A real-time audio time-scale modification library

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AudioTSM is a python library for real-time audio time-scale modification procedures, i.e. algorithms that change the speed of an audio signal without changing its pitch.

Source code repository and issue tracker:
Python Package Index:
MIT – see the file LICENSE for details.


Audiotsm should work with python 2.7 and python 3.4+.

You can install the latest version of audiotsm with pip:

pip install audiotsm

If you want to use the gstreamer plugins, you should install PyGObject and python-gst, and use the following command to install audiotsm:

pip install audiotsm[gstreamer]

If you want to play the output of the TSM procedures in real time, or to use the examples, you should install audiotsm as follow:

pip install audiotsm[stream]

Basic usage

The audiotsm package implements several time-scale modification procedures:

  • OLA (Overlap-Add);
  • WSOLA (Waveform Similarity-based Overlap-Add);
  • Phase Vocoder.

The OLA procedure should only be used on percussive audio signals. The WSOLA and the Phase Vocoder procedures are improvements of the OLA procedure, and should both give good results in most cases.

If you are unsure which procedure to choose, the Phase Vocoder should sound best in most cases. You can listen to the output of the different procedures on various audio files and at various speeds on the examples page.

Python API

Below is a basic example showing how to reduce the speed of a wav file by half using the phase vocoder procedure:

from audiotsm import phasevocoder
from audiotsm.io.wav import WavReader, WavWriter

with WavReader(input_filename) as reader:
    with WavWriter(output_filename, reader.channels, reader.samplerate) as writer:
        tsm = phasevocoder(reader.channels, speed=0.5)
        tsm.run(reader, writer)

A complete example can be found in the examples/audiotsmcli.py file. Read the documentation for more details.

GStreamer plugins

The TSM procedures are also available as GStreamer plugins. A simple example implementing a basic GStreamer pipeline can be found in the examples/audiotsmcli_gst.py file, and a more complete one showing how to use the plugins in a GTK audio player can be found in the examples/audiotsmgtk.py file. Read the documentation for more details.


If you are interested in time-scale modification procedures, I highly recommend reading A Review of Time-Scale Modification of Music Signals by Jonathan Driedger and Meinard Müller.

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