Web Audio Spectrogram

index.html

<script>
    console.clear();

    if (!window.AudioContext) {
        if (!window.webkitAudioContext) {
            alert('AudioContext not supported!');
        }
        window.AudioContext = window.webkitAudioContext;
    }

    if (!navigator.mediaDevices.getUserMedia) {
       alert('getUserMedia not supported!');
    }

    class MAGraph {
        constructor(periods) {
            this.periods = periods.map(Math.round);
            this.data = [];
            this.ma = null;

            this._mas = this.periods.map(p => ({
                slidingSum: 0,
                values: [],
            }));
        }
        
        get length() {
            return this.data.length;
        }

        add(x) {
            if(Array.isArray(x) || ArrayBuffer.isView(x)) {
                x.forEach(a => this.add(a));
                return;
            }

            this.data.push(x);
            
            this.periods.forEach((p, i) => {
                const data = i ? this._mas[i - 1].values
                               : this.data;
                MAGraph._calcMA(data, p, this._mas[i]);
            });

            if(!this.ma) {
                this.ma = this._mas[this.periods.length - 1].values;
            }
            //DEBUG
            if(this.data.length === 100) {
                //console.log('gma', JSON.stringify(this, null, 4));
            }
            //DEBUG
        }
        
        static _calcMA(data, p, maState) {
            const len = data.length,
                  x = data[len - 1];
            
            let sum = maState.slidingSum + x,
                maVal;
            if(len > p) {
                sum -= data[len - p -1];
                maVal = sum/p;
            }
            else {
                maVal = sum/len;
            }

            maState.values.push(maVal);
            maState.slidingSum = sum;
        }
    }
</script>
<script src="//unpkg.com/[email protected]"></script>
<script>//ABOUtils.Debug.alertErrors();</script>
<script src="//unpkg.com/chroma-js@1"></script>
<script src="//unpkg.com/[email protected]"></script>
<script src="//unpkg.com/vue@2"></script>

<main id="app">

    <ul class="tabitems">
        <li><button @click="view.tuner = true"  :class="{ active: view.tuner }">Tuner (WIP)</button></li>
        <li><button @click="view.tuner = false" :class="{ active: !view.tuner }">Unisons</button></li>
    </ul>

    <div id="tuner" class="tab" v-show="view.tuner">

        <h2>Time (waveform)</h2>
        <canvas id="kept-wave" height="0"></canvas>
        <div class="tools">
            <label id="tuner-target">
                <span>Target frequency</span>
                <input type="number" v-model.number="tuner.freq" />
            </label>
            <button id="keep-wave" @click="keepWave">Keep</button>
            <button id="restart" @click="restart">Restart</button>
        </div>
        <canvas id="tuner-wave"></canvas>

        <h2>Frequency (FFT)</h2>
        <canvas id="c2"></canvas>
    </div>

    <div id="unisons" class="tab" v-show="!view.tuner">
        <div class="tools">
            <button id="keep">Keep</button>
            <button id="restart" @click="restart">Restart</button>
            <label>
                <input type="checkbox" v-model="view.loudness" />
                Loudness mask
            </label>
            <label>
                <input type="checkbox" v-model="plot.squaredMagn" />
                Squared magnitude
            </label>
        </div>
        <div id="container">
            <canvas id="kept"></canvas>
            <canvas id="live"></canvas>
            <canvas v-show="view.loudness" id="loudness"></canvas>
        </div>

        <h2>
            For more information on how this is done, look at
            <a href="http://www.smartjava.org/content/exploring-html5-web-audio-visualizing-sound">this article</a>.
        </h2>
    </div>

