Refactoring of chrome speech recognition architecture (CL1.3)

content/browser/speech/speech_recognizer_impl.cc

Index: content/browser/speech/speech_recognizer_impl.cc
diff --git a/content/browser/speech/speech_recognizer_impl.cc b/content/browser/speech/speech_recognizer_impl.cc
index 84f46a5e69f593735d128a27b7c288ccaa381cff..a8abc2daa54ca3e7d5ffcdcdf1592485bf69d47a 100644
--- a/content/browser/speech/speech_recognizer_impl.cc
+++ b/content/browser/speech/speech_recognizer_impl.cc
@@ -8,20 +8,29 @@
 #include "base/time.h"
 #include "content/browser/browser_main_loop.h"
 #include "content/browser/speech/audio_buffer.h"
-#include "content/public/browser/speech_recognition_event_listener.h"
+#include "content/browser/speech/google_one_shot_remote_engine.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/speech_recognition_event_listener.h"
+#include "content/public/browser/speech_recognizer.h"
 #include "content/public/common/speech_recognition_result.h"
 #include "net/url_request/url_request_context_getter.h"
 
+#define UNREACHABLE_CONDITION() do { NOTREACHED(); return state_; } while(0)
+
 using content::BrowserMainLoop;
 using content::BrowserThread;
+using content::SpeechRecognitionError;
 using content::SpeechRecognitionEventListener;
+using content::SpeechRecognitionResult;
 using content::SpeechRecognizer;
 using media::AudioInputController;
-using std::string;
 
+// TODO(primiano) what about a watchdog here to avoid getting stuck if the
+// SpeechRecognitionEngine does not deliver a result (in reasonable time)?
 namespace {
-
+// Enables spontaneous transition from WaitingForSpeech to RecognizingSpeech,
+// which is required for the mock recognition engine which sends fake results.
+const bool skipSilenceDetectionForTesting = false;
 // The following constants are related to the volume level indicator shown in
 // the UI for recorded audio.
 // Multiplier used when new volume is greater than previous level.
@@ -44,6 +53,7 @@ bool DetectClipping(const speech::AudioChunk& chunk) {
   const int16* samples = chunk.SamplesData16();
   const int kThreshold = num_samples / 20;
   int clipping_samples = 0;
+
   for (int i = 0; i < num_samples; ++i) {
     if (samples[i] <= -32767 || samples[i] >= 32767) {
       if (++clipping_samples > kThreshold)
@@ -55,6 +65,7 @@ bool DetectClipping(const speech::AudioChunk& chunk) {
 
 }  // namespace
 
+// TODO(primiano) transitional, see description in speech_recognizer.h.
 SpeechRecognizer* SpeechRecognizer::Create(
     SpeechRecognitionEventListener* listener,
     int caller_id,
@@ -64,269 +75,486 @@ SpeechRecognizer* SpeechRecognizer::Create(
     bool filter_profanities,
     const std::string& hardware_info,
     const std::string& origin_url) {
-  return new speech::SpeechRecognizerImpl(
-      listener, caller_id, language, grammar, context_getter,
-      filter_profanities, hardware_info, origin_url);
+  speech::GoogleOneShotRemoteEngineConfig google_sr_config;
+  google_sr_config.language = language;
+  google_sr_config.grammar = grammar;
+  google_sr_config.audio_sample_rate =
+      speech::SpeechRecognizerImpl::kAudioSampleRate;
+  google_sr_config.audio_num_bits_per_sample =
+      speech::SpeechRecognizerImpl::kNumBitsPerAudioSample;
+  google_sr_config.filter_profanities = filter_profanities;
+  google_sr_config.hardware_info = hardware_info;
+  google_sr_config.origin_url = origin_url;
+
+  speech::GoogleOneShotRemoteEngine* google_sr_engine =
+      new speech::GoogleOneShotRemoteEngine(context_getter);
+  google_sr_engine->SetConfiguration(google_sr_config);
+
+  return new speech::SpeechRecognizerImpl(listener,
+                                          caller_id,
+                                          google_sr_engine);
 }
 
 namespace speech {
-
 const int SpeechRecognizerImpl::kAudioSampleRate = 16000;
-const int SpeechRecognizerImpl::kAudioPacketIntervalMs = 100;
 const ChannelLayout SpeechRecognizerImpl::kChannelLayout = CHANNEL_LAYOUT_MONO;
 const int SpeechRecognizerImpl::kNumBitsPerAudioSample = 16;
-const int SpeechRecognizerImpl::kNoSpeechTimeoutSec = 8;
+const int SpeechRecognizerImpl::kNoSpeechTimeoutMs = 8000;
 const int SpeechRecognizerImpl::kEndpointerEstimationTimeMs = 300;
 
