AnalyserNode

Constructor

AnalyserNode()

Creates a new instance of an AnalyserNode object.

Instance properties

Inherits properties from its parent, AudioNode.

AnalyserNode.fftSize

An unsigned long value representing the size of the FFT (Fast Fourier Transform) to be used to determine the frequency domain.

AnalyserNode.frequencyBinCount Read only

An unsigned long value half that of the FFT size. This generally equates to the number of data values you will have to play with for the visualization.

AnalyserNode.minDecibels

A double value representing the minimum power value in the scaling range for the FFT analysis data, for conversion to unsigned byte values — basically, this specifies the minimum value for the range of results when using getByteFrequencyData().

AnalyserNode.maxDecibels

A double value representing the maximum power value in the scaling range for the FFT analysis data, for conversion to unsigned byte values — basically, this specifies the maximum value for the range of results when using getByteFrequencyData().

AnalyserNode.smoothingTimeConstant

A double value representing the averaging constant with the last analysis frame — basically, it makes the transition between values over time smoother.

Instance methods

Inherits methods from its parent, AudioNode.

AnalyserNode.getFloatFrequencyData()

Copies the current frequency data into a Float32Array array passed into it.

AnalyserNode.getByteFrequencyData()

Copies the current frequency data into a Uint8Array (unsigned byte array) passed into it.

AnalyserNode.getFloatTimeDomainData()

Copies the current waveform, or time-domain, data into a Float32Array array passed into it.

AnalyserNode.getByteTimeDomainData()

Copies the current waveform, or time-domain, data into a Uint8Array (unsigned byte array) passed into it.

Examples

Basic usage

The following example shows basic usage of an AudioContext to create an AnalyserNode, then requestAnimationFrame and <canvas> to collect time domain data repeatedly and draw an "oscilloscope style" output of the current audio input. For more complete applied examples/information, check out our Voice-change-O-matic demo (see app.js lines 108-193 for relevant code).

const audioCtx = new AudioContext();

// …

const analyser = audioCtx.createAnalyser();
analyser.fftSize = 2048;

const bufferLength = analyser.frequencyBinCount;
const dataArray = new Uint8Array(bufferLength);
analyser.getByteTimeDomainData(dataArray);

// Connect the source to be analyzed
source.connect(analyser);

// Get a canvas defined with ID "oscilloscope"
const canvas = document.getElementById("oscilloscope");
const canvasCtx = canvas.getContext("2d");

// draw an oscilloscope of the current audio source

function draw() {
  requestAnimationFrame(draw);

  analyser.getByteTimeDomainData(dataArray);

  canvasCtx.fillStyle = "rgb(200 200 200)";
  canvasCtx.fillRect(0, 0, canvas.width, canvas.height);

  canvasCtx.lineWidth = 2;
  canvasCtx.strokeStyle = "rgb(0 0 0)";

  canvasCtx.beginPath();

  const sliceWidth = (canvas.width * 1.0) / bufferLength;
  let x = 0;

  for (let i = 0; i < bufferLength; i++) {
    const v = dataArray[i] / 128.0;
    const y = (v * canvas.height) / 2;

    if (i === 0) {
      canvasCtx.moveTo(x, y);
    } else {
      canvasCtx.lineTo(x, y);
    }

    x += sliceWidth;
  }

  canvasCtx.lineTo(canvas.width, canvas.height / 2);
  canvasCtx.stroke();
}

draw();

Specifications

Browser compatibility

See also

• Using the Web Audio API