LayoutTests/webaudio/waveshaper.html - WebKit - Git at Google

 <!DOCTYPE html>

 <html>
 <head>
 <script src="../resources/js-test-pre.js"></script>
 <script type="text/javascript" src="resources/audio-testing.js"></script>
 <script type="text/javascript" src="resources/buffer-loader.js"></script>
 </head>

 <body>

 <div id="description"></div>
 <div id="console"></div>

 <script>
 description("Tests that WaveShaperNode applies proper non-linear distortion.");

 var sampleRate = 44100;
 var lengthInSeconds = 4;
 var numberOfRenderFrames = sampleRate * lengthInSeconds;
 var numberOfCurveFrames = 65536;
 var inputBuffer;
 var waveShapingCurve;

 var context;

 function generateInputBuffer() {
     // Create mono input buffer.
     var buffer = context.createBuffer(1, numberOfRenderFrames, context.sampleRate);
     var data = buffer.getChannelData(0);

     // Generate an input vector with values from -1 -> +1 over a duration of lengthInSeconds.
     // This exercises the full nominal input range and will touch every point of the shaping curve.
     for (var i = 0; i < numberOfRenderFrames; ++i) {
         var x = i / numberOfRenderFrames; // 0 -> 1
         x = 2 * x - 1; // -1 -> +1
         data[i] = x;
     }

     return buffer;
 }

 // Generates a symmetric curve: Math.atan(5 * x) / (0.5 * Math.PI)
 // (with x == 0 corresponding to the center of the array)
 // This curve is arbitrary, but would be useful in the real-world.
 // To some extent, the actual curve we choose is not important in this test,
 // since the input vector walks through all possible curve values.
 function generateWaveShapingCurve() {
     var curve = new Float32Array(numberOfCurveFrames);

     var n = numberOfCurveFrames;
     var n2 = n / 2;

     for (var i = 0; i < n; ++i) {
         var x = (i - n2) / n2;
         var y = Math.atan(5 * x) / (0.5 * Math.PI);
     }

     return curve;
 }

 function checkShapedCurve(event) {
     var buffer = event.renderedBuffer;

     var inputData = inputBuffer.getChannelData(0);
     var outputData = buffer.getChannelData(0);

     var success = true;

     // Go through every sample and make sure it has been shaped exactly according to the shaping curve we gave it.
     for (var i = 0; i < buffer.length; ++i) {
         var input = inputData[i];

         // Calculate an index based on input -1 -> +1 with 0 being at the center of the curve data.
         var index = Math.floor(numberOfCurveFrames * 0.5 * (input + 1));

         // Clip index to the input range of the curve.
         // This takes care of input outside of nominal range -1 -> +1
         index = index < 0 ? 0 : index;
         index = index > numberOfCurveFrames - 1 ? numberOfCurveFrames - 1 : index;

         var expectedOutput = waveShapingCurve[index];

         var output = outputData[i];

         if (output != expectedOutput) {
             success = false;
             break;
         }
     }

     if (success) {
         testPassed("WaveShaperNode properly applied non-linear distortion.");
     } else {
         testFailed("WaveShaperNode did not properly apply non-linear distortion.");
     }

     finishJSTest();
 }

 function runTest() {
     if (window.testRunner) {
         testRunner.dumpAsText();
         testRunner.waitUntilDone();
     }

     window.jsTestIsAsync = true;

     // Create offline audio context.
     context = new webkitOfflineAudioContext(1, numberOfRenderFrames, sampleRate);

     // source -> waveshaper -> destination
     var source = context.createBufferSource();
     var waveshaper = context.createWaveShaper();
     source.connect(waveshaper);
     waveshaper.connect(context.destination);

     // Create an input test vector.
     inputBuffer = generateInputBuffer();
     source.buffer = inputBuffer;

     // We'll apply non-linear distortion according to this shaping curve.
     waveShapingCurve = generateWaveShapingCurve();
     waveshaper.curve = waveShapingCurve;

     source.noteOn(0);

     context.oncomplete = checkShapedCurve;
     context.startRendering();
 }

 runTest();

