LayoutTests/webaudio/resources/javascriptaudionode-testing.js

// For the current implementation of JavaScriptAudioNode, when it works with OfflineAudioContext (which runs much faster
// than real-time) the event.inputBuffer might be overwrite again before onaudioprocess ever get chance to be called.
// We carefully arrange the renderLengthInFrames and bufferSize to have exactly the same value to avoid this issue.
var renderLengthInFrames = 512;
var bufferSize = 512;

var context;

function createBuffer(context, numberOfChannels, length) {
    var audioBuffer = context.createBuffer(numberOfChannels, length, sampleRate);

    fillData(audioBuffer, numberOfChannels, audioBuffer.length);
    return audioBuffer;
}

function processAudioData(event) {
    buffer = event.outputBuffer;
    if (buffer.numberOfChannels != outputChannels)
        testFailed("numberOfOutputChannels doesn't match!");

    if (buffer.length != bufferSize)
        testFailed("length of buffer doesn't match!");

    buffer = event.inputBuffer;
    
    var success = checkStereoOnlyData(buffer, inputChannels, buffer.length);

    if (success) {
        testPassed("onaudioprocess was called with correct input data.");
    } else {
        testFailed("onaudioprocess was called with wrong input data.");
    }
}

function fillData(buffer, numberOfChannels, length) {
    for (var i = 0; i < numberOfChannels; ++i) {
        var data = buffer.getChannelData(i);

        for (var j = 0; j < length; ++j)
            if (i < 2)
                data[j] = i * 2 - 1;
            else
                data[j] = 0;
    }
}

// Both 2 to 8 upmix and 8 to 2 downmix are just directly copy the first two channels and left channels are zeroed.
function checkStereoOnlyData(buffer, numberOfChannels, length) {
    for (var i = 0; i < numberOfChannels; ++i) {
        var data = buffer.getChannelData(i);

        for (var j = 0; j < length; ++j) {
            if (i < 2) {
                if (data[j] != i * 2 - 1)
                    return false;
            } else {
                if (data[j] != 0)
                    return false;
            }
        }
    }
    return true;
}

function runJSNodeTest()
{
    // Create offline audio context.
    context = new webkitOfflineAudioContext(2, renderLengthInFrames, sampleRate);

    var sourceBuffer = createBuffer(context, sourceChannels, renderLengthInFrames);

    var bufferSource = context.createBufferSource();
    bufferSource.buffer = sourceBuffer;

    var jsnode = context.createScriptProcessor(bufferSize, inputChannels, outputChannels);

    bufferSource.connect(jsnode);
    jsnode.connect(context.destination);
    jsnode.onaudioprocess = processAudioData;

    bufferSource.start(0);
    context.oncomplete = finishJSTest;
    context.startRendering();
}