An IIR-based half-band decimator for downsampling audio by a factor of 2. More...

#include <iir_halfband_decimator.h>

Inheritance diagram for vital::IirHalfbandDecimator:

Public Types
enum	{ kAudio , kNumInputs }

Public Member Functions
	IirHalfbandDecimator ()
	Constructs an IirHalfbandDecimator and initializes its memory.

virtual	~IirHalfbandDecimator ()
	Virtual destructor.

virtual Processor *	clone () const override
	Cloning is not supported for this processor.

virtual void	process (int num_samples) override
	Processes audio data by decimating it (halving the sample rate).

void	reset (poly_mask reset_mask) override
	Resets the filter states (delay lines) for the specified voices.

force_inline void	setSharpCutoff (bool sharp_cutoff)
	Enables or disables the sharper 25-tap cutoff mode.

Public Member Functions inherited from vital::Processor
	Processor (int num_inputs, int num_outputs, bool control_rate=false, int max_oversample=1)
	Constructs a Processor with a given number of inputs/outputs and oversampling.

virtual	~Processor ()
	Virtual destructor.

virtual bool	hasState () const
	Indicates whether this Processor requires per-voice state.

virtual void	processWithInput (const poly_float *audio_in, int num_samples)
	An optional processing function taking explicit input buffer. Fallback is an assertion failure (not supported).

virtual void	init ()
	Called after constructor, used for any additional initialization. Subclasses can override. Sets the initialized flag.

virtual void	hardReset ()
	Called to perform a "hard" reset for all voices.

bool	initialized ()
	Returns whether this Processor has been initialized.

virtual void	setSampleRate (int sample_rate)
	Updates the sample rate of this Processor (scaled by oversampling).

virtual void	setOversampleAmount (int oversample)
	Sets the oversampling amount and updates the effective sample rate.

force_inline bool	enabled () const
	Checks if this Processor is enabled.

virtual void	enable (bool enable)
	Enables or disables this Processor.

force_inline int	getSampleRate () const
	Retrieves the current (effective) sample rate.

force_inline int	getOversampleAmount () const
	Retrieves the current oversampling factor.

force_inline bool	isControlRate () const
	Checks if this Processor is running at control rate (buffer_size == 1).

virtual void	setControlRate (bool control_rate)
	Sets whether this Processor runs at control rate.

force_inline poly_mask	getResetMask (int input_index) const
	Retrieves a mask indicating which voices triggered a note-on event. Compares the input's trigger_value to kVoiceOn.

force_inline void	clearOutputBufferForReset (poly_mask reset_mask, int input_index, int output_index) const
	Clears output samples for voices that are about to be reset, based on the trigger offset.

bool	inputMatchesBufferSize (int input=0)
	Checks whether the buffer size of a particular input matches the size needed by this Processor.

bool	checkInputAndOutputSize (int num_samples)
	Checks if all inputs and outputs have buffers big enough for `num_samples`.

virtual bool	isPolyphonic () const
	Checks if this Processor is polyphonic by querying its ProcessorRouter.

void	plug (const Output *source)
	Connects an external Output to this Processor's first input.

void	plug (const Output *source, unsigned int input_index)
	Connects an external Output to a specified input index.

void	plug (const Processor *source)
	Connects the first output of a Processor to this Processor's first input.

void	plug (const Processor *source, unsigned int input_index)
	Connects the first output of a Processor to a specified input index.

void	plugNext (const Output *source)
	Connects an external Output to the first available (unplugged) input.

void	plugNext (const Processor *source)
	Connects the first output of a Processor to the first available (unplugged) input.

void	useInput (Input *input)
	Uses an existing Input object as this Processor's first input.

void	useInput (Input *input, int index)
	Uses an existing Input object at a specified input index.

void	useOutput (Output *output)
	Uses an existing Output object as this Processor's first output.

void	useOutput (Output *output, int index)
	Uses an existing Output object at a specified output index.

int	connectedInputs ()
	Counts how many inputs are connected to a real source (not null_source_).

virtual void	unplugIndex (unsigned int input_index)
	Removes the connection at a specified input index, if any.

virtual void	unplug (const Output *source)
	Removes a connection to a given Output from all inputs.

virtual void	unplug (const Processor *source)
	Removes connections to all outputs from a given Processor.

virtual void	numInputsChanged ()
	Called when the number of inputs changes (e.g., new connections). Subclasses may override for dynamic behavior.

force_inline void	router (ProcessorRouter *router)
	Sets the ProcessorRouter that owns or manages this Processor.

force_inline ProcessorRouter *	router () const
	Returns the ProcessorRouter that currently owns this Processor.

