A method and apparatus for measuring the 'perceptual distance' between an approximate, reconstructed representation of a sensory signal (such as an audio or video signal) and the original sensory signal is provided. The perceptual distance in this context is a direct quantitative measure of the likelihood that a human observer can distinguish the original audio or video signal from the reconstructed approximation to the original audio or video signal. The method described herein applies to noisy compression techniques; the method provides the ability to predict the likelihood that the reconstructed noisy representation of the original signal will be distinguishable by a human observer from the original input representation. The method can be used to allocate bits in audio and video compression algorithms such that the signal reconstructed from compressed representation is perceptually similar to the original input signal when judged by a human observer. The method is based on a theory of the neurophysiological limitations of human sensory perception. Specifically, a 'neural encoding model' (NEM) summarizes the manner in which sensory signals are represented in the human brain. The NEM is analyzed in the context of detection theory which provides a mathematical framework for statistically quantifying the detectability of differences in the neural representation arising from differences in sensory input. This NEM approach has been validated by demonstrating its ability to predict a variety of published psychoacoustic data, including masking and many other phenomenon.
Data compression method and apparatus