LayoutTests/webaudio/resources/delay-testing.js

var sampleRate = 44100.0;

var renderLengthSeconds = 4;
var delayTimeSeconds = 0.5;
var toneLengthSeconds = 2;

function createToneBuffer(context, frequency, numberOfCycles, sampleRate) {
    var duration = numberOfCycles / frequency;
    var sampleFrameLength = duration * sampleRate;
    
    var audioBuffer = context.createBuffer(1, sampleFrameLength, sampleRate);

    var n = audioBuffer.length;
    var data = audioBuffer.getChannelData(0);

    for (var i = 0; i < n; ++i)
        data[i] = Math.sin(frequency * 2.0*Math.PI * i / sampleRate);

    return audioBuffer;
}

function checkDelayedResult(toneBuffer) {
    return function(event) {
        var renderedBuffer = event.renderedBuffer;

        var sourceData = toneBuffer.getChannelData(0);
        var renderedData = renderedBuffer.getChannelData(0);
    
        var delayTimeFrames = delayTimeSeconds * sampleRate;
        var toneLengthFrames = toneLengthSeconds * sampleRate;

        var success = true;
    
        var n = renderedBuffer.length;
    
        for (var i = 0; i < n; ++i) {
            if (i < delayTimeFrames) {
                // Check that initial portion is 0 (since signal is delayed).
                if (renderedData[i] != 0) {
                    testFailed("Initial portion is not 0 at frame " + i);
                    success = false;
                    break;
                }
            } else if (i >= delayTimeFrames && i < delayTimeFrames + toneLengthFrames) {
                // Make sure that the tone data is delayed by exactly the expected number of frames.
                var j = i - delayTimeFrames;
                if (renderedData[i] != sourceData[j]) {
                    testFailed("Actual data does not match expected data at frame " + i);
                    success = false;
                    break;
                }
            } else {
                // Make sure we have silence after the delayed tone.
                if (renderedData[i] != 0) {
                    testFailed("Final portion is not 0 at frame " + i);
                    success = false;
                    break;
                }
            }    
        }

        if (success) {
            testPassed("Test signal was correctly delayed by " + delayTimeSeconds + " sec.");
        } else {
            testFailed("Test signal was not correctly delayed by " + delayTimeSeconds + " sec.");
        }

        finishJSTest();
    }
}