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      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;
     25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
     26  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     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