akumpf/AudioPitchr

AudioPitchr is a Web Audio based analysis toolset for determining the musical structure of any arbitrary audio source in realtime.

AudioPitchr

Example: https://akumpf.github.io/AudioPitchr/example/

** EXPERIMENTAL ** This code is volatile and prone to large changes.

AudioPitchr is a Web Audio based analysis toolset for determining the musical structure of any arbitrary audio source in realtime.

Usage

AudioPitchr can be installed as an NPM module.

npm install AudioPitchr

Then, in javascript you can use it like this.

const audioCtx          = new AudioContext(); // consider OfflineAudioContext?
const audioSampleRate   = audioCtx.sampleRate;

const pitchr            = require("AudioPitchr");
const frameHop          = 1024*4;
const chromagram        = pitchr.Chromagram(frameHop,audioSampleRate);
const chromachord       = pitchr.Chromachord;  

const disallowSusChords = false;

let buff        = new Float32Array(4096);
let scriptNode  = audioCtx.createScriptProcessor(frameHop, 1, 1);
scriptNode.onaudioprocess = function(audioProcessingEvent) {
  // Mono-ize the input data (alternative, could apply to left and right separately)...
  let inputBuffer = audioProcessingEvent.inputBuffer;
  let outputBuffer = audioProcessingEvent.outputBuffer;
  buff.fill(0,0,buff.length);
  let buffDiv = outputBuffer.numberOfChannels;
  for (let channel = 0; channel < outputBuffer.numberOfChannels; channel++) {
    let inputData = inputBuffer.getChannelData(channel);
    let outputData = outputBuffer.getChannelData(channel);
    for (let sample = 0; sample < inputBuffer.length; sample++) {
      outputData[sample] = inputData[sample];
      buff[sample] += inputData[sample]/buffDiv;
    }
  }
  // --
  chroma.processAudioFrame(buff);
  if(chroma.isReady()){
    let cgram     = chroma.getChromagram();
    let bestChord = chromachord.detectChord(cgram,disallowSusChords);
    console.log(chromachord.getTextDesc(bestChord));
  }

Building

The source should be sufficient for most Node projects, but to build the combined audiopitchr.js bundle file, use browserify:

browserify index.js -o audiopitchr.js

License

AudioPitchr is released as open source under the GNU GPLv3 license.