[LAD] Constant-Q library and Vamp plugin

Chris Cannam cannam at all-day-breakfast.com
Sat Aug 9 13:42:18 UTC 2014

Announcing a new C++ library and Vamp plugin implementing the Constant-Q
transform of a time-domain signal.


The Constant-Q transform is a time-to-frequency-domain transform related
to the short-time Fourier transform, but with output bins spaced
logarithmically in frequency, rather than linearly. The output bins are
therefore linearly spaced in terms of musical pitch. The Constant-Q is
useful as a preliminary transform in various other methods such as note
transcription and key estimation techniques.

This library provides:

 * Forward transform: time-domain to complex Constant-Q bins
 * Forward spectrogram: time-domain to interpolated Constant-Q magnitude
 * Inverse transform: complex Constant-Q bins to time domain

The Vamp plugin provides:

 * Constant-Q magnitude spectrogram with high and low frequency extents
 defined in Hz
 * Constant-Q magnitude spectrogram with high and low frequency extents
 defined as MIDI pitch values
 * Pitch chromagram obtained by folding a Constant-Q spectrogram around
 into a single-octave range

The code is provided with full source under a liberal licence, and
plugin binaries are provided for Windows, OS/X, and Linux.

The method is drawn from Christian Schörkhuber and Anssi Klapuri,
"Constant-Q transform toolbox for music processing", SMC 2010. See the
file CITATION for details. If you use this code in research work, please
cite this paper.

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