AudioBufferSourceNode.playbackRate

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AudioBufferSourceNode 接口的playbackRate属性是是一个k-速率的 AudioParam ,用于定义音频资源的播放速度。

A value of 1.0 indicates it should play at the same speed as its sampling rate, values less than 1.0 cause the sound to play more slowly, while values greater than 1.0 result in audio playing faster than normal. The default value is 1.0. When set to another value, the AudioBufferSourceNode resamples the audio before sending it to the output.

Syntax

AudioBufferSourceNode.playbackRate.value = playbackRateProportion;

Value

An AudioParam whose value is a floating-point value indicating the playback rate of the audio as a decimal proportion of the original sampling rate.

Consider a sound buffer containing audio sampled at 44.1 kHz (44,100 samples per second). Let's see what a few values of playbackRate do:

  • A playbackRate of 1.0 plays the audio at full speed, or 44,100 Hz.
  • A playbackRate of 0.5 plays the audio at half speed, or 22,050 Hz.
  • A playbackRate of 2.0 doubles the audio's playback rate to 88,200 Hz.

Example

In this example, the AudioContext.decodeAudioData() function is used to decode an audio track, and put it into an AudioBufferSourceNode. Buttons are provided to play and stop the audio playback, and a slider control is used to change the playbackRate property value on the fly.

You can run the example live (or view the source.) Play the song and alter the playback rate for some fun results.

<input class="playback-rate-control" type="range" min="0.25" max="3" step="0.05" value="1">
<span class="playback-rate-value">1.0</span>
function getData() {
  source = audioCtx.createBufferSource();
  request = new XMLHttpRequest();

  request.open('GET', 'viper.ogg', true);

  request.responseType = 'arraybuffer';

  request.onload = function() {
    var audioData = request.response;

    audioCtx.decodeAudioData(audioData, function(buffer) {
        myBuffer = buffer;
        source.buffer = myBuffer;
        source.playbackRate.value = playbackControl.value;
        source.connect(audioCtx.destination);
        source.loop = true;
      },

      function(e){"Error with decoding audio data" + e.err});

  }

  request.send();
}

// wire up buttons to stop and play audio, and range slider control

play.onclick = function() {
  getData();
  source.start(0);
  play.setAttribute('disabled', 'disabled');
  playbackControl.removeAttribute('disabled');
}

stop.onclick = function() {
  source.stop(0);
  play.removeAttribute('disabled');
  playbackControl.setAttribute('disabled', 'disabled');
}

playbackControl.oninput = function() {
  source.playbackRate.value = playbackControl.value;
  playbackValue.innerHTML = playbackControl.value;
}

Specification

Specification Status Comment
Web Audio API
playbackRate
Working Draft

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
playbackRateChrome Full support 14Edge Full support 12Firefox Full support 25IE No support NoOpera Full support 15Safari Full support 6WebView Android Full support YesChrome Android Full support 18Firefox Android Full support 26Opera Android Full support 14Safari iOS Full support YesSamsung Internet Android Full support 1.0

Legend

Full support  
Full support
No support  
No support

See also