ProcessorRouter *	getTopLevelRouter () const
	Gets the topmost (root) ProcessorRouter by traversing parent routers.

virtual void	registerInput (Input *input, int index)
	Registers a new input, appending it to the input list.

virtual Output *	registerOutput (Output *output, int index)
	Registers a new Output in the output list at a specified index.

virtual void	registerInput (Input *input)
	Registers a new Input by appending it to the end of the input list.

virtual Output *	registerOutput (Output *output)
	Registers a new Output by appending it to the end of the output list.

force_inline int	numInputs () const
	Returns the total number of Input pointers (owned or otherwise).

force_inline int	numOutputs () const
	Returns the total number of Output pointers (owned or otherwise).

force_inline int	numOwnedInputs () const
	Returns how many Input objects this Processor owns.

force_inline int	numOwnedOutputs () const
	Returns how many Output objects this Processor owns.

force_inline Input *	input (unsigned int index=0) const
	Retrieves the Input pointer at a given index.

force_inline bool	isInputSourcePolyphonic (int index=0)
	Checks if the input source at a given index is polyphonic.

force_inline Input *	ownedInput (unsigned int index=0) const
	Retrieves an owned Input pointer at a given index.

force_inline Output *	output (unsigned int index=0) const
	Retrieves the Output pointer at a given index.

force_inline Output *	ownedOutput (unsigned int index=0) const
	Retrieves an owned Output pointer at a given index.

void	setPluggingStart (int start)
	Sets the position at which `plugNext` starts searching for an open input.

Static Public Attributes
static constexpr int	kNumTaps9 = 2
	Number of taps in the lighter (9-tap) filter mode.

static constexpr int	kNumTaps25 = 6
	Number of taps in the sharper (25-tap) filter mode.

static poly_float	kTaps9 [kNumTaps9]
	Coefficients for the 9-tap IIR half-band filter, stored as pairs of poly_float.

static poly_float	kTaps25 [kNumTaps25]
	Coefficients for the 25-tap IIR half-band filter, stored as pairs of poly_float.

Additional Inherited Members
Protected Member Functions inherited from vital::Processor
Output *	addOutput (int oversample=1)
	Creates and registers a new Output. Handles control rate vs. audio rate.

Input *	addInput ()
	Creates and registers a new Input, initially connected to null_source_.

Protected Attributes inherited from vital::Processor
std::shared_ptr< ProcessorState >	state_
	Shared state (sample rate, oversample, etc.)

int	plugging_start_
	The index at which `plugNext` starts searching for an unplugged input.

std::vector< std::shared_ptr< Input > >	owned_inputs_
	Inputs owned by this Processor.

std::vector< std::shared_ptr< Output > >	owned_outputs_
	Outputs owned by this Processor.

std::shared_ptr< std::vector< Input * > >	inputs_
	All inputs, owned or external.

std::shared_ptr< std::vector< Output * > >	outputs_
	All outputs, owned or external.

ProcessorRouter *	router_
	The ProcessorRouter that manages this Processor.

Static Protected Attributes inherited from vital::Processor
static const Output	null_source_
	A null (dummy) source used for unconnected inputs.

Detailed Description

An IIR-based half-band decimator for downsampling audio by a factor of 2.

This decimator uses an IIR half-band filter approach where each pair of input samples is combined into a single output sample. The filter can operate in two modes:

A faster, lighter mode using 9 taps.
A sharper cutoff mode using 25 taps.

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

Enumerator
kAudio	Main audio input for decimation.
kNumInputs	Total number of inputs for this processor.

Constructor & Destructor Documentation

◆ IirHalfbandDecimator()

vital::IirHalfbandDecimator::IirHalfbandDecimator ( )

Constructs an IirHalfbandDecimator and initializes its memory.

