frame corresponding to the frame; computing a motion image for the frame, wherein the motion image comprises a motion value for each pixel in the frame, and wherein the motion values are computed as differences between pixel values in a luminance component of the frame and corresponding pixel values in a luminance component of the reference frame; applying a first spatial noise filter to the motion image to obtain a final motion image, comprising: applying the first spatial noise filter to the motion image to obtain a spatially filtered motion image; subsampling the spatially filtered motion image by a sampling ratio r 2 , wherein r is the subsampled ration, and wherein applying the first spatial noise filter to each of the subsampled images to obtain r 2 spatially filtered subsampled images; and combining the r 2 spatially filtered subsampled images by reversing the subsampling to obtain the final motion image; computing a blending factor image for the frame, wherein the blending factor image comprises a blending factor for each pixel in the frame, and wherein the blending factors are computed based on corresponding motion values in the final motion image; generating a filtered frame, wherein the blending factors are applied to corresponding pixel values in the reference frame and the frame; and outputting the filtered frame.