AnalyserNode
============

The **`AnalyserNode`** interface represents a node able to provide real-time frequency and time-domain analysis information. It is an `AudioNode` that passes the audio stream unchanged from the input to the output, but allows you to take the generated data, process it, and create audio visualizations.

An `AnalyserNode` has exactly one input and one output. The node works even if the output is not connected.

![Without modifying the audio stream, the node allows to get the frequency and time-domain data associated to it, using a FFT.](/en-US/docs/Web/API/AnalyserNode/fttaudiodata_en.svg)

EventTarget

AudioNode

AnalyserNode

|  |  |
| --- | --- |
| Number of inputs | `1` |
| Number of outputs | `1` (but may be left unconnected) |
| Channel count mode | `"max"` |
| Channel count | `2` |
| Channel interpretation | `"speakers"` |

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
--------

**Note:** See the guide Visualizations with Web Audio API for more information on creating audio visualizations.

### 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).


```js
const audioCtx = new (window.AudioContext || window.webkitAudioContext)();

// …

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

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

// Connect the source to be analysed
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
--------------

| Specification |
| --- |
| Web Audio API # AnalyserNode |

Browser compatibility
---------------------

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See also
--------

* Using the Web Audio API