Audio signal processing method

A computer-implemented audio signal processing method for upmixing an input audio stereo signal (S) in a plurality of spatially distributed pseudo surround channels to define a height layer, said computer-implemented audio signal processing method comprising the steps of:

• receiving at least one input audio stereo signal (S);
• performing a pre-processing stage on the input audio stereo signal (S), said pre-processing stage comprising the steps of:
• performing Mid-Side decoding on the input audio stereo signal (S) to generate at least one Sum (SUM) signal and at least one Difference (DIFF) signal;
• performing polarity reversal on the at least one Difference (DIFF) signal;
• performing filtering by means of at least 2 (PF) filtering banks on the at least one polarity-reversed Difference (DIFF) signal;
• reconstructing at least 2 signals from the at least 2 filtering banks (PF) thereby obtaining upmixed output signals (O);
• performing high-pass filtering on at least one upmixed output signal (O) from the obtained upmixed output signals (O);
• performing a level adjustment on the high-pass filtered at least one upmixed output signal (O);
• and,
• routing the obtained upmixed output signals (O) obtained after high-pass filtering, and level adjustment to audio speaker channels (C) to feed Top Channels, thereby defining a matrix of spatially distributed channels forming the height layer.