Signal adaptive FIR/IIR predictors for minimizing entropy

摘要

The present document relates to coding. In particular, the present document relates to coding using linear prediction in combination with entropy encoding. A method (600) for determining a general prediction filter for a frame of an input signal (111) is described. The z-transform of the general prediction filter comprises an approximation to the z-transform of a finite impulse response, referred to as FIR, filter with the z variable of the FIR filter being replaced by the z-transform of an allpass filter. The FIR filter comprises a plurality of FIR coefficients (412). The allpass filter exhibits a pole defined by an adjustable pole parameter. The method (600) comprises determining the pole parameter and the plurality of FIR coefficients, such that an entropy of a frame of a prediction error signal (414) which is derived from the frame of the input signal (111) using the general prediction filter defined by the pole parameter and the plurality of FIR coefficients (412) is reduced.

主权项

1. A method, performed by an audio signal processing device, for determining a general prediction filter for a frame of an input signal, the z-transform of the general prediction filter being representable as a ratio of a first and second finite impulse response, referred to as FIR, filter comprising first and second sets of coefficients, respectively, and approximating the z transform of an intermediate filter, the method comprising:
determining an adjustable pole parameter and a plurality of FIR coefficients for the intermediate filter, such that an entropy of a frame of a prediction error signal which is derived from the frame of the input signal using the intermediate filter defined by the pole parameter and the plurality of FIR coefficients is reduced, wherein the intermediate filter comprises an FIR filter whose z variable is replaced by the z-transform of an allpass filter, the allpass filter exhibiting a pole defined by the adjustable pole parameter, wherein determining the pole parameter and the plurality of FIR coefficients comprises:
estimating the entropy of the frame of the prediction error signal obtained using the intermediate prediction filter defined by a set pole parameter and the plurality of FIR coefficients determined using the set pole parameter;repeating determining the plurality of FIR coefficients and estimating the entropy for a plurality of differently set pole parameters; andselecting the pole parameter from the plurality of differently set pole parameters which reduces the estimated entropy of the frame of the prediction error signal; and mapping the determined pole parameter and the determined plurality of FIR coefficients for the intermediate filter to the first and second sets of coefficients for the general prediction filter, whereby the general prediction filter is configured to exhibit an infinite impulse response when the adjustable pole parameter is not zero and a finite impulse response when the adjustable pole parameter is zero; wherein one or more of determining an adjustable pole parameter and mapping the determined pole parameter are implemented, at least in part, by one or more hardware elements within the audio signal processing device.