16

我想要一些关于如何最好地MediaStreamTrack在 Chrome/Canary 中获取音频 javascript 对象的麦克风活动级别的建议。该对象是返回的MediaStreamTrack音轨，作为 WebRTC javascript API 的一部分。MediaStreamgetUserMedia

4

3 回答 3

22

当麦克风有音频时，绿色条上下非常好：

在此处输入图像描述

<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>
于 2014-03-20T07:55:25.290 回答
6

您正在寻找的是webkitAudioContext和它的createMediaStreamSource方法。

这是一个绘制绿色条以充当 VU 表的代码示例：

navigator.webkitGetUserMedia({audio:true, video:true}, function(stream){
    audioContext = new webkitAudioContext();
    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");

    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);
    }

}

有关 AudioContext 的更多详细信息

于 2013-08-15T15:14:18.007 回答
5

更新：修改代码使用：

navigator.mediaDevices.getUserMedia(constraints).then(
    function(stream){
        // code ... 
    }).catch(function(err) {
        // code ... 
});

这是一个小提琴：https ://jsfiddle.net/elshnkhll/p07e5vcq/

于 2014-12-06T06:14:54.570 回答