1.2 KiB
1.2 KiB
SailTuner
SailTuner is a chromatic multi-temperament instrument tuner for Sailfish OS.
It gets audio data from microphone, find the fundamental frequency, and then display the note, the octave and the deviation according to note reference and temperament.
Pitch detection algorithm
The algorithm for fundamental frequency detection:
- high-pass filter (10Hz)
- zero-crossing detection with linear interpolation
- pattern recognition from regions, with time based standart deviation
- octave filtering: drop a frequency if already a higher octave for same note in some conditions
- post filter: wait few analyses to confirm or defect a note, and make a turning average for note deviation
The audio input rate is 16KHz ; audio frames are analysed every 1024 samples (64ms) and a note is confirmed after 4 chunks (256ms).
The note is found compared to an array of frequencies modulo one octave. The comparison array is built from a temperament and a 'A4' reference, default to 440Hz and equal temperament.
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Copyright
Licence: GPLv3
Author: Louis-Joseph Fournier
*First release date: 2016-??