Speech refactoring: Reimplemented speech_recognizer as a FSM. (CL1.5)

content/browser/speech/speech_recognizer_impl.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_BROWSER_SPEECH_SPEECH_RECOGNIZER_IMPL_H_
 #define CONTENT_BROWSER_SPEECH_SPEECH_RECOGNIZER_IMPL_H_
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/browser/speech/endpointer/endpointer.h"
 #include "content/browser/speech/speech_recognition_engine.h"
 #include "content/public/browser/speech_recognizer.h"
 #include "content/public/common/speech_recognition_error.h"
+#include "content/public/common/speech_recognition_result.h"
 #include "media/audio/audio_input_controller.h"
 #include "net/url_request/url_request_context_getter.h"
 
 namespace content {
 class SpeechRecognitionEventListener;
 struct SpeechRecognitionResult;
 }
 
 namespace media {
 class AudioInputController;
 class AudioManager;
 }
 
 namespace speech {
 
-// Records audio, sends recorded audio to server and translates server response
-// to recognition result.
+// TODO(primiano) Next CL: Remove the Impl suffix and the exported
+// /content/public/browser/speech_recognizer.h interface since this class should

[jam, 2012/04/12 16:22:59]

that'd be great! (the fewer interfaces in content/public the better). i'm
curious, how would extensions use this?

+// not be visible outside (currently we need it for speech input extension API).
+
+// Handles speech recognition for a session (identified by |caller_id|), taking
+// care of audio capture, silence detection/endpointer and interaction with the
+// SpeechRecognitionEngine.
 class CONTENT_EXPORT SpeechRecognizerImpl
     : public NON_EXPORTED_BASE(content::SpeechRecognizer),
       public media::AudioInputController::EventHandler,
       public NON_EXPORTED_BASE(SpeechRecognitionEngineDelegate) {
  public:
   static const int kAudioSampleRate;
   static const ChannelLayout kChannelLayout;
   static const int kNumBitsPerAudioSample;
   static const int kNoSpeechTimeoutMs;
   static const int kEndpointerEstimationTimeMs;
 
   SpeechRecognizerImpl(
-    content::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);
+      content::SpeechRecognitionEventListener* listener,
+      int caller_id,
+      SpeechRecognitionEngine* engine);
   virtual ~SpeechRecognizerImpl();
 
   // content::SpeechRecognizer methods.
   virtual void StartRecognition() OVERRIDE;
   virtual void AbortRecognition() OVERRIDE;
   virtual void StopAudioCapture() OVERRIDE;
   virtual bool IsActive() const OVERRIDE;
   virtual bool IsCapturingAudio() const OVERRIDE;
   const SpeechRecognitionEngine& recognition_engine() const;
 
+ private:
+  friend class SpeechRecognizerImplTest;
+
+  enum FSMState {
+    STATE_IDLE = 0,
+    STATE_STARTING,
+    STATE_ESTIMATING_ENVIRONMENT,
+    STATE_WAITING_FOR_SPEECH,
+    STATE_RECOGNIZING,
+    STATE_WAITING_FINAL_RESULT,
+    STATE_MAX = STATE_WAITING_FINAL_RESULT
+  };
+
+  enum FSMEvent {
+    EVENT_ABORT = 0,
+    EVENT_START,
+    EVENT_STOP_CAPTURE,
+    EVENT_AUDIO_DATA,
+    EVENT_ENGINE_RESULT,
+    EVENT_ENGINE_ERROR,
+    EVENT_AUDIO_ERROR,
+    EVENT_MAX = EVENT_AUDIO_ERROR
+  };
+
+  struct FSMEventArgs {
+    explicit FSMEventArgs(FSMEvent event_value);
+    ~FSMEventArgs();
+
+    FSMEvent event;
+    int audio_error_code;
+    scoped_refptr<AudioChunk> audio_data;
+    content::SpeechRecognitionResult engine_result;
+    content::SpeechRecognitionError engine_error;
+  };
+
+  // Entry point for pushing any new external event into the recognizer FSM.
+  void DispatchEvent(const FSMEventArgs& event_args);
+
+  // Defines the behavior of the recognizer FSM, selecting the appropriate
+  // transition according to the current state and event.
+  FSMState ExecuteTransitionAndGetNextState(const FSMEventArgs& args);
+
+  // Process a new audio chunk in the audio pipeline (endpointer, vumeter, etc).
+  void ProcessAudioPipeline(const AudioChunk& raw_audio);
+
+  // The methods below handle transitions of the recognizer FSM.
+  FSMState StartRecording(const FSMEventArgs& event_args);
+  FSMState StartRecognitionEngine(const FSMEventArgs& event_args);
+  FSMState WaitEnvironmentEstimationCompletion(const FSMEventArgs& event_args);
+  FSMState DetectUserSpeechOrTimeout(const FSMEventArgs& event_args);
+  FSMState StopCaptureAndWaitForResult(const FSMEventArgs& event_args);
+  FSMState ProcessIntermediateResult(const FSMEventArgs& event_args);
+  FSMState ProcessFinalResult(const FSMEventArgs& event_args);
+  FSMState Abort(const FSMEventArgs& event_args);
+  FSMState AbortWithError(const content::SpeechRecognitionError* error);
+  FSMState AbortWithError(const content::SpeechRecognitionError& error);
+  FSMState DetectEndOfSpeech(const FSMEventArgs& event_args);
+  FSMState DoNothing(const FSMEventArgs& event_args) const;
+  FSMState NotFeasible(const FSMEventArgs& event_args);
+
+  // Returns the time span of captured audio samples since the start of capture.
+  int GetElapsedTimeMs() const;

