Getting frequency data

[magicspacekiwi]

Hi there,

Sorry if this is the wrong place to ask for support. If there's a better place, please let me know!

I've been trying to use WAE to get the frequency data from an audio file. I think I understand how to load the audio data into a buffer, but I'm not sure how to use the API to step through and capture data with something like getByteFrequencyData

For example, in the native browser Web Audio API, I'm able to just play the audio data back and use getByteFrequencyData during each 'timeupdate' event.

How could I do something similar here? (I'm trying to get this working on a Node server) Thanks!

Here's what I've got so far.

const fs = require('fs')
const path = require('path')

const audioEngine = require('web-audio-engine')
const RenderingAudioContext = audioEngine.RenderingAudioContext

const audioData = fs.readFileSync(path.resolve('./audio/standard-wav.wav'))

const rAudioContext = new RenderingAudioContext()
const source = rAudioContext.createBufferSource()
const analyser = rAudioContext.createAnalyser()

rAudioContext.decodeAudioData(audioData).then((audioBuffer) => {
  source.buffer = audioBuffer
  source.connect(analyser)

  // How do I step through the buffer here and get the frequency data?
})

[mohayonao]

You should render manually when use RenderingAudioContext.

const fs = require("fs");
const path = require("path");

const audioEngine = require("web-audio-engine");
const RenderingAudioContext = audioEngine.RenderingAudioContext;
const audioData = fs.readFileSync(path.resolve("./Kalimba.wav"));

const rAudioContext = new RenderingAudioContext();
const source = rAudioContext.createBufferSource();
const analyser = rAudioContext.createAnalyser();

rAudioContext.decodeAudioData(audioData).then((audioBuffer) => {
  source.buffer = audioBuffer;
  source.connect(analyser);

  // prepare to render audio
  source.start(0);
  analyser.connect(rAudioContext.destination);

  // render 0 to 1 second
  rAudioContext.processTo(1);

  // get data
  const array = new Uint8Array(analyser.frequencyBinCount);

  analyser.getByteFrequencyData(array);

  console.log(array);
  console.log(`${ array.length } items`);
});

or more frequent analyse use with ScriptProcessorNode

const fs = require("fs");
const path = require("path");

const audioEngine = require("web-audio-engine");
const RenderingAudioContext = audioEngine.RenderingAudioContext;
const audioData = fs.readFileSync(path.resolve("./Kalimba.wav"));

const rAudioContext = new RenderingAudioContext();
const source = rAudioContext.createBufferSource();
const analyser = rAudioContext.createAnalyser();
const scriptProcessor = rAudioContext.createScriptProcessor(512, 1, 1);

rAudioContext.decodeAudioData(audioData).then((audioBuffer) => {
  source.buffer = audioBuffer;
  source.connect(analyser);

  // prepare to render audio
  source.start(0);
  analyser.connect(scriptProcessor);
  scriptProcessor.connect(rAudioContext.destination);

  scriptProcessor.onaudioprocess = (e) => {
    e.outputBuffer.getChannelData(0).set(e.inputBuffer.getChannelData(0));

    // get data
    const array = new Uint8Array(analyser.frequencyBinCount);

    analyser.getByteFrequencyData(array);

    console.log(array);
    console.log(`${ array.length } items`);
  };

  // render 0 to 1 second
  rAudioContext.processTo(1);
});

[magicspacekiwi]

Ah, okay. I used the first method - worked great! 🎉 Thank you.