First try on a fake analog volume control interface for use in audioproc_f.

webrtc/modules/audio_processing/test/identity_analog_volume_mapper.h

Index: webrtc/modules/audio_processing/test/identity_analog_volume_mapper.h
diff --git a/webrtc/modules/audio_processing/test/identity_analog_volume_mapper.h b/webrtc/modules/audio_processing/test/identity_analog_volume_mapper.h
new file mode 100644
index 0000000000000000000000000000000000000000..784b0f26d68ce6a21f8452af2740a91009b7f526
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+++ b/webrtc/modules/audio_processing/test/identity_analog_volume_mapper.h
@@ -0,0 +1,28 @@
+/*
+ *  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_TEST_IDENTITY_ANALOG_VOLUME_MAPPER_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_TEST_IDENTITY_ANALOG_VOLUME_MAPPER_H_
+
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/audio_processing/test/analog_volume_mapper.h"
+
+namespace webrtc {
+
+// An analog level mapper in which the level doesn't influence the
+// signal.
+class IdentityAnalogLevelMapper : public AnalogLevelMapper {

[AleBzk, 2017/04/21 10:35:49]

Great to have this! We might want to use it in audioproc_f when the simulation
is disabled (only if this improves readability).

[peah-webrtc, 2017/04/21 12:04:39]

I don't see the purpose of this class. I don't think we should simulate the
mic-gain, if we don't need to. If we want to have an example implementation of
the analog mapper I'd rather have a usable one, like a linear mapping, or a dB
mapping.

[aleloi, 2017/04/24 11:34:45]

I wanted to always use an AnalogLevelMapper instance in audioproc_f, even when
mic simulation is disabled. That way there would be less special cases between
mic simulation on and off. One way to do that was to use a fake mic that doesn't
affect the signal. Hence the Identity..LevelMapper.

+ public:
+  ~IdentityAnalogLevelMapper() = default;
+  float get_scaling_factor() const override { return 1.0f; }
+};
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_TEST_IDENTITY_ANALOG_VOLUME_MAPPER_H_