Energy shaping apparatus and energy shaping method

An energy shaping method for performing energy shaping in decoding of a multi-channel audio signal, said energy shaping method comprising:

• a splitting step of splitting an audio signal in a sub-band domain into diffuse signals indicating a reverberating component and direct signals indicating a non-reverberating component, the audio signal being obtained by performing a hybrid time-frequency transformation;
• a downmix step of generating a downmix signal by downmixing the direct signals;
• a filter processing step of generating a bandpass downmix signal and bandpass diffuse signals by bandpassing the downmix signal and the diffuse signals per sub-band, the diffuse signals being split on the sub-band basis;
• a normalization processing step of generating a normalized downmix signal and normalized diffuse signals, respectively, by normalizing the bandpass downmix signal and the bandpass diffuse signals with regard to respective energy;
• a scale factor computing step of computing, for each of predetermined time slots, a scale factor indicating magnitude of energy of the normalized downmix signal with respect to the energy of the normalized diffuse signals;
• a multiplying step of generating scale diffuse signals by multiplying each of the diffuse signals by a corresponding one of the scale factors;
• a high-pass processing step of generating high-pass diffuse signals by highpassing the scale diffuse signals;
• an adding step of generating addition signals by adding the high-pass diffuse signals and the direct signals;
• and
• a synthesis filter processing step of applying synthesis filtering to the addition signals and transforming the addition signals into time domain signals.

An integrated circuit which performs energy shaping in decoding of a multi-channel audio signal, said integrated circuit comprising:

• a splitter which splits an audio signal in a sub-band domain into diffuse signals indicating a reverberating component and direct signals indicating a non-reverberating component, the audio signals being obtained by performing a hybrid time-frequency transformation;
• a downmix circuit which generates a downmix signal by downmixing the direct signals;
• a filter which generates, respectively, a bandpass downmix signal and bandpass diffuse signals by bandpassing the downmix signal and the diffuse signals per sub-band, the diffuse signals being split on the sub-band basis;
• a normalization processing circuit which generates a normalized downmix signal and normalized diffuse signals by normalizing the bandpass downmix signal and the bandpass diffuse signals with regard to respective energy;
• a scale factor computing circuit which computes, for each of predetermined time slots, a scale factor indicating magnitude of energy of the normalized downmix signal with respect to the energy of the normalized diffuse signals;
• a multiplier which generates scale diffuse signals by multiplying each of the diffuse signals by a corresponding one of the scale factors;
• a high-pass processing circuit which generates high-pass diffuse signals by highpassing the scale diffuse signals;
• an adder which generates addition signals by adding the high-pass diffuse signals and the direct signals;
• and
• a synthesis filter which applies synthesis filtering to the addition signals and transforms the addition signals into time domain signals.