Constructor for IirHalfbandDecimator, defaults to the 9-tap (lighter) filter mode.

◆ ~IirHalfbandDecimator()

virtual vital::IirHalfbandDecimator::~IirHalfbandDecimator ( )

inlinevirtual

Virtual destructor.

Member Function Documentation

◆ clone()

virtual Processor * vital::IirHalfbandDecimator::clone ( ) const

inlineoverridevirtual

Cloning is not supported for this processor.

Returns: Returns nullptr, with an assertion failure.

Implements vital::Processor.

◆ process()

void vital::IirHalfbandDecimator::process ( int num_samples )

overridevirtual

Processes audio data by decimating it (halving the sample rate).

Processes the audio block, decimating by a factor of 2.

Parameters

num_samples	The number of output samples to process (input must have 2 * num_samples).
num_samples	Number of output samples. The input buffer must have 2 * num_samples samples.

Applies an IIR half-band filter with either 9 or 25 taps, depending on sharp_cutoff_. The result is written to the output buffer, halving the sample rate of the incoming signal.

Implements vital::Processor.

◆ reset()

void vital::IirHalfbandDecimator::reset ( poly_mask reset_mask )

overridevirtual

Resets the filter states (delay lines) for the specified voices.

Resets the decimator's internal memory for the specified voices.

Parameters

reset_mask	A bitmask specifying which voices to reset.
reset_mask	A bitmask specifying which voices to reset (unused here).

Clears all delay line states to 0, ensuring no leftover data affects the next block.

Reimplemented from vital::Processor.

◆ setSharpCutoff()

force_inline void vital::IirHalfbandDecimator::setSharpCutoff ( bool sharp_cutoff )

inline

Enables or disables the sharper 25-tap cutoff mode.

Parameters

sharp_cutoff If true, use 25 taps; if false, use 9 taps.

Member Data Documentation

◆ kNumTaps25

int vital::IirHalfbandDecimator::kNumTaps25 = 6

staticconstexpr

Number of taps in the sharper (25-tap) filter mode.

◆ kNumTaps9

int vital::IirHalfbandDecimator::kNumTaps9 = 2

staticconstexpr

Number of taps in the lighter (9-tap) filter mode.

◆ kTaps25

poly_float vital::IirHalfbandDecimator::kTaps25

static

Initial value:

= {
    { 0.093022421467960f, 0.024388383731296f },
    { 0.312318050871736f, 0.194029987625265f },
    { 0.548379093159427f, 0.433855675727187f },
    { 0.737198546150414f, 0.650124972769370f },
    { 0.872234992057129f, 0.810418671775866f },
    { 0.975497791832324f, 0.925979700943193f }
  }

Coefficients for the 25-tap IIR half-band filter, stored as pairs of poly_float.

Coefficients for the 25-tap IIR half-band filter, stored in poly_float pairs.

Each pair contains coefficients for two parallel paths (or for two lanes in poly_float).

◆ kTaps9

poly_float vital::IirHalfbandDecimator::kTaps9

static

Initial value:

= {
    { 0.167135116548925f, 0.0413554705262319f },
    { 0.742130012538075f, 0.3878932830211427f },
  }

Coefficients for the 9-tap IIR half-band filter, stored as pairs of poly_float.

Coefficients for the 9-tap IIR half-band filter, stored in poly_float pairs.

Each pair contains coefficients for two parallel paths (or for two lanes in poly_float).

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

/Users/davidvogel/repos/VitalHelp/src/synthesis/filters/iir_halfband_decimator.h
/Users/davidvogel/repos/VitalHelp/src/synthesis/filters/iir_halfband_decimator.cpp

Public Types

Public Member Functions

Static Public Attributes

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ anonymous enum

Constructor & Destructor Documentation

◆ IirHalfbandDecimator()

◆ ~IirHalfbandDecimator()

Member Function Documentation

◆ clone()

◆ process()

◆ reset()

◆ setSharpCutoff()

Member Data Documentation

◆ kNumTaps25

◆ kNumTaps9

◆ kTaps25

◆ kTaps9