llwindgen.h
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- /**
- * @file windgen.h
- * @brief Templated wind noise generation
- *
- * $LicenseInfo:firstyear=2002&license=viewergpl$
- *
- * Copyright (c) 2002-2010, 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