132 lines
3.8 KiB
HTML
132 lines
3.8 KiB
HTML
<!DOCTYPE html>
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<html>
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<head>
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<script src="../resources/js-test.js"></script>
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<script type="text/javascript" src="resources/audio-testing.js"></script>
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<script type="text/javascript" src="resources/buffer-loader.js"></script>
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</head>
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<body>
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<div id="description"></div>
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<div id="console"></div>
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<script>
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description("Tests that WaveShaperNode applies proper non-linear distortion.");
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var sampleRate = 44100;
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var lengthInSeconds = 4;
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var numberOfRenderFrames = sampleRate * lengthInSeconds;
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var numberOfCurveFrames = 65536;
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var inputBuffer;
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var waveShapingCurve;
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var context;
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function generateInputBuffer() {
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// Create mono input buffer.
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var buffer = context.createBuffer(1, numberOfRenderFrames, context.sampleRate);
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var data = buffer.getChannelData(0);
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// Generate an input vector with values from -1 -> +1 over a duration of lengthInSeconds.
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// This exercises the full nominal input range and will touch every point of the shaping curve.
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for (var i = 0; i < numberOfRenderFrames; ++i) {
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var x = i / numberOfRenderFrames; // 0 -> 1
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x = 2 * x - 1; // -1 -> +1
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data[i] = x;
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}
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return buffer;
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}
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// Generates a symmetric curve: Math.atan(5 * x) / (0.5 * Math.PI)
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// (with x == 0 corresponding to the center of the array)
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// This curve is arbitrary, but would be useful in the real-world.
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// To some extent, the actual curve we choose is not important in this test,
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// since the input vector walks through all possible curve values.
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function generateWaveShapingCurve() {
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var curve = new Float32Array(numberOfCurveFrames);
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var n = numberOfCurveFrames;
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var n2 = n / 2;
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for (var i = 0; i < n; ++i) {
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var x = (i - n2) / n2;
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var y = Math.atan(5 * x) / (0.5 * Math.PI);
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}
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return curve;
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}
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function checkShapedCurve(event) {
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var buffer = event.renderedBuffer;
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var inputData = inputBuffer.getChannelData(0);
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var outputData = buffer.getChannelData(0);
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var success = true;
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// Go through every sample and make sure it has been shaped exactly according to the shaping curve we gave it.
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for (var i = 0; i < buffer.length; ++i) {
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var input = inputData[i];
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// Calculate an index based on input -1 -> +1 with 0 being at the center of the curve data.
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var index = Math.floor(numberOfCurveFrames * 0.5 * (input + 1));
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// Clip index to the input range of the curve.
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// This takes care of input outside of nominal range -1 -> +1
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index = index < 0 ? 0 : index;
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index = index > numberOfCurveFrames - 1 ? numberOfCurveFrames - 1 : index;
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var expectedOutput = waveShapingCurve[index];
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var output = outputData[i];
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if (output != expectedOutput) {
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success = false;
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break;
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}
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}
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if (success) {
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testPassed("WaveShaperNode properly applied non-linear distortion.");
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} else {
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testFailed("WaveShaperNode did not properly apply non-linear distortion.");
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}
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finishJSTest();
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}
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function runTest() {
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window.jsTestIsAsync = true;
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// Create offline audio context.
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context = new OfflineAudioContext(1, numberOfRenderFrames, sampleRate);
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// source -> waveshaper -> destination
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var source = context.createBufferSource();
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var waveshaper = context.createWaveShaper();
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source.connect(waveshaper);
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waveshaper.connect(context.destination);
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// Create an input test vector.
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inputBuffer = generateInputBuffer();
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source.buffer = inputBuffer;
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// We'll apply non-linear distortion according to this shaping curve.
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waveShapingCurve = generateWaveShapingCurve();
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waveshaper.curve = waveShapingCurve;
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source.start(0);
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context.oncomplete = checkShapedCurve;
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context.startRendering();
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}
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runTest();
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</script>
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</body>
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</html>
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