Turn webrtc::Vad into a pure virtual interface

webrtc/common_audio/vad/include/vad.h

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_COMMON_AUDIO_VAD_INCLUDE_VAD_H_
 #define WEBRTC_COMMON_AUDIO_VAD_INCLUDE_VAD_H_
 
 #include "webrtc/base/checks.h"
+#include "webrtc/base/scoped_ptr.h"
 #include "webrtc/common_audio/vad/include/webrtc_vad.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
-// This is a C++ wrapper class for WebRtcVad.
 class Vad {
  public:
   enum Aggressiveness {
     kVadNormal = 0,
     kVadLowBitrate = 1,
     kVadAggressive = 2,
     kVadVeryAggressive = 3
   };
 
   enum Activity { kPassive = 0, kActive = 1, kError = -1 };
 
-  explicit Vad(enum Aggressiveness mode);
+  virtual ~Vad() = default;
 
-  virtual ~Vad();
-
+  // Calculates a VAD decision for the given audio frame. Valid sample rates
+  // are 8000, 16000, and 32000 Hz; the number of samples must be such that the
+  // frame is 10, 20, or 30 ms long.
   virtual Activity VoiceActivity(const int16_t* audio,
                                  size_t num_samples,
-                                 int sample_rate_hz);
+                                 int sample_rate_hz) = 0;
 
-  // Reset VAD state.
-  virtual void Reset();
-
- private:
-  VadInst* handle_;
-  Aggressiveness aggressiveness_;
+  // Resets VAD state.
+  virtual void Reset() = 0;
 };
 
+// Returns a Vad instance that's implemented on top of WebRtcVad.
+rtc::scoped_ptr<Vad> CreateVad(Vad::Aggressiveness aggressiveness);
+
 }  // namespace webrtc
+
 #endif  // WEBRTC_COMMON_AUDIO_VAD_INCLUDE_VAD_H_