Struct Biquad 

pub struct Biquad { /* private fields */ }

A biquad filter implementation for audio equalization.

This struct implements a second-order IIR filter using the biquad algorithm. It maintains internal state (x1, x2, y1, y2) for processing continuous audio streams. The filter coefficients are calculated based on the RBJ Audio EQ Cookbook formulas.

The filter supports shelf and peak responses for tone stack equalization.

Implementations

impl Biquad

pub fn new_shelf( shelf: ShelfType, sample_rate: f32, freq: f32, gain_db: f32, ) -> Self

Creates a new biquad shelf filter with the specified parameters.

Arguments

• shelf - The type of shelf filter (Low, High, or Peak).
• sample_rate - The sample rate of the audio signal (e.g., 44100.0).
• freq - The center/cutoff frequency in Hz.
• gain_db - The gain in decibels (positive for boost, negative for cut).

Returns

A new Biquad instance configured with the calculated coefficients.

pub fn process(&mut self, x: f32) -> f32

Processes a single audio sample through the biquad filter.

This method applies the filter to the input sample and updates the internal state for the next sample. It should be called for each sample in sequence.

Arguments

• x - The input audio sample.

Returns

The filtered output sample.

pub fn set_gain_db(&mut self, gain_db: f32)

Updates the gain of the biquad filter.

Recalculates the filter coefficients based on the new gain value while keeping the same frequency and shelf type. The internal state is preserved.

Arguments

• gain_db - The new gain in decibels.