1. A method for estimating visual quality of a video sequence, comprising: accessing spatial distortion for frames in a plurality of sliding windows that include a current frame in the video sequence; determining a factor indicating at least one of a large distortion density and a representative artifact level for each sliding window responsive to respective spatial distortion for frames in the each sliding window; determining temporal distortion for the current frame responsive to the determined factor; and determining the visual quality of the video sequence responsive to the temporal distortion of the current frame.