</main>

script.babel

//http://www.smartjava.org/content/exploring-html5-web-audio-visualizing-sound
//https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API/Visualizations_with_Web_Audio_API
(function() {
    "use strict";
    const ud = ABOUtils.DOM,
          uc = ABOUtils.Canvas,
          [$, $$] = ud.selectors();
    
    const _state = {
        tuner: {
            freq: 1300,
            magn: 200,
            //Sample values in seconds:
            sampleTimes: [0, .03, .1, .30, 1, 3],
            sampleLen: .01,
        },
        plot: {
            approxFPS: 200,
            zoom: /**/ [8, 2], //**/ [1,1],
            maxWidth: 1500,
            historySec: 3,
            smoothing: 0,  //0-1
            //https://en.wikipedia.org/wiki/Short-time_Fourier_transform
            //"The magnitude squared of the STFT yields the spectrogram representation (...)"
            //squaredMagn: true,
            deciRange: /**/ [-120, -20], //*/[-150, -50],
            //https://gka.github.io/chroma.js/
            colorScale: chroma.scale(['#000', '#a0a', '#66f', '#0f0', '#ff0', '#f00', '#fff'])
                            .mode('lrgb')
                            .colors(256, 'rgb'),
        },
        reset: {
            volume: {
                min: 10000, //0-255
                factor: 1.5,
            },
            loop:  false,
            clear: true,
        },
        view: {
            loudness: true,
            tuner: true,
        }
    };

    new Vue({
        el: '#app',
        data: _state,
        methods: {
            restart() {
                uiRestart = true;
            },
            keepWave() {
                const canv = $('#kept-wave'),
                      ctx = canv.getContext('2d');
                canv.width = canWave.width;
                canv.height = canWave.height;
                ctx.drawImage(canWave, 0,0);
            }
        },
    });


    // load the sound
    let audioContext, analyser, buffer, fps, freqStep;
    setupAudioNodes();

    //Init UI
    const canWave = $('#tuner-wave'),
          ctxWave = canWave.getContext('2d');
    const plt = _state.plot,
          uiWidth = Math.min(analyser.frequencyBinCount * plt.zoom[0], plt.maxWidth),
          uiHistory = Math.round(fps * plt.historySec * plt.zoom[1]),  //Height of spectogram
          uiLegend = 20,
          freqMarkers = [],
          canvas = new uc.CanvasPixelBuffer($('#live'), uiWidth, uiHistory + uiLegend);
    let uiStale = false,
        uiRestart = false;
    let stats;
    function initUI() {
        function getUIX(hz) {
            return Math.round(hz * plt.zoom[0] / freqStep);
        }

        //https://github.com/mrdoob/stats.js/
        stats = new Stats();
        stats.showPanel(0); // 0: fps, 1: ms, 2: mb, 3+: custom
        document.body.appendChild(stats.dom).id = 'stats';
        
        canWave.width = 1200;
        canWave.height = 200;
        
        //Draw legend (color scale and kHz):
        _state.plot.colorScale.forEach((c, i) => {
            for(let y = 0; y < uiLegend/2; y++) {
                canvas.setPixel(i, y, c);
            }
        });
        const step = 1000;
        let mark = 1, x = 0;
        while(x < uiWidth) {
            x = getUIX(mark * step);
            if(x > uiWidth) { break; }
            
            const h = .1 + (mark%5 ? 0 : .4) + (mark%10 ? 0 : .5);
            freqMarkers.push([x, h])
            mark ++;
        }
        freqMarkers.forEach(m => {
            let [x, h] = m;
            h *= uiLegend/2;
            for(let y = 0; y < h; y++) {
                canvas.setPixel(x, uiLegend/2 + y, [255, 255, 255]);
            }
        });
        
        //Paint the "Equal loudness contour":
        //https://en.wikipedia.org/wiki/Equal-loudness_contour
        const loud = $('#loudness');
        const ctx = loud.getContext('2d');
        loud.width = canvas.w;
        loud.height = canvas.h;
        function createGrad(hz1, hz2, color1, color2) {
            const x1 = getUIX(hz1),
                  x2 = getUIX(hz2),
                  grad = ctx.createLinearGradient(x1,0, x2,0);
            grad.addColorStop(0, color1);
            grad.addColorStop(1, color2);
            ctx.fillStyle = grad;
            ctx.fillRect(x1,uiLegend, (x2-x1),canvas.h);
        }
        createGrad(   0,  200, '#000f', '#0008');
        createGrad( 200, 1000, '#0008', '#0004');
        createGrad(1000, 1500, '#0004', '#0006');
        createGrad(1500, 3500, '#0006', '#0000');
        createGrad(3500,10000, '#0000', '#000a');
    }
    initUI();


    function setupAudioNodes() {
        const plt = _state.plot;
        