[bulach, 2012/04/12 16:20:16]

nit: maybe use base::TimeDelta instead of specifying the time unit?

[Primiano Tucci (use gerrit), 2012/04/12 17:38:05]

Hmm it is not a true time (not derived by system clock) but an "ideal"
measurement based on the amount of audio frames received (which stands on the
assumption that audio is captured at the specified rate), thus it is always
integral and multiple of a known base.

+
+  // Calculates the input volume to be displayed in the UI, triggering the
+  // OnAudioLevelsChange event accordingly.
+  void UpdateSignalAndNoiseLevels(const float& rms, bool clip_detected);
+
+  void CloseAudioControllerAsynchronously();
+  void SetAudioManagerForTesting(media::AudioManager* audio_manager);
+
   // AudioInputController::EventHandler methods.
   virtual void OnCreated(media::AudioInputController* controller) OVERRIDE {}
   virtual void OnRecording(media::AudioInputController* controller) OVERRIDE {}
   virtual void OnError(media::AudioInputController* controller,
                        int error_code) OVERRIDE;
   virtual void OnData(media::AudioInputController* controller,
-                      const uint8* data,
-                      uint32 size) OVERRIDE;
+                      const uint8* data, uint32 size) OVERRIDE;
+
+  // Callback called on IO thread by audio_controller->Close().
+  void OnAudioClosed(media::AudioInputController*);

[bulach, 2012/04/12 16:20:16]

nit: move this method up before the virtuals

[Primiano Tucci (use gerrit), 2012/04/12 17:38:05]

Oops, sorry, did it again! :/

 
   // SpeechRecognitionEngineDelegate methods.
   virtual void OnSpeechRecognitionEngineResult(
       const content::SpeechRecognitionResult& result) OVERRIDE;
   virtual void OnSpeechRecognitionEngineError(
       const content::SpeechRecognitionError& error) OVERRIDE;
 
- private:
-  friend class SpeechRecognizerImplTest;
-
-  void InformErrorAndAbortRecognition(
-      content::SpeechRecognitionErrorCode error);
-  void SendRecordedAudioToServer();
-
-  void HandleOnError(int error_code);  // Handles OnError in the IO thread.
-
-  // Handles OnData in the IO thread.
-  void HandleOnData(scoped_refptr<AudioChunk> raw_audio);
-
-  void OnAudioClosed(media::AudioInputController*);
-
-  // Helper method which closes the audio controller and frees it asynchronously
-  // without blocking the IO thread.
-  void CloseAudioControllerAsynchronously();
-
-  void SetAudioManagerForTesting(media::AudioManager* audio_manager);
-
   content::SpeechRecognitionEventListener* listener_;
   media::AudioManager* testing_audio_manager_;
   scoped_ptr<SpeechRecognitionEngine> recognition_engine_;
   Endpointer endpointer_;
   scoped_refptr<media::AudioInputController> audio_controller_;
-  scoped_refptr<net::URLRequestContextGetter> context_getter_;
   int caller_id_;
-  std::string language_;
-  std::string grammar_;
-  bool filter_profanities_;
-  std::string hardware_info_;
-  std::string origin_url_;
   int num_samples_recorded_;
   float audio_level_;
+  bool is_dispatching_event_;
+  FSMState state_;
 
   DISALLOW_COPY_AND_ASSIGN(SpeechRecognizerImpl);
 };
 
 }  // namespace speech
 
 #endif  // CONTENT_BROWSER_SPEECH_SPEECH_RECOGNIZER_IMPL_H_