1. Method for processing time-discrete sampled values representing an audio signal so as to obtain integer values, comprising the following steps: windowing the time-discrete sampled values with a window with a length corresponding to 2N time-discrete sampled values so as to provide windowed time-discrete sampled values for a conversion of the time-discrete sampled values in a spectral representation by means of a transform which may generate N output values from N input values, with the windowing comprising the following sub-steps: selecting a time-discrete sampled value from a quarter of the window and a time-discrete sampled value from another quarter of the window so as to obtain a vector of time-discrete sampled values; applying a square rotation matrix to the vector, the dimension of which coincides with the dimension of the vector, with the rotation matrix being adapted to be represented by a plurality of lifting matrices, with one lifting matrix only comprising one element which depends on the window and is unequal to 1 or 0, with the sub-step of applying comprising the following sub-steps: multiplying the vector by a lifting matrix so as to obtain a first result vector; rounding a component of the first result vector with a rounding function mapping a real number onto an integer number so as to obtain a rounded first result vector; sequentially carrying out the steps of multiplying and rounding with another lifting matrix until all lifting matrices have been processed so as to obtain a rotated vector comprising an integer windowed sampled value from the quarter of the window and an integer windowed sampled value from the other quarter of the window.