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)19double Loudness2Db(double loudness) { 20 return loudness * kLinear2DbScale / kLinear2LoudnessScale; 21 } 22 Linear2Loudness(double rms)23double Linear2Loudness(double rms) { 24 if (rms == 0) 25 return -15; 26 return kLinear2LoudnessScale * log(rms); 27 } 28 Db2Loudness(double db)29double Db2Loudness(double db) { 30 return db * kLinear2LoudnessScale / kLinear2DbScale; 31 } 32 Dbfs2Loudness(double dbfs)33double Dbfs2Loudness(double dbfs) { 34 return Db2Loudness(90 + dbfs); 35 } 36