A method and apparatus for determining an image noise estimate value in a digital video processing system using only a single video image. In the method and apparatus, SAD values in the video image are calculated. For each SAD value, a determination is made as to whether the SAD value falls within one or more of a plurality of predetermined SAD value ranges, each of which corresponds to a prospective image noise estimate value. The determination is made concurrently for all of the predetermined SAD value ranges. For each one of the SAD value ranges, the number of SAD values that fall within that predetermined SAD value range is counted. The prospective image noise estimate having a count value that meets predetermined criteria is then selected as the image noise estimate value in the digital video processing system.