gecko-dev/content/media/webaudio/test/blink/audio-testing.js

if (window.testRunner)
    testRunner.overridePreference("WebKitWebAudioEnabled", "1");

function writeString(s, a, offset) {
    for (var i = 0; i < s.length; ++i) {
        a[offset + i] = s.charCodeAt(i);
    }
}

function writeInt16(n, a, offset) {
    n = Math.floor(n);
   
    var b1 = n & 255;
    var b2 = (n >> 8) & 255;

    a[offset + 0] = b1;
    a[offset + 1] = b2;
}

function writeInt32(n, a, offset) {
    n = Math.floor(n);
    var b1 = n & 255;
    var b2 = (n >> 8) & 255;
    var b3 = (n >> 16) & 255;
    var b4 = (n >> 24) & 255;

    a[offset + 0] = b1;
    a[offset + 1] = b2;
    a[offset + 2] = b3;
    a[offset + 3] = b4;
}

function writeAudioBuffer(audioBuffer, a, offset) {
    var n = audioBuffer.length;
    var channels = audioBuffer.numberOfChannels;
   
    for (var i = 0; i < n; ++i) {
        for (var k = 0; k < channels; ++k) {
            var buffer = audioBuffer.getChannelData(k);
            var sample = buffer[i] * 32768.0;

            // Clip samples to the limitations of 16-bit.
            // If we don't do this then we'll get nasty wrap-around distortion.
            if (sample < -32768)
                sample = -32768;
            if (sample > 32767)
                sample = 32767;

            writeInt16(sample, a, offset);
            offset += 2;
        }
    }
}

function createWaveFileData(audioBuffer) {
    var frameLength = audioBuffer.length;
    var numberOfChannels = audioBuffer.numberOfChannels;
    var sampleRate = audioBuffer.sampleRate;
    var bitsPerSample = 16;
    var byteRate = sampleRate * numberOfChannels * bitsPerSample/8;
    var blockAlign = numberOfChannels * bitsPerSample/8;
    var wavDataByteLength = frameLength * numberOfChannels * 2; // 16-bit audio
    var headerByteLength = 44;
    var totalLength = headerByteLength + wavDataByteLength;

    var waveFileData = new Uint8Array(totalLength);
   
    var subChunk1Size = 16; // for linear PCM
    var subChunk2Size = wavDataByteLength;
    var chunkSize = 4 + (8 + subChunk1Size) + (8 + subChunk2Size);

    writeString("RIFF", waveFileData, 0);
    writeInt32(chunkSize, waveFileData, 4);
    writeString("WAVE", waveFileData, 8);
    writeString("fmt ", waveFileData, 12);
   
    writeInt32(subChunk1Size, waveFileData, 16);      // SubChunk1Size (4)
    writeInt16(1, waveFileData, 20);                  // AudioFormat (2)
    writeInt16(numberOfChannels, waveFileData, 22);   // NumChannels (2)
    writeInt32(sampleRate, waveFileData, 24);         // SampleRate (4)
    writeInt32(byteRate, waveFileData, 28);           // ByteRate (4)
    writeInt16(blockAlign, waveFileData, 32);         // BlockAlign (2)
    writeInt32(bitsPerSample, waveFileData, 34);      // BitsPerSample (4)
                                                     
    writeString("data", waveFileData, 36);            
    writeInt32(subChunk2Size, waveFileData, 40);      // SubChunk2Size (4)
   
    // Write actual audio data starting at offset 44.
    writeAudioBuffer(audioBuffer, waveFileData, 44);
   
    return waveFileData;
}

function createAudioData(audioBuffer) {
    return createWaveFileData(audioBuffer);
}

function finishAudioTest(event) {
    var audioData = createAudioData(event.renderedBuffer);
    testRunner.setAudioData(audioData);
    testRunner.notifyDone();
}

// Create an impulse in a buffer of length sampleFrameLength
function createImpulseBuffer(context, sampleFrameLength) {
    var audioBuffer = context.createBuffer(1, sampleFrameLength, context.sampleRate);
    var n = audioBuffer.length;
    var dataL = audioBuffer.getChannelData(0);

    for (var k = 0; k < n; ++k) {
        dataL[k] = 0;
    }
    dataL[0] = 1;

    return audioBuffer;
}

// Create a buffer of the given length with a linear ramp having values 0 <= x < 1.
function createLinearRampBuffer(context, sampleFrameLength) {
    var audioBuffer = context.createBuffer(1, sampleFrameLength, context.sampleRate);
    var n = audioBuffer.length;
    var dataL = audioBuffer.getChannelData(0);

    for (var i = 0; i < n; ++i)
        dataL[i] = i / n;

    return audioBuffer;
}

// Create a buffer of the given length having a constant value.
function createConstantBuffer(context, sampleFrameLength, constantValue) {
    var audioBuffer = context.createBuffer(1, sampleFrameLength, context.sampleRate);
    var n = audioBuffer.length;
    var dataL = audioBuffer.getChannelData(0);

    for (var i = 0; i < n; ++i)
        dataL[i] = constantValue;

    return audioBuffer;
}

// Create a stereo impulse in a buffer of length sampleFrameLength
function createStereoImpulseBuffer(context, sampleFrameLength) {
    var audioBuffer = context.createBuffer(2, sampleFrameLength, context.sampleRate);
    var n = audioBuffer.length;
    var dataL = audioBuffer.getChannelData(0);
    var dataR = audioBuffer.getChannelData(1);

    for (var k = 0; k < n; ++k) {
        dataL[k] = 0;
        dataR[k] = 0;
    }
    dataL[0] = 1;
    dataR[0] = 1;

    return audioBuffer;
}

// Convert time (in seconds) to sample frames.
function timeToSampleFrame(time, sampleRate) {
    return Math.floor(0.5 + time * sampleRate);
}

// Compute the number of sample frames consumed by start with
// the specified |grainOffset|, |duration|, and |sampleRate|.
function grainLengthInSampleFrames(grainOffset, duration, sampleRate) {
    var startFrame = timeToSampleFrame(grainOffset, sampleRate);
    var endFrame = timeToSampleFrame(grainOffset + duration, sampleRate);

    return endFrame - startFrame;
}

// True if the number is not an infinity or NaN
function isValidNumber(x) {
    return !isNaN(x) && (x != Infinity) && (x != -Infinity);
}

function shouldThrowTypeError(func, text) {
    var ok = false;
    try {
        func();
    } catch (e) {
        if (e instanceof TypeError) {
            ok = true;
        }
    }
    if (ok) {
        testPassed(text + " threw TypeError.");
    } else {
        testFailed(text + " should throw TypeError.");
    }
}