js前端 音频波形图像展示

1、前言

参考 关于谷歌浏览器的禁止autoplay政策 - Kaiqisan

2、后端代码

    @RequestMapping(value = "/coalAudio")
    @ResponseBody
    public void getAudio(HttpServletResponse response) throws Exception {
        String path = paramSetMapper.getParamByCode("coalAudioPath").getParamValue();
        File file = new File(path);
        if (!file.exists()) {
            throw new RuntimeException("音频文件不存在 --> 404");
        }
        OutputStream os = response.getOutputStream();
        FileInputStream fis = new FileInputStream(file);
        long length = file.length();
        // 播放进度
        int count = 0;
        // 播放百分比
        int percent = (int) (length * 1);
        String range = "0";
        int irange = Integer.parseInt(range);
        length = length - irange;

        response.addHeader("Accept-Ranges", "bytes");
        response.addHeader("Content-Length", length + "");
        response.addHeader("Content-Range", "bytes " + range + "-" + length + "/" + length);
        response.addHeader("Content-Type", "audio/mpeg;charset=UTF-8");

        int len = 0;
        byte[] b = new byte[1024];
        while ((len = fis.read(b)) != -1) {
            os.write(b, 0, len);
            count += len;
            if (count >= percent) {
                break;
            }
        }
        fis.close();
        os.close();
    }

3、前端代码

function draw_coalA1_audio_canvas() {
    var coalUrl = "/tcc/front/coalAudio";
    var gangueUrl = "/tcc/front/gangueAudio";
    var canvas = document.getElementById("coalA1_audio_canvas");
    var canvasCtx = canvas.getContext("2d");
    var audioContext = new AudioContext();
    var filter = audioContext.createBiquadFilter();

    let url2 = "";
    if (pickup_isBreak == 0 && audio_type == 0) {
        url2 = coalUrl;
    } else if (pickup_isBreak == 0 && audio_type == 1) {
        url2 = gangueUrl;
    }
    drawAudio(url2, canvas, canvasCtx, audioContext, filter);

    setInterval(function () {
        let url = "";
        if (pickup_isBreak == 0 && audio_type == 0) {
            url = coalUrl;
        } else if (pickup_isBreak == 0 && audio_type == 1) {
            url = gangueUrl;
        }
        drawAudio(url, canvas, canvasCtx, audioContext, filter);
    }, 1000);
}

function drawAudio(url, canvas, canvasCtx, audioContext, filter) {
    var request = new XMLHttpRequest(); //开一个请求
    request.open('POST', url, true); //往url请求数据
    request.responseType = 'arraybuffer'; //设置返回数据类型
    request.onload = function () {
        var audioData = request.response;
        if (audioData.byteLength < (1000 * 100)) {
            return 1;
        }
        audioContext.decodeAudioData(audioData, function (buffer) {
            var audioBufferSourceNode = audioContext.createBufferSource();
            var analyser = audioContext.createAnalyser();
            analyser.fftSize = 2048;
            audioBufferSourceNode.connect(analyser);
            analyser.connect(audioContext.destination);
            audioBufferSourceNode.buffer = buffer; //回调函数传入的参数
            audioBufferSourceNode.start(0); //部分浏览器是noteOn()函数，用法相同
            document.documentElement.removeEventListener('mouseenter', null, false);
            document.documentElement.addEventListener('mouseenter', () => {
                if (audioBufferSourceNode.context.state !== 'running')
                    audioBufferSourceNode.context.resume();
            });
            filter.type = 'highpass';
            filter.frequency.value = 600;
            filter.Q.value = 800;
            var bufferLength = analyser.frequencyBinCount;
            var dataArray = new Uint8Array(bufferLength);
            canvasCtx.clearRect(0, 0, 300, 300);

            function draw() {
                drawVisual = requestAnimationFrame(draw);
                analyser.getByteTimeDomainData(dataArray);
                canvasCtx.fillStyle = '#0e1a3b';
                canvasCtx.fillRect(0, 0, 300, 400);
                canvasCtx.lineWidth = 2;
                canvasCtx.strokeStyle = '#ffffff';
                canvasCtx.beginPath();
                var sliceWidth = 300 * 1.0 / bufferLength;
                var x = 0;
                for (var i = 0; i < bufferLength; i++) {
                    var v = dataArray[i] / 128.0;
                    var y = v * 200 / 3; //控制音频线在图的位置
                    if (i === 0) {
                        canvasCtx.moveTo(x, y);
                    } else {
                        canvasCtx.lineTo(x, y);
                    }
                    x += sliceWidth;
                }
                canvasCtx.lineTo(canvas.width, canvas.height / 2);
                canvasCtx.stroke();
            };
            draw();
        }, function (err) {
            console.log("!Fail to decode the file!" + url, err)
        });
    };
    request.send();
}

