Add test for backpressure on MediaStreamTrackProcessor (#36522)

* Add test for backpressure on MediaStreamTrackProcessor
web-platform-tests · Oct 19, 2022 · 1774ecf · 1774ecf · community-tc-integration · Oct 19, 2022
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commit 1774ecf
Showing 1 changed file with 69 additions and 0 deletions.
diff --git a/mediacapture-insertable-streams/MediaStreamTrackProcessor-backpressure.https.html b/mediacapture-insertable-streams/MediaStreamTrackProcessor-backpressure.https.html
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+<!doctype html>
+<html>
+<head>
+  <title>MediaStreamTrackProcessor backpressure</title>
+  <link rel="help" href="https://w3c.github.io/mediacapture-insertable-streams">
+</head>
+<body>
+  <h1 class="instructions">Description</h1>
+<p class="instructions">This test checks that MediaStreamTrackProcessor handles backpressure from a WHATWG stream pipeline.</p>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<script src=/resources/testdriver.js></script>
+<script src=/resources/testdriver-vendor.js></script>
+<script>
+
+  const height = 240;
+  const width = 320;
+
+  const inputCanvas = new OffscreenCanvas(width, height);
+  const inputCtx = inputCanvas.getContext('2d', {alpha: false});
+  inputCtx.fillStyle = 'black';
+  inputCtx.fillRect(0, 0, width, height);
+
+  const frameDuration = 40;
+
+  function makeUniformVideoFrame(timestamp) {
+    return new VideoFrame(inputCanvas, {timestamp, alpha: 'discard'});
+  }
+
+  promise_test(async t => {
+    // TODO: use  "new VideoTrackGenerator"
+    const generator = new MediaStreamTrackGenerator({kind: 'video'});
+    t.add_cleanup(() => generator.stop());
+
+    // Write frames for the duration of the test.
+    const writer = generator.writable.getWriter();
+    let timestamp = 0;
+    const intervalId = setInterval(
+      t.step_func(async () => {
+        if (generator.readyState === 'live') {
+          timestamp++;
+          await writer.write(makeUniformVideoFrame(timestamp));
+        }
+      }),
+      frameDuration);
+    t.add_cleanup(() => clearInterval(intervalId));
+    t.step_timeout(function() {
+      clearInterval(intervalId);
+      generator.stop();
+    }, 2000);
+    const processor = new MediaStreamTrackProcessor({track: generator});
+    let ts = 1;
+    await processor.readable.pipeTo(new WritableStream({
+      async write(frame) {
+        if (ts === 1) {
+          assert_equals(frame.timestamp, ts, "Timestamp mismatch");
+        } else {
+          assert_greater_than_equal(frame.timestamp, ts, "Backpressure should have resulted in skipping at least 3 frames");
+        }
+        frame.close();
+        ts+=3;
+        // Wait the equivalent of 3 frames
+        return new Promise((res) => t.step_timeout(res, 3*frameDuration));
+      }
+    }));
+  }, "Tests that backpressure forces MediaStreamTrackProcess to skip frames");
+</script>
+</body>
+</html>