This is a simple strobe tuner Android app. Of course, actual strobe tuners use spinning disks and a strobe light to achieve the illusion of moving bars. This app is a digital imitation of that effect. As this is my first serious Android app (and the fact that I'm not a UX type of guy), this app emphasizes accuracy and simplicity over fancy graphics and effects.
Here's a brief overview of how it works:
- Compute the autocorrelation of the audio signal. This should give a periodic plot with peaks where the signal perfectly overlaps with itself.
- Determine the period by computing the zero crossings. The actual implementation is via a grid search over some offset values.
- Compute the mean and standard deviation of the observed period and update a Kalman filter that gives a smoothed estimate of the period.
- Find the closest musical pitch in the 12-tone equal temperament system and compute the error in frequency and cents.
- Update the frame of the strobe graphic as a function of the elapsed time from the previous refresh and the error in cents.
The Strobe Tuner app requires the use of your device's microphone to record audio. This audio data is not persisted in any permanent storage and is processed on your device. No other personally identifiable information is used by the Strobe Tuner app.
This project is covered by the GNU General Public License v3. See the LICENSE file.