1 files changed, 58 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/semantics/embedded-content/media-elements/pitch-detector.js b/testing/web-platform/tests/html/semantics/embedded-content/media-elements/pitch-detector.js
new file mode 100644
index 0000000000..78f22ccd85
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/embedded-content/media-elements/pitch-detector.js
@@ -0,0 +1,58 @@
+// This should be removed when the webaudio/historical.html tests are passing.
+// Tracking bug: https://bugs.webkit.org/show_bug.cgi?id=204719
+window.AudioContext = window.AudioContext || window.webkitAudioContext;
+
+var FFT_SIZE = 2048;
+
+var audioContext;
+var sourceNode;
+
+function getPitchDetector(media) {
+  if(!audioContext) {
+    audioContext = new AudioContext();
+    sourceNode = audioContext.createMediaElementSource(media);
+  }
+
+  var analyser = audioContext.createAnalyser();
+  analyser.fftSize = FFT_SIZE;
+
+  sourceNode.connect(analyser);
+  analyser.connect(audioContext.destination);
+
+  return {
+      ensureStart() { return audioContext.resume(); },
+      detect() { return getPitch(analyser); },
+      cleanup() {
+        sourceNode.disconnect();
+        analyser.disconnect();
+      },
+  };
+}
+
+function getPitch(analyser) {
+  // Returns the frequency value for the nth FFT bin.
+  var binConverter = (bin) =>
+    (audioContext.sampleRate/2)*((bin)/(analyser.frequencyBinCount-1));
+
+  var buf = new Uint8Array(analyser.frequencyBinCount);
+  analyser.getByteFrequencyData(buf);
+  return findDominantFrequency(buf, binConverter);
+}
+
+// Returns the dominant frequency, +/- a certain margin.
+function findDominantFrequency(buf, binConverter) {
+  var max = 0;
+  var bin = 0;
+
+  for (var i=0;i<buf.length;i++) {
+    if(buf[i] > max) {
+      max = buf[i];
+      bin = i;
+    }
+  }
+
+  // The spread of frequencies within bins is constant and corresponds to
+  // (1/(FFT_SIZE-1))th of the sample rate. Use the value of bin #1 as a
+  // shorthand for that value.
+  return { value:binConverter(bin), margin:binConverter(1) };
+}
+\ No newline at end of file