minidsp_resample.c File Reference

Polyphase sinc resampler for offline sample rate conversion. More...

#include "minidsp.h"
#include "minidsp_internal.h"

Go to the source code of this file.

Macros
#define	RESAMPLE_NUM_PHASES   512
	Number of sub-phases in the polyphase filter table.

Functions
unsigned	MD_resample_output_len (unsigned input_len, double in_rate, double out_rate)
	Compute the output buffer size needed for resampling.
unsigned	MD_resample (const double *input, unsigned input_len, double *output, unsigned max_output_len, double in_rate, double out_rate, unsigned num_zero_crossings, double kaiser_beta)
	Resample a signal from one sample rate to another using polyphase sinc interpolation.

Detailed Description

Polyphase sinc resampler for offline sample rate conversion.

Definition in file minidsp_resample.c.

Macro Definition Documentation

RESAMPLE_NUM_PHASES

#define RESAMPLE_NUM_PHASES   512

Number of sub-phases in the polyphase filter table.

Definition at line 10 of file minidsp_resample.c.

Function Documentation

MD_resample()

unsigned MD_resample	(	const double *	input,
		unsigned	input_len,
		double *	output,
		unsigned	max_output_len,
		double	in_rate,
		double	out_rate,
		unsigned	num_zero_crossings,
		double	kaiser_beta )

Resample a signal from one sample rate to another using polyphase sinc interpolation.

Uses a fixed table of 512 sub-phases with linear interpolation and a Kaiser-windowed sinc anti-aliasing filter. Anti-aliasing cutoff is automatically set to \(\min(\mathrm{in\_rate}, \mathrm{out\_rate})/2\).

Parameters

input	Input signal of length input_len.
input_len	Number of input samples (must be > 0).
output	Output buffer (caller-allocated). Use MD_resample_output_len() to size it.
max_output_len	Capacity of output buffer. Must be >= MD_resample_output_len(input_len, in_rate, out_rate).
in_rate	Input sample rate in Hz (must be > 0).
out_rate	Output sample rate in Hz (must be > 0).
num_zero_crossings	Number of sinc zero-crossings per side. Higher = better quality. Typical: 32.
kaiser_beta	Kaiser window shape parameter. Typical: 10.0 for ~100 dB stopband.

Returns

Number of samples written to output.

double in[44100], out[48000];
MD_sine_wave(in, 44100, 1.0, 440.0, 44100.0);
unsigned n = MD_resample(in, 44100, out, 48000,
                         44100.0, 48000.0, 32, 10.0);

Definition at line 21 of file minidsp_resample.c.

MD_resample_output_len()

unsigned MD_resample_output_len	(	unsigned	input_len,
		double	in_rate,
		double	out_rate )

Compute the output buffer size needed for resampling.

Returns \(\lceil \mathrm{input\_len} \times \mathrm{out\_rate} / \mathrm{in\_rate} \rceil\).

Parameters

input_len	Number of input samples (must be > 0).
in_rate	Input sample rate in Hz (must be > 0).
out_rate	Output sample rate in Hz (must be > 0).

Returns

Required output buffer length.

unsigned n = MD_resample_output_len(44100, 44100.0, 48000.0);  // 48000

Definition at line 12 of file minidsp_resample.c.