        // create the audio context
        const context = audioContext = new AudioContext({
            //https://developer.mozilla.org/en-US/docs/Web/API/AudioContextOptions#Browser_compatibility
            //"Connecting AudioNodes from AudioContexts with different sample-rate is currently not supported."
            //  sampleRate: 8000,
        });
        
        //https://stackoverflow.com/questions/44502536/determining-frequencies-in-js-audiocontext-analysernode
        const sr = context.sampleRate;
        let samplesPerFrame = sr / plt.approxFPS;
        //Round the sample size to the nearest power of 2 (required for .fftSize):
        samplesPerFrame = Math.pow(2, Math.round(Math.log2(samplesPerFrame)));
        fps = sr/samplesPerFrame;
        console.log('spf', samplesPerFrame, 'fps', fps);
        
        const processor = context.createScriptProcessor(samplesPerFrame, 1, 1);
        processor.onaudioprocess = loop;
        processor.connect(context.destination);
        //The rest of the .connect() is done in the getUserMedia() promise below (when we get microphone data).
        
        // setup an analyzer
        analyser = context.createAnalyser();
        analyser.smoothingTimeConstant = plt.smoothing;
        //https://stackoverflow.com/questions/14789283/what-does-the-fft-data-in-the-web-audio-api-correspond-to
        analyser.fftSize = samplesPerFrame;
        analyser.minDecibels = plt.deciRange[0];
        analyser.maxDecibels = plt.deciRange[1];
        //console.log(analyser);
        
        const bins = analyser.frequencyBinCount;
        buffer = new Uint8Array(bins);
        const maxFreq = sr/2;
        freqStep = maxFreq / bins;
        console.log('Freq', 0, maxFreq, 'Step', freqStep, 'Bins', bins);

        navigator.mediaDevices.getUserMedia({
            audio: {
                //https://developer.mozilla.org/en-US/docs/Web/API/MediaTrackConstraints#Browser_compatibility
                //sampleRate: 8000,
            }
        })
        .then(stream => {
            //Mic stream
            const source = context.createMediaStreamSource(stream);
            source.connect(analyser);
            analyser.connect(processor);

            //requestAnimationFrame(loop);
        })
            .catch(err => {
            //console.dir(err);
            console.error('The following gUM error occured: ' + err);
        });
    }

    // we use information from the analyzer node to draw the volume
    function loop(e) {
        //if(_state.view.tuner) { return; }
        //console.log(e);
        //debugger;
        
        stats.begin();

        collectWave(e);
        analyser.getByteFrequencyData(buffer);
        drawSpectrogram(buffer);
        
        stats.end();
        //requestAnimationFrame(loop);
    }

    const wavesMaxLen = audioContext.sampleRate * 3.5,
          wavePeriod = Math.round(audioContext.sampleRate / _state.tuner.freq),
          waveMAPeriods = [wavePeriod/2, wavePeriod/3, wavePeriod/5, wavePeriod/7];
    console.log('MA samples', wavePeriod)
    let waveBuffer = new MAGraph(waveMAPeriods), //[],
        collectingWaves = false;
    function collectWave(e) {
        //Collect waveform data until we have 1s worth of data:
        let waveData = e.inputBuffer.getChannelData(0);
        //It takes a little time before we actually get microphone data..
        if(!collectingWaves) { collectingWaves = (waveData[0] !== 0); }
        if(collectingWaves && (waveBuffer.length < wavesMaxLen)) {

            waveBuffer.add(waveData); //.push.apply(waveBuffer, waveData);
            //console.log(waveBuffer.length);
            
