Purge AudioOutputDispatcher after close delay if no proxies exist.

This prevents transient audio creation errors from cumulatively
breaking audio output by blackholing everything to a fake audio
stream after fallback attempts are exhausted.

BUG=453560
TEST=new unittest, manual testing.

Review URL: https://codereview.chromium.org/899923003

Cr-Commit-Position: refs/heads/master@{#314910}

media/audio/audio_output_dispatcher_impl.cc

@@ -130,6 +130,10 @@ void AudioOutputDispatcherImpl::Shutdown() {
   DCHECK(HasOneRef()) << "Only the AudioManager should hold a reference";
 }
 
+bool AudioOutputDispatcherImpl::HasOutputProxies() const {
+  return idle_proxies_ || !proxy_to_physical_map_.empty();
+}
+
 bool AudioOutputDispatcherImpl::CreateAndOpenStream() {
   DCHECK(task_runner_->BelongsToCurrentThread());
   AudioOutputStream* stream = audio_manager_->MakeAudioOutputStream(

media/audio/audio_output_dispatcher_impl.h

@@ -60,6 +60,9 @@ class MEDIA_EXPORT AudioOutputDispatcherImpl : public AudioOutputDispatcher {
 
   void Shutdown() override;
 
+  // Returns true if there are any open AudioOutputProxy objects.
+  bool HasOutputProxies() const;
+
  private:
   friend class base::RefCountedThreadSafe<AudioOutputDispatcherImpl>;
   ~AudioOutputDispatcherImpl() override;

media/audio/audio_output_proxy_unittest.cc

@@ -674,4 +674,57 @@ TEST_F(AudioOutputResamplerTest, LowLatencyOpenEventuallyFails) {
   EXPECT_TRUE(stream2.start_called());
 }
 
+// Simulate failures to open both the low latency and the fallback high latency
+// stream and ensure AudioOutputResampler falls back to a fake stream.  Ensure
+// that after the close delay elapses, opening another stream succeeds with a
+// non-fake stream.
+TEST_F(AudioOutputResamplerTest, FallbackRecovery) {
+  MockAudioOutputStream fake_stream(&manager_, params_);
+
+  // Trigger the fallback mechanism until a fake output stream is created.
+#if defined(OS_WIN)
+  static const int kFallbackCount = 2;
+#else
+  static const int kFallbackCount = 1;
+#endif
+  EXPECT_CALL(manager(), MakeAudioOutputStream(_, _))
+      .Times(kFallbackCount)
+      .WillRepeatedly(Return(static_cast<AudioOutputStream*>(NULL)));
+  EXPECT_CALL(manager(),
+              MakeAudioOutputStream(
+                  AllOf(testing::Property(&AudioParameters::format,
+                                          AudioParameters::AUDIO_FAKE),
+                        testing::Property(&AudioParameters::sample_rate,
+                                          params_.sample_rate()),
+                        testing::Property(&AudioParameters::frames_per_buffer,
+                                          params_.frames_per_buffer())),
+                  _)).WillOnce(Return(&fake_stream));
+  EXPECT_CALL(fake_stream, Open()).WillOnce(Return(true));
+  AudioOutputProxy* proxy = new AudioOutputProxy(resampler_.get());
+  EXPECT_TRUE(proxy->Open());
+  CloseAndWaitForCloseTimer(proxy, &fake_stream);
+
+  // Once all proxies have been closed, AudioOutputResampler will start the
+  // reinitialization timer and execute it after the close delay elapses.
+  base::RunLoop run_loop;
+  message_loop_.PostDelayedTask(
+      FROM_HERE, run_loop.QuitClosure(),
+      base::TimeDelta::FromMilliseconds(2 * kTestCloseDelayMs));
+  run_loop.Run();
+
+  // Verify a non-fake stream can be created.
+  MockAudioOutputStream real_stream(&manager_, params_);
+  EXPECT_CALL(manager(),
+              MakeAudioOutputStream(
+                  testing::Property(&AudioParameters::format,
+                                    testing::Ne(AudioParameters::AUDIO_FAKE)),
+                  _)).WillOnce(Return(&real_stream));
+
+  // Stream1 should be able to successfully open and start.
+  EXPECT_CALL(real_stream, Open()).WillOnce(Return(true));
+  proxy = new AudioOutputProxy(resampler_.get());
+  EXPECT_TRUE(proxy->Open());
+  CloseAndWaitForCloseTimer(proxy, &real_stream);
+}
+
 }  // namespace media

