SynthLab SDK
SynthLab::BQFilterCore Class Reference

Implements Filters via BiQuad structures; includes one pole HPF and LPF. More...

#include <bqfiltercore.h>

Inheritance diagram for SynthLab::BQFilterCore:
SynthLab::ModuleCore

Public Member Functions

 BQFilterCore ()
 Construction: Cores follow the same construction pattern. More...
 
virtual ~BQFilterCore ()
 
virtual bool reset (CoreProcData &processInfo) override
 Resets object to initialized state. More...
 
virtual bool update (CoreProcData &processInfo) override
 Updates the object for the next block of audio processing. More...
 
virtual bool render (CoreProcData &processInfo) override
 Renders the output of the module. More...
 
virtual bool doNoteOn (CoreProcData &processInfo) override
 Note-on handler for the ModuleCore. More...
 
virtual bool doNoteOff (CoreProcData &processInfo) override
 Note-off handler for the ModuleCore. More...
 
void flushDelays ()
 
- Public Member Functions inherited from SynthLab::ModuleCore
 ModuleCore ()
 Constructs a ModuleCore. More...
 
virtual int32_t getState ()
 
virtual bool shutdown ()
 
virtual void setSustainOverride (bool sustain)
 
virtual void setStandAloneMode (bool b)
 
bool startGlideModulation (GlideInfo &glideInfo)
 
uint32_t getModuleType ()
 
const char * getModuleName ()
 
void * getModuleHandle ()
 
void setModuleHandle (void *handle)
 
uint32_t getModuleIndex ()
 
void setModuleIndex (uint32_t index)
 
int32_t getPreferredModuleIndex ()
 
void setPreferredModuleIndex (uint32_t index)
 
ModuleCoreDatagetModuleData ()
 provides access to the core data: More...
 

Protected Types

enum  {
  a0, a1, a2, b1,
  b2, c0, d0
}
 

Protected Attributes

BQAudioFilter filter [STEREO_CHANNELS]
 biquad audio filter objects
 
double sampleRate = 1.0
 fs
 
double outputAmp = 1.0
 output scaling
 
double midiPitch = 440.0
 midi note pitch
 
- Protected Attributes inherited from SynthLab::ModuleCore
uint32_t moduleType = UNDEFINED_MODULE
 type of module, LFO_MODULE, EG_MODULE, etc...
 
const char * moduleName = nullptr
 module name must be set in derived constructor
 
void * moduleHandle = nullptr
 used for dynamically loading cores from DLLs
 
uint32_t moduleIndex = 0
 index of this core
 
int32_t preferredIndex = -1
 preferred index of this DYNAMIC core
 
ModuleCoreData coreData
 core strings (16) and mod knob labels (4)
 
bool standAloneMode = false
 flag for stand-alone mode of operation outside of SynthLab
 
std::unique_ptr< GlideModulatorglideModulator
 built-in glide modulator for oscillators
 

Detailed Description

Implements Filters via BiQuad structures; includes one pole HPF and LPF.

Base Class: ModuleCore

  • Overrides the five (5) common functions plus a special getParameters() method to return a shared pointer to the parameters structure.
  • NOTE: These functions have identical names as the SynthModules that own them, however the arguments are different. ModuleCores use the CoreProcData structure for passing arguments into the cores because they are thunk-barrier compliant.
  • This means that the owning SynthModule must prepare this structure and populate it prior to function calls. The large majority of this preparation is done in the SynthModule constructor and is one-time in nature.

GUI Parameters: FilterParameters

  • GUI parameters are delivered into the core via the thunk-barrier compliant CoreProcData argument that is passed into each function identically
  • processInfo.moduleParameters contains a void* version of the GUI parameter structure pointer
  • the Core function casts the GUI parameter pointer prior to usage

Access to Modulators is done via the thunk-barrier compliant CoreProcData argument

  • processInfo.modulationInputs
  • processInfo.modulationOutputs

Access to audio buffers (I/O/FM) is done via the thunk-barrier compliant CoreProcData argument

  • processInfo.inputBuffers
  • processInfo.outputBuffers
  • processInfo.fmBuffers

Construction: Cores follow the same construction pattern

  • set the Module type and name parameters
  • expose the 16 module strings
  • expose the 4 mod knob label strings
  • intialize any internal variables

Standalone Mode:

  • These objects are designed to be internal members of the outer SynthModule that owns them. They may be used in standalone mode without modification, and you will use the CoreProcData structure to pass information into the functions.

