Adds SpeechRecognizer which provides a simple interface to record and recognize speech.

chrome/browser/speech/speech_recognizer.h

+// Copyright (c) 2010 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 CHROME_BROWSER_SPEECH_SPEECH_RECOGNIZER_H_
+#define CHROME_BROWSER_SPEECH_SPEECH_RECOGNIZER_H_
+
+#include "base/ref_counted.h"
+#include "base/scoped_ptr.h"
+#include "media/audio/audio_input_controller.h"
+#include "chrome/browser/speech/speech_recognition_request.h"
+#include <list>
+#include <string>
+
+namespace speech_input {
+
+// Records audio, sends recorded audio to server and translates server response
+// to recognition result.
+class SpeechRecognizer
+    : public base::RefCountedThreadSafe<SpeechRecognizer>,
+      public media::AudioInputController::EventHandler,
+      public SpeechRecognitionRequestDelegate {
+ public:
+  // Implemented by the caller to receive recognition events.
+  class Delegate {
+   public:
+    virtual void SetRecognitionResult(int render_view_id, bool error,
+                                      const string16& value) = 0;
+
+    // Invoked when audio recording stops, either due to the end pointer
+    // detecting silence in user input or if |StopRecording| was called. The
+    // delegate has to wait until |DidCompleteRecognition| is invoked before
+    // destroying the |SpeechRecognizer| object.
+    virtual void DidCompleteRecording(int render_view_id) = 0;
+
+    // This is guaranteed to be the last method invoked in the recognition
+    // sequence and the |SpeechRecognizer| object can be freed up if necessary.
+    virtual void DidCompleteRecognition(int render_view_id) = 0;
+
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  SpeechRecognizer(Delegate* delegate, int render_view_id);
+  ~SpeechRecognizer();
+
+  // Starts audio recording and does recognition after recording ends. The same
+  // SpeechRecognizer instance can be used multiple times for speech recognition
+  // though each recognition request can be made only after the previous one
+  // completes (i.e. after receiving Delegate::DidCompleteRecognition).
+  bool StartRecording();
+
+  // Stops recording audio and starts recognition.
+  void StopRecording();
+
+  // Stops recording audio and cancels recognition. Any audio recorded so far
+  // gets discarded.
+  void CancelRecognition();
+
+  // AudioInputController::EventHandler methods.
+  void OnCreated(media::AudioInputController* controller) { }
+  void OnRecording(media::AudioInputController* controller) { }
+  void OnError(media::AudioInputController* controller, int error_code);
+  void OnData(media::AudioInputController* controller, const uint8* data,
+              uint32 size);
+
+  // SpeechRecognitionRequest::Delegate methods.
+  void SetRecognitionResult(bool error, const string16& value);
+
+ private:
+  void ReleaseAudioBuffers();
+
+  void HandleOnError(int error_code);  // Handles OnError in the IO thread.
+
+  // Handles OnData in the IO thread. Takes ownership of |data|.
+  void HandleOnData(std::string* data);
+
+  Delegate* delegate_;
+  int render_view_id_;
+
+  // Buffer holding the recorded audio. Owns the strings inside the list.
+  typedef std::list<std::string*> AudioBufferQueue;
+  AudioBufferQueue audio_buffers_;
+
+  scoped_ptr<SpeechRecognitionRequest> request_;
+  scoped_refptr<media::AudioInputController> audio_controller_;
+
+  DISALLOW_COPY_AND_ASSIGN(SpeechRecognizer);
+};
+
+// This typedef is to workaround the issue with certain versions of
+// Visual Studio where it gets confused between multiple Delegate
+// classes and gives a C2500 error. (I saw this error on the try bots -
+// the workaround was not needed for my machine).
+typedef SpeechRecognizer::Delegate SpeechRecognizerDelegate;
+
+}  // namespace speech_input
+
+#endif  // CHROME_BROWSER_SPEECH_SPEECH_RECOGNIZER_H_