Make OS audio buffer size limits visible.

media/audio/audio_manager_unittest.cc

Index: media/audio/audio_manager_unittest.cc
diff --git a/media/audio/audio_manager_unittest.cc b/media/audio/audio_manager_unittest.cc
index 904ee12fd9847dffdbf3527025e3a8dd1cb09a87..3f1b0a74adebc53579a339ae46b986e34be5d92f 100644
--- a/media/audio/audio_manager_unittest.cc
+++ b/media/audio/audio_manager_unittest.cc
@@ -26,6 +26,7 @@
 #include "media/audio/fake_audio_log_factory.h"
 #include "media/audio/fake_audio_manager.h"
 #include "media/audio/test_audio_thread.h"
+#include "media/base/limits.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -33,6 +34,11 @@
 #include "media/audio/alsa/audio_manager_alsa.h"
 #endif  // defined(USE_ALSA)
 
+#if defined(OS_MACOSX)
+#include "media/audio/mac/audio_manager_mac.h"
+#include "media/base/mac/audio_latency_mac.h"
+#endif
+
 #if defined(OS_WIN)
 #include "base/win/scoped_com_initializer.h"
 #include "media/audio/win/audio_manager_win.h"
@@ -677,4 +683,131 @@ TEST_F(AudioManagerTest, AudioDebugRecording) {
   audio_manager_->DisableOutputDebugRecording();
 }
 
+#if defined(OS_MACOSX) || defined(USE_CRAS) || defined(USE_PULSEAUDIO)
+#if defined(OS_MACOSX)
+class TestAudioManagerBase : public AudioManagerMac {
+#elif defined(USE_CRAS)
+class TestAudioManagerBase : public AudioManagerCras {
+#elif defined(USE_PULSEAUDIO)
+class TestAudioManagerBase : public AudioManagerPulse {
+#endif
+ public:
+  TestAudioManagerBase(std::unique_ptr<AudioThread> audio_thread,
+                       AudioLogFactory* audio_log_factory)
+      : AudioManagerMac(std::move(audio_thread), audio_log_factory) {}
+
+  AudioParameters GetPreferredOutputStreamParametersForTesting(
+      const std::string& output_device_id,
+      const AudioParameters& input_params) {
+    return GetPreferredOutputStreamParameters(output_device_id, input_params);
+  }
+};  // namespace media
+
+class TestAudioSourceCallback : public AudioOutputStream::AudioSourceCallback {
+ public:
+  TestAudioSourceCallback(int expected_frames_per_buffer)
+      : event_(base::WaitableEvent::ResetPolicy::AUTOMATIC,
+               base::WaitableEvent::InitialState::NOT_SIGNALED),
+        expected_frames_per_buffer_(expected_frames_per_buffer){};
+  ~TestAudioSourceCallback() override{};
+
+  int OnMoreData(base::TimeDelta,
+                 base::TimeTicks,
+                 int,
+                 AudioBus* dest) override {
+    EXPECT_EQ(dest->frames(), expected_frames_per_buffer_);
+    event_.Signal();
+    return 0;
+  }
+
+  void OnError() override { FAIL(); }
+
+  base::WaitableEvent& event() { return event_; }

[o1ka, 2017/06/29 15:29:58]

Would be cleaner to pass a pointer to an event in the constructor instead of
providing an accessor to it here, but up to you.

[Andrew MacPherson, 2017/06/29 15:56:37]

Done.

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TestAudioSourceCallback);
+
+  base::WaitableEvent event_;
+  int expected_frames_per_buffer_;

[o1ka, 2017/06/29 15:29:58]

const int

[Andrew MacPherson, 2017/06/29 15:56:37]

Done.

+};
+
+TEST_F(AudioManagerTest, CheckMinimumAudioBufferSizes) {
+  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());
+
+  CreateAudioManagerForTesting<TestAudioManagerBase>();
+  DCHECK(audio_manager_);
+
+  TestAudioManagerBase* test_audio_manager_base =
+      static_cast<TestAudioManagerBase*>(audio_manager_.get());
+
+  AudioParameters default_params =
+      test_audio_manager_base->GetPreferredOutputStreamParametersForTesting(
+          "", AudioParameters());
+  ASSERT_LT(default_params.frames_per_buffer(),
+            media::limits::kMaxAudioBufferSize);
+
+#if defined(OS_MACOSX)
+  // On OSX the preferred output buffer size is higher than the minimum
+  // but users may request the minimum size explicitly.
+  ASSERT_GT(default_params.frames_per_buffer(),
+            GetMinAudioBufferSizeMacOS(media::limits::kMinAudioBufferSize,
+                                       default_params.sample_rate()));
+#elif defined(USE_CRAS)
+  // On CRAS the preferred output buffer size varies per board and may be as low
+  // as the minimum for some boards.
+  ASSERT_GE(params.frames_per_buffer(), media::limits::kMinAudioBufferSize);
+#elif defined(USE_PULSEAUDIO)
+  ASSERT_EQ(params.frames_per_buffer(), media::limits::kMinAudioBufferSize);
+#else
+  NOTREACHED();
+#endif
+
+  AudioParameters params;
+
+  AudioParameters min_params = default_params;
+  // Ensure that values below the minimum size are clamped to the minimum.
+  min_params.set_frames_per_buffer(media::limits::kMinAudioBufferSize / 2);
+  params =
+      test_audio_manager_base->GetPreferredOutputStreamParametersForTesting(
+          "", min_params);
+  ASSERT_EQ(params.frames_per_buffer(), media::limits::kMinAudioBufferSize);
+
+  AudioParameters max_params = default_params;
+  // Ensure that values above the maximum size are clamped to the maximum.
+  max_params.set_frames_per_buffer(media::limits::kMaxAudioBufferSize * 2);
+  params =
+      test_audio_manager_base->GetPreferredOutputStreamParametersForTesting(
+          "", max_params);
+  ASSERT_EQ(params.frames_per_buffer(), media::limits::kMaxAudioBufferSize);
+}
+
+TEST_F(AudioManagerTest, CheckMinimumAudioBufferSizesCallbacks) {

[o1ka, 2017/06/29 15:29:58]

Could you add a comment describing is verified in the test?

[Andrew MacPherson, 2017/06/29 15:56:37]

Done.

+  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());
+
+  CreateAudioManagerForTesting<TestAudioManagerBase>();
+  DCHECK(audio_manager_);
+
+  TestAudioManagerBase* test_audio_manager_base =
+      static_cast<TestAudioManagerBase*>(audio_manager_.get());
+
+  AudioParameters min_params =
+      test_audio_manager_base->GetPreferredOutputStreamParametersForTesting(
+          "", AudioParameters());
+  min_params.set_frames_per_buffer(media::limits::kMinAudioBufferSize);
+
+  // Create an output stream with the minimum buffer size parameters and ensure
+  // that no errors are returned.
+  AudioOutputStream* stream =
+      audio_manager_->MakeAudioOutputStreamProxy(min_params, "");
+  ASSERT_TRUE(stream);
+  EXPECT_TRUE(stream->Open());
+
+  TestAudioSourceCallback source(min_params.frames_per_buffer());
+  stream->Start(&source);
+  source.event().Wait();
+  stream->Stop();
+  stream->Close();
+}
+#endif
+
 }  // namespace media