 SpeechRecognizerImpl::SpeechRecognizerImpl(
     SpeechRecognitionEventListener* listener,
     int caller_id,
-    const std::string& language,
-    const std::string& grammar,
-    net::URLRequestContextGetter* context_getter,
-    bool filter_profanities,
-    const std::string& hardware_info,
-    const std::string& origin_url)
+    SpeechRecognitionEngine* engine)
     : listener_(listener),
-      caller_id_(caller_id),
-      language_(language),
-      grammar_(grammar),
-      filter_profanities_(filter_profanities),
-      hardware_info_(hardware_info),
-      origin_url_(origin_url),
-      context_getter_(context_getter),
-      codec_(AudioEncoder::CODEC_FLAC),
-      encoder_(NULL),
+      testing_audio_manager_(NULL),
+      recognition_engine_(engine),
       endpointer_(kAudioSampleRate),
-      num_samples_recorded_(0),
-      audio_level_(0.0f),
-      audio_manager_(NULL) {
+      caller_id_(caller_id),
+      event_dispatch_nesting_level_(0),
+      state_(kIdle),
+      event_args_(NULL) {
+  DCHECK(listener_ != NULL);
+  DCHECK(recognition_engine_ != NULL);
   endpointer_.set_speech_input_complete_silence_length(
       base::Time::kMicrosecondsPerSecond / 2);
   endpointer_.set_long_speech_input_complete_silence_length(
       base::Time::kMicrosecondsPerSecond);
   endpointer_.set_long_speech_length(3 * base::Time::kMicrosecondsPerSecond);
   endpointer_.StartSession();
+  recognition_engine_->set_delegate(this);
 }
 
 SpeechRecognizerImpl::~SpeechRecognizerImpl() {
-  // Recording should have stopped earlier due to the endpointer or
-  // |StopRecording| being called.
-  DCHECK(!audio_controller_.get());
-  DCHECK(!request_.get() || !request_->HasPendingRequest());
-  DCHECK(!encoder_.get());
   endpointer_.EndSession();
 }
 
-bool SpeechRecognizerImpl::StartRecognition() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  DCHECK(!audio_controller_.get());
-  DCHECK(!request_.get() || !request_->HasPendingRequest());
-  DCHECK(!encoder_.get());
-
-  // The endpointer needs to estimate the environment/background noise before
-  // starting to treat the audio as user input. In |HandleOnData| we wait until
-  // such time has passed before switching to user input mode.
-  endpointer_.SetEnvironmentEstimationMode();
-
-  encoder_.reset(AudioEncoder::Create(codec_, kAudioSampleRate,
-                                      kNumBitsPerAudioSample));
-  int samples_per_packet = (kAudioSampleRate * kAudioPacketIntervalMs) / 1000;
-  AudioParameters params(AudioParameters::AUDIO_PCM_LINEAR, kChannelLayout,
-                         kAudioSampleRate, kNumBitsPerAudioSample,
-                         samples_per_packet);
-  audio_controller_ = AudioInputController::Create(
-      audio_manager_ ? audio_manager_ : BrowserMainLoop::GetAudioManager(),
-      this, params);
-  DCHECK(audio_controller_.get());
-  VLOG(1) << "SpeechRecognizer starting record.";
-  num_samples_recorded_ = 0;
-  audio_controller_->Record();
-
-  return true;
+// -------  Methods that trigger Finite State Machine (FSM) events ------------
+
+// NOTE: all the external events and request should be enqueued (PostTask), even
+// if they come from the same (IO) thread, in order to preserve the relationship
+// of causality between events.
+// Imagine what would happen if a Start has been enqueued from another thread
+// (but not yet processed) and we suddenly issue a Stop from the IO thread.
+// Furthermore, even if you are sure to not interleave start and stop requests,
+// asynchronous event processing mixed with synchronous callback can cause very
+// mind-breaking side effects.
+// For instance, if someone could call Abort synchronously (instead of posting
+// the event on the queue), it will receive interleaved callbacks (e.g. an error
+// or the audio-end event) before the Abort call is effectively ended.
+// Is your (caller) code ready for this?
+
+void SpeechRecognizerImpl::StartRecognition() {
+  FSMEventArgs args;
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&SpeechRecognizerImpl::DispatchEvent,
+                                     this, kStartRequest, args));
 }
 