            //First batch of wave data.
            //Normalize the start of a wave to have consistent rendering (avoid jumping):
            if((waveBuffer.length > wavePeriod) && !waveBuffer.__sampleOffset) {
                const data = waveBuffer.ma;
                let x = wavePeriod,
                    y1, y2;
                for(; x < data.length; x++) {
                    y1 = data[x-1];
                    y2 = data[x];
                    if((y1 < 0) && (y2 >= 0)) { break; }
                }
                if(x >= data.length) {
                    //No usable data yet:
                    return;
                }
                else {
                    waveBuffer.__sampleOffset = x;
                }
            }

            if(waveBuffer.__sampleOffset) {
                drawStrobe(waveBuffer);
            }
        }
    }
    
    function clear() {
        //canvas.clear();
        canvas.targetContext.clearRect(0, uiLegend, canvas.w,canvas.h);
        canvas.sync();
    }

    let row = 0,
        volPrev = 0;
    const colorSeparator = [0, 0, 0];
    function drawSpectrogram(array) {

        const plt = _state.plot,
              res = _state.reset,
              volTrigger = res.volume,
              [pxW, pxH] = plt.zoom;

        //Auto-reset by volume
        const volCurr = array.reduce((a, b) => a + b, 0); //Math.max.apply(Math, array);
        if((volCurr > volTrigger.min) && (volCurr > (volPrev * volTrigger.factor)) ) {
            uiRestart = true;
            console.log('Reset by volume', Math.round(volPrev), volCurr);
        }
        volPrev = (volCurr + 2*volPrev)/3;
        
        //Loop display?
        if((row >= uiHistory) && !uiRestart) {
            if(res.loop) { uiRestart = true; }
            else { return; }
        }
        
        if(uiRestart) {
            row = 0;
            uiRestart = false;
            waveBuffer = new MAGraph(waveMAPeriods); //[];
            if(res.clear) {
                clear();
            }
        }

        function drawRow(y, color) {
            let x = 0, pxColor;
            for (let i = 0; i < array.length; i++) {
                if(x >= uiWidth) { break; }

                // draw each pixel with the specific color
                if(color) { pxColor = color; }
                else {
                    const magn = plt.squaredMagn ? Math.round(array[i] * array[i] / 255) : array[i];
                    pxColor = plt.colorScale[magn];
                }
                for(let xx = 0; xx < pxW; xx++) {
                    canvas.setPixel(x, y,     pxColor);
                    //canvas.setPixel(x, y + 1, colorSeparator);
                    x++;
                }
            }
        }
        
        for(let yy = 0; yy < pxH; yy++) {
            drawRow(uiLegend + row + yy);
        }
        drawRow(uiLegend + row + pxH, colorSeparator);

        //canvas.render();
        row = (row + pxH);
        uiStale = true;
    }
    
    
    const c2 = $('#c2'),
          ctx2 = c2.getContext('2d'),
          h2 = 255.5;
    let b2 = new Float32Array(analyser.frequencyBinCount);
    c2.width = uiWidth;
    c2.height = h2 + 5;
    let maxB2 = -99999, minB2 = 99999;
    function drawFreq() {
        const plt = _state.plot,
              [pxW, pxH] = plt.zoom;
        let x = 0;

        ctx2.clearRect(0,0, uiWidth, h2 + 999);

        //Mark every kHz:
        freqMarkers.forEach(m => {
            const x = m[0] + .5,
                  h = m[1] * h2;
            ctx2.beginPath();
            ctx2.strokeStyle = 'white';
            ctx2.moveTo(x, 0);
            ctx2.lineTo(x, h);
            ctx2.stroke();
        });

        //(Logarithmic) decibels from -255 to 0?
        //Same as getByteFrequencyData with min/maxDecibels -255/0
        analyser.getFloatFrequencyData(b2);
        ctx2.strokeStyle = 'lime';
        drawGraph(ctx2, b2, x => x * pxW, y => -y);

        //Decibels within min/maxDecibels
        analyser.getByteFrequencyData(buffer);
        ctx2.strokeStyle = 'hotpink';
        drawGraph(ctx2, buffer, x => x * pxW, y => h2 - y);
    }
    
    //TODO..
    function drawStrobe(waveform) {
        const sr = audioContext.sampleRate,
              tun = _state.tuner,
              sampleBatch = Math.round(tun.sampleLen * sr),
              sampleStarts = tun.sampleTimes.map(x => Math.round(x * sr));
        
        const sampleGraphW = canWave.width / tun.sampleTimes.length,
              zoomX = sampleGraphW / sampleBatch,
              centerY = Math.round(canWave.height/2) + .5,
              multY = tun.magn;

