Continuously variable time scale modification of digital audio signals

A method for time scale modification of a multi-channel digital audio input signal, each input channel comprising input samples, to form a multi-channel digital audio output signal, each output channel comprising output samples, said method comprising the steps of:

• a) obtaining said input channels;
• b) for each of said input channels, independently:
• i) selecting an input block of N/2 input samples;
• ii) selecting an output block of N/2 output samples from a corresponding one of said output channels;
• iii) determining an optimal offset T for an overlap of a beginning of said input block with a beginning of said output block, wherein −N/2≦T<N/2, said offset determining comprising calculating a correlation function between discrete frequency transforms of said N/2 input samples and discrete frequency transforms of said N/2 output samples, wherein a maximum value of an inverse discrete frequency transform of said correlation function occurs for said optimal offset T;
• and
• iv) overlapping said input block with said output block to form said corresponding output channel, wherein said input block beginning is offset from said output block beginning by T samples;
• and
• c) combining said output channels to form said multi-channel digital audio output signal.

A digital signal processor comprising a processing unit configured to perform method steps for time scale modification of a digital audio input signal comprising input samples to form a digital audio output signal comprising output samples, said method steps comprising:

• a) selecting an input block of N/2 input samples;
• b) selecting an output block of N/2 output samples;
• c) determining an optimal offset T for an overlap of a beginning of said input block with a beginning of said output block, wherein −N/2≦T<N/2, wherein said offset determining comprises calculating a correlation function between discrete frequency transforms of said N/2 input samples and discrete frequency transforms of said N/2 output samples, wherein a maximum value of an inverse discrete frequency transform of said correlation function occurs for said optimal offset T;
• and
• d) overlapping said input block with said output block to form said output signal, wherein said input block beginning is offset from said output block beginning by T samples.