TempiFFT demonstrates how to input audio via AVFoundation for recording or processing and implements an FFT to display a real-time spectrum plot of incoming audio.

What's an FFT? Short for Fast Fourier Transform, it's a method for deconstructing an audio signal (or any time-based signal for that matter) into its constituent frequencies and intensities. The FFT function is a crucial component for nearly all audio DSP.

Doesn't Apple's Accelerate framework already include an FFT? Yes, and this project makes use of it. But Accelerate's FFT function (vDSP_fft_zrip) isn't trivial to call or set up correctly (esp. from Swift) and is just one necessary ingredient to a functional FFT.

What's “logical banding”? Actually I made that term up so maybe there's a better name for it, but logical banding adds an interface on top of the raw FFT data so that you can, for example, analyze the data at 5 bands per octave across a 6 octave range.

How do you pronounce Tempi? TEMP-ee.

• Swift
• iOS
• AVFoundation
• DSP (Fast Fourier Transform)
• CoreGraphics

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