Index: LayoutTests/webaudio/osc-low-freq.html |
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+<!doctype html> |
+<html> |
+ <head> |
+ <title>Test Custom Oscillator at Very Low Frequency</title> |
+ <script src="../resources/js-test.js"></script> |
+ <script src="resources/compatibility.js"></script> |
+ <script src="resources/audio-testing.js"></script> |
+ </head> |
+ |
+ <body> |
+ <script> |
+ description("Test Custom Oscillator at Very Low Frequency"); |
+ window.jsTestIsAsync = true; |
+ |
+ // Create a custom oscillator and verify that the parts of a periodic wave that should be |
+ // ignored really are ignored. |
+ |
+ var sampleRate = 48000; |
+ var highSampleRate = 192000; |
hongchan
2015/07/22 21:01:19
This is unused.
Raymond Toy
2015/07/23 15:33:09
Done.
|
+ |
+ // The desired frequency of the oscillator. The value to be used depends on the |
+ // implementation of the PeriodicWave and should be less than then lowest fundamental |
+ // frequency. The lowest frequency is the Nyquist frequency divided by the max number of |
+ // partials used for the FFT. In the current implementation, the max number of partials is |
+ // 2048 so the lowest frequency is 24000/2048 = 11.78 Hz. |
hongchan
2015/07/22 21:01:19
Partials are not linearly arranged over the freque
Raymond Toy
2015/07/23 15:33:09
I've rewritten the comment. Let me if it's better.
|
+ var desiredFrequencyHz = 1; |
+ |
+ // Minimum allowed SNR between the actual oscillator and the expected result. Experimentally |
+ // determined. |
+ var snrThreshold = 130; |
+ |
+ var context; |
+ var osc; |
+ var actual; |
+ |
+ var audit = Audit.createTaskRunner(); |
+ |
+ function checkSineResult(result, freq, rate) { |
hongchan
2015/07/22 21:01:19
Perhaps would |checkCosineResult| fit better for t
Raymond Toy
2015/07/23 15:33:09
Done.
|
+ // Compute the SNR between the actual result and expected cosine wave |
hongchan
2015/07/22 21:01:19
How about moving this to the line 37? Also a perio
Raymond Toy
2015/07/23 15:33:09
Done.
|
+ var signal = 0; |
+ var noise = 0; |
+ var omega = 2 * Math.PI * freq / rate; |
+ |
+ actual = result.getChannelData(0); |
+ |
+ for (var k = 0; k < actual.length; ++k) { |
+ var x = Math.cos(omega * k); |
+ var diff = x - actual[k]; |
+ signal += x * x; |
+ noise += diff * diff; |
+ } |
+ |
+ var snr = 10 * Math.log10(signal / noise); |
+ |
+ Should("SNR of " + desiredFrequencyHz + " Hz sine wave", snr).beGreaterThanOrEqualTo(snrThreshold); |
+ testPassed("PeriodicWave coefficients that must be ignored were correctly ignored."); |
+ } |
+ |
+ function runTest() { |
+ context = new OfflineAudioContext(1, sampleRate, sampleRate); |
+ osc = context.createOscillator(); |
+ |
+ // Create the custom oscillator. For simplicity of testing, we use just a cosine wave, but |
+ // the initial elements of the real and imaginary parts are explicitly set to non-zero to |
+ // test that they are ignored. |
+ var r = new Float32Array(2); |
+ var i = new Float32Array(2); |
+ r[0] = 1; // DC component to be ignored |
+ r[1] = 1; // Fundamental |
+ i[0] = 1; // Sine term that doesn't actually exist in a Fourier series |
+ i[1] = 0; |
+ var wave = context.createPeriodicWave(r, i); |
+ |
+ osc.setPeriodicWave(wave); |
+ osc.frequency.value = desiredFrequencyHz; |
+ osc.connect(context.destination); |
+ osc.start(); |
+ context.startRendering().then(function (b) { |
hongchan
2015/07/22 21:01:19
Let's use |buffer| instead of |b|.
|
+ checkSineResult(b, desiredFrequencyHz, sampleRate); |
+ }).then(finishJSTest); |
+ }; |
+ |
+ runTest(); |
+ successfullyParsed = true; |
+ </script> |
+ </body> |
+</html> |