 void SpeechRecognizerImpl::AbortRecognition() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  DCHECK(audio_controller_.get() || request_.get());
-
-  // Stop recording if required.
-  if (audio_controller_.get()) {
-    CloseAudioControllerSynchronously();
-  }
-
-  VLOG(1) << "SpeechRecognizer canceling recognition.";
-  encoder_.reset();
-  request_.reset();
+  FSMEventArgs args;
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&SpeechRecognizerImpl::DispatchEvent,
+                                     this, kAbortRequest, args));
 }
 
 void SpeechRecognizerImpl::StopAudioCapture() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-
-  // If audio recording has already stopped and we are in recognition phase,
-  // silently ignore any more calls to stop recording.
-  if (!audio_controller_.get())
-    return;
-
-  CloseAudioControllerSynchronously();
+  FSMEventArgs args;
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&SpeechRecognizerImpl::DispatchEvent,
+                                     this, kStopCaptureRequest, args));
+}
 
-  listener_->OnSoundEnd(caller_id_);
-  listener_->OnAudioEnd(caller_id_);
+bool SpeechRecognizerImpl::IsActive() const {
+  // Checking the FSM state from another thread (thus, while the FSM is
+  // potentially concurrently evolving) is meaningless.
+  // If you're doing it, probably you have some design issues.
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  return state_ != kIdle;
+}
 
-  // UploadAudioChunk requires a non-empty final buffer. So we encode a packet
-  // of silence in case encoder had no data already.
-  std::vector<short> samples((kAudioSampleRate * kAudioPacketIntervalMs) /
-                             1000);
-  AudioChunk dummy_chunk(reinterpret_cast<uint8*>(&samples[0]),
-                         samples.size() * sizeof(short),
-                         encoder_->bits_per_sample() / 8);
-  encoder_->Encode(dummy_chunk);
-  encoder_->Flush();
-  scoped_ptr<AudioChunk> encoded_data(encoder_->GetEncodedDataAndClear());
-  DCHECK(!encoded_data->IsEmpty());
-  encoder_.reset();
-
-  // If we haven't got any audio yet end the recognition sequence here.
-  if (request_ == NULL) {
-    // Guard against the listener freeing us until we finish our job.
-    scoped_refptr<SpeechRecognizerImpl> me(this);
-    listener_->OnRecognitionEnd(caller_id_);
-  } else {
-    request_->UploadAudioChunk(*encoded_data, true /* is_last_chunk */);
-  }
+bool SpeechRecognizerImpl::IsCapturingAudio() const {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO)); // See IsActive().
+  return state_ >= kStartingRecognition && state_ <= kRecognizingSpeech;
 }
 
 // Invoked in the audio thread.
 void SpeechRecognizerImpl::OnError(AudioInputController* controller,
                                    int error_code) {
+  FSMEventArgs args;
+  args.audio_error_code = error_code;
   BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
-                         base::Bind(&SpeechRecognizerImpl::HandleOnError,
-                                    this, error_code));
+                          base::Bind(&SpeechRecognizerImpl::DispatchEvent,
+                                     this, kAudioError, args));
 }
 
-void SpeechRecognizerImpl::HandleOnError(int error_code) {
-  LOG(WARNING) << "SpeechRecognizer::HandleOnError, code=" << error_code;
-
-  // Check if we are still recording before canceling recognition, as
-  // recording might have been stopped after this error was posted to the queue
-  // by |OnError|.
-  if (!audio_controller_.get())
+void SpeechRecognizerImpl::OnData(AudioInputController* controller,
+                                  const uint8* data, uint32 size) {
+  if (size == 0)  // This could happen when audio capture stops and is normal.
     return;
 
-  InformErrorAndAbortRecognition(content::SPEECH_RECOGNITION_ERROR_AUDIO);
+  FSMEventArgs args;
+  args.audio_data = new AudioChunk(data, static_cast<size_t>(size),
+                                   kNumBitsPerAudioSample / 8);
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&SpeechRecognizerImpl::DispatchEvent,
+                                     this, kAudioData, args));
 }
 
