AudioVisualizerUtils

The AudioVisualizerUtils class contains utility functions to help deal with common audio tasks.

Here’s a list of the functions available:

• map
• filterFrequencies
• getFrequencyInterval

map

map(n, start1, stop1, start2, stop2): number

The map function maps a number value n from one interval, [start1, stop1], to another interval, [start2, stop2].

filterFrequencies

filterFrequencies(lowFrequency, highFrequency, dataArray, sampleRate): Uint8Array

The filterFrequencies function returns a Uint8Array containing the frequency data from dataArray but filtered between lowFrequency and highFrequency. This function also requires the sampleRate of the audio. The default value for low frequency is 20 and the default value for high frequency is 20000 in Hz.

getFrequencyInterval

getFrequencyInterval(lowFrequency, highFrequency, nBars, dataArray, sampleRate): number

The getFrequencyInterval function returns a number representing the interval required to cover the dataArray nBars times, having in consideration the frequency range passed.

See an example bellow:

import { AudioVisualizerUtils } from 'react-audio-visualizers-core';

const sampleRate = 44000;
const lowFrequency = 20;
const highFrequency = 20000;
const nPoints = 5;
const dataArray = new Uint8Array(Array.from(Array(sampleRate / 2), () => Math.random() * 255));
const output = AudioVisualizerUtils.getFrequencyInterval(lowFrequency, highFrequency, nPoints, dataArray, sampleRate);

// output: 3996 
console.log(output);

For an audio with sample rate of 44000Hz, filtered between 20Hz and 20000Hz, the function produces the value 3996, which means that if we want to divide the frequency data in 5 points we can iterate the dataArray with a 3996 interval.