aac/libPCMutils/src/limiter.cpp - nest-cam/4320010/aac - Git at Google


 /* -----------------------------------------------------------------------------------------------------------
 Software License for The Fraunhofer FDK AAC Codec Library for Android

 © Copyright  1995 - 2013 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
   All rights reserved.

  1.    INTRODUCTION
 The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software that implements
 the MPEG Advanced Audio Coding ("AAC") encoding and decoding scheme for digital audio.
 This FDK AAC Codec software is intended to be used on a wide variety of Android devices.

 AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient general perceptual
 audio codecs. AAC-ELD is considered the best-performing full-bandwidth communications codec by
 independent studies and is widely deployed. AAC has been standardized by ISO and IEC as part
 of the MPEG specifications.

 Patent licenses for necessary patent claims for the FDK AAC Codec (including those of Fraunhofer)
 may be obtained through Via Licensing (www.vialicensing.com) or through the respective patent owners
 individually for the purpose of encoding or decoding bit streams in products that are compliant with
 the ISO/IEC MPEG audio standards. Please note that most manufacturers of Android devices already license
 these patent claims through Via Licensing or directly from the patent owners, and therefore FDK AAC Codec
 software may already be covered under those patent licenses when it is used for those licensed purposes only.

 Commercially-licensed AAC software libraries, including floating-point versions with enhanced sound quality,
 are also available from Fraunhofer. Users are encouraged to check the Fraunhofer website for additional
 applications information and documentation.

 2.    COPYRIGHT LICENSE

 Redistribution and use in source and binary forms, with or without modification, are permitted without
 payment of copyright license fees provided that you satisfy the following conditions:

 You must retain the complete text of this software license in redistributions of the FDK AAC Codec or
 your modifications thereto in source code form.

 You must retain the complete text of this software license in the documentation and/or other materials
 provided with redistributions of the FDK AAC Codec or your modifications thereto in binary form.
 You must make available free of charge copies of the complete source code of the FDK AAC Codec and your
 modifications thereto to recipients of copies in binary form.

 The name of Fraunhofer may not be used to endorse or promote products derived from this library without
 prior written permission.

 You may not charge copyright license fees for anyone to use, copy or distribute the FDK AAC Codec
 software or your modifications thereto.

 Your modified versions of the FDK AAC Codec must carry prominent notices stating that you changed the software
 and the date of any change. For modified versions of the FDK AAC Codec, the term
 "Fraunhofer FDK AAC Codec Library for Android" must be replaced by the term
 "Third-Party Modified Version of the Fraunhofer FDK AAC Codec Library for Android."

 3.    NO PATENT LICENSE

 NO EXPRESS OR IMPLIED LICENSES TO ANY PATENT CLAIMS, including without limitation the patents of Fraunhofer,
 ARE GRANTED BY THIS SOFTWARE LICENSE. Fraunhofer provides no warranty of patent non-infringement with
 respect to this software.

 You may use this FDK AAC Codec software or modifications thereto only for purposes that are authorized
 by appropriate patent licenses.

 4.    DISCLAIMER

 This FDK AAC Codec software is provided by Fraunhofer on behalf of the copyright holders and contributors
 "AS IS" and WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, including but not limited to the implied warranties
 of merchantability and fitness for a particular purpose. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 CONTRIBUTORS BE LIABLE for any direct, indirect, incidental, special, exemplary, or consequential damages,
 including but not limited to procurement of substitute goods or services; loss of use, data, or profits,
 or business interruption, however caused and on any theory of liability, whether in contract, strict
 liability, or tort (including negligence), arising in any way out of the use of this software, even if
 advised of the possibility of such damage.

 5.    CONTACT INFORMATION

 Fraunhofer Institute for Integrated Circuits IIS
 Attention: Audio and Multimedia Departments - FDK AAC LL
 Am Wolfsmantel 33
 91058 Erlangen, Germany

 www.iis.fraunhofer.de/amm
 amm-info@iis.fraunhofer.de
 ----------------------------------------------------------------------------------------------------------- */

 /************************  FDK PCM postprocessor module  *********************

    Author(s):   Matthias Neusinger
    Description: Hard limiter for clipping prevention

 *******************************************************************************/

 #include "limiter.h"


 struct TDLimiter {
   unsigned int  attack;
   FIXP_DBL      attackConst, releaseConst;
   unsigned int  attackMs, releaseMs, maxAttackMs;
   FIXP_PCM      threshold;
   unsigned int  channels, maxChannels;
   unsigned int  sampleRate, maxSampleRate;
   FIXP_DBL      cor, max;
   FIXP_DBL*     maxBuf;
   FIXP_DBL*     delayBuf;
   unsigned int  maxBufIdx, delayBufIdx;
   FIXP_DBL      smoothState0;
   FIXP_DBL      minGain;

