1. A method of encoding video, the method comprising: calculating a motion compensated error signal of a portion of a first image in a plurality of images of a video sequence; generating a sum of a plurality of motion compensated error signals, each motion compensated error signal in the plurality of motion compensated error signals (i) calculated for a portion of a second image other than the first image in the plurality of images and (ii) weighted based on proximity of the second image to the first image in the video sequence; identifying a visual masking strength for the portion of the first image based on the motion compensated error signal of the portion of the first image and the sum of the plurality of motion compensated error signals, wherein the visual masking strength quantifies a degree to which coding artifacts are not perceptible to a viewer due to complexity of the portion of the first image; and encoding at least a part of the first image based on the visual masking strength.