METHOD AND APPARATUS FOR PROCESSING AN AUDIO SIGNAL, AUDIO DECODER AND AUDIO ENCODER

A method for processing an audio signal (100) includes processing audio frames of the audio signal at an audio decoder by filtering the frames using an audio codec postfilter for reducing a level of coding noise between signal harmonics; and using linear predictive filtering for removing (S102, S104, S300-S308, S400-S402) a discontinuity (106a, 106b) between a filtered past frame and a filtered current frame of the audio signal. The method includes filtering the current frame of the audio signal and removing the discontinuity by modifying a beginning portion of the filtered current frame by a signal obtained by linear predictive filtering a predefined signal with initial states of the linear predictive filter defined on the basis of a last part of the unfiltered past frame filtered using the set of filter parameters for filtering the current frame. The audio codec postfilter is defined as follows: Hz=1−Bz/1−Az⋅z−⊤ where B(z) and A(z) are two FIR filters, the H(z) filter parameters are the coefficients of the FIR filters B(z) and A(z), and T indicates the pitch lag.