-void SpeechRecognizerImpl::OnData(AudioInputController* controller,
-                                  const uint8* data, uint32 size) {
-  if (size == 0)  // This could happen when recording stops and is normal.
-    return;
-  AudioChunk* raw_audio = new AudioChunk(data, static_cast<size_t>(size),
-                                         kNumBitsPerAudioSample / 8);
+void SpeechRecognizerImpl::OnSpeechEngineResult(
+    const content::SpeechRecognitionResult& result) {
+  FSMEvent event = kRecognitionResult;
+  FSMEventArgs args;
+  args.speech_result = result;
   BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
-                          base::Bind(&SpeechRecognizerImpl::HandleOnData,
-                                     this, raw_audio));
+                          base::Bind(&SpeechRecognizerImpl::DispatchEvent,
+                                     this, event, args));
 }
 
-void SpeechRecognizerImpl::HandleOnData(AudioChunk* raw_audio) {
-  scoped_ptr<AudioChunk> free_raw_audio_on_return(raw_audio);
-  // Check if we are still recording and if not discard this buffer, as
-  // recording might have been stopped after this buffer was posted to the queue
-  // by |OnData|.
-  if (!audio_controller_.get())
-    return;
+void SpeechRecognizerImpl::OnSpeechEngineError(
+    const content::SpeechRecognitionError& error) {
+  FSMEvent event = kRecognitionError;
+  FSMEventArgs args;
+  args.error = error;
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&SpeechRecognizerImpl::DispatchEvent,
+                                     this, event, args));
+}
+
+// -----------------------  Core FSM implementation ---------------------------
+
+void SpeechRecognizerImpl::DispatchEvent(FSMEvent event, FSMEventArgs args) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  DCHECK_LE(event, kMaxEvent);
+  DCHECK_LE(state_, kMaxState);
+  // Event dispatching must be sequential, otherwise it will break all the rules
+  // and the assumptions of the finite state automata model.
+  DCHECK_EQ(event_dispatch_nesting_level_, 0);
+  ++event_dispatch_nesting_level_;
+  // Guard against the delegate freeing us until we finish processing the event.
+  scoped_refptr<SpeechRecognizerImpl> me(this);
 
-  bool speech_was_heard_before_packet = endpointer_.DidStartReceivingSpeech();
-
-  encoder_->Encode(*raw_audio);
-  float rms;
-  endpointer_.ProcessAudio(*raw_audio, &rms);
-  bool did_clip = DetectClipping(*raw_audio);
-  num_samples_recorded_ += raw_audio->NumSamples();
-
-  if (request_ == NULL) {
-    // This was the first audio packet recorded, so start a request to the
-    // server to send the data and inform the listener.
-    listener_->OnAudioStart(caller_id_);
-    request_.reset(new SpeechRecognitionRequest(context_getter_.get(), this));
-    request_->Start(language_, grammar_, filter_profanities_,
-                    hardware_info_, origin_url_, encoder_->mime_type());
+  event_ = event;
+  event_args_ = &args;
+
+  if (event == kAudioData)
+    ProcessAudioPipeline();
+  // The audio pipeline must be processed before the ProcessEvent, otherwise it
+  // would take actions according to the future state and not the current one.
+  state_ = ProcessEvent(event);
+
+  // Cleanup event args.
+  if (args.audio_data)
+    delete args.audio_data;
+  event_args_ = NULL;
+  --event_dispatch_nesting_level_;
+}
+
+// ----------- Contract for all the FSM evolution functions below -------------
+//  - Are guaranteed to be executed in the IO thread;
+//  - Are guaranteed to be not reentrant (themselves and each other);
+//  - event_args_ is guaranteed to be non NULL;
+//  - event_args_ members are guaranteed to be stable during the call;
+//  - The class won't be freed in the meanwhile due to callbacks;
+
+// TODO(primiano) the audio pipeline is currently serial. However, the
+// clipper->endpointer->vumeter chain and the sr_engine could be parallelized.
+// We should profile the execution to see if it would be worth or not.
+void SpeechRecognizerImpl::ProcessAudioPipeline() {
+  const bool always = true;
+  const bool route_audio_to_clipper    = always;
+  const bool route_audio_to_endpointer = state_ >= kEstimatingEnvironment &&
+                                         state_ <= kRecognizingSpeech;
+  const bool route_audio_to_sr_engine  = route_audio_to_endpointer;
+  const bool route_audio_to_vumeter    = state_ >= kWaitingForSpeech      &&
+                                         state_ <= kRecognizingSpeech;
+
+  AudioChunk& recorded_audio_data = *(event_args_->audio_data);
+
+  num_samples_recorded_ += recorded_audio_data.NumSamples();
+
+  if (route_audio_to_clipper) {
+    clipper_detected_clip_ = DetectClipping(recorded_audio_data);
+  }
+  if (route_audio_to_endpointer) {
+    endpointer_.ProcessAudio(recorded_audio_data, &rms_);
   }
+  if (route_audio_to_vumeter) {
+    DCHECK(route_audio_to_endpointer); // Depends on endpointer due to |rms_|.
+    UpdateSignalAndNoiseLevels(rms_);
+  }
+  if (route_audio_to_sr_engine) {
+    DCHECK(recognition_engine_.get());
+    recognition_engine_->TakeAudioChunk(recorded_audio_data);
+  }
+}
 
