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/* dywapitchtrack.h
Dynamic Wavelet Algorithm Pitch Tracking library
Released under the MIT open source licence
Copyright (c) 2010 Antoine Schmitt
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
/* Documentation
The dywapitchtrack library computes the pitch of an audio stream in real time.
The pitch is the main frequency of the waveform (the 'note' being played or sung).
It is expressed as a float in Hz.
Unlike the human ear, pitch detection is difficult to achieve for computers. Many
algorithms have been designed and experimented, but there is no 'best' algorithm.
They all depend on the context and the tradeoffs acceptable in terms of speed and
latency. The context includes the quality and 'cleanness' of the audio : obviously
polyphonic sounds (multiple instruments playing different notes at the same time)
are extremely difficult to track, percussive or noisy audio has no pitch, most
real-life audio have some noisy moments, some instruments have a lot of harmonics,
etc...
The dywapitchtrack is based on a custom-tailored algorithm which is of very high quality:
both very accurate (precision < 0.05 semitones), very low latency (< 23 ms) and
very low error rate. It has been thoroughly tested on human voice.
It can best be described as a dynamic wavelet algorithm (dywa):
The heart of the algorithm is a very powerful wavelet algorithm, described in a paper
by Eric Larson and Ross Maddox : "Real-Time Time-Domain Pitch Tracking Using Wavelets"
http://online.physics.uiuc.edu/courses/phys498pom/NSF_REU_Reports/2005_reu/Real-Time_Time-Domain_Pitch_Tracking_Using_Wavelets.pdf
This central algorithm has been improved by adding dynamic tracking, to reduce the
common problems of frequency-halving and voiced/unvoiced errors. This dynamic tracking
explains the need for a tracking structure (dywapitchtracker). The dynamic tracking assumes
that the main function dywapitch_computepitch is called repeatedly, as it follows the pitch
over time and makes assumptions about human voice capabilities and reallife conditions
(as documented inside the code).
Note : The algorithm currently assumes a 44100Hz audio sampling rate. If you use a different
samplerate, you can just multiply the resulting pitch by the ratio between your samplerate and 44100.
*/
/* Usage
// Allocate your audio buffers and start the audio stream.
// Allocate a 'dywapitchtracker' structure.
// Start the pitch tracking by calling 'dywapitch_inittracking'.
dywapitchtracker pitchtracker;
dywapitch_inittracking(&pitchtracker);
// For each available audio buffer, call 'dywapitch_computepitch'
double thepitch = dywapitch_computepitch(&pitchtracker, samples, start, count);
*/
#ifndef dywapitchtrack__H
#define dywapitchtrack__H
#ifdef __cplusplus
extern "C" {
#endif
// structure to hold tracking data
typedef struct _dywapitchtracker {
double _prevPitch;
int _pitchConfidence;
} dywapitchtracker;
// returns the number of samples needed to compute pitch for fequencies equal and above the given minFreq (in Hz)
// useful to allocate large enough audio buffer
// ex : for frequencies above 130Hz, you need 1024 samples (assuming a 44100 Hz samplerate)
int dywapitch_neededsamplecount(int minFreq);
// call before computing any pitch, passing an allocated dywapitchtracker structure
void dywapitch_inittracking(dywapitchtracker *pitchtracker);
// computes the pitch. Pass the inited dywapitchtracker structure
// samples : a pointer to the sample buffer
// startsample : the index of teh first sample to use in teh sample buffer
// samplecount : the number of samples to use to compte the pitch
// return 0.0 if no pitch was found (sound too low, noise, etc..)
double dywapitch_computepitch(dywapitchtracker *pitchtracker, const double * samples, int startsample, int samplecount);
#ifdef __cplusplus
} // extern "C"
#endif
#endif
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