javascript - WebRTC MediaStream 的麦克风事件级别

Question

我想要一些关于如何在 Chrome/Canary 中最好地获取音频 MediaStreamTrack javascript 对象的麦克风事件级别的建议。 MediaStreamTrack 对象是 getUserMedia 返回的 MediaStream 的音轨，作为 WebRTC javascript API 的一部分。

Answer 1

当麦克风有音频时，上下绿色条非常漂亮:

<script type="text/javascript">
navigator.webkitGetUserMedia({audio:true, video:true}, function(stream){
    // audioContext = new webkitAudioContext(); deprecated  OLD!!
    audioContext = new AudioContext(); // NEW!!
    analyser = audioContext.createAnalyser();
    microphone = audioContext.createMediaStreamSource(stream);
    javascriptNode = audioContext.createJavaScriptNode(2048, 1, 1);

    analyser.smoothingTimeConstant = 0.3;
    analyser.fftSize = 1024;

    microphone.connect(analyser);
    analyser.connect(javascriptNode);
    javascriptNode.connect(audioContext.destination);

    //canvasContext = $("#canvas")[0].getContext("2d");
    canvasContext = document.getElementById("test");
    canvasContext= canvasContext.getContext("2d");

    javascriptNode.onaudioprocess = function() {
        var array =  new Uint8Array(analyser.frequencyBinCount);
        analyser.getByteFrequencyData(array);
        var values = 0;

        var length = array.length;
        for (var i = 0; i < length; i++) {
            values += array[i];
        }

        var average = values / length;
        canvasContext.clearRect(0, 0, 60, 130);
        canvasContext.fillStyle = '#00ff00';
        canvasContext.fillRect(0,130-average,25,130);
    }

}  
);
</script>
<canvas id="test" style="background-color: black;"></canvas>