Audio signal processing apparatus and method for processing an input audio signal

An audio signal processing apparatus for processing an input audio signal into an output audio signal, wherein the audio signal processing apparatus comprises:

• at least one processor;
• and
• a non-transitory computer-readable storage medium coupled to the at least one processor and storing programming instructions for execution by the at least one processor, wherein the programming instructions instruct the at least one processor to:
• decompose the input audio signal into a direct audio signal and a diffuse audio signal using a decomposer;
• modify the direct audio signal to obtain a modified direct audio signal by extending an upper cutoff frequency of a frequency range of the direct audio signal, wherein extending the upper cutoff frequency of the frequency range of the direct audio signal comprises using a bandwidth extender, the bandwidth extender comprising:
• a plurality of bandpass filters configured to extract a plurality of direct audio signal components from the direct audio signal, wherein each direct audio signal component is associated with a corresponding frequency band of a plurality of frequency bands defined by the plurality of bandpass filters, and wherein the bandwidth extender further comprises an energy estimator configured to estimate, for each frequency band of the plurality of frequency bands, the energy of the direct audio signal component associated with the corresponding frequency band;
• a harmonics generator configured to generate, based on a first direct audio signal component of the plurality of direct audio signal components, an adjustment direct audio signal component containing harmonics of the first direct audio signal component for adjusting a second direct audio signal component of the plurality of direct audio signal components, when the energy of the second direct audio signal component is smaller than a target energy of the second direct audio signal component;
• and
• a scaler configured to scale the adjustment direct audio signal component for the second direct audio signal component using a scaling factor determined based on the energy of the first direct audio signal component, wherein the scaler is configured to determine the scaling factor Gh for scaling the adjustment direct audio signal component for the second direct audio signal component based on the following equation:
• G
• h
• =
• T
• h
• E
• h
• ,
• wherein Th denotes the target energy of the adjustment direct audio signal component for the second direct audio signal component and Eh denotes the energy of the adjustment direct audio signal component for the second direct audio signal component and wherein Th and Eh are defined by the following equations:
• Th=Tx−l·Ex, and
• Eh=β2·El,
• wherein Ex denotes the energy of the second direct audio signal component, El denotes the energy of the first direct audio signal component, l denotes a leakage factor and β2 denotes a second adjustment factor;
• and
• combine the modified direct audio signal with the diffuse audio signal to obtain the output audio signal.

An audio signal processing apparatus for processing an input audio signal into an output audio signal, wherein the audio signal processing apparatus comprises:

• a decomposer configured to decompose the input audio signal into a direct audio signal and a diffuse audio signal;
• a modifier configured to modify the direct audio signal in order to obtain a modified direct audio signal, wherein the modifier comprises a bandwidth extender configured to extend an upper cutoff frequency of a frequency range of the direct audio signal;
• and
• a combiner configured to combine the modified direct audio signal with the diffuse audio signal to obtain the output audio signal;
• wherein the bandwidth extender comprises a plurality of bandpass filters configured to extract a plurality of direct audio signal components from the direct audio signal, wherein each direct audio signal component is associated with a corresponding frequency band of a plurality of frequency bands defined by the plurality of bandpass filters, and wherein the bandwidth extender further comprises an energy estimator configured to estimate, for each frequency band of the plurality of frequency bands, the energy of the direct audio signal component associated with the corresponding frequency band;
• wherein the bandwidth extender further comprises a harmonics generator configured to generate, based on a first direct audio signal component of the plurality of direct audio signal components, an adjustment direct audio signal component containing harmonics of the first direct audio signal component for adjusting a second direct audio signal component of the plurality of direct audio signal components, when the energy of the second direct audio signal component is smaller than a target energy of the second direct audio signal component;
• and
• wherein the target energy of the second direct audio signal component is determined based on the following equation:
• Tx=β1Tx-1,
• wherein Tx denotes the target energy of the second direct audio signal component, Tx-1 denotes the target energy of a direct audio signal component associated with the frequency band directly below the frequency band of the second direct audio signal component and β1 denotes a first adjustment factor with β1<1.