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1
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2 Constant-Q Library
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3 ==================
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4
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5 A C++ library and Vamp plugin implementing the Constant-Q transform
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6 of a time-domain signal.
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7
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8 https://code.soundsoftware.ac.uk/projects/constant-q-cpp
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9
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10 The Constant-Q transform is a time-to-frequency-domain transform
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11 related to the short-time Fourier transform, but with output bins
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12 spaced logarithmically in frequency, rather than linearly. The output
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13 bins are therefore linearly spaced in terms of musical pitch.
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14
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15 This implementation is reasonably fast and is causal, operating
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16 block-by-block on the input, though with quite high latency depending
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17 on the frequency range specified. By default it produces output at a
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18 higher time resolution than some other implementations, using multiple
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19 kernel atoms per time block. The inverse transform is approximate
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20 rather than exact (see the paper cited below for details).
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21
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22
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23 About this library
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24 ------------------
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25
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26 This library provides:
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27
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28 * Forward transform: time-domain to complex Constant-Q bins
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29 * Forward spectrogram: time-domain to interpolated Constant-Q
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30 magnitude spectrogram
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31 * Inverse transform: complex Constant-Q bins to time domain
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32
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33 The Vamp plugin provides:
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34
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35 * Constant-Q magnitude spectrogram with high and low frequency
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36 extents defined in Hz
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37 * Constant-Q magnitude spectrogram with high and low frequency
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38 extents defined as MIDI pitch values
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39 * Pitch chromagram obtained by folding a Constant-Q spectrogram
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40 around into a single-octave range
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41
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42
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43 Building the library and plugin
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44 -------------------------------
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45
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46 To compile this code, use "make -f <file>" where <file> is one of
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47 Makefile.linux, Makefile.osx, Makefile.mingw32 depending on
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48 platform. These files set up some flags and include Makefile.inc,
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49 which defines the input files and so forth. You could equally write
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50 your own Makefile which does the same.
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51
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52 The Vamp plugin part of the build expects to find a compiled version
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53 of the Vamp Plugin SDK in a neighbouring folder (../vamp-plugin-sdk).
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54 The unit tests also require Boost headers to be available.
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55
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56 Note that this code uses the KissFFT library (compiled from source
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57 bundled here) in its non-default double-precision mode via the use of
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58 the flag -Dkiss_fft_scalar=double in Makefile.inc. If you want to
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59 build this code using an external KissFFT library or custom build
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60 scripts, you may need to do some work to ensure you have the right
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61 configuration.
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62
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63
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64 Credits
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65 -------
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66
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67 The method is drawn from Christian Schörkhuber and Anssi Klapuri,
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68 "Constant-Q transform toolbox for music processing", SMC 2010. See the
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69 file CITATION for details. If you use this code in research work,
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70 please cite this paper.
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71
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72 The C++ implementation is by Chris Cannam, Copyright 2014-2015 Queen
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73 Mary, University of London.
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74
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75 The library is provided under a liberal BSD/MIT-style open source
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76 licence. See the file COPYING for more information.
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77
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