Reland "Refactor audio manager for Android to avoid heavy tasks at startup"

media/audio/android/audio_manager_android.cc

Index: media/audio/android/audio_manager_android.cc
diff --git a/media/audio/android/audio_manager_android.cc b/media/audio/android/audio_manager_android.cc
index 3464d89a30f4ccd9f8dd4a0c167162d69dbb631f..e67700c1b4d3aed10c5159d83341d6a988041da1 100644
--- a/media/audio/android/audio_manager_android.cc
+++ b/media/audio/android/audio_manager_android.cc
@@ -37,9 +37,6 @@ static void AddDefaultDevice(AudioDeviceNames* device_names) {
 // Maximum number of output streams that can be open simultaneously.
 static const int kMaxOutputStreams = 10;
 
-static const int kAudioModeNormal = 0x00000000;
-static const int kAudioModeInCommunication = 0x00000003;
-
 static const int kDefaultInputBufferSize = 1024;
 static const int kDefaultOutputBufferSize = 2048;
 
@@ -126,12 +123,17 @@ AudioOutputStream* AudioManagerAndroid::MakeAudioOutputStream(
     const AudioParameters& params,
     const std::string& device_id,
     const std::string& input_device_id) {
+  bool had_no_streams = HadNoAudioStreams();
   AudioOutputStream* stream =
       AudioManagerBase::MakeAudioOutputStream(params, std::string(),
           std::string());
-  if (stream && output_stream_count() == 1) {
-    SetAudioMode(kAudioModeInCommunication);
-  }
+
+  // The audio manager for Android creates streams intended for real-time
+  // VoIP sessions and therefore sets the audio mode to MODE_IN_COMMUNICATION.
+  // If a Bluetooth headset is used, the audio stream will use the SCO
+  // channel and therefore have a limited bandwidth (8-16kHz).
+  if (stream && had_no_streams)
+    SetCommunicationAudioModeOn(true);
 
   {
     base::AutoLock lock(streams_lock_);
@@ -143,22 +145,37 @@ AudioOutputStream* AudioManagerAndroid::MakeAudioOutputStream(
 
 AudioInputStream* AudioManagerAndroid::MakeAudioInputStream(
     const AudioParameters& params, const std::string& device_id) {
+  bool had_no_streams = HadNoAudioStreams();
   AudioInputStream* stream =
       AudioManagerBase::MakeAudioInputStream(params, device_id);
+
+  // The audio manager for Android creates streams intended for real-time
+  // VoIP sessions and therefore sets the audio mode to MODE_IN_COMMUNICATION.
+  // If a Bluetooth headset is used, the audio stream will use the SCO
+  // channel and therefore have a limited bandwidth (8kHz).
+  if (stream && had_no_streams)
+    SetCommunicationAudioModeOn(true);
   return stream;
 }
 
 void AudioManagerAndroid::ReleaseOutputStream(AudioOutputStream* stream) {
   AudioManagerBase::ReleaseOutputStream(stream);
-  if (!output_stream_count()) {
-    SetAudioMode(kAudioModeNormal);
-  }
+
+  // Restore the audio mode which was used before the first communication-
+  // mode stream was created.
+  if (HadNoAudioStreams())
+    SetCommunicationAudioModeOn(false);
   base::AutoLock lock(streams_lock_);
   streams_.erase(static_cast<OpenSLESOutputStream*>(stream));
 }
 
 void AudioManagerAndroid::ReleaseInputStream(AudioInputStream* stream) {
   AudioManagerBase::ReleaseInputStream(stream);
+
+  // Restore the audio mode which was used before the first communication-
+  // mode stream was created.
+  if (HadNoAudioStreams())
+    SetCommunicationAudioModeOn(false);
 }
 
 AudioOutputStream* AudioManagerAndroid::MakeLinearOutputStream(
@@ -189,11 +206,14 @@ AudioInputStream* AudioManagerAndroid::MakeLowLatencyInputStream(
     const AudioParameters& params, const std::string& device_id) {
   DCHECK_EQ(AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
   DLOG_IF(ERROR, device_id.empty()) << "Invalid device ID!";
-  // Utilize the device ID to select the correct input device.
+  // Use the device ID to select the correct input device.
   // Note that the input device is always associated with a certain output
   // device, i.e., this selection does also switch the output device.
   // All input and output streams will be affected by the device selection.
-  SetAudioDevice(device_id);
+    if (!SetAudioDevice(device_id)) {
+    LOG(ERROR) << "Unable to select audio device!";
+    return NULL;
+  }
 
   if (params.effects() != AudioParameters::NO_EFFECTS) {
     // Platform effects can only be enabled through the AudioRecord path.
@@ -252,6 +272,10 @@ AudioParameters AudioManagerAndroid::GetPreferredOutputStreamParameters(
       sample_rate, bits_per_sample, buffer_size, AudioParameters::NO_EFFECTS);
 }
 
+bool AudioManagerAndroid::HadNoAudioStreams() {
+  return output_stream_count() == 0 && input_stream_count() == 0;
+}
+
 // static
 bool AudioManagerAndroid::RegisterAudioManager(JNIEnv* env) {
   return RegisterNativesImpl(env);
@@ -286,13 +310,13 @@ void AudioManagerAndroid::DoSetMuteOnAudioThread(bool muted) {
   }
 }
 
-void AudioManagerAndroid::SetAudioMode(int mode) {
-  Java_AudioManagerAndroid_setMode(
+void AudioManagerAndroid::SetCommunicationAudioModeOn(bool on) {
+  Java_AudioManagerAndroid_setCommunicationAudioModeOn(
       base::android::AttachCurrentThread(),
-      j_audio_manager_.obj(), mode);
+      j_audio_manager_.obj(), on);
 }
 
-void AudioManagerAndroid::SetAudioDevice(const std::string& device_id) {
+bool AudioManagerAndroid::SetAudioDevice(const std::string& device_id) {
   JNIEnv* env = AttachCurrentThread();
 
   // Send the unique device ID to the Java audio manager and make the
@@ -302,7 +326,7 @@ void AudioManagerAndroid::SetAudioDevice(const std::string& device_id) {
       env,
       device_id == AudioManagerBase::kDefaultDeviceId ?
           std::string() : device_id);
-  Java_AudioManagerAndroid_setDevice(
+  return Java_AudioManagerAndroid_setDevice(
       env, j_audio_manager_.obj(), j_device_id.obj());
 }