Worldlex Wiki Decorrelation is a general term for any process that is used to reduce autocorrelation within a signal, or cross-correlation within a set of signals, while preserving other aspects of the signal. A frequently used method of decorrelation is the use of a matched linear filter to reduce the autocorrelation of a signal as far as possible. Since the minimum possible autocorrelation for a given signal energy is achieved by equalising the power spectrum of the signal to be similar to that of a white noise signal, this is often referred to as signal whitening.
Process
Signal processing
Most decorrelation algorithms are linear, but there are also non-linear decorrelation algorithms.
Many data compression algorithms incorporate a decorrelation stage. For example, many transform coders first apply a fixed linear transformation that would, on average, have the effect of decorrelating a typical signal of the class to be coded, prior to any later processing. This is typically a Karhunen–Loève transform, or a simplified approximation such as the discrete cosine transform.
By comparison, sub-band coders do not generally have an explicit decorrelation step, but instead exploit the already-existing reduced correlation within each of the sub-bands of the signal, due to the relative flatness of each sub-band of the power spectrum in many classes of signals.
Linear predictive coders can be modelled as an attempt to decorrelate signals by subtracting the best possible linear prediction from the input signal, leaving a whitened residual signal.
Decorrelation techniques can also be used for many other purposes, such as reducing crosstalk in a multi-channel signal, or in the design of echo cancellers.
En traitement d'images, les techniques de décorrélation peuvent être utilisées pour accentuer ou étirer les différences de couleur présentes dans chaque pixel d'une image. On parle généralement d'« étirement par décorrélation ».
Neuroscience
En neurosciences , la décorrélation est utilisée dans l'analyse des réseaux neuronaux du système visuel humain. Les signaux bruts provenant des cônes et des bâtonnets subissent de nombreuses étapes de traitement avant d'être pris en charge par le cortex visuel . Ces étapes impliquent généralement une décorrélation, à la fois spatiale ( suppression de l'environnement au niveau de la rétine) et temporelle (traitement du mouvement au niveau du corps genouillé latéral ).
Cryptographie
En cryptographie , la décorrélation est utilisée dans la conception des chiffrements (voir Théorie de la décorrélation ) et dans la conception des générateurs de nombres aléatoires matériels .