   FIXP_DBL      additionalGainPrev;
   FIXP_DBL      additionalGainFilterState;
   FIXP_DBL      additionalGainFilterState1;
 };

 /* create limiter */
 TDLimiterPtr createLimiter(
                            unsigned int  maxAttackMs,
                            unsigned int  releaseMs,
                            INT_PCM       threshold,
                            unsigned int  maxChannels,
                            unsigned int  maxSampleRate
                            )
 {
   TDLimiterPtr limiter = NULL;
   unsigned int attack, release;
   FIXP_DBL attackConst, releaseConst, exponent;
   INT e_ans;

   /* calc attack and release time in samples */
   attack = (unsigned int)(maxAttackMs * maxSampleRate / 1000);
   release = (unsigned int)(releaseMs * maxSampleRate / 1000);

   /* alloc limiter struct */
   limiter = (TDLimiterPtr)FDKcalloc(1, sizeof(struct TDLimiter));
   if (!limiter) return NULL;

   /* alloc max and delay buffers */
   limiter->maxBuf   = (FIXP_DBL*)FDKcalloc(attack + 1, sizeof(FIXP_DBL));
   limiter->delayBuf = (FIXP_DBL*)FDKcalloc(attack * maxChannels, sizeof(FIXP_DBL));

   if (!limiter->maxBuf || !limiter->delayBuf) {
     destroyLimiter(limiter);
     return NULL;
   }

   /* attackConst = pow(0.1, 1.0 / (attack + 1)) */
   exponent = invFixp(attack+1);
   attackConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
   attackConst = scaleValue(attackConst, e_ans);

   /* releaseConst  = (float)pow(0.1, 1.0 / (release + 1)) */
   exponent = invFixp(release + 1);
   releaseConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
   releaseConst = scaleValue(releaseConst, e_ans);

   /* init parameters */
   limiter->attackMs      = maxAttackMs;
   limiter->maxAttackMs   = maxAttackMs;
   limiter->releaseMs     = releaseMs;
   limiter->attack        = attack;
   limiter->attackConst   = attackConst;
   limiter->releaseConst  = releaseConst;
   limiter->threshold     = (FIXP_PCM)threshold;
   limiter->channels      = maxChannels;
   limiter->maxChannels   = maxChannels;
   limiter->sampleRate    = maxSampleRate;
   limiter->maxSampleRate = maxSampleRate;

   resetLimiter(limiter);

   return limiter;
 }


 /* reset limiter */
 TDLIMITER_ERROR resetLimiter(TDLimiterPtr limiter)
 {
   if (limiter != NULL) {

     limiter->maxBufIdx = 0;
     limiter->delayBufIdx = 0;
     limiter->max = (FIXP_DBL)0;
     limiter->cor = FL2FXCONST_DBL(1.0f/(1<<1));
     limiter->smoothState0 = FL2FXCONST_DBL(1.0f/(1<<1));
     limiter->minGain = FL2FXCONST_DBL(1.0f/(1<<1));

     limiter->additionalGainPrev = FL2FXCONST_DBL(1.0f/(1<<TDL_GAIN_SCALING));
     limiter->additionalGainFilterState = FL2FXCONST_DBL(1.0f/(1<<TDL_GAIN_SCALING));
     limiter->additionalGainFilterState1 = FL2FXCONST_DBL(1.0f/(1<<TDL_GAIN_SCALING));

     FDKmemset(limiter->maxBuf,   0, (limiter->attack + 1) * sizeof(FIXP_DBL) );
     FDKmemset(limiter->delayBuf, 0, limiter->attack * limiter->channels * sizeof(FIXP_DBL) );
   }
   else {
     return TDLIMIT_INVALID_HANDLE;
   }

   return TDLIMIT_OK;
 }


 /* destroy limiter */
 TDLIMITER_ERROR destroyLimiter(TDLimiterPtr limiter)
 {
   if (limiter != NULL) {
     FDKfree(limiter->maxBuf);
     FDKfree(limiter->delayBuf);

     FDKfree(limiter);
   }
   else {
     return TDLIMIT_INVALID_HANDLE;
   }
   return TDLIMIT_OK;
 }

