1 files changed, 102 insertions, 0 deletions
diff --git a/testing/web-platform/tests/webaudio/resources/audiobuffersource-testing.js b/testing/web-platform/tests/webaudio/resources/audiobuffersource-testing.js
new file mode 100644
index 0000000000..2233641914
--- /dev/null
+++ b/testing/web-platform/tests/webaudio/resources/audiobuffersource-testing.js
@@ -0,0 +1,102 @@
+function createTestBuffer(context, sampleFrameLength) {
+  let audioBuffer =
+      context.createBuffer(1, sampleFrameLength, context.sampleRate);
+  let channelData = audioBuffer.getChannelData(0);
+
+  // Create a simple linear ramp starting at zero, with each value in the buffer
+  // equal to its index position.
+  for (let i = 0; i < sampleFrameLength; ++i)
+    channelData[i] = i;
+
+  return audioBuffer;
+}
+
+function checkSingleTest(renderedBuffer, i, should) {
+  let renderedData = renderedBuffer.getChannelData(0);
+  let offsetFrame = i * testSpacingFrames;
+
+  let test = tests[i];
+  let expected = test.expected;
+  let description;
+
+  if (test.description) {
+    description = test.description;
+  } else {
+    // No description given, so create a basic one from the given test
+    // parameters.
+    description =
+        'loop from ' + test.loopStartFrame + ' -> ' + test.loopEndFrame;
+    if (test.offsetFrame)
+      description += ' with offset ' + test.offsetFrame;
+    if (test.playbackRate && test.playbackRate != 1)
+      description += ' with playbackRate of ' + test.playbackRate;
+  }
+
+  let framesToTest;
+
+  if (test.renderFrames)
+    framesToTest = test.renderFrames;
+  else if (test.durationFrames)
+    framesToTest = test.durationFrames;
+
+  // Verify that the output matches
+  let prefix = 'Case ' + i + ': ';
+  should(
+      renderedData.slice(offsetFrame, offsetFrame + framesToTest),
+      prefix + description)
+      .beEqualToArray(expected);
+
+  // Verify that we get all zeroes after the buffer (or duration) has passed.
+  should(
+      renderedData.slice(
+          offsetFrame + framesToTest, offsetFrame + testSpacingFrames),
+      prefix + description + ': tail')
+      .beConstantValueOf(0);
+}
+
+function checkAllTests(renderedBuffer, should) {
+  for (let i = 0; i < tests.length; ++i)
+    checkSingleTest(renderedBuffer, i, should);
+}
+
+
+// Create the actual result by modulating playbackRate or detune AudioParam of
+// ABSN. |modTarget| is a string of AudioParam name, |modOffset| is the offset
+// (anchor) point of modulation, and |modRange| is the range of modulation.
+//
+//   createSawtoothWithModulation(context, 'detune', 440, 1200);
+//
+// The above will perform a modulation on detune within the range of
+// [1200, -1200] around the sawtooth waveform on 440Hz.
+function createSawtoothWithModulation(context, modTarget, modOffset, modRange) {
+  let lfo = context.createOscillator();
+  let amp = context.createGain();
+
+  // Create a sawtooth generator with the signal range of [0, 1].
+  let phasor = context.createBufferSource();
+  let phasorBuffer = context.createBuffer(1, sampleRate, sampleRate);
+  let phasorArray = phasorBuffer.getChannelData(0);
+  let phase = 0, phaseStep = 1 / sampleRate;
+  for (let i = 0; i < phasorArray.length; i++) {
+    phasorArray[i] = phase % 1.0;
+    phase += phaseStep;
+  }
+  phasor.buffer = phasorBuffer;
+  phasor.loop = true;
+
+  // 1Hz for audible (human-perceivable) parameter modulation by LFO.
+  lfo.frequency.value = 1.0;
+
+  amp.gain.value = modRange;
+  phasor.playbackRate.value = modOffset;
+
+  // The oscillator output should be amplified accordingly to drive the
+  // modulation within the desired range.
+  lfo.connect(amp);
+  amp.connect(phasor[modTarget]);
+
+  phasor.connect(context.destination);
+
+  lfo.start();
+  phasor.start();
+}