Module Strings, zero-indexed for your GUI Control:

  • No_Filter, _1PLPF, _1PHPF, BQ_LPF2, BQ_HPF2

ModKnob Strings, for fixed GUI controls by index constant

  • MOD_KNOB_A = "Key Track"
  • MOD_KNOB_B = "Drive"
  • MOD_KNOB_C = "EG Int"
  • MOD_KNOB_D = "BP Int"

Render:

  • processes all audio samples in block
  • processes from input buffer to output buffer using pointers in the CoreProcData argument
Author
Will Pirkle http://www.willpirkle.com
Remarks
This object is included and described in further detail in Designing Software Synthesizer Plugins in C++ 2nd Ed. by Will Pirkle
Version
Revision : 1.0
Date
Date : 2021 / 04 / 26

Constructor & Destructor Documentation

◆ BQFilterCore()

SynthLab::BQFilterCore::BQFilterCore ( )

Construction: Cores follow the same construction pattern.

simple default constructor

  • set the Module type and name parameters
  • expose the 16 module strings
  • expose the 4 mod knob label strings
  • intialize any internal variables

Core Specific:

  • implements a few of the filters from Will Pirkle's FX Plugin book
  • includes one pole HPF, LPF
Returns
the newly constructed object

◆ ~BQFilterCore()

virtual SynthLab::BQFilterCore::~BQFilterCore ( )
inlinevirtual

Destructor is empty: all resources are smart pointers

Member Function Documentation

◆ doNoteOff()

bool SynthLab::BQFilterCore::doNoteOff ( CoreProcData processInfo)
overridevirtual

Note-off handler for the ModuleCore.

  • parameters are accessed via the processInfo.moduleParameters pointer
  • MIDI note information is accessed via processInfo.noteEvent

Core Specific:

  • nothing to do here
Parameters
processInfois the thunk-barrier compliant data structure for passing all needed parameters
Returns
true if successful, false otherwise

Implements SynthLab::ModuleCore.

◆ doNoteOn()

bool SynthLab::BQFilterCore::doNoteOn ( CoreProcData processInfo)
overridevirtual

Note-on handler for the ModuleCore.

  • parameters are accessed via the processInfo.moduleParameters pointer
  • MIDI note information is accessed via processInfo.noteEvent

Core Specific:

  • saves MIDI pitch in case of key-tracking modulation
  • flushes biquad state variable delay lines
Parameters
processInfois the thunk-barrier compliant data structure for passing all needed parameters
Returns
true if successful, false otherwise

Implements SynthLab::ModuleCore.

◆ flushDelays()

void SynthLab::BQFilterCore::flushDelays ( )
inline

flush biquad delays on reset and new note events

◆ render()

bool SynthLab::BQFilterCore::render ( CoreProcData processInfo)
overridevirtual

Renders the output of the module.

  • processes from input buffer to output buffer using pointers in the CoreProcData argument Core Specific:
  • filter sub-objects perform processing
  • implements drive control with arc-tangent waveshaper
Parameters
processInfothe thunk-barrier compliant data structure for passing all needed parameters
Returns
true if successful, false otherwise

Implements SynthLab::ModuleCore.

◆ reset()

bool SynthLab::BQFilterCore::reset ( CoreProcData processInfo)
overridevirtual

Resets object to initialized state.

ModuleCore Overrides

  • parameters are accessed via the processInfo.moduleParameters pointer
  • initializes sample rate dependent stuff via processInfo.sampleRate
  • calculates intitial coefficients
  • sets initial state variables
Parameters
processInfothe thunk-barrier compliant data structure for passing all needed parameters
Returns
true if successful, false otherwise

Implements SynthLab::ModuleCore.

◆ update()

bool SynthLab::BQFilterCore::update ( CoreProcData processInfo)
overridevirtual

Updates the object for the next block of audio processing.

  • parameters are accessed via the processInfo.moduleParameters pointer
  • modulator inputs are accessied via processInfo.modulationInputs
  • mod knob values are accessed via parameters->modKnobValue[] Core Specific:
  • calculates fc modulation value from input modulators, kBipolarMod and kEGMod
  • calculates key-tracking modulation value (if enabled)
  • calculated the coefficients for various filters based on user selection
Parameters
processInfothe thunk-barrier compliant data structure for passing all needed parameters
Returns
true if successful, false otherwise

Implements SynthLab::ModuleCore.


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