60 lines
1.2 KiB
C++
60 lines
1.2 KiB
C++
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/*
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* DMOUtils.cpp
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* ------------
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* Purpose: Utility functions shared by DMO plugins
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* Notes : none
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* Authors: OpenMPT Devs
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* The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
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*/
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#include "stdafx.h"
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#include "DMOUtils.h"
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#ifndef NO_PLUGINS
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#include "../../Sndfile.h"
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#endif // !NO_PLUGINS
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OPENMPT_NAMESPACE_BEGIN
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#ifndef NO_PLUGINS
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namespace DMO
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{
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// Computes (log2(x) + 1) * 2 ^ (shiftL - shiftR) (x = -2^31...2^31)
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float logGain(float x, int32 shiftL, int32 shiftR)
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{
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uint32 intSample = static_cast<uint32>(static_cast<int64>(x));
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const uint32 sign = intSample & 0x80000000;
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if(sign)
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intSample = (~intSample) + 1;
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// Multiply until overflow (or edge shift factor is reached)
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while(shiftL > 0 && intSample < 0x80000000)
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{
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intSample += intSample;
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shiftL--;
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}
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// Unsign clipped sample
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if(intSample >= 0x80000000)
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{
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intSample &= 0x7FFFFFFF;
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shiftL++;
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}
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intSample = (shiftL << (31 - shiftR)) | (intSample >> shiftR);
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if(sign)
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intSample = ~intSample | sign;
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return static_cast<float>(static_cast<int32>(intSample));
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}
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} // namespace DMO
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#else
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MPT_MSVC_WORKAROUND_LNK4221(Distortion)
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#endif // !NO_PLUGINS
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OPENMPT_NAMESPACE_END
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