1. A signal-processing system comprising: a processing component; and a signal-processing routine executed by the processing component that, at each of one or more currently considered scales of resolution greater than a lowest resolution scale, processes an input signal to produce an output signal by downscaling either the input signal or a signal derived from the input signal to produce an input signal for a next-lower resolution scale, upscaling a signal received from a lower-resolution scale to produce a first intermediate signal from which an output signal to a next-higher-resolution scale is produced, and robustly filtering at least one of the input signal or the intermediate signal.