1 /*
2  * Copyright (c) 2011-2015, Intel Corporation
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without modification,
6  * are permitted provided that the following conditions are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright notice, this
9  * list of conditions and the following disclaimer.
10  *
11  * 2. Redistributions in binary form must reproduce the above copyright notice,
12  * this list of conditions and the following disclaimer in the documentation and/or
13  * other materials provided with the distribution.
14  *
15  * 3. Neither the name of the copyright holder nor the names of its contributors
16  * may be used to endorse or promote products derived from this software without
17  * specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
21  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
23  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
24  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29  */
30 
31 #pragma once
32 
33 #include "LinearParameterAdaptation.h"
34 #include <cmath>
35 #include <limits>
36 
37 /**
38  * This class is used to perform a logarithmic adapation of type:
39  * (slopeNumerator / slopeDenominator) * log(parameter) + offset
40  * Since log(x) == -INFINITY , we can define FloorValue as a
41  *       x -> 0
42  * a lower bound limit for the adaptation
43  */
44 class CLogarithmicParameterAdaptation : public CLinearParameterAdaptation
45 {
46 public:
47     CLogarithmicParameterAdaptation();
48 
49     /**
50      * Conversions must satisfy the following: f(f'(a)) = a
51      * Let f=fromUserValue and f'=toUserValue
52      * if y = f(log(x)/log(base)), then
53      * f'(y) * log(base) = log (x)
54      * exp(f'(y)*log(base)) = x
55      */
56     virtual int64_t fromUserValue(double dValue) const;
57     virtual double toUserValue(int64_t iValue) const;
58 
59     virtual void showProperties(std::string &strResult) const;
60 
61     virtual bool fromXml(const CXmlElement &xmlElement, CXmlSerializingContext &serializingContext);
62 
63 private:
64     /**
65      * _dLogarithmBase characterizes the new logarithm logB(x) with
66      * the following property: logB(x) = log(x) / log(_dLogarithmBase).
67      * log being the base-e logarithm.
68      *
69      * std::exp(1) == e^1 == e == natural logarithm base
70      * Make sure there is no precision lose by using std::exp overload that
71      * return the same type as _dLogarithmBase
72      */
73     double _dLogarithmBase{std::exp(decltype(_dLogarithmBase){1})};
74     /**
75      * _dFloorValue reflects the lower bound for volume attenuation
76      */
77     double _dFloorValue{-std::numeric_limits<double>::infinity()};
78 };
79