FX Class: Guitar Distortion

Interactive example

Overview

The Guitar Distortion audio effect is used to mimic the sound of amplified electric musical instruments, usually by increasing their gain and simulating their saturation going into overdrive, producing a "fuzzy", "growling", or "gritty" tone. This effect has Marshall cabinet, ADA cabinet and V-Twin preamp simulation, 5-band equalizer, bass and treble tone controls and two distortion sound paths (similar to Boss DS-1 and Tyrian).

Implementation example

Additional frequency range limiting is possible with the bassFrequency and trebleFrequency properties.

The drive property acts as the overall distortion ratio from 0 to 1.

Amp cabinet simulation can be added using marshall, ada and vtwin switches.

Pedal simulation can be enabled using distortion0 (similar to Boss DS-1) and distortion1 (similar to Tyrian).

Guitar distortion is is an FX class, it expects both an input and output buffer. The process() function should be called on every loop of the audio processing block. One instance allocates around 32 kb memory.

class SuperpoweredFilterProcessor extends SuperpoweredWebAudio.AudioWorkletProcessor {

    // Called when the AudioWorklet is ready to start processing audio
    onReady() {
        this.effect = new this.Superpowered.GuitarDistortion(
            this.samplerate
        );
        this.effect.enabled = true;
        this.effect.distortion1 = true;
        this.effect.marshall = true;
        this.effect.drive = 0.2;
        this.effect.gainDecibel = -20;
    }

    // Runs before the node is destroyed.
    // Clean up memory and objects here (such as free allocated linear memory or destruct Superpowered objects).
    onDestruct() {
        this.effect.destruct();
    }

    // messages are received from the main scope through this method.
    onMessageFromMainScope(message) {
        if (typeof message.gainDecibel !== 'undefined') this.effect.gainDecibel = message.gainDecibel;
        if (typeof message.drive !== 'undefined') this.effect.drive = message.drive;
        if (typeof message.bassFrequency !== 'undefined') this.effect.bassFrequency = message.bassFrequency;
        if (typeof message.trebleFrequency !== 'undefined') this.effect.trebleFrequency = message.trebleFrequency;
        if (typeof message.eq80HzDecibel !== 'undefined') this.effect.eq80HzDecibel = message.eq80HzDecibel;
        if (typeof message.eq240HzDecibel !== 'undefined') this.effect.eq250HzDecibel = message.eq240HzDecibel;
        if (typeof message.eq750HzDecibel !== 'undefined') this.effect.eq750HzDecibel = message.eq750HzDecibel;
        if (typeof message.eq2200HzDecibel !== 'undefined') this.effect.eq2200HzDecibel = message.eq2200HzDecibel;
        if (typeof message.eq6600HzDecibel !== 'undefined') this.effect.eq6600HzDecibel = message.eq6600HzDecibel;
        if (typeof message.distortion0 !== 'undefined') this.effect.distortion0 = message.distortion0;
        if (typeof message.distortion1 !== 'undefined') this.effect.distortion1 = message.distortion1;
        if (typeof message.marshall !== 'undefined') this.effect.marshall = message.marshall;
        if (typeof message.ada !== 'undefined') this.effect.ada = message.ada;
        if (typeof message.vtwin !== 'undefined') this.effect.vtwin = message.vtwin;
        if (typeof message.enabled !== 'undefined') this.effect.enabled = Boolean(message.enabled);
    }

    processAudio(inputBuffer, outputBuffer, buffersize, parameters) {
        // Ensure the samplerate is in sync on every audio processing callback
        this.effect.samplerate = this.samplerate;

        // Render the output buffers
        if (!this.effect.process(inputBuffer.pointer, outputBuffer.pointer, buffersize)) {
            for (let n = 0; n < buffersize * 2 ; n++) outputBuffer.array[n] = inputBuffer.array[n];
        }
    }
}

#include "SuperpoweredGuitarDistortion.h"

void initEffect() {
    effect = new Superpowered::GuitarDistortion(44100);
    effect->enabled = true;
}

void configureEffect() {
    effect->enabled = true;
    effect->distortion1 = true;
    effect->marshall = true;
    effect->drive = 0.2;
    effect->gainDecibel = -20;
}

void processAudio(float *interleavedInput, float *interleavedOutput, unsigned int numberOfFrames, unsigned int samplerate) {
    // Ensure the samplerate is in sync on every audio processing callback
    effect->samplerate = samplerate;

    // Render the output buffers
    bool outputChanged = effect->process(interleavedInput, interleavedOutput, numberOfFrames);
    ...
}

Properties

Number

boolean

Number

float

Number

boolean

Number

boolean

Number

float

Number

float

Number

float

Number

float

Number

float

Number

float

Number

float

Number

boolean

Number

float

Number

boolean

Boolean

bool

Number

unsigned int

Methods

• constructor

  METHOD

  Creates a GuitarDistortion instance.

  Parameters

  Name	Type	Description
  samplerate	Number	The initial sample rate in Hz.

  Returns

  Type	Description
  Superpowered.GuitarDistortion	The constructed instance.

• constructor

  METHOD

  Creates a GuitarDistortion instance.

  Parameters

  Name	Type	Default	Description
  samplerate	unsigned int		The initial sample rate in Hz.

  Returns

  Type	Description
  Superpowered::GuitarDistortion	The constructed instance.

• destruct

  METHOD

  Destructor to free Linear Memory.

  Parameters

  None

  Returns

  None

• process

  METHOD

  Processes/renders the audio. Always call it in the audio processing callback, regardless if the effect is enabled or not for smooth, audio-artifact free operation. It's never blocking for real-time usage.

  Parameters

  Name	Type	Description
  input	Number (pointer in Linear Memory)	32-bit interleaved stereo input.
  output	Number (pointer in Linear Memory)	32-bit interleaved stereo output.
  numberOfFrames	Number	Number of frames to process. Recommendations for best performance: multiply of 4, minimum 64.

  Returns

  Type	Description
  Boolean	If process() returns with true, the contents of output are replaced with the audio output. If process() returns with false, it indicates silence. The contents of output are not changed in this case (not overwritten with zeros).

• process

  METHOD

  Processes/renders the audio. Always call it in the audio processing callback, regardless if the effect is enabled or not for smooth, audio-artifact free operation. It's never blocking for real-time usage. You can change all effect properties on any thread, concurrently with process().

  Parameters

  Name	Type	Default	Description
  input	float *		32-bit interleaved stereo input.
  output	float *		32-bit interleaved stereo output.
  numberOfFrames	unsigned int		Number of frames to process. Recommendations for best performance: multiply of 4, minimum 64.

  Returns

  Type	Description
  bool	If process() returns with true, the contents of output are replaced with the audio output. If process() returns with false, it indicates silence. The contents of output are not changed in this case (not overwritten with zeros).