xtos_bandpass_init

Initializes a fourth-order band-pass baseline made from a second-order high-pass followed by low-pass.

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Declaration

#include <xtos/signal.h>

int xtos_bandpass_init(struct xtos_bandpass_filter *filter,
                       double sample_rate_hz,
                       double low_cut_hz,
                       double high_cut_hz);

Parameters

Parameter	Type	Description
filter	struct xtos_bandpass_filter *	Non-NULL caller-owned filter state.
sample_rate_hz	double	Sampling rate in Hz; must be positive, with no explicit finite check.
low_cut_hz	double	Low cutoff in Hz; must be positive, with no explicit finite check.
high_cut_hz	double	High cutoff in Hz; must exceed low_cut and be below fs/2, with no explicit finite check.

Return value

Returns 0 on success and -1 on failure. Success clears history in both stages.

Errors

errno	Condition
EINVAL	filter is NULL, or fs, low, and high fail the positive-value and low<high<fs/2 constraints.

Notes

Both biquads use a fixed Q of about 0.7071; the public implementation has no isfinite check.
Initialization and reinitialization clear state and create a transient; recompute coefficients after rate or cutoff changes.

Example

Source

This reference describes headers and implementation at OpenXTOS commit dd313955ad57542bcd2af8827157d1bbd0cf5e83.