AGC2 as a new APM sub-module operating with hard-coded gain.

webrtc/modules/audio_processing/agc2/agc2_impl.h

+/*
+ *  Copyright (c) 2017 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_AGC2_AGC2_IMPL_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_AGC2_AGC2_IMPL_H_
+
+#include <string>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/base/criticalsection.h"
+#include "webrtc/modules/audio_processing/agc2/agc2.h"
+#include "webrtc/modules/audio_processing/include/audio_processing.h"
+
+namespace webrtc {
+
+// Adaptive Gain Control 2 (AGC2) is an alternative gain control module meant
+// to replace the previous AGC, the implementation of which is distributed
+// across several classes (namely, GainControlImpl,
+// GainControlForExperimentalAgc, AgcManagerDirect and Agc).
+// TODO(alessiob, aleloi): Make the changes listed below.
+// In addition to reorganizing the code, AGC2 also includes the following
+// changes:
+// - it switches to floating point, replacing the fixed point analysis of the
+//   legacy AGC;
+// - it does not work in the band split domain.

[aleloi, 2017/05/02 10:11:53]

A few points from peah's list are worth mentioning. 'Can operate at several
modes in parallel' etc.

[AleBzk, 2017/05/02 11:31:54]

I realized that maybe we want to document only what is implemented. Since the
goal of this CL is having an AGC that only implements fixed gain and that can be
used in combination with the existing AGC (to allow adaptive gain in cascade
with fixed gain), we could adapt this whole comment accordingly. WDYT?

[peah-webrtc, 2017/05/02 11:45:20]

That makes sense. I don't think the comment needs the todo list though. Those
parts should be clear from looking at the code.

+class Agc2Impl : public Agc2 {
+ public:
+  explicit Agc2Impl(rtc::CriticalSection* crit);

[peah-webrtc, 2017/05/02 11:01:08]

If this API is not public, you don't need to bother with critical sections. I
think we should only have locks inside APM and not in it's submodules.

[AleBzk, 2017/05/02 15:42:51]

Acknowledged.

+  ~Agc2Impl() override;
+
+  static bool Validate(const AudioProcessing::Config::Agc2& config);
+  static std::string ToString(const AudioProcessing::Config::Agc2& config);
+
+ private:
+  rtc::CriticalSection* const crit_;
+  RTC_DISALLOW_COPY_AND_ASSIGN(Agc2Impl);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AGC2_AGC2_IMPL_H_