based on local contrast and directional edges may be used independently the input to the perceptual analysis is a media signal 100 such as an image or audio signal for the sake of an example we describe an implementation for still images in this case the media signal is an image or part of an image one aspect of the perceptual analysis 102 computes a measure of directional edges 104 at positions throughout the media signal the method uses this measure to compute data to control changes to the input signal in a manner that reduces perceptibility of those changes for example the control data may be used to suppress a change to a sample or set of samples of a media signal as a function of the measure of directional edges at the position of the sample or samples in the media signal another aspect of the perceptual analysis 106 computes a measure of local contrast at positions in the media signal it then computes perceptual sensitivity at these positions based on the local contrast measurements and a perceptual model that models human sensitivity to contrast the perceptual analysis uses the results of the directional edge and local contrast perceptual modeling to compute a control vector 110 elements of the control vector correspond to samples of the media signal the magnitude of these elements reflect the relative impact that changes to corresponding samples are expected to have in perceptibility a larger element value in the control vector means.