-  scoped_ptr<AudioChunk> encoded_data(encoder_->GetEncodedDataAndClear());
-  DCHECK(!encoded_data->IsEmpty());
-  request_->UploadAudioChunk(*encoded_data, false /* is_last_chunk */);
-
-  if (endpointer_.IsEstimatingEnvironment()) {
-    // Check if we have gathered enough audio for the endpointer to do
-    // environment estimation and should move on to detect speech/end of speech.
-    if (num_samples_recorded_ >= (kEndpointerEstimationTimeMs *
-                                  kAudioSampleRate) / 1000) {
-      endpointer_.SetUserInputMode();
-      listener_->OnEnvironmentEstimationComplete(caller_id_);
-    }
-    return;  // No more processing since we are still estimating environment.
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::ProcessEvent(
+    FSMEvent event) {
+  switch (state_) {
+    case kIdle:
+      switch (event) {
+        // TODO(primiano) restore UNREACHABLE_CONDITION above when speech
+        // input extensions are fixed.
+        case kAbortRequest:       return DoNothing(); //UNREACHABLE_CONDITION();
+        case kStartRequest:       return InitializeAndStartRecording();
+        case kStopCaptureRequest: return DoNothing(); //UNREACHABLE_CONDITION();
+        case kAudioData:          return DoNothing(); // Corner cases related to
+        case kRecognitionResult:  return DoNothing(); // queued messages being
+        case kRecognitionError:   return DoNothing(); // lately dispatched.
+        case kAudioError:         return DoNothing();
+      }
+      break;
+    case kStartingRecognition:
+      switch (event) {
+        case kAbortRequest:       return Abort();
+        case kStartRequest:       UNREACHABLE_CONDITION();
+        case kStopCaptureRequest: return Abort();
+        case kAudioData:          return StartSpeechRecognition();
+        case kRecognitionResult:  UNREACHABLE_CONDITION();
+        case kRecognitionError:   return Abort();
+        case kAudioError:         return Abort();
+      }
+      break;
+    case kEstimatingEnvironment:
+      switch (event) {
+        case kAbortRequest:       return Abort();
+        case kStartRequest:       UNREACHABLE_CONDITION();
+        case kStopCaptureRequest: return StopCaptureAndWaitForResult();
+        case kAudioData:          return EnvironmentEstimation();
+        case kRecognitionResult:  return ProcessIntermediateRecognitionResult();
+        case kRecognitionError:   return Abort();
+        case kAudioError:         return Abort();
+      }
+      break;
+    case kWaitingForSpeech:
+      switch (event) {
+        case kAbortRequest:       return Abort();
+        case kStartRequest:       UNREACHABLE_CONDITION();
+        case kStopCaptureRequest: return StopCaptureAndWaitForResult();
+        case kAudioData:          return DetectUserSpeechOrTimeout();
+        case kRecognitionResult:  return ProcessIntermediateRecognitionResult();
+        case kRecognitionError:   return Abort();
+        case kAudioError:         return Abort();
+      }
+      break;
+    case kRecognizingSpeech:
+      switch (event) {
+        case kAbortRequest:       return Abort();
+        case kStartRequest:       UNREACHABLE_CONDITION();
+        case kStopCaptureRequest: return StopCaptureAndWaitForResult();
+        case kAudioData:          return DetectEndOfSpeech();
+        case kRecognitionResult:  return ProcessIntermediateRecognitionResult();
+        case kRecognitionError:   return Abort();
+        case kAudioError:         return Abort();
+      }
+      break;
+    case kWaitingFinalResult:
+      switch (event) {
+        case kAbortRequest:       return Abort();
+        case kStartRequest:       UNREACHABLE_CONDITION();
+        case kStopCaptureRequest: return DoNothing();
+        case kAudioData:          return DoNothing();
+        case kRecognitionResult:  return ProcessFinalRecognitionResult();
+        case kRecognitionError:   return Abort();
+        case kAudioError:         return Abort();
+      }
+      break;
   }
+  UNREACHABLE_CONDITION();
+}
 
