HTML5 getUserMedia/AudioContext 打造音谱图形化

需求是分析音频，用图形化展示。

思路：

　　1、回想当年使用的播放器，如XX静听 一般就2种图形化展示 一个是条形柱 一个是波纹

　　2、分析数据转化成图像 这个是canvas常用的，之前做过的canvas分析图像数据，做滤镜做变形都是一把好手，这里当然 图形化也交给canvas了。

　　3、既然是分析音频，那当然要将音频转化成数据，才可以进行分析，而关于音频的HTML API 就有 audio标签 ，而麦克风访问就有getUserMedia了。什么？你问我咋知道这个api的？我只能告诉你 去查MDN 、W3C 这类网站...

首先我们要得到音频数据，这里我们用了2个途径得到，一个是音频流，一个是麦克风

1、api兼容

window.AudioContext = (window.AudioContext || window.webkitAudioContext || window.mozAudioContext);
window.requestAnimationFrame = window.requestAnimationFrame || window.webkitRequestAnimationFrame;
try {
    audioCtx = new AudioContext;
    console.log(‘浏览器支持AudioContext‘);
} catch(e) {
    console.log(‘浏览器不支持AudioContext‘, e);
};

2、得到麦克风数据

//开始监听
if (navigator.getUserMedia) {
    console.log(‘浏览器支持getUserMedia‘);
    apiMedia.className = "checked";
    navigator.getUserMedia(
    // 我们只获取麦克风数据，这里还可以设置video为true来获取摄像头数据
    {
        audio: true
    },
    onSccess, onErr)
} else {
    console.log(‘浏览器不支持getUserMedia‘);
    apiMedia.className = "false";
};

通过onSccess来得到数据，介入分析

// Success callback
function onSccess(stream) {
    //将声音输入对像
    source = audioCtx.createMediaStreamSource(stream);
    source.connect(analyser);
    analyser.connect(distortion);
    distortion.connect(biquadFilter);
    biquadFilter.connect(convolver);
    convolver.connect(gainNode);
    gainNode.connect(audioCtx.destination);

    visualize();//分析音频
}

同样，文件的也是一样的

if (mediaSetting == "file") {
    loadFile();
    //得到数据源
    source=audioCtx.createMediaElementSource(audio);
    //连接节点
    source.connect(analyser);
    analyser.connect(distortion);
    distortion.connect(gainNode);
    gainNode.connect(audioCtx.destination);
}

visualize();//分析音频

得到了数据，接下来就交个canvas君吧

//波纹1
if (visualSetting == "wave1") {
    analyser.fftSize = 2048;
    var bufferLength = analyser.fftSize;
    console.log(bufferLength);
    var dataArray = new Uint8Array(bufferLength);
    canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);

    draw = function() {
        drawVisual = requestAnimationFrame(draw);
        analyser.getByteTimeDomainData(dataArray);

        canvasCtx.fillStyle = ‘#000‘;
        canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);
        canvasCtx.lineWidth = 2;
        canvasCtx.strokeStyle = ‘#4aeb46‘;
        canvasCtx.beginPath();

        var sliceWidth = WIDTH * 1.0 / bufferLength;
        var x = 0;

        for (var i = 0; i < bufferLength; i++) {
            var v = dataArray[i] / 128.0;
            var y = v * HEIGHT / 2;
            if (i === 0) {
                canvasCtx.moveTo(x, y);
            } else {
                canvasCtx.lineTo(x, y);
            }
            x += sliceWidth;
        }
        canvasCtx.lineTo(canvas.width, canvas.height / 2);
        canvasCtx.stroke();
    };
    draw();
}

//circle
else if (visualSetting == "circle") {
    // analyser.fftSize = 1024;
    // var bufferLength = analyser.fftSize;
    // var dataArray = new Uint8Array(bufferLength);
    analyser.fftSize = 128;
    var frequencyData = new Uint8Array(analyser.frequencyBinCount);
    var count = analyser.frequencyBinCount;
    var circles = [];
    var circleMaxWidth = (HEIGHT*0.66) >> 0;
    canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);
    canvasCtx.lineWidth = 1;

    for(var i = 0; i < count; i++ ){
        circles.push(i/count*circleMaxWidth)
    }

    draw = function() {
        canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);
        analyser.getByteFrequencyData(frequencyData);
        drawVisual = requestAnimationFrame(draw);
        for(var i = 0; i < circles.length; i++) {
            var v = frequencyData[i] / 128.0;
            var y = v * HEIGHT / 2;
            var circle = circles[i];
            canvasCtx.beginPath();
            canvasCtx.arc(WIDTH/2,HEIGHT/2, y/2, Math.PI * 2, false);
            canvasCtx.stroke()
        }                        

    };
    draw();
}

//柱形条
else if (visualSetting == "bar") {
    analyser.fftSize = 256;
    var bufferLength = analyser.frequencyBinCount;
    console.log(bufferLength);
    var dataArray = new Uint8Array(bufferLength);
    canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);

    var gradient = canvasCtx.createLinearGradient(0, 0, 0, 200);
    gradient.addColorStop(1, ‘#0f0‘);
    gradient.addColorStop(0.5, ‘#ff0‘);
    gradient.addColorStop(0, ‘#f00‘);
    var barWidth = 10;
    var gap = 2; //间距
    var capHeight = 2;//顶部高度
    var capStyle = ‘#fff‘;
    var barNum = WIDTH / (barWidth + gap); //bar个数
    var capYPositionArray = [];
    var step = Math.round(dataArray.length / barNum); 

    draw = function() {
        drawVisual = requestAnimationFrame(draw);
        analyser.getByteFrequencyData(dataArray);
        canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);

        for (var i = 0; i < barNum; i++) {
            var value = dataArray[i * step];
            if (capYPositionArray.length < Math.round(barNum)) {
                capYPositionArray.push(value);
            };
            canvasCtx.fillStyle = capStyle;
            //顶端帽子
            if (value < capYPositionArray[i]) {
                canvasCtx.fillRect(i * 12, HEIGHT - (--capYPositionArray[i]), barWidth, capHeight);
            } else {
                canvasCtx.fillRect(i * 12, HEIGHT - value, barWidth, capHeight);
                capYPositionArray[i] = value;
            };
            canvasCtx.fillStyle = gradient;//渐变
            canvasCtx.fillRect(i * 12 , HEIGHT - value + capHeight, barWidth, HEIGHT-2); //绘制bar
        }
    };
    draw();
}

完整代码 github