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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script src="../resources/js-test.js"></script>
<script src="resources/audio-testing.js"></script>
</head>
<body>
<div id="description"></div>
<div id="console"></div>
<script>
description("Test scaling of FFT data for AnalyserNode");
// The number of analysers. We have analysers from size for each of the possible sizes of 32,
// 64, 128, 256, 512, 1024 and 2048.
var numberOfAnalysers = 7;
var sampleRate = 44100;
var context;
var osc;
var oscFrequency = sampleRate/32;
var analysers = new Array(7);
var peakValue = new Array(7);
// For a 0dBFS sine wave, we would expect the FFT magnitude to be 0dB as well, but the
// analyzer node applies a Blackman window (to smooth the estimate). This reduces the energy
// of the signal so the FFT peak is less than 0dB. The threshold value given here was
// determined experimentally.
//
// See https://code.google.com/p/chromium/issues/detail?id=341596.
var peakThreshold = [-8.41, -7.54, -7.54, -7.54, -7.54, -7.54, -7.54];
function checkResult() {
var allTestsPassed = true;
for (var n = 0; n < analysers.length; ++n) {
// Grab the FFT data from each analyser.
var fftSize = analysers[n].fftSize;
var fftData = new Float32Array(fftSize);
analysers[n].getFloatFrequencyData(fftData);
// Compute the frequency bin that should contain the peak.
var expectedBin = fftSize * (oscFrequency / sampleRate);
// Find the actual bin by finding the bin containing the peak.
var actualBin = 0;
peakValue[n] = -1000;
for (k = 0; k < analysers[n].frequencyBinCount; ++k) {
if (fftData[k] > peakValue[n]) {
actualBin = k;
peakValue[n] = fftData[k];
}
}
var success = true;
if (actualBin == expectedBin) {
testPassed("Actual FFT peak in the expected position (" + expectedBin + ")");
} else {
success = false;
testFailed("Actual FFT peak (" + actualBin + ") differs from expected (" + expectedBin + ")");
}
if (peakValue[n] >= peakThreshold[n]) {
testPassed("Peak value is near 0 dBFS as expected");
} else {
success = false;
testFailed("Peak value of " + peakValue[n]
+ " is incorrect. (Expected approximately "
+ peakThreshold[n] + ")");
}
if (success) {
testPassed("Analyser correctly scaled FFT data of size " + fftSize);
} else {
testFailed("Analyser incorrectly scaled FFT data of size " + fftSize);
}
allTestsPassed = allTestsPassed && success;
}
if (allTestsPassed) {
testPassed("All Analyser tests passed.");
} else {
testFailed("At least one Analyser test failed.");
}
finishJSTest();
}
function runTests() {
if (window.testRunner) {
testRunner.dumpAsText();
testRunner.waitUntilDone();
}
window.jsTestIsAsync = true;
context = new webkitOfflineAudioContext(1, 2048, sampleRate);
// Use a sine wave oscillator as the reference source signal.
osc = context.createOscillator();
osc.type = "sine";
osc.frequency.value = oscFrequency;
osc.connect(context.destination);
// Create an analyser node for each of the possible valid sizes.
for (var order = 5; order < 12; ++order) {
analysers[order - 5] = context.createAnalyser();
// No smoothing so between frames to simplify testing.
analysers[order - 5].smoothingTimeConstant = 0;
analysers[order - 5].fftSize = 1 << order;
osc.connect(analysers[order - 5]);
}
osc.start(0);
context.oncomplete = checkResult;
context.startRendering();
}
runTests();
successfullyParsed = true;
</script>
</body>
</html>