Efficient combined harmonic transposition

A method for generating a high frequency component of a signal from a low frequency component of the signal, the method comprising:

• providing a set of analysis subband signals from the low frequency component of the signal;
• wherein the set of analysis subband signals comprises at least two analysis subband signals;
• determining a set of synthesis subband signals from the set of analysis subband signals, such that an nth synthesis subband signal of the set of synthesis subband signals is determined from a kth analysis subband signal and a (k+1)th analysis subband signal of the set of analysis subband signals;
• wherein a magnitude of the nth synthesis subband signal is determined from a product of an exponentiated magnitude of the kth analysis subband signal and an exponentiated magnitude of the (k+1)th analysis subband signal;
• wherein a sum of an exponent of the exponentiated magnitude of the kth analysis subband signal and an exponent of the exponentiated magnitude of the (k+1)th analysis subband signal equals one;
• wherein a phase of the nth synthesis subband signal depends on a transposition order T;
• and
• generating the high frequency component of the signal based on the set of synthesis subband signals.

A non-transitory computer readable storage medium comprising a sequence of instructions, wherein, when executed by an audio signal processing device, the sequence of instructions causes the device to perform a method for generating a high frequency component of a signal from a low frequency component of the signal, the method comprising:

• providing a set of analysis subband signals from the low frequency component of the signal;
• wherein the set of analysis subband signals comprises at least two analysis subband signals;
• determining a set of synthesis subband signals from the set of analysis subband signals, such that an nth synthesis subband signal of the set of synthesis subband signals is determined from a kth analysis subband signal and a (k+1)th analysis subband signal of the set of analysis subband signals;
• wherein a magnitude of the nth synthesis subband signal is determined from a product of an exponentiated magnitude of the kth analysis subband signal and an exponentiated magnitude of the (k+1)th analysis subband signal;
• wherein a sum of an exponent of the exponentiated magnitude of the kth analysis subband signal and an exponent of the exponentiated magnitude of the (k+1)th analysis subband signal equals one;
• wherein a phase of the nth synthesis subband signal depends on a transposition order T;
• and
• generating the high frequency component of the signal based on the set of synthesis subband signals.