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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/audio-testing.js"></script> |
| 8 </head> |
| 9 |
| 10 <body> |
| 11 <script> |
| 12 description("Test Custom Oscillator at Very Low Frequency"); |
| 13 window.jsTestIsAsync = true; |
| 14 |
| 15 // Create a custom oscillator and verify that the parts of a periodic wave
that should be |
| 16 // ignored really are ignored. |
| 17 |
| 18 var sampleRate = 48000; |
| 19 |
| 20 // The desired frequency of the oscillator. The value to be used depends
on the |
| 21 // implementation of the PeriodicWave and should be less than then lowest
fundamental |
| 22 // frequency. The lowest frequency is the Nyquist frequency divided by the
max number of |
| 23 // coefficients used for the FFT. In the current implementation, the max n
umber of |
| 24 // coefficients is 2048 (for a sample rate of 48 kHz) so the lowest freque
ncy is 24000/2048 = |
| 25 // 11.78 Hz. |
| 26 var desiredFrequencyHz = 1; |
| 27 |
| 28 // Minimum allowed SNR between the actual oscillator and the expected resu
lt. Experimentally |
| 29 // determined. |
| 30 var snrThreshold = 130; |
| 31 |
| 32 var context; |
| 33 var osc; |
| 34 var actual; |
| 35 |
| 36 var audit = Audit.createTaskRunner(); |
| 37 |
| 38 // Compute the SNR between the actual result and expected cosine wave |
| 39 function checkCosineResult(result, freq, sampleRate) { |
| 40 var signal = 0; |
| 41 var noise = 0; |
| 42 var omega = 2 * Math.PI * freq / sampleRate; |
| 43 |
| 44 actual = result.getChannelData(0); |
| 45 |
| 46 for (var k = 0; k < actual.length; ++k) { |
| 47 var x = Math.cos(omega * k); |
| 48 var diff = x - actual[k]; |
| 49 signal += x * x; |
| 50 noise += diff * diff; |
| 51 } |
| 52 |
| 53 var snr = 10 * Math.log10(signal / noise); |
| 54 |
| 55 Should("SNR of " + desiredFrequencyHz + " Hz sine wave", snr).beGreaterT
hanOrEqualTo(snrThreshold); |
| 56 testPassed("PeriodicWave coefficients that must be ignored were correctl
y ignored."); |
| 57 } |
| 58 |
| 59 function runTest() { |
| 60 context = new OfflineAudioContext(1, sampleRate, sampleRate); |
| 61 osc = context.createOscillator(); |
| 62 |
| 63 // Create the custom oscillator. For simplicity of testing, we use just
a cosine wave, but |
| 64 // the initial elements of the real and imaginary parts are explicitly s
et to non-zero to |
| 65 // test that they are ignored. |
| 66 var r = new Float32Array(2); |
| 67 var i = new Float32Array(2); |
| 68 r[0] = 1; // DC component to be ignored |
| 69 r[1] = 1; // Fundamental |
| 70 i[0] = 1; // Sine term that doesn't actually exist in a Fourier series |
| 71 i[1] = 0; |
| 72 var wave = context.createPeriodicWave(r, i); |
| 73 |
| 74 osc.setPeriodicWave(wave); |
| 75 osc.frequency.value = desiredFrequencyHz; |
| 76 osc.connect(context.destination); |
| 77 osc.start(); |
| 78 context.startRendering().then(function (buffer) { |
| 79 checkCosineResult(buffer, desiredFrequencyHz, sampleRate); |
| 80 }).then(finishJSTest); |
| 81 }; |
| 82 |
| 83 runTest(); |
| 84 successfullyParsed = true; |
| 85 </script> |
| 86 </body> |
| 87 </html> |
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Chromium Code Reviews
Issue 1180613007:
Allow larger arrays up to size 8192 for PeriodicWave (Closed)
Base URL: svn://svn.chromium.org/blink/trunk