【H5 音乐播放实例】第五节 音轨制作

//获取随机颜色
function randomColor(){
    var r = Math.floor(Math.random()*256);
    var g = Math.floor(Math.random()*256);
    var b = Math.floor(Math.random()*256);
    return "rgb("+r+","+g+","+b+")";//IE7不支出rgb
};

window.onload = function(){

    //给音乐播放器（audio）添加一个timeupdate时间
    document.getElementById("music").ontimeupdate = function(){

        var currentTime = Math.floor(this.currentTime); //获取当前时间

       
        var m = parseInt(currentTime / 60);//分钟
        var s = parseInt(currentTime % 60);//秒钟
        var time = (m<10?("0"+m):m)+":"+(s<10?("0"+s):s); //格式化

        //console.log(time); //打印出来看看

        // 百分比 = 当前时长 ÷ 总时长 × 100%
        var total = this.duration;//总时长
        //console.log(currentTime + '=======' + total);
        //console.log( Math.floor(currentTime / total * 100) + "%" );


        document.getElementsByClassName("progress")[0].style.width = Math.floor(currentTime / total * 100) + "%" ;

    }

    //音轨制作

    var box = document.getElementsByClassName('mbox')[0];  //获取承载音轨的父盒子

    var allWidth = box.clientWidth;//获取承载音轨盒子的宽度

    var itemWidth = 5;


    var len = (allWidth / itemWidth );     //计算一共出现多少条音轨 

    var html = '';                  //动态拼接音轨

    for(var i = 0;i < len ; i ++){
        html+="<span class='item' style='left:"+(i * itemWidth)+"px;background:"+randomColor()+";'></span>";
    }

    box.innerHTML += html;           //添加音轨

    var audio = document.getElementById("music");

    //1:音频上下文
    window.AudioContext = window.AudioContext || window.webkitAudioContext || window.mozAudioContext || window.msAudioContext;
    /*动画执行的兼容写法*/
    window.requestAnimationFrame = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.msRequestAnimationFrame;


    //2:初始化音轨对象
    var audioContext = new window.AudioContext();

    var flag = null; //控制是否解析的开关变量

    //拿到播放器去解析音乐文件
    var audioBufferSouceNode = audioContext.createMediaElementSource(audio);

    audio.onplay = function(){
        flag = true;
        //创建解析对象
        var analyser = audioContext.createAnalyser();
        parse(analyser,function(array){
            console.log(array); //打印解析出来的音轨节点
            for(var i = 0;i < len ; i ++){
                document.getElementsByClassName('item')[i].style.height = array[i] + 'px';
            }
        });
    }

    audio.onpause = function(){
        for(var i = 0;i < len ; i ++){
            document.getElementsByClassName('item')[i].style.height = 1 + 'px';
        }
        flag = false;
    }


    function parse(analyser,callback){
        if(!flag){
            return;
        }
        audioBufferSouceNode.connect(analyser); 
        analyser.connect(audioContext.destination);
        var array = new Uint8Array(analyser.frequencyBinCount);
        analyser.getByteFrequencyData(array);
        if(callback) callback(array);
        requestAnimationFrame(function(){
            parse(analyser,callback);
        });
    }

}

.item {
    position:absolute;
    width:5px;
    height:1px;
    left:0px;
    bottom:0px;
    opacity: 0.5;
}