如何從HTML5中的視頻中提取音頻？

Question

如何從HTML5 Javascript中的視頻中提取音軌作爲原始音頻數據？即一組樣本？

我對HTML5 Video API完全陌生，所以一個例子會很棒。

Answer 1

Web Audio API正是你想要的。特別是，您想將MediaElementAudioSourceNode加入AnalyserNode。不幸的是，Web Audio API只在Chrome中實現（有些在FF中實現），甚至是Chrome doesn't have full support for MediaElementAudioSourceNode yet。

var context = new webkitAudioContext(); 

// feed video into a MediaElementSourceNode, and feed that into AnalyserNode 
// due to a bug in Chrome, this must run after onload 
var videoElement = document.querySelector('myVideo'); 
var mediaSourceNode = context.createMediaElementSource(videoElement); 
var analyserNode = context.createAnalyser(); 
mediaSourceNode.connect(analyserNode); 
analyserNode.connect(context.destination); 

videoElement.play(); 

// run this part on loop to sample the current audio position 
sample = new Float32Array(analyser.frequencyBinCount); 
analyser.getFloatFrequencyData(sample);