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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 var highSampleRate = 192000; | |
hongchan
2015/07/22 21:01:19
This is unused.
Raymond Toy
2015/07/23 15:33:09
Done.
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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 // partials used for the FFT. In the current implementation, the max numbe r of partials is | |
25 // 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.
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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 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.
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39 // 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.
| |
40 var signal = 0; | |
41 var noise = 0; | |
42 var omega = 2 * Math.PI * freq / rate; | |
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 (b) { | |
hongchan
2015/07/22 21:01:19
Let's use |buffer| instead of |b|.
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79 checkSineResult(b, desiredFrequencyHz, sampleRate); | |
80 }).then(finishJSTest); | |
81 }; | |
82 | |
83 runTest(); | |
84 successfullyParsed = true; | |
85 </script> | |
86 </body> | |
87 </html> | |
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