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| 1 <!doctype html> | |
| 2 <html> | |
| 3 <head> | |
| 4 <title>Test Custom Oscillator at Very Low Frequency</title> | |
| 5 <script src="../resources/js-test.js"></script> | |
| 6 <script src="resources/compatibility.js"></script> | |
| 7 <script src="resources/audit-util.js"></script> | |
| 8 <script src="resources/audio-testing.js"></script> | |
| 9 </head> | |
| 10 | |
| 11 <body> | |
| 12 <script> | |
| 13 description("Test Custom Oscillator at Very Low Frequency"); | |
| 14 window.jsTestIsAsync = true; | |
| 15 | |
| 16 // Create a custom oscillator and verify that the parts of a periodic wave
that should be | |
| 17 // ignored really are ignored. | |
| 18 | |
| 19 var sampleRate = 48000; | |
| 20 | |
| 21 // The desired frequency of the oscillator. The value to be used depends
on the | |
| 22 // implementation of the PeriodicWave and should be less than then lowest
fundamental | |
| 23 // frequency. The lowest frequency is the Nyquist frequency divided by the
max number of | |
| 24 // coefficients used for the FFT. In the current implementation, the max n
umber of | |
| 25 // coefficients is 2048 (for a sample rate of 48 kHz) so the lowest freque
ncy is 24000/2048 = | |
| 26 // 11.78 Hz. | |
| 27 var desiredFrequencyHz = 1; | |
| 28 | |
| 29 // Minimum allowed SNR between the actual oscillator and the expected resu
lt. Experimentally | |
| 30 // determined. | |
| 31 var snrThreshold = 130; | |
| 32 | |
| 33 var context; | |
| 34 var osc; | |
| 35 var actual; | |
| 36 | |
| 37 var audit = Audit.createTaskRunner(); | |
| 38 | |
| 39 // Compute the SNR between the actual result and expected cosine wave | |
| 40 function checkCosineResult(result, freq, sampleRate) { | |
| 41 var signal = 0; | |
| 42 var noise = 0; | |
| 43 var omega = 2 * Math.PI * freq / sampleRate; | |
| 44 | |
| 45 actual = result.getChannelData(0); | |
| 46 | |
| 47 for (var k = 0; k < actual.length; ++k) { | |
| 48 var x = Math.cos(omega * k); | |
| 49 var diff = x - actual[k]; | |
| 50 signal += x * x; | |
| 51 noise += diff * diff; | |
| 52 } | |
| 53 | |
| 54 var snr = 10 * Math.log10(signal / noise); | |
| 55 | |
| 56 Should("SNR of " + desiredFrequencyHz + " Hz sine wave", snr, { | |
| 57 brief: true | |
| 58 }).beGreaterThanOrEqualTo(snrThreshold); | |
| 59 testPassed("PeriodicWave coefficients that must be ignored were correctl
y ignored."); | |
| 60 } | |
| 61 | |
| 62 function runTest() { | |
| 63 context = new OfflineAudioContext(1, sampleRate, sampleRate); | |
| 64 osc = context.createOscillator(); | |
| 65 | |
| 66 // Create the custom oscillator. For simplicity of testing, we use just
a cosine wave, but | |
| 67 // the initial elements of the real and imaginary parts are explicitly s
et to non-zero to | |
| 68 // test that they are ignored. | |
| 69 var r = new Float32Array(2); | |
| 70 var i = new Float32Array(2); | |
| 71 r[0] = 1; // DC component to be ignored | |
| 72 r[1] = 1; // Fundamental | |
| 73 i[0] = 1; // Sine term that doesn't actually exist in a Fourier series | |
| 74 i[1] = 0; | |
| 75 var wave = context.createPeriodicWave(r, i); | |
| 76 | |
| 77 osc.setPeriodicWave(wave); | |
| 78 osc.frequency.value = desiredFrequencyHz; | |
| 79 osc.connect(context.destination); | |
| 80 osc.start(); | |
| 81 context.startRendering().then(function (buffer) { | |
| 82 checkCosineResult(buffer, desiredFrequencyHz, sampleRate); | |
| 83 }).then(finishJSTest); | |
| 84 }; | |
| 85 | |
| 86 runTest(); | |
| 87 successfullyParsed = true; | |
| 88 </script> | |
| 89 </body> | |
| 90 </html> | |
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Chromium Code Reviews
Issue 2581463002:
Refactor WebAudio test directory (Closed)
