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1 /*
2  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #include "webrtc/modules/audio_processing/agc/utility.h"
12 
13 #include <math.h>
14 
15 static const double kLog10 = 2.30258509299;
16 static const double kLinear2DbScale = 20.0 / kLog10;
17 static const double kLinear2LoudnessScale = 13.4 / kLog10;
18 
Loudness2Db(double loudness)19 double Loudness2Db(double loudness) {
20   return loudness * kLinear2DbScale / kLinear2LoudnessScale;
21 }
22 
Linear2Loudness(double rms)23 double Linear2Loudness(double rms) {
24   if (rms == 0)
25     return -15;
26   return kLinear2LoudnessScale * log(rms);
27 }
28 
Db2Loudness(double db)29 double Db2Loudness(double db) {
30   return db * kLinear2LoudnessScale / kLinear2DbScale;
31 }
32 
Dbfs2Loudness(double dbfs)33 double Dbfs2Loudness(double dbfs) {
34   return Db2Loudness(90 + dbfs);
35 }
36