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| 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
| 2 <html> |
| 3 <head> |
| 4 <script src="../resources/js-test.js"></script> |
| 5 <script src="resources/audio-testing.js"></script> |
| 6 </head> |
| 7 |
| 8 <body> |
| 9 <div id="description"></div> |
| 10 <div id="console"></div> |
| 11 |
| 12 <script> |
| 13 description("Test scaling of FFT data for AnalyserNode"); |
| 14 |
| 15 // The number of analysers. We have analysers from size for each of the po
ssible sizes of 32, |
| 16 // 64, 128, 256, 512, 1024 and 2048. |
| 17 var numberOfAnalysers = 7; |
| 18 var sampleRate = 44100; |
| 19 var context; |
| 20 var osc; |
| 21 var oscFrequency = sampleRate/32; |
| 22 var analysers = new Array(7); |
| 23 var peakValue = new Array(7); |
| 24 |
| 25 // For a 0dBFS sine wave, we would expect the FFT magnitude to be 0dB as w
ell, but the |
| 26 // analyzer node applies a Blackman window (to smooth the estimate). This
reduces the energy |
| 27 // of the signal so the FFT peak is less than 0dB. The threshold value gi
ven here was |
| 28 // determined experimentally. |
| 29 // |
| 30 // See https://code.google.com/p/chromium/issues/detail?id=341596. |
| 31 var peakThreshold = [-8.41, -7.54, -7.54, -7.54, -7.54, -7.54, -7.54]; |
| 32 |
| 33 function checkResult() { |
| 34 var allTestsPassed = true; |
| 35 |
| 36 for (n = 0; n < analysers.length; ++n) { |
| 37 // Grab the FFT data from each analyser. |
| 38 var fftSize = analysers[n].fftSize; |
| 39 var fftData = new Float32Array(fftSize); |
| 40 analysers[n].getFloatFrequencyData(fftData); |
| 41 |
| 42 // Compute the frequency bin that should contain the peak. |
| 43 var expectedBin = fftSize * (oscFrequency / sampleRate); |
| 44 |
| 45 // Find the actual bin by finding the bin containing the peak. |
| 46 var actualBin = 0; |
| 47 peakValue[n] = -1000; |
| 48 for (k = 0; k < analysers[n].frequencyBinCount; ++k) { |
| 49 if (fftData[k] > peakValue[n]) { |
| 50 actualBin = k; |
| 51 peakValue[n] = fftData[k]; |
| 52 } |
| 53 } |
| 54 |
| 55 var success = true; |
| 56 |
| 57 if (actualBin == expectedBin) { |
| 58 testPassed("Actual FFT peak in the expected position (" + expe
ctedBin + ")"); |
| 59 } else { |
| 60 success = false; |
| 61 testFailed("Actual FFT peak (" + actualBin + ") differs from e
xpected (" + expectedBin + ")"); |
| 62 } |
| 63 |
| 64 if (peakValue[n] >= peakThreshold[n]) { |
| 65 testPassed("Peak value is near 0 dBFS as expected"); |
| 66 } else { |
| 67 success = false; |
| 68 testFailed("Peak value of " + peakValue[n] |
| 69 + " is incorrect. (Expected approximately " |
| 70 + peakThreshold[n] + ")"); |
| 71 } |
| 72 |
| 73 if (success) { |
| 74 testPassed("Analyser correctly scaled FFT data of size " + fft
Size); |
| 75 } else { |
| 76 testFailed("Analyser incorrectly scaled FFT data of size " + f
ftSize); |
| 77 } |
| 78 allTestsPassed = allTestsPassed && success; |
| 79 } |
| 80 |
| 81 if (allTestsPassed) { |
| 82 testPassed("All Analyser tests passed."); |
| 83 } else { |
| 84 testFailed("At least one Analyser test failed."); |
| 85 } |
| 86 |
| 87 finishJSTest(); |
| 88 } |
| 89 |
| 90 function runTests() { |
| 91 if (window.testRunner) { |
| 92 testRunner.dumpAsText(); |
| 93 testRunner.waitUntilDone(); |
| 94 } |
| 95 |
| 96 window.jsTestIsAsync = true; |
| 97 |
| 98 context = new webkitOfflineAudioContext(1, 2048, sampleRate); |
| 99 |
| 100 // Use a sine wave oscillator as the reference source signal. |
| 101 osc = context.createOscillator(); |
| 102 osc.type = "sine"; |
| 103 osc.frequency.value = oscFrequency; |
| 104 osc.connect(context.destination); |
| 105 |
| 106 // Create an analyser node for each of the possible valid sizes. |
| 107 for (order = 5; order < 12; ++order) { |
| 108 analysers[order - 5] = context.createAnalyser(); |
| 109 // No smoothing so between frames to simplify testing. |
| 110 analysers[order - 5].smoothingTimeConstant = 0; |
| 111 analysers[order - 5].fftSize = 1 << order; |
| 112 osc.connect(analysers[order - 5]); |
| 113 } |
| 114 |
| 115 osc.start(); |
| 116 context.oncomplete = checkResult; |
| 117 context.startRendering(); |
| 118 } |
| 119 |
| 120 runTests(); |
| 121 successfullyParsed = true; |
| 122 </script> |
| 123 </body> |
| 124 </html> |
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Chromium Code Reviews
Issue 156993002:
Use correct FFT scaling for WebAudio AnalyserNode (Closed)
Base URL: svn://svn.chromium.org/blink/trunk