-  // Check if we have waited too long without hearing any speech.
-  bool speech_was_heard_after_packet = endpointer_.DidStartReceivingSpeech();
-  if (!speech_was_heard_after_packet &&
-      num_samples_recorded_ >= kNoSpeechTimeoutSec * kAudioSampleRate) {
-    InformErrorAndAbortRecognition(
-        content::SPEECH_RECOGNITION_ERROR_NO_SPEECH);
-    return;
+SpeechRecognizerImpl::FSMState
+SpeechRecognizerImpl::InitializeAndStartRecording() {
+  DCHECK(recognition_engine_.get());
+  DCHECK(audio_controller_.get() == NULL);
+  AudioManager* audio_manager = (testing_audio_manager_ != NULL) ?
+                                 testing_audio_manager_ :
+                                 BrowserMainLoop::GetAudioManager();
+  DCHECK(audio_manager != NULL);
+
+  VLOG(1) << "SpeechRecognizerImpl starting audio capture.";
+  num_samples_recorded_ = 0;
+  rms_ = 0;
+  audio_level_ = 0;
+  clipper_detected_clip_ = false;
+  listener_->OnRecognitionStart(caller_id_);
+
+  if (!audio_manager->HasAudioInputDevices()) {
+    return Abort(SpeechRecognitionError(content::SPEECH_RECOGNITION_ERROR_AUDIO,
+                                        content::AUDIO_ERROR_NO_MIC));
+  }
+
+  if (audio_manager->IsRecordingInProcess()) {
+    return Abort(SpeechRecognitionError(content::SPEECH_RECOGNITION_ERROR_AUDIO,
+                                        content::AUDIO_ERROR_MIC_IN_USE));
+  }
+
+  const int samples_per_packet = kAudioSampleRate *
+      recognition_engine_->GetDesiredAudioChunkDurationMs() / 1000;
+  AudioParameters params(AudioParameters::AUDIO_PCM_LINEAR, kChannelLayout,
+                         kAudioSampleRate, kNumBitsPerAudioSample,
+                         samples_per_packet);
+  audio_controller_ = AudioInputController::Create(audio_manager, this, params);
+
+  if (audio_controller_.get() == NULL) {
+    return Abort(
+        SpeechRecognitionError(content::SPEECH_RECOGNITION_ERROR_AUDIO));
+  }
+
+  // The endpointer needs to estimate the environment/background noise before
+  // starting to treat the audio as user input. We wait in the state
+  // kEstimatingEnvironment until such interval has elapsed before switching
+  // to user input mode.
+  endpointer_.SetEnvironmentEstimationMode();
+  audio_controller_->Record();
+  return kStartingRecognition;
+}
+
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::StartSpeechRecognition() {
+  // This was the first audio packet recorded, so start a request to the
+  // engine to send the data and inform the delegate.
+  DCHECK(recognition_engine_.get());
+  recognition_engine_->Initialize();
+  listener_->OnAudioStart(caller_id_);
+  // TODO(primiano) this is a little hack, since TakeAudioChunk() is already
+  // called by ProcessAudioPipeline(). I hate it since it weakens the
+  // architectural beauty of this class. But it is the best tradeoff, unless we
+  // allow the drop the first audio chunk captured after opening the audio dev.
+  recognition_engine_->TakeAudioChunk(*(event_args_->audio_data));
+  return kEstimatingEnvironment;
+}
+
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::EnvironmentEstimation() {
+  DCHECK(endpointer_.IsEstimatingEnvironment());
+  if (GetElapsedTimeMs() >= kEndpointerEstimationTimeMs) {
+    endpointer_.SetUserInputMode();
+    listener_->OnEnvironmentEstimationComplete(caller_id_);
+    return kWaitingForSpeech;
+  } else {
+    return kEstimatingEnvironment;
   }
+}
 
-  if (!speech_was_heard_before_packet && speech_was_heard_after_packet)
+SpeechRecognizerImpl::FSMState
+SpeechRecognizerImpl::DetectUserSpeechOrTimeout() {
+  if (skipSilenceDetectionForTesting)
+    return kRecognizingSpeech;
+
+  if (endpointer_.DidStartReceivingSpeech()) {
     listener_->OnSoundStart(caller_id_);
+    return kRecognizingSpeech;
+  } else if (GetElapsedTimeMs() >= kNoSpeechTimeoutMs) {
+    return Abort(
+        SpeechRecognitionError(content::SPEECH_RECOGNITION_ERROR_NO_SPEECH));
+  } else {
+    return kWaitingForSpeech;
+  }
+}
 
