Introduce cadence based VideoRendererAlgorithm.

media/filters/video_cadence_estimator_unittest.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/stringprintf.h"
+#include "media/filters/video_cadence_estimator.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+// See VideoCadenceEstimator header for more details.
+static const int kMinimumAcceptableTimeBetweenGlitchesSecs = 8;

[xhwang, 2015/04/28 16:01:08]

nit: "static" not needed.

[DaleCurtis, 2015/04/28 21:45:24]

Done.

+
+// Slows down the given |fps| according to NTSC field reduction standards; see
+// http://en.wikipedia.org/wiki/Frame_rate#Digital_video_and_television
+static double NTSC(double fps) {
+  return fps / 1.001;
+}
+
+static base::TimeDelta Interval(double hertz) {
+  return base::TimeDelta::FromSecondsD(1.0 / hertz);
+}
+
+static void VerifyCadence(VideoCadenceEstimator* estimator,
+                          double frame_hertz,
+                          double render_hertz,
+                          int expected_cadence) {
+  SCOPED_TRACE(base::StringPrintf("Checking %.03f fps into %0.03f", frame_hertz,
+                                  render_hertz));
+  estimator->Reset();
+  const base::TimeDelta acceptable_drift = Interval(frame_hertz) / 2;
+  const bool found_cadence = estimator->UpdateCadenceEstimate(
+      Interval(render_hertz), Interval(frame_hertz), acceptable_drift);
+  EXPECT_EQ(found_cadence, estimator->has_cadence());
+  EXPECT_EQ(!!expected_cadence, estimator->has_cadence());
+
+  // Nothing further to test.
+  if (!expected_cadence)
+    return;
+
+  // Spot check a few frame indices.
+  if (frame_hertz <= render_hertz) {
+    EXPECT_EQ(expected_cadence, estimator->GetCadenceForFrame(0));
+    EXPECT_EQ(expected_cadence, estimator->GetCadenceForFrame(1));
+    EXPECT_EQ(expected_cadence, estimator->GetCadenceForFrame(2));
+  } else {
+    EXPECT_EQ(1, estimator->GetCadenceForFrame(0));
+    EXPECT_EQ(0, estimator->GetCadenceForFrame(1));
+    EXPECT_EQ(1, estimator->GetCadenceForFrame(expected_cadence));
+    EXPECT_EQ(0, estimator->GetCadenceForFrame(expected_cadence + 1));
+  }
+}
+
+// Spot check common display and frame rate pairs for correctness.
+TEST(VideoCadenceEstimatorTest, CadenceCalculations) {
+  VideoCadenceEstimator estimator(
+      base::TimeDelta::FromSeconds(kMinimumAcceptableTimeBetweenGlitchesSecs));
+  estimator.disable_cadence_hysteresis_for_testing();
+
+  VerifyCadence(&estimator, 24, 60, 0);
+  VerifyCadence(&estimator, NTSC(24), 60, 0);
+  VerifyCadence(&estimator, 25, 60, 0);
+  VerifyCadence(&estimator, NTSC(30), 60, 2);
+  VerifyCadence(&estimator, 30, 60, 2);
+  VerifyCadence(&estimator, 50, 60, 0);
+  VerifyCadence(&estimator, NTSC(60), 60, 1);
+  VerifyCadence(&estimator, 120, 60, 2);
+
+  // 50Hz is common in the EU.
+  VerifyCadence(&estimator, NTSC(24), 50, 0);
+  VerifyCadence(&estimator, 24, 50, 0);
+  VerifyCadence(&estimator, NTSC(25), 50, 2);
+  VerifyCadence(&estimator, 25, 50, 2);
+  VerifyCadence(&estimator, NTSC(30), 50, 0);
+  VerifyCadence(&estimator, 30, 50, 0);
+  VerifyCadence(&estimator, NTSC(60), 50, 0);
+  VerifyCadence(&estimator, 60, 50, 0);
+
+  VerifyCadence(&estimator, 25, NTSC(60), 0);
+  VerifyCadence(&estimator, 120, NTSC(60), 0);
+  VerifyCadence(&estimator, 1, NTSC(60), 60);
+}
+
+TEST(VideoCadenceEstimatorTest, CadenceVariesWithAcceptableDrift) {
+  VideoCadenceEstimator estimator(
+      base::TimeDelta::FromSeconds(kMinimumAcceptableTimeBetweenGlitchesSecs));
+  estimator.disable_cadence_hysteresis_for_testing();
+
+  const base::TimeDelta render_interval = Interval(NTSC(60));
+  const base::TimeDelta frame_interval = Interval(120);
+
+  base::TimeDelta acceptable_drift = frame_interval / 2;
+  bool found_cadence = estimator.UpdateCadenceEstimate(
+      render_interval, frame_interval, acceptable_drift);
+  EXPECT_FALSE(found_cadence);
+  EXPECT_FALSE(estimator.has_cadence());
+
+  // Increasing the acceptable drift should be result in more permissive
+  // detection of cadence.
+  acceptable_drift = render_interval;
+  found_cadence = estimator.UpdateCadenceEstimate(
+      render_interval, frame_interval, acceptable_drift);
+  EXPECT_TRUE(found_cadence);
+  EXPECT_TRUE(estimator.has_cadence());
+  EXPECT_EQ(2, estimator.get_cadence_for_testing());
+}
+
+TEST(VideoCadenceEstimatorTest, CadenceVariesWithAcceptableGlitchTime) {
+  scoped_ptr<VideoCadenceEstimator> estimator(new VideoCadenceEstimator(
+      base::TimeDelta::FromSeconds(kMinimumAcceptableTimeBetweenGlitchesSecs)));
+  estimator->disable_cadence_hysteresis_for_testing();
+
+  const base::TimeDelta render_interval = Interval(NTSC(60));
+  const base::TimeDelta frame_interval = Interval(120);
+  const base::TimeDelta acceptable_drift = frame_interval / 2;
+
+  bool found_cadence = estimator->UpdateCadenceEstimate(
+      render_interval, frame_interval, acceptable_drift);
+  EXPECT_FALSE(found_cadence);
+  EXPECT_FALSE(estimator->has_cadence());
+
+  // Decreasing the acceptable glitch time should be result in more permissive
+  // detection of cadence.
+  estimator.reset(new VideoCadenceEstimator(base::TimeDelta::FromSeconds(
+      kMinimumAcceptableTimeBetweenGlitchesSecs / 2)));
+  estimator->disable_cadence_hysteresis_for_testing();

[xhwang, 2015/04/28 16:01:08]

Can you also test with the hysteresis enabled? 

[DaleCurtis, 2015/04/28 21:45:24]

Whoops, forgot about that. Done.

+  found_cadence = estimator->UpdateCadenceEstimate(
+      render_interval, frame_interval, acceptable_drift);
+  EXPECT_TRUE(found_cadence);
+  EXPECT_TRUE(estimator->has_cadence());
+  EXPECT_EQ(2, estimator->get_cadence_for_testing());
+}
+
+}  // namespace media