30 lines
1.2 KiB
Markdown
30 lines
1.2 KiB
Markdown
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# SailTuner
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SailTuner is a chromatic multi-temperament instrument tuner for [Sailfish OS](https://sailfishos.org/).
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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.
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### Pitch detection algorithm
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The algorithm for fundamental frequency detection:
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- high-pass filter (10Hz)
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- zero-crossing detection with linear interpolation
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- pattern recognition from regions, with time based standart deviation
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- octave filtering: drop a frequency if already a higher octave for same note in some conditions
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- post filter: wait few analyses to confirm or defect a note, and make a turning average for note deviation
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The audio input rate is 16KHz ; audio frames are analysed every 1024 samples (64ms) and a note is confirmed after 4 chunks (256ms).
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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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======
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### Copyright
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*Licence: GPLv3*
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*Author: Louis-Joseph Fournier*
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*First release date: 2016-??
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https://github.com/LouJo/SailTuner
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