1. A noise reduction system for an image frame, comprising: a module that collects an input frame and a past filtered frame and calculates the absolute difference of the input frame and the past filtered frame; a noise estimation module that calculates a global noise variance from each frame by comparing the input and the past filtered frames, calculates a local mean of the input frame, and converts the global noise variance into a local noise variance using a parameter-based model; an adapted spatio-temporal filter that filters the local noise variance along with the input and the past filtered frames and outputs a current filtered frame; and a frame buffer storing the current filtered frame for use as the next past filtered frame.