-  // Calculate the input volume to display in the UI, smoothing towards the
-  // new level.
-  float level = (rms - kAudioMeterMinDb) /
-      (kAudioMeterDbRange / kAudioMeterRangeMaxUnclipped);
-  level = std::min(std::max(0.0f, level), kAudioMeterRangeMaxUnclipped);
-  if (level > audio_level_) {
-    audio_level_ += (level - audio_level_) * kUpSmoothingFactor;
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::DetectEndOfSpeech() {
+  if (endpointer_.speech_input_complete()) {
+    return StopCaptureAndWaitForResult();
   } else {
-    audio_level_ += (level - audio_level_) * kDownSmoothingFactor;
+    return kRecognizingSpeech;
   }
+}
 
-  float noise_level = (endpointer_.NoiseLevelDb() - kAudioMeterMinDb) /
-      (kAudioMeterDbRange / kAudioMeterRangeMaxUnclipped);
-  noise_level = std::min(std::max(0.0f, noise_level),
-      kAudioMeterRangeMaxUnclipped);
+SpeechRecognizerImpl::FSMState
+SpeechRecognizerImpl::StopCaptureAndWaitForResult() {
+  DCHECK(state_ >= kEstimatingEnvironment && state_ <= kRecognizingSpeech);
+
+  VLOG(1) << "Concluding recognition";
+  CloseAudioControllerSynchronously();
+  recognition_engine_->AudioChunksEnded();
 
-  listener_->OnAudioLevelsChange(caller_id_, did_clip ? 1.0f : audio_level_,
-                                 noise_level);
+  if (state_ > kWaitingForSpeech)
+    listener_->OnSoundEnd(caller_id_);
 
-  if (endpointer_.speech_input_complete())
-    StopAudioCapture();
+  listener_->OnAudioEnd(caller_id_);
+  return kWaitingFinalResult;
 }
 
-void SpeechRecognizerImpl::SetRecognitionResult(
-    const content::SpeechRecognitionResult& result) {
-  if (result.error != content::SPEECH_RECOGNITION_ERROR_NONE) {
-    InformErrorAndAbortRecognition(result.error);
-    return;
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::Abort() {
+  // TODO(primiano) Should raise SPEECH_RECOGNITION_ERROR_ABORTED in lack of
+  // other specific error sources (so that it was an explicit abort request).
+  // However, SPEECH_RECOGNITION_ERROR_ABORTED is not caught in UI layers
+  // and currently would cause an exception. JS will probably need it in future.
+  SpeechRecognitionError error;
+  bool has_error = false;
+  if (event_ == kAudioError) {
+    has_error = true;
+    error.code = content::SPEECH_RECOGNITION_ERROR_AUDIO;
+  } else if (event_ == kRecognitionError) {
+    has_error = true;
+    error = event_args_->error;
   }
+  return Abort(has_error, error);
+}
+
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::Abort(
+    const SpeechRecognitionError& error) {
+  return Abort(true, error);
+}
+
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::Abort(
+    bool has_error, const SpeechRecognitionError& error) {
+  if (audio_controller_)
+    CloseAudioControllerSynchronously();
+
+  VLOG(1) << "SpeechRecognizerImpl canceling recognition. " <<
+             error.code << " " << error.details;
+
+  // The recognition engine is initialized only after kStartingRecognition.
+  if (state_ > kStartingRecognition) {
+    DCHECK(recognition_engine_.get());
+    recognition_engine_->Cleanup();
+    //TODO(primiano) reset the engine? Why, after all?
+    //recognition_engine_.reset();
+  }
+
+  if (state_ > kWaitingForSpeech && state_ < kWaitingFinalResult)
+    listener_->OnSoundEnd(caller_id_);
+
+  if (state_ > kStartingRecognition && state_ < kWaitingFinalResult)
+    listener_->OnAudioEnd(caller_id_);
+
+  if (has_error)
+    listener_->OnRecognitionError(caller_id_, error);
 
-  // Guard against the listener freeing us until we finish our job.
-  scoped_refptr<SpeechRecognizerImpl> me(this);
-  listener_->OnRecognitionResult(caller_id_, result);
   listener_->OnRecognitionEnd(caller_id_);
+
+  return kIdle;
 }
 
