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