Improved PVSOLA Time Stretching and Pitch Shifting for Polyphonic Audio

Sebastian Kraft; Martin Holters; Adrian Von Dem Knesebeck; Udo Zölzer
DAFx-2012 - York
An advanced phase vocoder technique for high quality audio pitch shifting and time stretching is described. Its main concept is based on the PVSOLA time stretching algorithm which is already known to give good results on monophonic speech. Some enhancements are proposed to add the ability to process polyphonic material at equal quality by distinguishing between sinusoidal and noisy frequency components. Furthermore, the latency is reduced to get closer to a real time implementation. The new algorithm is embedded into a flexible pitch shifting and time stretching framework by adding transient detection and resampling. A subjective listening test is used to evaluate the new algorithm and to verify the improvements.