Revision 765629 of AudioBuffer

<p>{{APIRef("Web Audio API")}}</p>

<div>
<p>The <code>AudioBuffer</code> interface represents a short audio asset residing in memory, created from an audio file using the {{ domxref("AudioContext.decodeAudioData()") }} method, or from raw data using {{ domxref("AudioContext.createBuffer()") }}. Once put into an AudioBuffer, the audio can then be played by being passed into an {{ domxref("AudioBufferSourceNode") }}.</p>
</div>

<p>Objects of these types are designed to hold small audio snippets, typically less than 45&nbsp;s. For longer sounds, objects implementing the {{domxref("MediaElementAudioSourceNode")}} are more suitable. The buffer contains data in the following format:&nbsp; non-interleaved IEEE754 32-bit linear PCM with a nominal range between <code>-1</code> and <code>+1</code>, that is, 32bits floating point buffer, with each samples between -1.0 and 1.0. If the {{domxref("AudioBuffer")}} has multiple channels, they are stored in separate buffer.</p>

<h2 id="Properties">Properties</h2>

<dl>
 <dt>{{domxref("AudioBuffer.sampleRate")}} {{readonlyInline}}</dt>
 <dd>Returns a float representing the sample rate, in samples per second, of the PCM data stored in the buffer.</dd>
 <dt>{{domxref("AudioBuffer.length")}} {{readonlyInline}}</dt>
 <dd>Returns an integer representing the length, in sample-frames, of the PCM data stored in the buffer.</dd>
 <dt>{{domxref("AudioBuffer.duration")}} {{readonlyInline}}</dt>
 <dd>Returns a double representing the duration, in seconds, of the PCM data stored in the buffer.</dd>
 <dt>{{domxref("AudioBuffer.numberOfChannels")}} {{readonlyInline}}</dt>
 <dd>Returns an integer representing the number of discrete audio channels described by the PCM data stored in the buffer.</dd>
</dl>

<h2 id="Methods">Methods</h2>

<dl>
 <dt>{{domxref("AudioBuffer.getChannelData()")}}</dt>
 <dd>Returns a {{jsxref("Float32Array")}} containing the PCM data associated with the channel, defined by the <code>channel</code> parameter (with <code>0</code> representing the first channel).</dd>
 <dt>{{domxref("AudioBuffer.copyFromChannel()")}}</dt>
 <dd>Copies the samples from the specified channel of the <span class="idlType"><code>AudioBuffer</code></span> to the <code>destination</code> array.</dd>
 <dt>{{domxref("AudioBuffer.copyToChannel()")}}</dt>
 <dd>Copies the samples to the specified channel of the <span class="idlType"><code>AudioBuffer</code></span>, from the <code>source</code> array.</dd>
</dl>

<h2 id="Example">Example</h2>

<p>The following simple example shows how to create an <code>AudioBuffer</code> and fill it with random white noise. You can find the full source code at our <a href="https://github.com/mdn/audio-buffer">audio-buffer demo</a> repository; a <a href="https://mdn.github.io/audio-buffer/">running live</a> version is also available.</p>

<pre class="brush: js;highlight:[7,14,27]">
// Stereo
var channels = 2;

// Create an empty two second stereo buffer at the
// sample rate of the AudioContext
var frameCount = audioCtx.sampleRate * 2.0;
var myArrayBuffer = audioCtx.createBuffer(channels, frameCount, audioCtx.sampleRate);

button.onclick = function() {
  // Fill the buffer with white noise;
  // just random values between -1.0 and 1.0
  for (var channel = 0; channel &lt; channels; channel++) {
    // This gives us the actual array that contains the data
    var nowBuffering = myArrayBuffer.getChannelData(channel);
    for (var i = 0; i &lt; frameCount; i++) {
      // Math.random() is in [0; 1.0]
      // audio needs to be in [-1.0; 1.0]
      nowBuffering[i] = Math.random() * 2 - 1;
    }
  }

  // Get an AudioBufferSourceNode.
  // This is the AudioNode to use when we want to play an AudioBuffer
  var source = audioCtx.createBufferSource();

  // set the buffer in the AudioBufferSourceNode
  source.buffer = myArrayBuffer;

  // connect the AudioBufferSourceNode to the
  // destination so we can hear the sound
  source.connect(audioCtx.destination);

  // start the source playing
  source.start();

}
</pre>

<h2 id="Specification">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('Web Audio API', '#the-audiobuffer-interface', 'AudioBuffer')}}</td>
   <td>{{Spec2('Web Audio API')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>14 {{property_prefix("webkit")}}</td>
   <td>{{CompatGeckoDesktop(25)}}</td>
   <td>{{CompatNo}}</td>
   <td>15&nbsp;{{property_prefix("webkit")}}<br />
    22 (unprefixed)</td>
   <td>6 {{property_prefix("webkit")}}</td>
  </tr>
  <tr>
   <td><code>copyFromChannel()</code> and <code>copyToChannel()</code></td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatGeckoDesktop(27)}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Chrome</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS</th>
   <th>IE Phone</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatNo}}</td>
   <td>28&nbsp;{{property_prefix("webkit")}}</td>
   <td>{{CompatGeckoMobile(25)}}</td>
   <td>1.2</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>6&nbsp;{{property_prefix("webkit")}}</td>
  </tr>
  <tr>
   <td><code>copyFromChannel()</code> and <code>copyToChannel()</code></td>
   <td>{{CompatNo}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatGeckoMobile(27)}}</td>
   <td>&nbsp;</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="/en-US/docs/Web/API/Web_Audio_API/Using_Web_Audio_API">Using the Web Audio API</a></li>
</ul>