FFT

Structs

struct RealFFT

Real-valued FFT implementation using Cooley-Tukey algorithm.

If you're looking to create an FFT-based FX, look to the FFTProcessable trait used in conjunction with FFTProcess instead. This struct is a lower-level implementation that provides FFT and inverse FFT on fixed windows of real values. FFTProcessable structs will enable you to send audio samples (such as in a custom struct's .next() fn) into and out of an FFT, doing some manipulation of the magnitudes and phases in between. (FFTProcess has this RealFFT struct inside of it.)

Traits: AnyType, Copyable, ImplicitlyDestructible, Movable

RealFFT Parameters

Name	Type	Default	Description
num_chans	Int	1	Number of channels for SIMD processing.

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RealFFT Functions

struct RealFFT . fn init

Initialize the RealFFT struct. All internal buffers and lookup tables are set up here based on the Parameters. fn init Signature

__init__(out self, window_size: Int)

fn init Arguments

Name	Type	Default	Description
window_size	Int	—	—

fn init Returns : Self

Static Method

This is a static method.

struct RealFFT . fn fft

Compute the FFT of the input real-valued samples. The resulting magnitudes and phases are stored in the internal mags and phases lists.

fn fft Signature

fft(mut self, input: List[SIMD[DType.float64, num_chans]])

fn fft Arguments

Name	Type	Default	Description
input	List	—	The input real-valued samples to transform. This can be a List of SIMD vectors for multi-channel processing or a List of Float64 for single-channel processing.

struct RealFFT . fn fft

Compute the FFT of the input real-valued samples. The resulting magnitudes and phases are stored in the provided lists.

fn fft Signature

fft(mut self, input: List[SIMD[DType.float64, num_chans]], mut mags: List[SIMD[DType.float64, num_chans]], mut phases: List[SIMD[DType.float64, num_chans]])

fn fft Arguments

Name	Type	Default	Description
input	List	—	The input real-valued samples to transform. This can be a List of SIMD vectors for multi-channel processing or a List of Float64 for single-channel processing.
mags	List	—	A mutable list to store the magnitudes of the FFT result.
phases	List	—	A mutable list to store the phases of the FFT result.

struct RealFFT . fn ifft

Compute the inverse FFT using the internal magnitudes and phases. The output real-valued samples are written to the provided output list.

fn ifft Signature

ifft(mut self, mut output: List[SIMD[DType.float64, num_chans]])

fn ifft Arguments

Name	Type	Default	Description
output	List	—	A mutable list to store the output real-valued samples.

struct RealFFT . fn ifft

Compute the inverse FFT using the provided magnitudes and phases. The output real-valued samples are written to the provided output list.

fn ifft Signature

ifft(mut self, mags: List[SIMD[DType.float64, num_chans]], phases: List[SIMD[DType.float64, num_chans]], mut output: List[SIMD[DType.float64, num_chans]])

fn ifft Arguments

Name	Type	Default	Description
mags	List	—	A list of magnitudes for the inverse FFT.
phases	List	—	A list of phases for the inverse FFT.
output	List	—	A mutable list to store the output real-valued samples.

struct RealFFT . fn fft_frequencies

Compute the FFT bin center frequencies. This implementation is based on Librosa's eponymous function.

fn fft_frequencies Signature

fft_frequencies(sr: Float64, n_fft: Int, min_bin: Int = 0, num_bins: Int = -1) -> List[Float64]

fn fft_frequencies Arguments

Name	Type	Default	Description
sr	Float64	—	The sample rate of the audio signal.
n_fft	Int	—	The size of the FFT.
min_bin	Int	0	The minimum FFT bin index to include.
num_bins	Int	-1	The number of FFT bins to include. Defaults to all bins from min_bin to n_fft//2.

fn fft_frequencies Returns : List A List of Float64 representing the center frequencies of each FFT bin.

Static Method

This is a static method.

struct RealFFT . fn buf_analysis

Compute the Short-Time Fourier Transform (STFT) of a buffer.

fn buf_analysis Signature

buf_analysis[input_window_shape: Int = WindowType.hann](buf: Buffer, chan: Int, start_frame: Int, var num_frames: Int, window_size: Int, hop_size: Int) -> Tuple[List[List[Float64]], List[List[Float64]]]

fn buf_analysis Parameters

Name	Type	Default	Description
input_window_shape	Int	WindowType.hann	The type of window to apply to each frame before computing the FFT.

fn buf_analysis Arguments

Name	Type	Default	Description
buf	Buffer	—	The input audio buffer to analyze.
chan	Int	—	The channel index to analyze from the buffer.
start_frame	Int	—	The starting frame index in the buffer to begin analysis.
num_frames	Int	—	The number of frames to analyze from the starting frame.
window_size	Int	—	The size of the FFT window.
hop_size	Int	—	The hop size between successive windows.

fn buf_analysis Returns : Tuple A tuple containing two lists of lists of Float64 representing the magnitudes and phases of the STFT for each frame and frequency bin.

Static Method

This is a static method.

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