-void SpeechRecognizerImpl::InformErrorAndAbortRecognition(
-    content::SpeechRecognitionErrorCode error) {
-  DCHECK_NE(error, content::SPEECH_RECOGNITION_ERROR_NONE);
-  AbortRecognition();
+SpeechRecognizerImpl::FSMState
+SpeechRecognizerImpl::ProcessIntermediateRecognitionResult() {
+// This is in preparation for future speech recognition functions.
+//  DCHECK(continuous_mode_);
+//  const SpeechRecognitionResult& result = event_args_->speech_result;
+//  VLOG(1) << "Got intermediate result";
+//  listener_->OnRecognitionResult(caller_id_, result);
+  NOTREACHED();
+  return state_;
+}
 
-  // Guard against the listener freeing us until we finish our job.
-  scoped_refptr<SpeechRecognizerImpl> me(this);
-  listener_->OnRecognitionError(caller_id_, error);
+SpeechRecognizerImpl::FSMState
+SpeechRecognizerImpl::ProcessFinalRecognitionResult() {
+  const SpeechRecognitionResult& result = event_args_->speech_result;
+  VLOG(1) << "Got valid result";
+  recognition_engine_->Cleanup();
+  listener_->OnRecognitionResult(caller_id_, result);
+  listener_->OnRecognitionEnd(caller_id_);
+  return kIdle;
+}
+
+SpeechRecognizerImpl::FSMState SpeechRecognizerImpl::DoNothing() const {
+  return state_; // Just keep the current state.
 }
 
 void SpeechRecognizerImpl::CloseAudioControllerSynchronously() {
-  VLOG(1) << "SpeechRecognizer stopping record.";
+  DCHECK(audio_controller_);
+  VLOG(1) << "SpeechRecognizerImpl stopping audio capture.";
 
   // TODO(satish): investigate the possibility to utilize the closure
   // and switch to async. version of this method. Compare with how
@@ -338,17 +566,45 @@ void SpeechRecognizerImpl::CloseAudioControllerSynchronously() {
   audio_controller_ = NULL;  // Releases the ref ptr.
 }
 
-void SpeechRecognizerImpl::SetAudioManagerForTesting(
-    AudioManager* audio_manager) {
-  audio_manager_ = audio_manager;
+int SpeechRecognizerImpl::GetElapsedTimeMs() const {
+  return num_samples_recorded_ * 1000 / kAudioSampleRate;
 }
 
-bool SpeechRecognizerImpl::IsActive() const {
-  return (request_.get() != NULL);
+void SpeechRecognizerImpl::UpdateSignalAndNoiseLevels(const float& rms) {
+  // Calculate the input volume to display in the UI, smoothing towards the
+  // new level.
+  // TODO(primiano) Do we really need all this floating point arith here?
+  // Perhaps it might be quite expensive on mobile.
+  float level = (rms - kAudioMeterMinDb) /
+      (kAudioMeterDbRange / kAudioMeterRangeMaxUnclipped);
+  level = std::min(std::max(0.0f, level), kAudioMeterRangeMaxUnclipped);
+  if (level > audio_level_) {
+    audio_level_ += (level - audio_level_) * kUpSmoothingFactor;
+  } else {
+    audio_level_ += (level - audio_level_) * kDownSmoothingFactor;
+  }
+
+  float noise_level = (endpointer_.NoiseLevelDb() - kAudioMeterMinDb) /
+      (kAudioMeterDbRange / kAudioMeterRangeMaxUnclipped);
+  noise_level = std::min(std::max(0.0f, noise_level),
+                         kAudioMeterRangeMaxUnclipped);
+
+  listener_->OnAudioLevelsChange(
+      caller_id_, clipper_detected_clip_ ? 1.0f : audio_level_, noise_level);
 }
 
-bool SpeechRecognizerImpl::IsCapturingAudio() const {
-  return (audio_controller_.get() != NULL);
+const SpeechRecognitionEngine&
+    SpeechRecognizerImpl::recognition_engine() const {
+  return *(recognition_engine_.get());
+}
+
+void SpeechRecognizerImpl::SetAudioManagerForTesting(
+    AudioManager* audio_manager) {
+  testing_audio_manager_ = audio_manager;
+}
+
+SpeechRecognizerImpl::FSMEventArgs::FSMEventArgs()
+    : audio_error_code(0), audio_data(NULL) {
 }
 
 }  // namespace speech