An audio time-stretching and pitch-shifting library and utility program.
Written by Chris Cannam, email@example.com. Published by Particular Programs Ltd t/a Breakfast Quay. Copyright 2007-2023 Particular Programs Ltd.
Rubber Band is a library and utility program that permits changing the tempo and pitch of an audio recording independently of one another.
Rubber Band Library is distributed under the GNU General Public License (GPL). You can redistribute it and/or modify it under the terms of the GPL; either version 2 of the License, or (at your option) any later version. See the file COPYING for more information.
If you wish to distribute code using Rubber Band Library under terms other than those of the GNU General Public License, you must obtain a commercial licence from us before doing so. In particular, you may not legally distribute through any Apple App Store unless you have a commercial licence. See https://breakfastquay.com/rubberband/ for licence terms.
If you have obtained a valid commercial licence, your licence supersedes this README and the enclosed COPYING file and you may redistribute and/or modify Rubber Band under the terms described in that licence. Please refer to your licence agreement for more details.
Rubber Band includes a .NET interface generously contributed by
Jonathan Gilbert under a BSD-like licence. The files in the
dotnet/rubberband-sharp directories fall
under this licence. If you make use of this interface, please ensure
you comply with the terms of its licence.
Rubber Band may link with other libraries or be compiled with other source code, depending on its build configuration. It is your responsibility to ensure that you redistribute these only in accordance with their own licence terms, regardless of the conditions under which you are redistributing the Rubber Band code itself. The licences for some relevant library code are as follows, to the best of our knowledge. See also the file COMPILING.md for more details.
Please refer to the file COMPILING.md for details of how to configure and build the library.
Rubber Band consists of:
The Rubber Band Library code. This is the code that will normally
be used by your applications. The headers for this are in the
rubberband/ directory, and the source code is in
The Rubber Band Library may also depend upon external resampler
and FFT code, if so configured; see section 7 of COMPILING.md for
The Rubber Band command-line tool. This is in
This program uses Rubber Band Library and also requires libsndfile
(http://www.mega-nerd.com/libsndfile/, licensed under the GNU Lesser
General Public License) for audio file loading.
A pitch-shifter audio effects plugin in LADSPA and LV2 formats.
These are in
ladspa-lv2/. They require the LADSPA SDK header
ladspa.h and LV2 header
lv2.h respectively (not included).
A Vamp audio analysis plugin which may be used to inspect the
dynamic stretch ratios and other decisions taken by the Rubber Band
Library when in use. This is in
vamp/. It requires the Vamp
plugin SDK (https://www.vamp-plugins.org/develop.html) (not included).
The Rubber Band command-line tool builds as
basic incantation is
$ rubberband -t <timeratio> -p <semitones> <infile.wav> <outfile.wav>
$ rubberband -t 1.5 -p 2.0 test.wav output.wav
stretches the file
test.wav to 50% longer than its original
duration, shifts it up in pitch by a whole tone, and writes the output
Several further options are available: run
rubberband -h for help.
The most important are the options
-3. These select between
two different processing engines, known as the R2 (Faster) engine and
the R3 (Finer) engine. The R3 engine produces higher-quality results
than R2 for most material, especially complex mixes, vocals and other
sounds that have soft onsets and smooth pitch changes, and music with
substantial bass content. However, it uses much more CPU than the R2
The R2 engine was the only method available in Rubber Band Library up
to versions 2.x, and for compatibility it remains the default (in the
case that neither
-3 is requested explicitly) whenever the
command-line tool is invoked as
rubberband. The R3 engine is the
default if the tool is invoked as
Many further options are available, most of which only have an effect
when using the R2 engine. In particular, different types of music may
benefit from different "crispness" options (
-c flag, with a
numerical argument from 0 to 6).
Rubber Band has a public API that consists of one C++ class, called
RubberBandStretcher in the
RubberBand namespace. You should
#include <rubberband/RubberBandStretcher.h> to use this class.
There is extensive documentation in the class header.
A header with C language bindings is also provided in
<rubberband/rubberband-c.h>. This is a wrapper around the C++
implementation, and as the implementation is the same, it also
requires linkage against the C++ standard libraries. It is not yet
documented separately from the C++ header. You should include only
one of the two headers, not both.
A .NET interface is also included, contributed by Jonathan Gilbert;
see the files in the
dotnet directory for details.
The source code for the command-line utility (
provides a good example of how to use Rubber Band in offline mode; the
pitch shifter plugin (
ladspa-lv2/RubberBandPitchShifter.cpp) may be
used as an example of Rubber Band in real-time mode.
IMPORTANT: Please ensure you have read and understood the licensing terms for Rubber Band before using it in your application. This library is provided under the GNU General Public License, which means that any application that uses it must also be published under the GPL or a compatible licence (i.e. with its full source code also available for modification and redistribution) unless you have separately acquired a commercial licence from the author.