regl-audio

Tools for working with audio in regl. This module has the following components:

• An analyser
• A microphone connection

Examples:

• Beat detection
• Cepstrum
• Pitch detection

Examples

Here is a simple beat detector:

const regl = require('regl')()

const drawBeats = regl({
  vert: `
  precision highp float;

  attribute vec2 position;
  varying vec2 uv;

  void main () {
    uv = position;
    gl_Position = vec4(position, 0, 1);
  }
  `,

  frag: `
  precision highp float;

  varying vec2 uv;

  uniform float beats[16];

  void main () {
    float intensity = 0.0;

    float bin = floor(8.0 * (1.0 + uv.x));

    for (int i = 0; i < 16; ++i) {
      if (abs(float(i) - bin) < 0.25) {
        intensity += step(0.25 * abs(uv.y), beats[i]);
      }
    }
    gl_FragColor = vec4(intensity, 0, 0, 1);
  }
  `,

  attributes: {
    position: [
      -4, 0,
      4, 4,
      4, -4
    ]
  },

  count: 3
})

require('regl-audio/microphone')({
  regl,
  beats: 16,
  name: '',
  done: (microphone) => {
    regl.frame(() => {
      microphone(({beats}) => {
        drawBeats()
      })
    })
  }
})

regl-audio/analyser

This module takes a WebAudio analyser node and returns a scope command giving convenient access to stats from the analyser.

• PCM time domain data
• STFT frequency domain data
• Beats
• Pitch

API

const audio = require('regl-audio/analyser')(options)

The constructor for the analyser takes the following arguments:

Parameter	Description	Default
regl	A handle to a regl instance	Required
analyser	A WebAudio analyser node	Required
name	A prefix for the analyser output.	''
sampleRate	The sample rate of the audio source in Hz	44100
beats	The number of beats to detect grouped by pitch	16
beatTime	Duration of moving average for beats in seconds	1
beatThreshold	Cutoff for beat detection (must be between 0.5 and 1)	0.8
pitches	Number of pitches to detect	4
maxPitch	Maximum detectable pitch in Hz	10000
pitchTime	Duration of moving average for pitch in seconds	0.25

audio(block)

The result is a regl scope command with the following properties:

Context	Description
sampleCount	Number of samples
freq	Array of frequencies
time	Array of PCM time samples
cepstrum	The cepstrum of the signal
timeTexture	Current time information in texture
freqTexture	Current frequency information in texture
volume	Volume of the current signal
beats	Array of detected beats sorted from low to high pitch. Each beat is a scalar in [0, 1]
pitches	Array of detected pitches sorted from loudest to softest in Hz

Uniform	Type	Description
sampleCount	float	Number of samples in texture
time	sampler2D	A sampler storing the PCM time data
freq	sampler2D	A sampler storing the frequency data
volume	float	Volume of the signal
beats	float[NUM_PITCHES]	An array of beats
pitches	float[NUM_PITCHES]	The array of detected pitches

Note that these context variables are optionally prefixed depending on the name parameter.

regl-audio/microphone

A short cut which gives you an analyser node connected to the microphone input from the computer. Note that this must be run on a secure domain.

API

const mic = require('regl-audio/microphone')(options)

The options are the same as above, except that it takes a webaudio context via the options.audioContext parameter instead of an analyser node. By default everything is prefixed with mic_ though this can be changed by passing some alternative to name.

License

(c) 2016 Mikola Lysenko. MIT License