minidsp_fir.c File Reference

FIR filtering and convolution: direct time-domain methods and FFT overlap-add fast convolution. More...

#include "minidsp.h"

Include dependency graph for minidsp_fir.c:

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Functions
static unsigned	next_pow2 (unsigned n)
	Return the next power-of-two >= n (n must be > 0).
unsigned	MD_convolution_num_samples (unsigned signal_len, unsigned kernel_len)
	Compute the output length of a full linear convolution.
void	MD_convolution_time (const double *signal, unsigned signal_len, const double *kernel, unsigned kernel_len, double *out)
	Time-domain full linear convolution (direct sum-of-products).
void	MD_moving_average (const double *signal, unsigned signal_len, unsigned window_len, double *out)
	Causal moving-average FIR filter with zero-padded startup.
void	MD_fir_filter (const double *signal, unsigned signal_len, const double *coeffs, unsigned num_taps, double *out)
	Apply a causal FIR filter with arbitrary coefficients.
void	MD_convolution_fft_ola (const double *signal, unsigned signal_len, const double *kernel, unsigned kernel_len, double *out)
	Full linear convolution using FFT overlap-add (offline).

Detailed Description

FIR filtering and convolution: direct time-domain methods and FFT overlap-add fast convolution.

Definition in file minidsp_fir.c.

Function Documentation

MD_convolution_fft_ola()

void MD_convolution_fft_ola	(	const double *	signal,
		unsigned	signal_len,
		const double *	kernel,
		unsigned	kernel_len,
		double *	out
	)

Full linear convolution using FFT overlap-add (offline).

Produces the same output as MD_convolution_time() but is faster for longer kernels by processing blocks in the frequency domain.

Parameters

signal	Input signal of length signal_len.
signal_len	Number of input samples (must be > 0).
kernel	FIR kernel of length kernel_len.
kernel_len	Number of FIR taps (must be > 0).
out	Output buffer of length signal_len + kernel_len - 1.

Definition at line 87 of file minidsp_fir.c.

MD_convolution_num_samples()

unsigned MD_convolution_num_samples	(	unsigned	signal_len,
		unsigned	kernel_len
	)

Compute the output length of a full linear convolution.

For input length N and kernel length M, full convolution length is N+M-1.

Definition at line 17 of file minidsp_fir.c.

MD_convolution_time()

void MD_convolution_time	(	const double *	signal,
		unsigned	signal_len,
		const double *	kernel,
		unsigned	kernel_len,
		double *	out
	)

Time-domain full linear convolution (direct sum-of-products).

Computes: out[n] = sum_{k=0}^{kernel_len-1} signal[n-k] * kernel[k] with out-of-range signal samples treated as zero.

Parameters

signal	Input signal of length signal_len.
signal_len	Number of input samples (must be > 0).
kernel	FIR kernel of length kernel_len.
kernel_len	Number of FIR taps (must be > 0).
out	Output buffer of length signal_len + kernel_len - 1.

Definition at line 24 of file minidsp_fir.c.

MD_fir_filter()

void MD_fir_filter	(	const double *	signal,
		unsigned	signal_len,
		const double *	coeffs,
		unsigned	num_taps,
		double *	out
	)

Apply a causal FIR filter with arbitrary coefficients.

Computes: out[n] = sum_{k=0}^{num_taps-1} coeffs[k] * signal[n-k] with out-of-range signal samples treated as zero.

Parameters

signal	Input signal of length signal_len.
signal_len	Number of input samples (must be > 0).
coeffs	FIR coefficients of length num_taps.
num_taps	Number of FIR taps (must be > 0).
out	Output buffer of length signal_len.

Definition at line 67 of file minidsp_fir.c.

MD_moving_average()

void MD_moving_average	(	const double *	signal,
		unsigned	signal_len,
		unsigned	window_len,
		double *	out
	)

Causal moving-average FIR filter with zero-padded startup.

Computes: out[n] = (1/window_len) * sum_{k=0}^{window_len-1} signal[n-k] where out-of-range samples (n-k < 0) are treated as zero.

Parameters

signal	Input signal of length signal_len.
signal_len	Number of input samples (must be > 0).
window_len	Moving-average window length (must be > 0).
out	Output buffer of length signal_len.

Definition at line 47 of file minidsp_fir.c.

next_pow2()

static unsigned next_pow2 ( unsigned  n )

static

Return the next power-of-two >= n (n must be > 0).

Definition at line 10 of file minidsp_fir.c.