function playCoalAudio1() {
    var url = "/tcc/front/coalAudio";
    var canvas = document.getElementById("coalA1_audio_canvas");
    var canvasCtx = canvas.getContext("2d");
    //首先实例化AudioContext对象 很遗憾浏览器不兼容，只能用兼容性写法；audioContext用于音频处理的接口，并且工作原理是将AudioContext创建出来的各种节点(AudioNode)相互连接，音频数据流经这些节点并作出相应处理。
    //总结就一句话 AudioContext 是音频对象，就像 new Date()是一个时间对象一样
    var AudioContext = window.AudioContext || window.webkitAudioContext || window.mozAudioContext;
    if (!AudioContext) {
        alert("您的浏览器不支持audio API，请更换浏览器（chrome、firefox）再尝试，另外本人强烈建议使用谷歌浏览器！")
    }
    var audioContext = new AudioContext(); //实例化
    var filter = audioContext.createBiquadFilter();

    // 总结一下接下来的步骤
    // 1 先获取音频文件（目前只支持单个上传）
    // 2 读取音频文件，读取后，获得二进制类型的音频文件
    // 3 对读取后的二进制文件进行解码

    function getData() {
        var request = new XMLHttpRequest(); //开一个请求
        request.open('POST', url, true); //往url请求数据
        request.responseType = 'arraybuffer'; //设置返回数据类型
        request.onload = function () {
            var audioData = request.response;
            //数据缓冲完成之后，进行解码
            audioContext.decodeAudioData(audioData, function (buffer) {
                //source.buffer = buffer;  //将解码出来的数据放入source中
                // 创建AudioBufferSourceNode 用于播放解码出来的buffer的节点
                var audioBufferSourceNode = audioContext.createBufferSource();
                // 创建AnalyserNode 用于分析音频频谱的节点
                var analyser = audioContext.createAnalyser();
                //fftSize (Fast Fourier Transform) 是快速傅里叶变换，一般情况下是固定值2048。具体作用是什么我也不太清除，但是经过研究，
                // 这个值可以决定音频频谱的密集程度。值大了，频谱就松散，值小就密集。
                // analyser.fftSize = 256;
                analyser.fftSize = 2048;
                // 连接节点,audioContext.destination是音频要最终输出的目标，
                // 我们可以把它理解为声卡。所以所有节点中的最后一个节点应该再
                // 连接到audioContext.destination才能听到声音。
                audioBufferSourceNode.connect(analyser);
                analyser.connect(audioContext.destination);
                //console.log(audioContext.destination)
                // 播放音频
                audioBufferSourceNode.buffer = buffer; //回调函数传入的参数
                audioBufferSourceNode.start(0); //部分浏览器是noteOn()函数，用法相同

                document.documentElement.removeEventListener('mouseenter', null, false);
                document.documentElement.addEventListener('mouseenter', () => {
                    if (audioBufferSourceNode.context.state !== 'running')
                        audioBufferSourceNode.context.resume();
                });

                //波形设置
                filter.type = 'highpass';
                filter.frequency.value = 600;
                filter.Q.value = 800;

                //可视化 创建数据
                var bufferLength = analyser.frequencyBinCount;
                var dataArray = new Uint8Array(bufferLength);
                canvasCtx.clearRect(0, 0, 300, 300);

                function draw() {
                    drawVisual = requestAnimationFrame(draw);
                    analyser.getByteTimeDomainData(dataArray);
                    canvasCtx.fillStyle = '#0e1a3b';
                    canvasCtx.fillRect(0, 0, 300, 400);
                    canvasCtx.lineWidth = 2;
                    canvasCtx.strokeStyle = '#ffffff';

                    canvasCtx.beginPath();
                    var sliceWidth = 300 * 1.0 / bufferLength;
                    var x = 0;
                    for (var i = 0; i < bufferLength; i++) {
                        var v = dataArray[i] / 128.0;
                        var y = v * 200 / 3; //控制音频线在图的位置
                        if (i === 0) {
                            canvasCtx.moveTo(x, y);
                        } else {
                            canvasCtx.lineTo(x, y);
                        }
                        x += sliceWidth;
                    }
                    canvasCtx.lineTo(canvas.width, canvas.height / 2);
                    canvasCtx.stroke();
                };

                draw();
            }, function (err) {
                // alert('!Fail to decode the file!'); //解码出错处理
                console.log("!Fail to decode the file!", err)
            });
        };
        request.send();
    }

    if (pickup_isBreak == 0 && audio_type == 0) {
        getData();
    }

    setInterval(function () {
        if (pickup_isBreak == 0 && audio_type == 0) {
            getData();
        }
    }, 1000);
}