1 files changed, 116 insertions, 0 deletions
diff --git a/testing/web-platform/tests/webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-playbackrate-zero.html b/testing/web-platform/tests/webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-playbackrate-zero.html
new file mode 100644
index 0000000000..5624054e32
--- /dev/null
+++ b/testing/web-platform/tests/webaudio/the-audio-api/the-audiobuffersourcenode-interface/audiobuffersource-playbackrate-zero.html
@@ -0,0 +1,116 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>
+      audiobuffersource-playbackrate-zero.html
+    </title>
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+    <script src="/webaudio/resources/audit-util.js"></script>
+    <script src="/webaudio/resources/audit.js"></script>
+  </head>
+  <body>
+    <script id="layout-test-code">
+      // Sample rate should be power of 128 to observe the change of AudioParam
+      // at the beginning of rendering quantum. (playbackRate is k-rate) This is
+      // the minimum sample rate in the valid sample rate range.
+      let sampleRate = 8192;
+
+      // The render duration in seconds, and the length in samples.
+      let renderDuration = 1.0;
+      let renderLength = renderDuration * sampleRate;
+
+      let context = new OfflineAudioContext(1, renderLength, sampleRate);
+      let audit = Audit.createTaskRunner();
+
+
+      // Task: Render the actual buffer and compare with the reference.
+      audit.define('synthesize-verify', (task, should) => {
+        let ramp = context.createBufferSource();
+        let rampBuffer = createLinearRampBuffer(context, renderLength);
+        ramp.buffer = rampBuffer;
+
+        ramp.connect(context.destination);
+        ramp.start();
+
+        // Leave the playbackRate as 1 for the first half, then change it
+        // to zero at the exact half. The zero playback rate should hold the
+        // sample value of the buffer index at the moment. (sample-and-hold)
+        ramp.playbackRate.setValueAtTime(1.0, 0.0);
+        ramp.playbackRate.setValueAtTime(0.0, renderDuration / 2);
+
+        context.startRendering()
+            .then(function(renderedBuffer) {
+              let data = renderedBuffer.getChannelData(0);
+              let rampData = rampBuffer.getChannelData(0);
+              let half = rampData.length / 2;
+              let passed = true;
+              let i;
+
+              for (i = 1; i < rampData.length; i++) {
+                if (i < half) {
+                  // Before the half position, the actual should match with the
+                  // original ramp data.
+                  if (data[i] !== rampData[i]) {
+                    passed = false;
+                    break;
+                  }
+                } else {
+                  // From the half position, the actual value should not change.
+                  if (data[i] !== rampData[half]) {
+                    passed = false;
+                    break;
+                  }
+                }
+              }
+
+              should(passed, 'The zero playbackRate')
+                  .message(
+                      'held the sample value correctly',
+                      'should hold the sample value. ' +
+                          'Expected ' + rampData[half] + ' but got ' + data[i] +
+                          ' at the index ' + i);
+            })
+            .then(() => task.done());
+      });
+
+      audit.define('subsample start with playback rate 0', (task, should) => {
+        let context = new OfflineAudioContext(1, renderLength, sampleRate);
+        let rampBuffer = new AudioBuffer(
+            {length: renderLength, sampleRate: context.sampleRate});
+        let data = new Float32Array(renderLength);
+        let startValue = 5;
+        for (let k = 0; k < data.length; ++k) {
+          data[k] = k + startValue;
+        }
+        rampBuffer.copyToChannel(data, 0);
+
+        let src = new AudioBufferSourceNode(
+            context, {buffer: rampBuffer, playbackRate: 0});
+
+        src.connect(context.destination);
+
+        // Purposely start the source between frame boundaries
+        let startFrame = 27.3;
+        src.start(startFrame / context.sampleRate);
+
+        context.startRendering()
+            .then(audioBuffer => {
+              let actualStartFrame = Math.ceil(startFrame);
+              let audio = audioBuffer.getChannelData(0);
+
+              should(
+                  audio.slice(0, actualStartFrame),
+                  `output[0:${actualStartFrame - 1}]`)
+                  .beConstantValueOf(0);
+              should(
+                  audio.slice(actualStartFrame), `output[${actualStartFrame}:]`)
+                  .beConstantValueOf(startValue);
+            })
+            .then(() => task.done());
+      });
+
+      audit.run();
+    </script>
+  </body>
+</html>