 /* apply limiter */
 TDLIMITER_ERROR applyLimiter(TDLimiterPtr limiter,
                  INT_PCM*    samples,
                  FIXP_DBL*    pGain,
                  const INT*   gain_scale,
                  const UINT   gain_size,
                  const UINT   gain_delay,
                  const UINT   nSamples)
 {
   unsigned int i, j;
   FIXP_PCM tmp1, tmp2;
   FIXP_DBL tmp, old, gain, additionalGain, additionalGainUnfiltered;
   FIXP_DBL minGain = FL2FXCONST_DBL(1.0f/(1<<1));

   FDK_ASSERT(gain_size == 1);
   FDK_ASSERT(gain_delay <= nSamples);

   if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

   {
     unsigned int channels       = limiter->channels;
     unsigned int attack         = limiter->attack;
     FIXP_DBL     attackConst    = limiter->attackConst;
     FIXP_DBL     releaseConst   = limiter->releaseConst;
     FIXP_DBL     threshold      = FX_PCM2FX_DBL(limiter->threshold)>>TDL_GAIN_SCALING;

     FIXP_DBL     max            = limiter->max;
     FIXP_DBL*    maxBuf         = limiter->maxBuf;
     unsigned int maxBufIdx      = limiter->maxBufIdx;
     FIXP_DBL     cor            = limiter->cor;
     FIXP_DBL*    delayBuf       = limiter->delayBuf;
     unsigned int delayBufIdx    = limiter->delayBufIdx;

     FIXP_DBL     smoothState0   = limiter->smoothState0;
     FIXP_DBL     additionalGainSmoothState = limiter->additionalGainFilterState;
     FIXP_DBL     additionalGainSmoothState1 = limiter->additionalGainFilterState1;

     for (i = 0; i < nSamples; i++) {

       if (i < gain_delay) {
         additionalGainUnfiltered = limiter->additionalGainPrev;
       } else {
         additionalGainUnfiltered = pGain[0];
       }

       /* Smooth additionalGain */
       /* [b,a] = butter(1, 0.01) */
       static const FIXP_SGL b[] = { FL2FXCONST_SGL(0.015466*2.0), FL2FXCONST_SGL( 0.015466*2.0) };
       static const FIXP_SGL a[] = { FL2FXCONST_SGL(1.000000), FL2FXCONST_SGL(-0.96907) };
       /* [b,a] = butter(1, 0.001) */
       //static const FIXP_SGL b[] = { FL2FXCONST_SGL(0.0015683*2.0), FL2FXCONST_SGL( 0.0015683*2.0) };
       //static const FIXP_SGL a[] = { FL2FXCONST_SGL(1.0000000), FL2FXCONST_SGL(-0.99686) };
       additionalGain = - fMult(additionalGainSmoothState, a[1]) + fMultDiv2( additionalGainUnfiltered, b[0]) + fMultDiv2(additionalGainSmoothState1, b[1]);
       additionalGainSmoothState1 = additionalGainUnfiltered;
       additionalGainSmoothState = additionalGain;

       /* Apply the additional scaling that has no delay and no smoothing */
       if (gain_scale[0] > 0) {
         additionalGain <<= gain_scale[0];
       } else {
         additionalGain >>= gain_scale[0];
       }

       /* get maximum absolute sample value of all channels, including the additional gain. */
       tmp1 = (FIXP_PCM)0;
       for (j = 0; j < channels; j++) {
           tmp2 = (FIXP_PCM)samples[i * channels + j];
           if (tmp2 == (FIXP_PCM)SAMPLE_MIN) /* protect fAbs from -1.0 value */
               tmp2 = (FIXP_PCM)(SAMPLE_MIN+1);
         tmp1 = fMax(tmp1, fAbs(tmp2));
       }
       tmp = SATURATE_LEFT_SHIFT(fMultDiv2(tmp1, additionalGain), 1, DFRACT_BITS);

       /* set threshold as lower border to save calculations in running maximum algorithm */
       tmp = fMax(tmp, threshold);

       /* running maximum */
       old = maxBuf[maxBufIdx];
       maxBuf[maxBufIdx] = tmp;

       if (tmp >= max) {
         /* new sample is greater than old maximum, so it is the new maximum */
         max = tmp;
       }
       else if (old < max) {
         /* maximum does not change, as the sample, which has left the window was
            not the maximum */
       }
       else {
         /* the old maximum has left the window, we have to search the complete
            buffer for the new max */
         max = maxBuf[0];
         for (j = 1; j <= attack; j++) {
           if (maxBuf[j] > max) max = maxBuf[j];
         }
       }
       maxBufIdx++;
       if (maxBufIdx >= attack+1) maxBufIdx = 0;

