Constrained filter encoding of polyphonic signals

摘要

Signals of different channels (c 1 -c N ) are combined into one mono signal (x). A set of adaptive filters, preferably one for each channel (c 1 -c N ), is derived in a respective filter adaptation unit (30:1-30:N). When an adaptive filter is applied to the mono signal (x) it reconstructs the signal of the respective channel (c 1 -c N ) under a perceptual constraint. The perceptual constraint is a gain and/or shape constraint. The gain constraint allows the preservation of the relative energy between the channels (c 1 -c N ) while the shape constraint allows more stability by avoiding unnecessary filtering of spectral nulls. The transmitted parameters are the mono signal (x), in encoded form, and the parameters (p 1 -p N ) of the adaptive filters, preferably also encoded. The receiver reconstructs the signal of the different channels by applying the adaptive filters and possibly some additional post-processing.