media/audio/audio_output_resampler.cc

@@ -11,6 +11,7 @@
 #include "base/numerics/safe_conversions.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
+#include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_output_dispatcher_impl.h"
@@ -153,7 +154,13 @@ AudioOutputResampler::AudioOutputResampler(AudioManager* audio_manager,
     : AudioOutputDispatcher(audio_manager, input_params, output_device_id),
       close_delay_(close_delay),
       output_params_(output_params),
-      streams_opened_(false) {
+      original_output_params_(output_params),
+      streams_opened_(false),
+      reinitialize_timer_(FROM_HERE,
+                          close_delay_,
+                          base::Bind(&AudioOutputResampler::Reinitialize,
+                                     base::Unretained(this)),
+                          false) {
   DCHECK(input_params.IsValid());
   DCHECK(output_params.IsValid());
   DCHECK_EQ(output_params_.format(), AudioParameters::AUDIO_PCM_LOW_LATENCY);
@@ -168,6 +175,24 @@ AudioOutputResampler::~AudioOutputResampler() {
   DCHECK(callbacks_.empty());
 }
 
+void AudioOutputResampler::Reinitialize() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(streams_opened_);
+
+  // We can only reinitialize the dispatcher if it has no active proxies. Check
+  // if one has been created since the reinitialization timer was started.
+  if (dispatcher_->HasOutputProxies())
+    return;
+
+  // Log a trace event so we can get feedback in the field when this happens.
+  TRACE_EVENT0("audio", "AudioOutputResampler::Reinitialize");
+
+  dispatcher_->Shutdown();
+  output_params_ = original_output_params_;
+  streams_opened_ = false;
+  Initialize();
+}
+
 void AudioOutputResampler::Initialize() {
   DCHECK(!streams_opened_);
   DCHECK(callbacks_.empty());
@@ -282,6 +307,14 @@ void AudioOutputResampler::CloseStream(AudioOutputProxy* stream_proxy) {
     delete it->second;
     callbacks_.erase(it);
   }
+
+  // Start the reinitialization timer if there are no active proxies and we're
+  // not using the originally requested output parameters.  This allows us to
+  // recover from transient output creation errors.
+  if (!dispatcher_->HasOutputProxies() && callbacks_.empty() &&
+      !output_params_.Equals(original_output_params_)) {
+    reinitialize_timer_.Reset();
+  }
 }
 
 void AudioOutputResampler::Shutdown() {

media/audio/audio_output_resampler.h

@@ -10,9 +10,10 @@
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
+#include "base/timer/timer.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_manager.h"
-#include "media/audio/audio_output_dispatcher.h"
+#include "media/audio/audio_output_dispatcher_impl.h"
 #include "media/audio/audio_parameters.h"
 
 namespace media {
@@ -29,12 +30,7 @@ class OnMoreDataConverter;
 //
 // AOR will automatically fall back from AUDIO_PCM_LOW_LATENCY to
 // AUDIO_PCM_LINEAR if the output device fails to open at the requested output
-// parameters.
-//
-// TODO(dalecurtis): Ideally the low latency path will be as reliable as the
-// high latency path once we have channel mixing and support querying for the
-// hardware's configured bit depth.  Monitor the UMA stats for fallback and
-// remove fallback support once it's stable.  http://crbug.com/148418
+// parameters. If opening still fails, it will fallback to AUDIO_FAKE.
 class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher {
  public:
   AudioOutputResampler(AudioManager* audio_manager,
@@ -60,11 +56,14 @@ class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher {
   // appropriate output parameters in error situations.
   void SetupFallbackParams();
 
-  // Used to initialize and reinitialize |dispatcher_|.
+  // Used to reinitialize |dispatcher_|.
+  void Reinitialize();
+
+  // Used to initialize |dispatcher_|.
   void Initialize();
 
   // Dispatcher to proxy all AudioOutputDispatcher calls too.
-  scoped_refptr<AudioOutputDispatcher> dispatcher_;
+  scoped_refptr<AudioOutputDispatcherImpl> dispatcher_;
 
   // Map of outstanding OnMoreDataConverter objects.  A new object is created
   // on every StartStream() call and destroyed on CloseStream().
@@ -74,13 +73,22 @@ class MEDIA_EXPORT AudioOutputResampler : public AudioOutputDispatcher {
   // Used by AudioOutputDispatcherImpl; kept so we can reinitialize on the fly.
   base::TimeDelta close_delay_;
 
-  // AudioParameters used to setup the output stream.
+  // AudioParameters used to setup the output stream; changed upon fallback.
   AudioParameters output_params_;
 
+  // The original AudioParameters we were constructed with.
+  const AudioParameters original_output_params_;
+
   // Whether any streams have been opened through |dispatcher_|, if so we can't
   // fallback on future OpenStream() failures.
   bool streams_opened_;
 
+  // The reinitialization timer provides a way to recover from temporary failure
+  // states by clearing the dispatcher if all proxies have been closed and none
+  // have been created within |close_delay_|.  Without this, audio may be lost
+  // to a fake stream indefinitely for transient errors.
+  base::Timer reinitialize_timer_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioOutputResampler);
 };