       /* calc gain */
       /* gain is downscaled by one, so that gain = 1.0 can be represented */
       if (max > threshold) {
         gain = fDivNorm(threshold, max)>>1;
       }
       else {
         gain = FL2FXCONST_DBL(1.0f/(1<<1));
       }

       /* gain smoothing, method: TDL_EXPONENTIAL */
       /* first order IIR filter with attack correction to avoid overshoots */

       /* correct the 'aiming' value of the exponential attack to avoid the remaining overshoot */
       if (gain < smoothState0) {
         cor = fMin(cor, fMultDiv2((gain - fMultDiv2(FL2FXCONST_SGL(0.1f*(1<<1)),smoothState0)), FL2FXCONST_SGL(1.11111111f/(1<<1)))<<2);
       }
       else {
         cor = gain;
       }

       /* smoothing filter */
       if (cor < smoothState0) {
         smoothState0 = fMult(attackConst,(smoothState0 - cor)) + cor;  /* attack */
         smoothState0 = fMax(smoothState0, gain); /* avoid overshooting target */
       }
       else {
         /* sign inversion twice to round towards +infinity,
            so that gain can converge to 1.0 again,
            for bit-identical output when limiter is not active */
         smoothState0 = -fMult(releaseConst,-(smoothState0 - cor)) + cor; /* release */
       }

       gain = smoothState0;

       /* lookahead delay, apply gain */
       for (j = 0; j < channels; j++) {

         tmp = delayBuf[delayBufIdx * channels + j];
         delayBuf[delayBufIdx * channels + j] = fMult((FIXP_PCM)samples[i * channels + j], additionalGain);

         /* Apply gain to delayed signal */
         if (gain < FL2FXCONST_DBL(1.0f/(1<<1)))
           tmp = fMult(tmp,gain<<1);

         samples[i * channels + j] = FX_DBL2FX_PCM((FIXP_DBL)SATURATE_LEFT_SHIFT(tmp,TDL_GAIN_SCALING,DFRACT_BITS));
       }
       delayBufIdx++;
       if (delayBufIdx >= attack) delayBufIdx = 0;

       /* save minimum gain factor */
       if (gain < minGain) minGain = gain;
     }


     limiter->max = max;
     limiter->maxBufIdx = maxBufIdx;
     limiter->cor = cor;
     limiter->delayBufIdx = delayBufIdx;

     limiter->smoothState0 = smoothState0;
     limiter->additionalGainFilterState = additionalGainSmoothState;
     limiter->additionalGainFilterState1 = additionalGainSmoothState1;

     limiter->minGain = minGain;

     limiter->additionalGainPrev = pGain[0];

     return TDLIMIT_OK;
   }
 }

 /* get delay in samples */
 unsigned int getLimiterDelay(TDLimiterPtr limiter)
 {
   FDK_ASSERT(limiter != NULL);
   return limiter->attack;
 }

 /* set number of channels */
 TDLIMITER_ERROR setLimiterNChannels(TDLimiterPtr limiter, unsigned int nChannels)
 {
   if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

   if (nChannels > limiter->maxChannels) return TDLIMIT_INVALID_PARAMETER;

   limiter->channels = nChannels;
   //resetLimiter(limiter);

   return TDLIMIT_OK;
 }

 /* set sampling rate */
 TDLIMITER_ERROR setLimiterSampleRate(TDLimiterPtr limiter, unsigned int sampleRate)
 {
   unsigned int attack, release;
   FIXP_DBL attackConst, releaseConst, exponent;
   INT e_ans;

   if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

   if (sampleRate > limiter->maxSampleRate) return TDLIMIT_INVALID_PARAMETER;

   /* update attack and release time in samples */
   attack = (unsigned int)(limiter->attackMs * sampleRate / 1000);
   release = (unsigned int)(limiter->releaseMs * sampleRate / 1000);

   /* attackConst = pow(0.1, 1.0 / (attack + 1)) */
   exponent = invFixp(attack+1);
   attackConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
   attackConst = scaleValue(attackConst, e_ans);

   /* releaseConst  = (float)pow(0.1, 1.0 / (release + 1)) */
   exponent = invFixp(release + 1);
   releaseConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
   releaseConst = scaleValue(releaseConst, e_ans);

   limiter->attack        = attack;
   limiter->attackConst   = attackConst;
   limiter->releaseConst  = releaseConst;
   limiter->sampleRate    = sampleRate;

   /* reset */
   //resetLimiter(limiter);

   return TDLIMIT_OK;
 }

 /* set attack time */
 TDLIMITER_ERROR setLimiterAttack(TDLimiterPtr limiter, unsigned int attackMs)
 {
   unsigned int attack;
   FIXP_DBL attackConst, exponent;
   INT e_ans;

   if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

   if (attackMs > limiter->maxAttackMs) return TDLIMIT_INVALID_PARAMETER;