        //Clear the graph, and draw a 0 line and target wave length:
        ctxWave.clearRect(0,0, canWave.width, canWave.height);
        ctxWave.strokeStyle = 'gray';
        drawGraph(ctxWave, [centerY, centerY], x => x * canWave.width);
        ctxWave.strokeStyle = 'yellow';
        drawGraph(ctxWave, [centerY*1.1, centerY*1.1], x => x * zoomX * wavePeriod);

        sampleStarts.forEach((ss, i) => {
            const sampleStart = waveform.__sampleOffset + ss;
            const data = waveform.data.slice(sampleStart, sampleStart + sampleBatch),
                  ma = waveform.ma.slice(sampleStart, sampleStart + sampleBatch);
            //Not enough data yet for this sample batch:
            if(data.length === 0) { return; }
            
            const xStart = Math.round(i * sampleGraphW) + .5;

            ctxWave.strokeStyle = 'green';
            drawGraph(ctxWave, data, x => xStart + (x * zoomX), y => y*multY + centerY);
            ctxWave.strokeStyle = 'yellow';
            drawGraph(ctxWave,   ma, x => xStart + (x * zoomX), y => y*multY + centerY);
            
            //Divider line between batches:
            if(i) {
                ctxWave.strokeStyle = 'silver';
                drawGraph(ctxWave, [0, 200], x => xStart);
            }
        });
    }
    
    function drawGraph(ctx, data, modX, modY) {
        if(modY) {
            data = data.map(modY);
        }

        ctx.beginPath();
        let x;
        for (var i = 0, len = data.length; i < len; i++) {
            x = modX ? modX(i) : i;
            (i === 0) ? ctx.moveTo(x, data[i])
                      : ctx.lineTo(x, data[i]);
        }
        ctx.stroke();
    }


    let renders = 0;
    (function render() {
        if(uiStale) {
            canvas.render();
            //if(renders % 4 === 0)
            {
                drawFreq();
            }
            uiStale = false;
            renders++;
        }
        requestAnimationFrame(render);
    })();
    
    
    $('#keep').onclick = function(e) {
        const kept = $('#kept'),
              w = kept.width  = canvas.w,
              h = kept.height = uiLegend - 2; //canvas.h;
        kept.getContext('2d').drawImage($('#live'), 0,uiLegend, w,h, 0,0, w,h);

        uiRestart = true;
    }

})();

style.scss

$color-bg: black;
$color-tab: #333;


body {
    font-family: Georgia, sans-serif;
    background: $color-bg;
    color: #eee;

    ul {
        margin: 0;
        padding: 0;
        list-style: none;
    }

    button, input {
        font: inherit;
    }
    button {
        cursor: pointer;
        padding: .3em .6em;
    }

    canvas {
        display: block;
    }
}

.tabitems {
    display: flex;
    li:not(:first-child) {
        margin-left: .5em;
    }
    
    button {
        padding: 1em;
        border: none;
        background: rgba($color-tab, .5);
        color: #eee;

        &:focus {
            outline: .2em dashed $color-tab;
        }
        &:hover, &.active {
            background: $color-tab;
        }
    }
}
.tab {
    padding: 1em;
    > :first-child {
        margin-top: 0;
    }
    > :last-child {
        margin-bottom: 0;
    }

    background: $color-tab;
    color: #eee;
}

#tuner {
    canvas {
        background: black;
    }
}

.tools {
    margin-bottom: .5em;
    
    input[type="number"] {
        width: 6ch;
        text-align: right;
    }
}

#container {
    position: relative;

    #kept {
        position: absolute;
        top: 0; left: 0;
        //opacity: .35;
    }
    #live {
        position: relative;
        z-index: 1;
    }
    #loudness {
        position: absolute;
        top: 0; left: 0;
        z-index: 2;
    }
}

#stats {
    //position: absolute !important;
    left: auto !important;
    right: 0;
}

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License.

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A Pen by Andreas Borgen on CodePen.

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