tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
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audiobuffersource-testing.js (3310B)

      1 function createTestBuffer(context, sampleFrameLength) {
      2  let audioBuffer =
      3      context.createBuffer(1, sampleFrameLength, context.sampleRate);
      4  let channelData = audioBuffer.getChannelData(0);
      5 
      6  // Create a simple linear ramp starting at zero, with each value in the buffer
      7  // equal to its index position.
      8  for (let i = 0; i < sampleFrameLength; ++i)
      9    channelData[i] = i;
     10 
     11  return audioBuffer;
     12 }
     13 
     14 function checkSingleTest(renderedBuffer, i, should) {
     15  let renderedData = renderedBuffer.getChannelData(0);
     16  let offsetFrame = i * testSpacingFrames;
     17 
     18  let test = tests[i];
     19  let expected = test.expected;
     20  let description;
     21 
     22  if (test.description) {
     23    description = test.description;
     24  } else {
     25    // No description given, so create a basic one from the given test
     26    // parameters.
     27    description =
     28        'loop from ' + test.loopStartFrame + ' -> ' + test.loopEndFrame;
     29    if (test.offsetFrame)
     30      description += ' with offset ' + test.offsetFrame;
     31    if (test.playbackRate && test.playbackRate != 1)
     32      description += ' with playbackRate of ' + test.playbackRate;
     33  }
     34 
     35  let framesToTest;
     36 
     37  if (test.renderFrames)
     38    framesToTest = test.renderFrames;
     39  else if (test.durationFrames)
     40    framesToTest = test.durationFrames;
     41 
     42  // Verify that the output matches
     43  let prefix = 'Case ' + i + ': ';
     44  should(
     45      renderedData.slice(offsetFrame, offsetFrame + framesToTest),
     46      prefix + description)
     47      .beEqualToArray(expected);
     48 
     49  // Verify that we get all zeroes after the buffer (or duration) has passed.
     50  should(
     51      renderedData.slice(
     52          offsetFrame + framesToTest, offsetFrame + testSpacingFrames),
     53      prefix + description + ': tail')
     54      .beConstantValueOf(0);
     55 }
     56 
     57 function checkAllTests(renderedBuffer, should) {
     58  for (let i = 0; i < tests.length; ++i)
     59    checkSingleTest(renderedBuffer, i, should);
     60 }
     61 
     62 
     63 // Create the actual result by modulating playbackRate or detune AudioParam of
     64 // ABSN. |modTarget| is a string of AudioParam name, |modOffset| is the offset
     65 // (anchor) point of modulation, and |modRange| is the range of modulation.
     66 //
     67 //   createSawtoothWithModulation(context, 'detune', 440, 1200);
     68 //
     69 // The above will perform a modulation on detune within the range of
     70 // [1200, -1200] around the sawtooth waveform on 440Hz.
     71 function createSawtoothWithModulation(context, modTarget, modOffset, modRange) {
     72  let lfo = context.createOscillator();
     73  let amp = context.createGain();
     74 
     75  // Create a sawtooth generator with the signal range of [0, 1].
     76  let phasor = context.createBufferSource();
     77  let phasorBuffer = context.createBuffer(1, sampleRate, sampleRate);
     78  let phasorArray = phasorBuffer.getChannelData(0);
     79  let phase = 0, phaseStep = 1 / sampleRate;
     80  for (let i = 0; i < phasorArray.length; i++) {
     81    phasorArray[i] = phase % 1.0;
     82    phase += phaseStep;
     83  }
     84  phasor.buffer = phasorBuffer;
     85  phasor.loop = true;
     86 
     87  // 1Hz for audible (human-perceivable) parameter modulation by LFO.
     88  lfo.frequency.value = 1.0;
     89 
     90  amp.gain.value = modRange;
     91  phasor.playbackRate.value = modOffset;
     92 
     93  // The oscillator output should be amplified accordingly to drive the
     94  // modulation within the desired range.
     95  lfo.connect(amp);
     96  amp.connect(phasor[modTarget]);
     97 
     98  phasor.connect(context.destination);
     99 
    100  lfo.start();
    101  phasor.start();
    102 }