4 New Audio Time Stretching Algorithms

Under construction...

 

This page is a preview of 4 new audio time stretching algorithms currently in development.

The algorithms have the code-names "Quantum", "Tachyon", "Schrödinger" and "Heisenberg".

Audio examples
Performance comparison
Software
Scientific References
Musical References
History

Audio examples

A few audio examples are much better than a lot of words...

Notes:

Original Electronic [1]
Time stretching ratio Quantum Tachyon Schrödinger Heisenberg
0.5
0.9
1.3
2.0
4.0
Cycle
2.0, 0.6, 1.5, 5/9
0.2
20
 
Original Pop [2]
Time stretching ratio Quantum Tachyon Schrödinger Heisenberg
0.5
0.9
1.3
2.0
4.0
Cycle
2.0, 0.6, 1.5, 5/9
0.2
20
 
Original Guitar [3]
Time stretching ratio Quantum Tachyon Schrödinger Heisenberg
0.5
0.9
1.3
2.0
4.0
Cycle
2.0, 0.6, 1.5, 5/9
0.2
20
 
Original New Age [4]
Time stretching ratio Quantum Tachyon Schrödinger Heisenberg
0.5
0.9
1.3
2.0
4.0
Cycle
2.0, 0.6, 1.5, 5/9
0.2
20
 

Performance Comparison

High quality comes with a price, usually slow processing speed. The following table shows an approximation, for each algorithm, of the time required to produce one minute of time stretched audio (stereo, 44.1 kHz) on a 3 GHz processor. It also shows the relative quality (subjective, your opinion might differ), the minimum and maximum supported time stretching ratios, and the main goals:

Time to produce 1 min Quality (Subjective) Transformation ratios
Max / Recommanded
Main Goals
Quantum 5 - 6 seconds 😐 Medium 😐 0.25 - 4 / 0.7 - 1.3 Best speed/quality trade-off, simplicity
Tachyon 10 - 15 minutes 😱 Highest 😃 0.25 - 4 / 0.5 - 2 Highest quality at any price
Schrödinger < 2 seconds 😃 Lowest 😒 0.25 - 4 / 0.8 - 1.2 Fastest speed, for solo, open source
Heisenberg ~ 30 seconds 😒 Medium 😐 0.01 - 1000 / 0.1 - 100 Huge transformation ratios, pleasant sound

Software

The algorithms are all proptotypes. Development is in progress. For the moment only the Quantum algorithm is available as a command-line, beta version.

This page will be updated as progress is made...

Download

Download TimeStretchQuantum.7z, a beta-version of the Quantum audio time stretching algorithm, as a command-line tool.

Usage

java -jar TimeStretchQuantum.jar <input file> <time-stretch ratio> <output-file>

Limitations

Scientific References

The science behind these algorithms...

[1] Zdeněk Průša and Nicki Holighaus, "Phase Vocoder Done Right", 25th European Signal Processing Conference, EUSIPCO, 2017 (1), (2)
[2] N. Juillerat, "Audio Time Stretching with Controllable Phase Coherence", 142nd Audio Engineering Society Convention, AES 142, 2017 (2)
[3] N. Juillerat, B. Hirsbrunner, "Audio Time Stretching with an Adaptive Multiresolution Phase Vocoder", IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP 2017 (2), (4)
[4] Derry FitzGerald, "Harmonic/Percussive Separation using Median Filtering", proc. of the 13th intl. conf on Digital Audio Effects, 2010 (3)
[5] 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, IASTED SIP 2008 (2), (4)
[6] Tan Roland K. C. and Lin Amerson H. J, "A Time-Scale Modification Algorithm Based on the Subband Time-Domain Technique for Broad-Band Signal Applications", Journal of the Audio Engineering Society, vol. 48, no. 5, pp. 437-449, 2000 (3)
[7] Jean Laroche and Mark Dolson, "Improved Phase Vocoder Time-Scale Modification of Audio", IEEE Transactions on Speech and Signal Processing, vol. 7, no. 3, May 1999 (4)
[8] Werner Verhelst, Marc Roelands, "An Overlap-Add Technique Based on Waveform Similarity (WSOLA) for High Quality Time-Scale Modification of Speech", IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP 1993 (3)

Notes:

Musical References

[1] Jean-Michel Jarre, "Oxygène part. 4", Oxygène, Disques Dreyfus, 1977
[2] Peter Gabriel, "Sledgehammer", Secret World Live, Geffen Records, 1986
[3] (Unknown) Sample n° 4 (Guitare) from "Comparatif Time Stretching et Pitch Shifting", Audiofanzine, 2008
[4] Melanie G 'MySweetDarkness', "The Morn", Through the Shadow and the Light, Everlasting Dream, 2007

History

PitchTech home page