Phase-vocoder pitch-shifting
AssigneeCreative Technology Ltd
InventorsJean Laroche, Mark Dolson
Life of this patent
Estimating the term…
Abstract
A system for pitch-shifting an audio signal wherein resampling is done in the frequency domain. The system includes a method for pitch-shifting a signal by converting the signal to a frequency domain representation and then identifying a specific region in the frequency domain representation. The region being located at a first frequency location. Next, the region is shifted to a second frequency location to form a adjusted frequency domain representation. Finally, the adjusted frequency domain representation is transformed to a time domain signal representing the input signal with shifted pitch. This eliminates the expensive time domain resampling stage and allows the computational costs to become independent of the pitch modification factor.
Claims31
A method for pitch-shifting an audio signal comprising:
- converting the signal to a frequency domain representation, wherein the frequency domain representation comprises at least one signal characteristic associated with a plurality of frequency bins;
- identifying at least one frequency bin in the frequency domain representation based on the signal characteristics of multiple frequency bins;
- defining a first region in the frequency domain representation associated with the at least one frequency bin, wherein the first region comprises at least a first portion of the frequency bins;
- shifting the signal characteristic associated with the first region in the frequency domain representation to a second region in the frequency domain representation, wherein the second region comprises at least a second portion of the frequency bins, and therein forming an adjusted frequency domain representation;
- and
- transforming the adjusted frequency domain representation to a time domain signal.
Apparatus for pitch-shifting an audio signal comprising:
- a transform module having logic to receive the signal and to produce a frequency domain representation of the signal, wherein the frequency domain representation comprises at least one signal characteristic associated with a plurality of frequency bins;
- a detector coupled to the transform module having logic to receive the frequency domain representation of the signal and to detect at least one frequency bin from the plurality of frequency bins based on the signal characteristics of multiple frequency bins, the detector further comprising logic to identify a first region comprising at least a first portion of the frequency bins associated with the at least one frequency bin;
- a frequency processor coupled to the detector and having logic to receive the frequency domain representation and to shift the signal characteristic associated with the first region to a second region, wherein the second region comprises at least a second portion of the frequency bins and therein forming an adjusted frequency domain representation;
- and
- an inverse transform module coupled to the frequency processor and having logic to receive the adjusted frequency domain representation and to transform the adjusted frequency domain representation to a time domain signal.
A method for pitch-shifting an audio signal comprising:
- converting the audio signal to a frequency domain representation, wherein the frequency domain representation comprises amplitude and phase values associated with a plurality of frequency bins;
- identifying at least one peak in the frequency domain representation based on the amplitude values of multiple frequency bins;
- defining a region of frequency bins associated with the at least one peak;
- shifting the region to a new region in the frequency domain representation, therein forming an adjusted frequency domain representation;
- and
- transforming the adjusted frequency domain representation to a time domain signal.
Dependencies are inferred from the claim text.