Introduce AudioDiscardHelper. Refactor audio decoders to use it.

media/base/audio_discard_helper_unittest.cc

Index: media/base/audio_discard_helper_unittest.cc
diff --git a/media/base/audio_discard_helper_unittest.cc b/media/base/audio_discard_helper_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1a6b592120da4b8425361e606a89b28cb334c1b9
--- /dev/null
+++ b/media/base/audio_discard_helper_unittest.cc
@@ -0,0 +1,214 @@
+// 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 "base/memory/scoped_ptr.h"
+#include "media/base/audio_buffer.h"
+#include "media/base/audio_discard_helper.h"
+#include "media/base/buffers.h"
+#include "media/base/decoder_buffer.h"
+#include "media/base/test_helpers.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+static const int kSampleRate = 48000;
+
+static scoped_refptr<DecoderBuffer> CreateEncodedBuffer(
+    base::TimeDelta timestamp,
+    base::TimeDelta duration) {
+  scoped_refptr<DecoderBuffer> result(new DecoderBuffer(1));
+  result->set_timestamp(timestamp);
+  result->set_duration(duration);
+  return result;
+}
+
+static scoped_refptr<AudioBuffer> CreateDecodedBuffer(int frames) {
+  return MakeAudioBuffer(kSampleFormatPlanarF32,
+                         CHANNEL_LAYOUT_MONO,
+                         1,
+                         kSampleRate,
+                         0.0f,
+                         0.01f,
+                         frames,
+                         kNoTimestamp(),
+                         kNoTimestamp());
+}
+
+TEST(AudioDiscardHelperTest, TimeDeltaToFrames) {
+  AudioDiscardHelper discard_helper(kSampleRate);
+
+  EXPECT_EQ(0, discard_helper.TimeDeltaToFrames(base::TimeDelta()));
+  EXPECT_EQ(
+      kSampleRate / 100,
+      discard_helper.TimeDeltaToFrames(base::TimeDelta::FromMilliseconds(10)));
+
+  // Ensure partial frames are always rounded up.  The equation below calculates
+  // a frame count with a fractional part < 0.5.
+  const int small_remainder =
+      base::Time::kMicrosecondsPerSecond * (kSampleRate - 0.9) / kSampleRate;
+  EXPECT_EQ(kSampleRate,
+            discard_helper.TimeDeltaToFrames(
+                base::TimeDelta::FromMicroseconds(small_remainder)));
+}
+
+TEST(AudioDiscardHelperTest, BasicProcessBuffers) {
+  AudioDiscardHelper discard_helper(kSampleRate);
+  ASSERT_FALSE(discard_helper.initialized());
+
+  const base::TimeDelta kTimestamp = base::TimeDelta();
+
+  // Use an estimated duration which doesn't match the number of decoded frames
+  // to ensure the helper is correctly setting durations based on output frames.
+  const base::TimeDelta kEstimatedDuration =
+      base::TimeDelta::FromMilliseconds(9);
+  const base::TimeDelta kActualDuration = base::TimeDelta::FromMilliseconds(10);
+  const int kTestFrames = discard_helper.TimeDeltaToFrames(kActualDuration);
+
+  scoped_refptr<DecoderBuffer> encoded_buffer =
+      CreateEncodedBuffer(kTimestamp, kEstimatedDuration);
+  scoped_refptr<AudioBuffer> decoded_buffer = CreateDecodedBuffer(kTestFrames);
+
+  // Verify the basic case where nothing is discarded.
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  ASSERT_TRUE(discard_helper.initialized());
+  EXPECT_EQ(kTimestamp, decoded_buffer->timestamp());
+  EXPECT_EQ(kActualDuration, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames, decoded_buffer->frame_count());
+
+  // Verify a Reset() takes us back to an uninitialized state.
+  discard_helper.Reset(0);
+  ASSERT_FALSE(discard_helper.initialized());
+
+  // Verify a NULL output buffer returns false.
+  ASSERT_FALSE(discard_helper.ProcessBuffers(encoded_buffer, NULL));
+}
+
+TEST(AudioDiscardHelperTest, ProcessBuffersWithInitialDiscard) {
+  AudioDiscardHelper discard_helper(kSampleRate);
+  ASSERT_FALSE(discard_helper.initialized());
+
+  const base::TimeDelta kTimestamp = base::TimeDelta();
+  const base::TimeDelta kDuration = base::TimeDelta::FromMilliseconds(10);
+  const int kTestFrames = discard_helper.TimeDeltaToFrames(kDuration);
+
+  // Tell the helper we want to discard half of the initial frames.
+  discard_helper.Reset(kTestFrames / 2);
+
+  scoped_refptr<DecoderBuffer> encoded_buffer =
+      CreateEncodedBuffer(kTimestamp, kDuration);
+  scoped_refptr<AudioBuffer> decoded_buffer = CreateDecodedBuffer(kTestFrames);
+
+  // Verify half the frames end up discarded.
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  ASSERT_TRUE(discard_helper.initialized());
+  EXPECT_EQ(kTimestamp, decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration / 2, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames / 2, decoded_buffer->frame_count());
+}
+
+TEST(AudioDiscardHelperTest, ProcessBuffersWithLargeInitialDiscard) {
+  AudioDiscardHelper discard_helper(kSampleRate);
+  ASSERT_FALSE(discard_helper.initialized());
+
+  const base::TimeDelta kTimestamp = base::TimeDelta();
+  const base::TimeDelta kDuration = base::TimeDelta::FromMilliseconds(10);
+  const int kTestFrames = discard_helper.TimeDeltaToFrames(kDuration);
+
+  // Tell the helper we want to discard 1.5 buffers worth of frames.
+  discard_helper.Reset(kTestFrames * 1.5);
+
+  scoped_refptr<DecoderBuffer> encoded_buffer =
+      CreateEncodedBuffer(kTimestamp, kDuration);
+  scoped_refptr<AudioBuffer> decoded_buffer = CreateDecodedBuffer(kTestFrames);
+
+  // The first call should fail since no output buffer remains.
+  ASSERT_FALSE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  ASSERT_TRUE(discard_helper.initialized());
+
+  // Generate another set of buffers and expect half the output frames.
+  encoded_buffer = CreateEncodedBuffer(kTimestamp + kDuration, kDuration);
+  decoded_buffer = CreateDecodedBuffer(kTestFrames);
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+
+  // The timestamp should match that of the initial buffer.
+  EXPECT_EQ(kTimestamp, decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration / 2, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames / 2, decoded_buffer->frame_count());
+}
+
+TEST(AudioDiscardHelperTest, AllowNonMonotonicTimestamps) {
+  AudioDiscardHelper discard_helper(kSampleRate);
+  ASSERT_FALSE(discard_helper.initialized());
+
+  const base::TimeDelta kTimestamp = base::TimeDelta();
+  const base::TimeDelta kDuration = base::TimeDelta::FromMilliseconds(10);
+  const int kTestFrames = discard_helper.TimeDeltaToFrames(kDuration);
+
+  scoped_refptr<DecoderBuffer> encoded_buffer =
+      CreateEncodedBuffer(kTimestamp, kDuration);
+  scoped_refptr<AudioBuffer> decoded_buffer = CreateDecodedBuffer(kTestFrames);
+
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  ASSERT_TRUE(discard_helper.initialized());
+  EXPECT_EQ(kTimestamp, decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames, decoded_buffer->frame_count());
+
+  // Process the same input buffer again to ensure input timestamps which go