 </script>

 <script src="../resources/js-test-post.js"></script>
 </body>
 </html>
	<!DOCTYPE html>

	<html>
	<head>
	<script src="../resources/js-test-pre.js"></script>
	<script type="text/javascript" src="resources/audio-testing.js"></script>
	<script type="text/javascript" src="resources/buffer-loader.js"></script>
	</head>

	<body>

	<div id="description"></div>
	<div id="console"></div>

	<script>
	description("Tests that WaveShaperNode applies proper non-linear distortion.");

	var sampleRate = 44100;
	var lengthInSeconds = 4;
	var numberOfRenderFrames = sampleRate * lengthInSeconds;
	var numberOfCurveFrames = 65536;
	var inputBuffer;
	var waveShapingCurve;

	var context;

	function generateInputBuffer() {
	// Create mono input buffer.
	var buffer = context.createBuffer(1, numberOfRenderFrames, context.sampleRate);
	var data = buffer.getChannelData(0);

	// Generate an input vector with values from -1 -> +1 over a duration of lengthInSeconds.
	// This exercises the full nominal input range and will touch every point of the shaping curve.
	for (var i = 0; i < numberOfRenderFrames; ++i) {
	var x = i / numberOfRenderFrames; // 0 -> 1
	x = 2 * x - 1; // -1 -> +1
	data[i] = x;
	}

	return buffer;
	}

	// Generates a symmetric curve: Math.atan(5 * x) / (0.5 * Math.PI)
	// (with x == 0 corresponding to the center of the array)
	// This curve is arbitrary, but would be useful in the real-world.
	// To some extent, the actual curve we choose is not important in this test,
	// since the input vector walks through all possible curve values.
	function generateWaveShapingCurve() {
	var curve = new Float32Array(numberOfCurveFrames);

	var n = numberOfCurveFrames;
	var n2 = n / 2;

	for (var i = 0; i < n; ++i) {
	var x = (i - n2) / n2;
	var y = Math.atan(5 * x) / (0.5 * Math.PI);
	}

	return curve;
	}

	function checkShapedCurve(event) {
	var buffer = event.renderedBuffer;

	var inputData = inputBuffer.getChannelData(0);
	var outputData = buffer.getChannelData(0);

	var success = true;

	// Go through every sample and make sure it has been shaped exactly according to the shaping curve we gave it.
	for (var i = 0; i < buffer.length; ++i) {
	var input = inputData[i];

	// Calculate an index based on input -1 -> +1 with 0 being at the center of the curve data.
	var index = Math.floor(numberOfCurveFrames * 0.5 * (input + 1));

	// Clip index to the input range of the curve.
	// This takes care of input outside of nominal range -1 -> +1
	index = index < 0 ? 0 : index;
	index = index > numberOfCurveFrames - 1 ? numberOfCurveFrames - 1 : index;

	var expectedOutput = waveShapingCurve[index];

	var output = outputData[i];

	if (output != expectedOutput) {
	success = false;
	break;
	}
	}

	if (success) {
	testPassed("WaveShaperNode properly applied non-linear distortion.");
	} else {
	testFailed("WaveShaperNode did not properly apply non-linear distortion.");
	}

	finishJSTest();
	}

	function runTest() {
	if (window.testRunner) {
	testRunner.dumpAsText();
	testRunner.waitUntilDone();
	}

	window.jsTestIsAsync = true;

	// Create offline audio context.
	context = new webkitOfflineAudioContext(1, numberOfRenderFrames, sampleRate);

	// source -> waveshaper -> destination
	var source = context.createBufferSource();
	var waveshaper = context.createWaveShaper();
	source.connect(waveshaper);
	waveshaper.connect(context.destination);

	// Create an input test vector.
	inputBuffer = generateInputBuffer();
	source.buffer = inputBuffer;

	// We'll apply non-linear distortion according to this shaping curve.
	waveShapingCurve = generateWaveShapingCurve();
	waveshaper.curve = waveShapingCurve;

	source.noteOn(0);

	context.oncomplete = checkShapedCurve;
	context.startRendering();
	}

	runTest();

	</script>

	<script src="../resources/js-test-post.js"></script>
	</body>
	</html>