Reland of added functionality for specifying the initial signal level to use for the gain estimation

webrtc/modules/audio_processing/include/audio_processing.h

 /*
  *  Copyright (c) 2012 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_MODULES_AUDIO_PROCESSING_INCLUDE_AUDIO_PROCESSING_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_INCLUDE_AUDIO_PROCESSING_H_
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include <math.h>
 #include <stddef.h>  // size_t
 #include <stdio.h>  // FILE
 #include <vector>
 
 #include "webrtc/base/arraysize.h"
+#include "webrtc/base/optional.h"
 #include "webrtc/base/platform_file.h"
 #include "webrtc/modules/audio_processing/beamformer/array_util.h"
 #include "webrtc/modules/audio_processing/include/config.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
 struct AecCore;
 
 class AudioFrame;
@@ skipping 211 matching lines @@
   // processing. It is being introduced gradually and until it is fully
   // introduced, it is prone to change.
   // TODO(peah): Remove this comment once the new config scheme is fully rolled
   // out.
   //
   // The parameters and behavior of the audio processing module are controlled
   // by changing the default values in the AudioProcessing::Config struct.
   // The config is applied by passing the struct to the ApplyConfig method.
   struct Config {
     struct LevelController {
+      LevelController();
+      ~LevelController();

[the sun, 2016/09/14 10:00:59]

is the dtor really necessary?

[peah-webrtc, 2016/09/16 07:11:07]

clang complains if I remove it. So I guess it is needed.

       bool enabled = false;
+
+      // Sets the initial peak level to use inside the level controller in order
+      // to compute the signal gain. The unit for the peak level is dBFS and
+      // the allowed range is [-100, 0].
+      rtc::Optional<float> initial_level;

[the sun, 2016/09/14 10:00:59]

Why don't we always have an initial level?

[peah-webrtc, 2016/09/16 07:11:06]

We do. One way would be to hardcode the default initial value as a default
parameter, but I thought it was better to hardcode the default initial value as
a constant that is local to the level controller. I thought it made sense to
gather the code that controls the LevelController behavior in one place.

WDYT?

[the sun, 2016/09/16 08:00:40]

If I picture myself as someone who'd consider using the LC, I'd actually prefer
having the default value right here in the Config. For one thing, if the default
is changed down the line, it'd be easier for me to spot that, since it would be
visible as an interface change.

[peah-webrtc, 2016/09/16 11:36:05]

That is true. I agree.

     } level_controller;
   };
 
   // TODO(mgraczyk): Remove once all methods that use ChannelLayout are gone.
   enum ChannelLayout {
     kMono,
     // Left, right.
     kStereo,
     // Mono, keyboard, and mic.
     kMonoAndKeyboard,
@@ skipping 724 matching lines @@
   // This does not impact the size of frames passed to |ProcessStream()|.
   virtual int set_frame_size_ms(int size) = 0;
   virtual int frame_size_ms() const = 0;
 
  protected:
   virtual ~VoiceDetection() {}
 };
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_INCLUDE_AUDIO_PROCESSING_H_