<!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() {
    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();
    </script>
  </body>
</html>