Fft

Auto-generated from src/stdlib/fft.mcrs — do not edit manually.

API

• dft_noop
• dft_real
• dft_magnitude
• dft_power
• dft_freq_bin

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dft_noop v2.0.0

Default no-op completion callback for dft_coro. Does nothing.

fn dft_noop(): void

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dft_real v2.0.0

Compute the Discrete Fourier Transform of input[0..n-1].

Output arrays must be pre-allocated to length n and filled with zeros before calling.

Formula: X[k] = Σ x[j] * (cos(2πkj/n) - i·sin(2πkj/n))

fn dft_real(input: int[], n: int, out_re: int[], out_im: int[])

Parameters

Parameter	Description
input	Signal samples in fixed-point ×10000
n	Number of samples (≤ 16 recommended)
out_re	Pre-allocated output array for real parts (×10000)
out_im	Pre-allocated output array for imaginary parts (×10000)

Example

let re: int[] = [0, 0, 0, 0]
let im: int[] = [0, 0, 0, 0]
dft_real(sig, 4, re, im)

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dft_magnitude v2.0.0

Return the magnitude of DFT bin k: |X[k]| = sqrt(re[k]² + im[k]²) in ×10000.

Note: squaring ×10000 values can reach ~10⁹ per term, which fits in int32 for amplitudes ≤ ~46340. For larger amplitudes, scale the input before calling.

fn dft_magnitude(re: int[], im: int[], k: int): int

Parameters

Parameter	Description
re	Real output array from dft_real
im	Imaginary output array from dft_real
k	Bin index

Returns: Magnitude of bin k in ×10000 fixed-point

Example

let mag: int = dft_magnitude(re, im, 1)

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dft_power v2.0.0

Return the power spectrum value for bin k: re[k]²/10000 + im[k]²/10000.

Division by 10000 prevents int32 overflow for values up to ~46340 (×10000). The result is in ×10000 scale (power units).

fn dft_power(re: int[], im: int[], k: int): int

Parameters

Parameter	Description
re	Real output array from dft_real
im	Imaginary output array from dft_real
k	Bin index

Returns: Power of bin k in ×10000 units

Example

let power: int = dft_power(re, im, 2)

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dft_freq_bin v2.0.0

Return the frequency (Hz) corresponding to DFT bin k.

Formula: freq = sample_rate_hz * k / n

fn dft_freq_bin(sample_rate_hz: int, n: int, k: int): int

Parameters

Parameter	Description
sample_rate_hz	Sampling rate in Hz (e.g. 20 for Minecraft tick rate)
n	Transform size (number of samples)
k	Bin index in range [0, n-1]

Returns: Frequency in Hz for bin k

Example

let freq: int = dft_freq_bin(20, 8, 3)

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