[wolenetz, 2014/04/28 21:52:07]

nit: timestamp really isn't going backwards in time here, just staying the same,
right?

[DaleCurtis, 2014/04/28 23:09:03]

kTimestamp on buffer 2 is now behind kTimestamp+kDuration which is where current
time points after buffer 1 is processed.

+  // backwards in time are not errors.
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  EXPECT_EQ(kTimestamp + kDuration, decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames, decoded_buffer->frame_count());
+}
+
+TEST(AudioDiscardHelperTest, DiscardPadding) {

[wolenetz, 2014/04/28 21:52:07]

Versus ProcessBuffersWithInitialDiscard and InitialDiscardAndDiscardPadding,
these tests don't confirm *which* chunk of the decoded_buffer is trimmed
(TrimStart() or TrimEnd()). Please include such verification.

[DaleCurtis, 2014/04/28 23:09:03]

Done.  Doing so required improving the accuracy of MakeTestBuffer(), which was
cumulatively adding to get the next step value.

+  AudioDiscardHelper discard_helper(kSampleRate);
+  ASSERT_FALSE(discard_helper.initialized());
+
+  const base::TimeDelta kTimestamp = base::TimeDelta();
+  const base::TimeDelta kDuration = base::TimeDelta::FromMilliseconds(10);
+  const int kTestFrames = discard_helper.TimeDeltaToFrames(kDuration);
+
+  scoped_refptr<DecoderBuffer> encoded_buffer =
+      CreateEncodedBuffer(kTimestamp, kDuration);
+  scoped_refptr<AudioBuffer> decoded_buffer = CreateDecodedBuffer(kTestFrames);
+
+  // Set a discard padding equivalent to half the buffer.
+  encoded_buffer->set_discard_padding(kDuration / 2);
+
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  ASSERT_TRUE(discard_helper.initialized());
+  EXPECT_EQ(kTimestamp, decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration / 2, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames / 2, decoded_buffer->frame_count());
+}
+
+TEST(AudioDiscardHelperTest, InitialDiscardAndDiscardPadding) {
+  AudioDiscardHelper discard_helper(kSampleRate);
+  ASSERT_FALSE(discard_helper.initialized());
+
+  const base::TimeDelta kTimestamp = base::TimeDelta();
+  const base::TimeDelta kDuration = base::TimeDelta::FromMilliseconds(10);
+  const int kTestFrames = discard_helper.TimeDeltaToFrames(kDuration);
+
+  scoped_refptr<DecoderBuffer> encoded_buffer =
+      CreateEncodedBuffer(kTimestamp, kDuration);
+  scoped_refptr<AudioBuffer> decoded_buffer = CreateDecodedBuffer(kTestFrames);
+
+  // Set a discard padding equivalent to a quarter of the buffer.
+  encoded_buffer->set_discard_padding(kDuration / 4);
+
+  // Set an initial discard of a quarter of the buffer.
+  discard_helper.Reset(kTestFrames / 4);
+
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  ASSERT_TRUE(discard_helper.initialized());
+  EXPECT_EQ(kTimestamp, decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration / 2, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames / 2, decoded_buffer->frame_count());
+}
+

[wolenetz, 2014/04/28 21:52:07]

nit: remove extra line.

[DaleCurtis, 2014/04/28 23:09:03]

Done.

+
+}  // namespace media