Windowed-sinc sample rate converter optimized for real-time DSP. More...

#include <Resampler.h>

Public Types
enum class	Quality { Draft , Normal , High , Ultra }

Public Member Functions
void	prepare (double sourceRate, double targetRate, Quality quality=Quality::Normal)
	Prepares the resampler for a given rate conversion.

void	prepare (const AudioSpec &spec, double targetRate, Quality quality=Quality::Normal)
	Prepares the resampler using AudioSpec (unified API).

void	reset () noexcept
	Resets the internal state (delay lines, all channels) to zero.

std::vector< T >	process (const T *input, int inputLength)
	Resamples an entire buffer (offline batch processing).

int	processBlock (const T input, int inputLength, T output) noexcept
	Resamples a block of audio in single-channel streaming mode.

int	processBlock (AudioBufferView< T > input, AudioBufferView< T > output) noexcept
	Resamples multi-channel audio using AudioBufferView (streaming).

int	getMaxOutputSamples (int inputLength) const noexcept
	Returns the maximum number of output samples for a given input length.

double	getRatio () const noexcept
	Returns the conversion ratio (targetRate / sourceRate).

int	getLatency () const noexcept
	Returns the streaming latency in output samples.

Detailed Description

template<typename T>
class dspark::Resampler< T >

Windowed-sinc sample rate converter optimized for real-time DSP.

Quality tiers trade CPU for image/alias rejection and passband flatness. Measured on the float instantiation (each column states its test):

Quality	Taps	20 kHz image (48->96)	26 kHz alias (96->44.1)	20 kHz gain (44.1->48)
Draft	8	-12 dB	-10 dB	-3.3 dB
Normal	32	-56 dB	-27 dB	-0.6 dB
High	64	-140 dB	-69 dB	-0.02 dB
Ultra	128	-139 dB	-143 dB	flat

The middle column probes the transition band right at the target Nyquist: only Ultra's kernel is long enough to keep it in the deep stopband. For extreme downsampling ratios (beyond ~8:1) no fixed tap count can hold the anti-alias transition band; cascade two resamplers instead.

Template Parameters

T	Sample type (float or double).

Definition at line 68 of file Resampler.h.

Member Enumeration Documentation

◆ Quality

template<typename T >

enum class dspark::Resampler::Quality

strong

Enumerator
Draft	8-point sinc, fastest (previews; HF response drops early)
Normal	32-point sinc, balanced (~-56 dB worst-case images)
High	64-point sinc, high quality (~-140 dB beyond the transition band)
Ultra	128-point sinc, mastering grade (deep stopband even at the band edge)

Definition at line 71 of file Resampler.h.

Member Function Documentation

◆ getLatency()

template<typename T >

int dspark::Resampler< T >::getLatency ( ) const

inlinenoexcept

Returns the streaming latency in output samples.

The streaming path (processBlock) delays the signal by exactly sincPoints/2 input samples – the sinc kernel's group delay – which this getter reports rounded to the nearest output sample. The offline process() path is already time-aligned and has zero latency.

Definition at line 246 of file Resampler.h.

◆ getMaxOutputSamples()

template<typename T >

int dspark::Resampler< T >::getMaxOutputSamples ( int inputLength ) const

inlinenoexcept

Returns the maximum number of output samples for a given input length.

Parameters

inputLength Number of input samples.

Returns: Maximum possible output samples.

Definition at line 227 of file Resampler.h.

◆ getRatio()

template<typename T >

double dspark::Resampler< T >::getRatio ( ) const

inlinenoexcept

Returns the conversion ratio (targetRate / sourceRate).

Definition at line 236 of file Resampler.h.

◆ prepare() [1/2]

template<typename T >

void dspark::Resampler< T >::prepare	(	const AudioSpec &	spec,
		double	targetRate,
		Quality	quality = `Quality::Normal`
	)

inline

Prepares the resampler using AudioSpec (unified API).

Pre-allocates multi-channel states. MUST be called outside the audio thread.

Parameters

spec	Audio environment (sampleRate, numChannels used).
targetRate	Target sample rate in Hz.
quality	Interpolation quality (default: Normal).

Definition at line 114 of file Resampler.h.

◆ prepare() [2/2]

template<typename T >

void dspark::Resampler< T >::prepare	(	double	sourceRate,
		double	targetRate,
		Quality	quality = `Quality::Normal`
	)

inline

Prepares the resampler for a given rate conversion.

Allocates internal buffers. MUST be called outside the audio thread.

Parameters

sourceRate	Source sample rate in Hz.
targetRate	Target sample rate in Hz.
quality	Interpolation quality (default: Normal).

Definition at line 88 of file Resampler.h.

◆ process()

template<typename T >

std::vector< T > dspark::Resampler< T >::process	(	const T *	input,
		int	inputLength
	)

inline

Resamples an entire buffer (offline batch processing).

Stateless and time-aligned: output sample k interpolates the input at position k / getRatio() exactly (no latency; the buffer edges are zero-padded). Allocates the output vector – offline use only.

Parameters

input	Source audio samples.
inputLength	Number of input samples.

Returns: Vector of resampled output samples (ceil(inputLength * ratio)).

Definition at line 149 of file Resampler.h.

◆ processBlock() [1/2]

template<typename T >

int dspark::Resampler< T >::processBlock	(	AudioBufferView< T >	input,
		AudioBufferView< T >	output
	)

inlinenoexcept

Resamples multi-channel audio using AudioBufferView (streaming).

Processes each channel sequentially with its independent state.

Parameters

input	Input audio buffer view.
output	Output audio buffer view (pre-allocated).

Returns: Number of output samples produced per channel.

Definition at line 200 of file Resampler.h.

◆ processBlock() [2/2]

template<typename T >

int dspark::Resampler< T >::processBlock	(	const T *	input,
		int	inputLength,
		T *	output
	)

inlinenoexcept

Resamples a block of audio in single-channel streaming mode.

Parameters

input	Input audio samples.
inputLength	Number of input samples.
output	Output buffer (must hold at least getMaxOutputSamples()).

Returns: Number of output samples produced.

Definition at line 186 of file Resampler.h.

◆ reset()

template<typename T >

void dspark::Resampler< T >::reset ( )

inlinenoexcept

Resets the internal state (delay lines, all channels) to zero.

Safe to call from the audio thread after prepare(): the assigns below only refill storage that prepare() already sized (no reallocation).

Definition at line 127 of file Resampler.h.

The documentation for this class was generated from the following file:

Core/Resampler.h

Public Types

Public Member Functions

Detailed Description

Member Enumeration Documentation

◆ Quality

Member Function Documentation

◆ getLatency()

◆ getMaxOutputSamples()

◆ getRatio()

◆ prepare() [1/2]

◆ prepare() [2/2]

◆ process()

◆ processBlock() [1/2]

◆ processBlock() [2/2]

◆ reset()