Comparison of pitch shifting and time stretching techniques

This small comparison of audio pitch shifting and time stretching algorithms was done as a part of the PitchTech research project. This is in no way a formal comparison. This is just audio excerpts that allow one to get an idea on the differences and artifacts of various algorithms.

Music 1
Listen to original music
Technique Pitch shifted (1.3) Time stretched (1.6)
Time Domain WSOLA Listen Listen
Ocean Listen Listen
Rollers Listen Listen
Standard Phase Vocoder Listen Listen
Improved Phase Vocoder Listen Listen
Multi-Scale Phase Vocoder Listen Listen
Rainbow (beta version) Listen Listen

Music 2
Listen to original music
Technique Pitch shifted (1.3) Time stretched (1.6)
Time Domain WSOLA Listen Listen
Ocean Listen Listen
Rollers Listen Listen
Standard Phase Vocoder Listen Listen
Phase-Locked Vocoder Listen Listen
Multi-Scale Phase Vocoder Listen Listen
Rainbow (beta version) Listen Listen

Music 3
Listen to original music
Technique Pitch shifted (1.3) Time stretched (1.6)
Time Domain WSOLA Listen Listen
Ocean Listen Listen
Rollers Listen Listen
Standard Phase Vocoder Listen Listen
Phase-Locked Vocoder Listen Listen
Multi-Scale Phase Vocoder Listen Listen
Rainbow (beta version) Listen Listen

Music 4
Listen to original music
Technique Pitch shifted (1.3) Time stretched (1.6)
Time Domain WSOLA Listen Listen
Ocean Listen Listen
Rollers Listen Listen
Standard Phase Vocoder Listen Listen
Phase-Locked Vocoder Listen Listen
Multi-Scale Phase Vocoder Listen Listen
Rainbow (beta version) Listen Listen

Music 5
Listen to original music
Technique Pitch shifted (1.3) Time stretched (1.6)
Time Domain WSOLA Listen Listen
Ocean Listen Listen
Rollers Listen Listen
Standard Phase Vocoder Listen Listen
Phase-Locked Vocoder Listen Listen
Multi-Scale Phase Vocoder Listen Listen
Rainbow (beta version) Listen Listen

References (scientific publications)

Time Domain WSOLA

W. Verhelst, M. Roelands, An overlap-add technique based on waveform similarity (WSOLA) forhigh quality time-scale modification of speech, IEEE International Conference on Acoustics, Speech, and Signal Processing, pp. 554 - 557 vol. 2, 1993.

Open source implementation that was used: SoundTouch


Ocean

Unpublished yet. A demo page is available here.


Rollers

N. Juillerat, S. Schubiger-Banz, S. M. Arisona, Low Latency Audio Pitch Shifting in the Time Domain IEEE International Conference on Audio, Language and Image Processing, pp. 29 - 35, 2008.


Standard Phase Vocoder

The DSP Dimension: Pitch shifting using the Fourier Transform


Improved Phase Vocoder

J. Laroche, M. Dolson, New phase-vocoder technique for real-time pitch-shifting, chorusing, harmonizing and other exotic audio modifications, Journal of the Audio Engineering Society, vol. 47, pp. 928 - 936, November 1999.

Used implementation: "Pitch Shift" effect of PitchTech, quality 2.


Multi-Scale Phase Vocoder

N. Juillerat, S. Schubiger-Banz, S. M. Arisona, Enhancing the Quality of Audio Transformations Using the Multi-Scale Short-Time Fourier Transform, IASTED International Conference on Signal Processing, 2008.

Used implementation: "Pitch Shift" effect of PitchTech, quality 6.


Rainbow

N. Juillerat, S. Schubiger-Banz, S. M. Arisona, A Hybrid Time and Frequency Domain Audio Pitch Shifting Algorithm, 125th Audio Engineering Society Convention, 2008.