Introduce AudioClock to improve playback delay calculations.

media/filters/audio_clock_unittest.cc

Index: media/filters/audio_clock_unittest.cc
diff --git a/media/filters/audio_clock_unittest.cc b/media/filters/audio_clock_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2f280d161cff63aa0e6097c6fe1a04407940fc9c
--- /dev/null
+++ b/media/filters/audio_clock_unittest.cc
@@ -0,0 +1,177 @@
+// Copyright 2014 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 "media/base/audio_timestamp_helper.h"
+#include "media/base/buffers.h"
+#include "media/filters/audio_clock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+class AudioClockTest : public testing::Test {
+ public:
+  AudioClockTest()
+      : sample_rate_(10),
+        timestamp_helper_(sample_rate_),
+        clock_(sample_rate_) {
+    timestamp_helper_.SetBaseTimestamp(base::TimeDelta());
+  }
+
+  virtual ~AudioClockTest() {}
+
+  void WroteAudio(int frames, int delay_frames, float playback_rate) {
+    timestamp_helper_.AddFrames(static_cast<int>(frames * playback_rate));
+    clock_.WroteAudio(
+        frames, delay_frames, playback_rate, timestamp_helper_.GetTimestamp());
+  }
+
+  void WroteSilence(int frames, int delay_frames) {
+    clock_.WroteSilence(frames, delay_frames);
+  }
+
+  int CurrentMediaTimestampInMilliseconds() {
+    return clock_.CurrentMediaTimestamp().InMilliseconds();
+  }
+
+  int LastEndpointTimestampInMilliseconds() {
+    return clock_.LastEndpointTimestamp().InMilliseconds();
+  }
+
+  const int sample_rate_;
+  AudioTimestampHelper timestamp_helper_;
+  AudioClock clock_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AudioClockTest);
+};
+
+TEST_F(AudioClockTest, TimestampsStartAtNoTimestamp) {
+  EXPECT_EQ(kNoTimestamp(), clock_.CurrentMediaTimestamp());
+  EXPECT_EQ(kNoTimestamp(), clock_.LastEndpointTimestamp());
+}
+
+TEST_F(AudioClockTest, Playback) {
+  // The first time we write data we should expect a negative time matching the
+  // current delay.
+  WroteAudio(10, 20, 1.0);
+  EXPECT_EQ(-2000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(1000, LastEndpointTimestampInMilliseconds());
+
+  // The media time should keep advancing as we write data.
+  WroteAudio(10, 20, 1.0);
+  EXPECT_EQ(-1000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(2000, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 1.0);
+  EXPECT_EQ(0, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(3000, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 1.0);
+  EXPECT_EQ(1000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(4000, LastEndpointTimestampInMilliseconds());
+
+  // Introduce a rate change to slow down time. Current time will keep advancing
+  // by one second until it hits the the slowed down audio.

[scherkus (not reviewing), 2014/04/30 19:13:58]

note to self: s/the the/the/

[scherkus (not reviewing), 2014/05/02 19:26:05]

Done.

+  WroteAudio(10, 20, 0.5);
+  EXPECT_EQ(2000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(4500, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 0.5);
+  EXPECT_EQ(3000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(5000, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 0.5);
+  EXPECT_EQ(4000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(5500, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 0.5);
+  EXPECT_EQ(4500, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(6000, LastEndpointTimestampInMilliseconds());
+
+  // Introduce a rate change to speed up time. Current time will keep advancing
+  // by half a second until it hits the the sped up audio.
+  WroteAudio(10, 20, 2);
+  EXPECT_EQ(5000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(8000, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 2);
+  EXPECT_EQ(5500, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(10000, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 2);
+  EXPECT_EQ(6000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(12000, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 20, 2);
+  EXPECT_EQ(8000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(14000, LastEndpointTimestampInMilliseconds());
+
+  // Write silence to simulate reaching end of stream.
+  WroteSilence(10, 20);
+  EXPECT_EQ(10000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(14000, LastEndpointTimestampInMilliseconds());
+
+  WroteSilence(10, 20);
+  EXPECT_EQ(12000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(14000, LastEndpointTimestampInMilliseconds());
+
+  WroteSilence(10, 20);
+  EXPECT_EQ(14000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(14000, LastEndpointTimestampInMilliseconds());
+
+  // At this point media time should stop increasing.
+  WroteSilence(10, 20);
+  EXPECT_EQ(14000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(14000, LastEndpointTimestampInMilliseconds());
+}
+
+TEST_F(AudioClockTest, AlternatingAudioAndSilence) {
+  // Buffer #1: [0, 1000)
+  WroteAudio(10, 20, 1.0);
+  EXPECT_EQ(-2000, CurrentMediaTimestampInMilliseconds());
+
+  // Buffer #2: 1000ms of silence
+  WroteSilence(10, 20);
+  EXPECT_EQ(-1000, CurrentMediaTimestampInMilliseconds());
+
+  // Buffer #3: [1000, 2000), buffer #1 is at front
+  WroteAudio(10, 20, 1.0);
+  EXPECT_EQ(0, CurrentMediaTimestampInMilliseconds());
+
+  // Buffer #4: 1000ms of silence, time shouldn't advance
+  WroteSilence(10, 20);
+  EXPECT_EQ(0, CurrentMediaTimestampInMilliseconds());
+
+  // Buffer #5: [2000, 3000), buffer #3 is at front
+  WroteAudio(10, 20, 1.0);
+  EXPECT_EQ(1000, CurrentMediaTimestampInMilliseconds());
+}
+
+TEST_F(AudioClockTest, ZeroDelay) {
+  // The first time we write data we should expect the first timestamp
+  // immediately.
+  WroteAudio(10, 0, 1.0);
+  EXPECT_EQ(0, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(1000, LastEndpointTimestampInMilliseconds());
+
+  // Ditto for all subsequent buffers.
+  WroteAudio(10, 0, 1.0);
+  EXPECT_EQ(1000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(2000, LastEndpointTimestampInMilliseconds());
+
+  WroteAudio(10, 0, 1.0);
+  EXPECT_EQ(2000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(3000, LastEndpointTimestampInMilliseconds());
+
+  // Ditto for silence.
+  WroteSilence(10, 0);
+  EXPECT_EQ(3000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(3000, LastEndpointTimestampInMilliseconds());
+
+  WroteSilence(10, 0);
+  EXPECT_EQ(3000, CurrentMediaTimestampInMilliseconds());
+  EXPECT_EQ(3000, LastEndpointTimestampInMilliseconds());
+}
+
+}  // namespace media