FX Class: Roll

Interactive example

Overview

The Roll effect a loops the incoming audio synchronized to the current tempo, independently from the player outputting it.

The wet property controls the mix of the effect with the original audio between 0 and 1.

One instance allocates around 1600 kb memory.

Implementation example

class SuperpoweredRollProcessor extends SuperpoweredWebAudio.AudioWorkletProcessor {

    // Called when the AudioWorklet is ready to start processing audio
    onReady() {
        this.roll = new this.Superpowered.Roll(
            44100 // The initial sample rate in Hz.
            96000 // The max samplerate that the roll may need to go up to
        );
        this.roll.enabled = true;
    }

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

    // The shape of the message we pass from our main thread is up to you
    onMessageFromMainScope(message) {

        // Here is an example of how to apply changes to the Three Band EQ instance
        if (typeof message.bpm !== 'undefined') this.roll.bits = message.bpm;
        if (typeof message.beats !== 'undefined') this.roll.beats = message.beats;
        if (typeof message.wet !== 'undefined') this.roll.wet = message.wet;
    }

    // This is the process loop which is passed pointers to buffers
    // from the WebAudio API (inputBuffer and outputBuffer), with the buffersize (128 samples when running as a native AudioWorklet)
    processAudio(inputBuffer, outputBuffer, buffersize) {
        // Ensure the samplerate is in sync on every audio processing callback
        this.roll.samplerate = this.samplerate;

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

#include "SuperpoweredRoll.h"

void initRollEffect() {
    const unsigned int sampleRate = 44100;
    const unsigned int maxSampleRate = 88200;
    roll = new Superpowered::Roll(sampleRate, maxSampleRate);
    roll->enabled = true;
}

void configureEffect() {
    roll->wet = 0.5;
    roll->bpm = 128;
    roll->beats = 1;

}

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

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

Properties

Number

float

Number

float

Number

float

Boolean

bool

Number

unsigned int

Methods

• constructor

  METHOD

  Creates a Roll instance.

  Parameters

  Name	Type	Description
  samplerate	Number	The initial sample rate in Hz.
  maximumSamplerate	Number	The maximum sample rate in Hz to support. The higher the larger the memory usage.

  Returns

  Type	Description
  Superpowered.Roll	The constructed instance.

• constructor

  METHOD

  Creates a Roll instance.

  Parameters

  Name	Type	Default	Description
  samplerate	unsigned int		The initial sample rate in Hz.
  maximumSamplerate	unsigned int	96000	The maximum sample rate in Hz to support. The higher the larger the memory usage.

  Returns

  Type	Description
  Superpowered::Roll	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).