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 | | tempo | Initial guess of tempo for song in beats per second | 100/60 | | maxTempo| Number of tempo bins to count up to | binSize / 4 | | tempoBufferSize | Number of samples to compute tempo from | 4096 |

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 | | tempo | float | Tempo of song |

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