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How do I convert a video of something oscillating to a frequency I can synthesize and tune my guitar to?

Michael Petrotta
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Stuve Villge
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2 Answers2

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You can get a first order approximation to the oscillation by watching the video and using a stopwatch. Hit start on the stopwatch and start counting oscillations. When you reach 10 oscillations, hit stop. Divide the time by 10 and you have seconds/cycle. Take its reciprocal to get cycles/second, or Hz.

But if you could see it oscillating, and not a blur of motion, the frequency was probably < 5 Hz. We don't see very well at more than 20 Hz (hence the > 20 frames/sec for video). Conversely, we don't hear very well below 20 Hz. Maybe you mean you'll tune your guitar to a harmonic of the flax frequency (disclaimer, not a musician).

Also, this question is probably more suited for http://dsp.stackexchange.com.

mtrw
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If the object is not moving with respect to the camera you could grep a pixel (or perhaps an averaged area of pixels) at the border of the object. Generate a time series from that: pixel(time). This time series you could fourier transform and get the peak frequency from that, which should respond to the frequency of the wobbling.

André Bergner
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