1 files changed, 85 insertions, 0 deletions
diff --git a/dom/media/gtest/TestDriftCompensation.cpp b/dom/media/gtest/TestDriftCompensation.cpp
new file mode 100644
index 0000000000..f19a9b28fb
--- /dev/null
+++ b/dom/media/gtest/TestDriftCompensation.cpp
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+#include "DriftCompensation.h"
+#include "mozilla/SpinEventLoopUntil.h"
+
+using namespace mozilla;
+
+class DriftCompensatorTest : public ::testing::Test {
+ public:
+  const TrackRate mRate = 44100;
+  const TimeStamp mStart;
+  const RefPtr<DriftCompensator> mComp;
+
+  DriftCompensatorTest()
+      : mStart(TimeStamp::Now()),
+        mComp(MakeRefPtr<DriftCompensator>(GetCurrentEventTarget(), mRate)) {
+    mComp->NotifyAudioStart(mStart);
+    // NotifyAudioStart dispatched a runnable to update the audio mStart time on
+    // the video thread. Because this is a test, the video thread is the current
+    // thread. We spin the event loop until we know the mStart time is updated.
+    {
+      bool updated = false;
+      NS_DispatchToCurrentThread(
+          NS_NewRunnableFunction(__func__, [&] { updated = true; }));
+      SpinEventLoopUntil("DriftCompensatorTest::DriftCompensatorTest"_ns,
+                         [&] { return updated; });
+    }
+  }
+
+  // Past() is half as far from `mStart` as `aNow`.
+  TimeStamp Past(TimeStamp aNow) {
+    return mStart + (aNow - mStart) / (int64_t)2;
+  }
+
+  // Future() is twice as far from `mStart` as `aNow`.
+  TimeStamp Future(TimeStamp aNow) { return mStart + (aNow - mStart) * 2; }
+};
+
+TEST_F(DriftCompensatorTest, Initialized) {
+  EXPECT_EQ(mComp->GetVideoTime(mStart, mStart), mStart);
+}
+
+TEST_F(DriftCompensatorTest, SlowerAudio) {
+  // 10s of audio took 20 seconds of wall clock to play out
+  mComp->NotifyAudio(mRate * 10);
+  TimeStamp now = mStart + TimeDuration::FromSeconds(20);
+  EXPECT_EQ((mComp->GetVideoTime(now, mStart) - mStart).ToSeconds(), 0.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, Past(now)) - mStart).ToSeconds(), 5.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, now) - mStart).ToSeconds(), 10.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, Future(now)) - mStart).ToSeconds(), 20.0);
+}
+
+TEST_F(DriftCompensatorTest, NoDrift) {
+  // 10s of audio took 10 seconds of wall clock to play out
+  mComp->NotifyAudio(mRate * 10);
+  TimeStamp now = mStart + TimeDuration::FromSeconds(10);
+  EXPECT_EQ((mComp->GetVideoTime(now, mStart) - mStart).ToSeconds(), 0.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, Past(now)) - mStart).ToSeconds(), 5.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, now) - mStart).ToSeconds(), 10.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, Future(now)) - mStart).ToSeconds(), 20.0);
+}
+
+TEST_F(DriftCompensatorTest, NoProgress) {
+  // 10s of audio took 0 seconds of wall clock to play out
+  mComp->NotifyAudio(mRate * 10);
+  TimeStamp now = mStart;
+  TimeStamp future = mStart + TimeDuration::FromSeconds(5);
+  EXPECT_EQ((mComp->GetVideoTime(now, mStart) - mStart).ToSeconds(), 0.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, future) - mStart).ToSeconds(), 5.0);
+}
+
+TEST_F(DriftCompensatorTest, FasterAudio) {
+  // 20s of audio took 10 seconds of wall clock to play out
+  mComp->NotifyAudio(mRate * 20);
+  TimeStamp now = mStart + TimeDuration::FromSeconds(10);
+  EXPECT_EQ((mComp->GetVideoTime(now, mStart) - mStart).ToSeconds(), 0.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, Past(now)) - mStart).ToSeconds(), 10.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, now) - mStart).ToSeconds(), 20.0);
+  EXPECT_EQ((mComp->GetVideoTime(now, Future(now)) - mStart).ToSeconds(), 40.0);
+}