| <!DOCTYPE html> |
| |
| <html> |
| <head> |
| <script src="../resources/js-test.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() { |
| 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.start(0); |
| |
| context.oncomplete = checkShapedCurve; |
| context.startRendering(); |
| } |
| |
| runTest(); |
| |
| </script> |
| </body> |
| </html> |
