137 lines
4.1 KiB
C++
137 lines
4.1 KiB
C++
/**
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* @file windgen.h
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* @brief Templated wind noise generation
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*
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* $LicenseInfo:firstyear=2002&license=viewergpl$
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*
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* Copyright (c) 2002-2009, Linden Research, Inc.
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*
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* Second Life Viewer Source Code
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* The source code in this file ("Source Code") is provided by Linden Lab
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* to you under the terms of the GNU General Public License, version 2.0
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* ("GPL"), unless you have obtained a separate licensing agreement
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* ("Other License"), formally executed by you and Linden Lab. Terms of
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* the GPL can be found in doc/GPL-license.txt in this distribution, or
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* online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
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*
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* There are special exceptions to the terms and conditions of the GPL as
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* it is applied to this Source Code. View the full text of the exception
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* in the file doc/FLOSS-exception.txt in this software distribution, or
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* online at
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* http://secondlifegrid.net/programs/open_source/licensing/flossexception
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*
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* By copying, modifying or distributing this software, you acknowledge
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* that you have read and understood your obligations described above,
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* and agree to abide by those obligations.
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*
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* ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
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* WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
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* COMPLETENESS OR PERFORMANCE.
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* $/LicenseInfo$
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*/
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#ifndef WINDGEN_H
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#define WINDGEN_H
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#include "llcommon.h"
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#include "llrand.h"
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template <class MIXBUFFERFORMAT_T>
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class LLWindGen
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{
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public:
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LLWindGen() :
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mTargetGain(0.f),
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mTargetFreq(100.f),
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mTargetPanGainR(0.5f),
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mbuf0(0.0),
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mbuf1(0.0),
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mbuf2(0.0),
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mbuf3(0.0),
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mbuf4(0.0),
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mbuf5(0.0),
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mY0(0.0),
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mY1(0.0),
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mCurrentGain(0.f),
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mCurrentFreq(100.f),
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mCurrentPanGainR(0.5f) {};
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static const U32 getInputSamplingRate() {return mInputSamplingRate;}
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// newbuffer = the buffer passed from the previous DSP unit.
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// numsamples = length in samples-per-channel at this mix time.
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// stride = number of bytes between start of each sample.
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// NOTE: generates L/R interleaved stereo
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MIXBUFFERFORMAT_T* windGenerate(MIXBUFFERFORMAT_T *newbuffer, int numsamples, int stride)
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{
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U8 *cursamplep = (U8*)newbuffer;
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double bandwidth = 50.0F;
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double a0,b1,b2;
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// calculate resonant filter coeffs
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b2 = exp(-(F_TWO_PI) * (bandwidth / mInputSamplingRate));
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while (numsamples--)
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{
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mCurrentFreq = (float)((0.999 * mCurrentFreq) + (0.001 * mTargetFreq));
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mCurrentGain = (float)((0.999 * mCurrentGain) + (0.001 * mTargetGain));
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mCurrentPanGainR = (float)((0.999 * mCurrentPanGainR) + (0.001 * mTargetPanGainR));
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b1 = (-4.0 * b2) / (1.0 + b2) * cos(F_TWO_PI * (mCurrentFreq / mInputSamplingRate));
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a0 = (1.0 - b2) * sqrt(1.0 - (b1 * b1) / (4.0 * b2));
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double nextSample;
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// start with white noise
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nextSample = ll_frand(2.0f) - 1.0f;
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// apply pinking filter
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mbuf0 = 0.997f * mbuf0 + 0.0126502f * nextSample;
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mbuf1 = 0.985f * mbuf1 + 0.0139083f * nextSample;
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mbuf2 = 0.950f * mbuf2 + 0.0205439f * nextSample;
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mbuf3 = 0.850f * mbuf3 + 0.0387225f * nextSample;
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mbuf4 = 0.620f * mbuf4 + 0.0465932f * nextSample;
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mbuf5 = 0.250f * mbuf5 + 0.1093477f * nextSample;
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nextSample = mbuf0 + mbuf1 + mbuf2 + mbuf3 + mbuf4 + mbuf5;
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// do a resonant filter on the noise
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nextSample = (double)( a0 * nextSample - b1 * mY0 - b2 * mY1 );
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mY1 = mY0;
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mY0 = nextSample;
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nextSample *= mCurrentGain;
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MIXBUFFERFORMAT_T sample;
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sample = llfloor(((F32)nextSample*32768.f*(1.0f - mCurrentPanGainR))+0.5f);
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*(MIXBUFFERFORMAT_T*)cursamplep = llclamp(sample, (MIXBUFFERFORMAT_T)-32768, (MIXBUFFERFORMAT_T)32767);
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cursamplep += stride;
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sample = llfloor(((F32)nextSample*32768.f*mCurrentPanGainR)+0.5f);
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*(MIXBUFFERFORMAT_T*)cursamplep = llclamp(sample, (MIXBUFFERFORMAT_T)-32768, (MIXBUFFERFORMAT_T)32767);
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cursamplep += stride;
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}
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return newbuffer;
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}
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F32 mTargetGain;
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F32 mTargetFreq;
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F32 mTargetPanGainR;
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private:
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static const U32 mInputSamplingRate = 44100;
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F64 mbuf0;
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F64 mbuf1;
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F64 mbuf2;
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F64 mbuf3;
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F64 mbuf4;
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F64 mbuf5;
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F64 mY0;
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F64 mY1;
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F32 mCurrentGain;
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F32 mCurrentFreq;
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F32 mCurrentPanGainR;
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};
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#endif
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