   /* calculate attack time in samples */
   attack = (unsigned int)(attackMs * limiter->sampleRate / 1000);

   /* attackConst = pow(0.1, 1.0 / (attack + 1)) */
   exponent = invFixp(attack+1);
   attackConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
   attackConst = scaleValue(attackConst, e_ans);

   limiter->attack        = attack;
   limiter->attackConst   = attackConst;
   limiter->attackMs      = attackMs;

   return TDLIMIT_OK;
 }

 /* set release time */
 TDLIMITER_ERROR setLimiterRelease(TDLimiterPtr limiter, unsigned int releaseMs)
 {
   unsigned int release;
   FIXP_DBL releaseConst, exponent;
   INT e_ans;

   if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

   /* calculate  release time in samples */
   release = (unsigned int)(releaseMs * limiter->sampleRate / 1000);

   /* releaseConst  = (float)pow(0.1, 1.0 / (release + 1)) */
   exponent = invFixp(release + 1);
   releaseConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
   releaseConst = scaleValue(releaseConst, e_ans);

   limiter->releaseConst  = releaseConst;
   limiter->releaseMs     = releaseMs;

   return TDLIMIT_OK;
 }

 /* set limiter threshold */
 TDLIMITER_ERROR setLimiterThreshold(TDLimiterPtr limiter, INT_PCM threshold)
 {
   if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

   limiter->threshold = (FIXP_PCM)threshold;

   return TDLIMIT_OK;
 }

	/* -----------------------------------------------------------------------------------------------------------
	Software License for The Fraunhofer FDK AAC Codec Library for Android

	© Copyright 1995 - 2013 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
	All rights reserved.

	1. INTRODUCTION
	The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software that implements
	the MPEG Advanced Audio Coding ("AAC") encoding and decoding scheme for digital audio.
	This FDK AAC Codec software is intended to be used on a wide variety of Android devices.

	AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient general perceptual
	audio codecs. AAC-ELD is considered the best-performing full-bandwidth communications codec by
	independent studies and is widely deployed. AAC has been standardized by ISO and IEC as part
	of the MPEG specifications.

	Patent licenses for necessary patent claims for the FDK AAC Codec (including those of Fraunhofer)
	may be obtained through Via Licensing (www.vialicensing.com) or through the respective patent owners
	individually for the purpose of encoding or decoding bit streams in products that are compliant with
	the ISO/IEC MPEG audio standards. Please note that most manufacturers of Android devices already license
	these patent claims through Via Licensing or directly from the patent owners, and therefore FDK AAC Codec
	software may already be covered under those patent licenses when it is used for those licensed purposes only.

	Commercially-licensed AAC software libraries, including floating-point versions with enhanced sound quality,
	are also available from Fraunhofer. Users are encouraged to check the Fraunhofer website for additional
	applications information and documentation.

	2. COPYRIGHT LICENSE

	Redistribution and use in source and binary forms, with or without modification, are permitted without
	payment of copyright license fees provided that you satisfy the following conditions:

	You must retain the complete text of this software license in redistributions of the FDK AAC Codec or
	your modifications thereto in source code form.

	You must retain the complete text of this software license in the documentation and/or other materials
	provided with redistributions of the FDK AAC Codec or your modifications thereto in binary form.
	You must make available free of charge copies of the complete source code of the FDK AAC Codec and your
	modifications thereto to recipients of copies in binary form.

	The name of Fraunhofer may not be used to endorse or promote products derived from this library without
	prior written permission.

	You may not charge copyright license fees for anyone to use, copy or distribute the FDK AAC Codec
	software or your modifications thereto.

	Your modified versions of the FDK AAC Codec must carry prominent notices stating that you changed the software
	and the date of any change. For modified versions of the FDK AAC Codec, the term
	"Fraunhofer FDK AAC Codec Library for Android" must be replaced by the term
	"Third-Party Modified Version of the Fraunhofer FDK AAC Codec Library for Android."

	3. NO PATENT LICENSE

	NO EXPRESS OR IMPLIED LICENSES TO ANY PATENT CLAIMS, including without limitation the patents of Fraunhofer,
	ARE GRANTED BY THIS SOFTWARE LICENSE. Fraunhofer provides no warranty of patent non-infringement with
	respect to this software.

	You may use this FDK AAC Codec software or modifications thereto only for purposes that are authorized
	by appropriate patent licenses.

	4. DISCLAIMER

	This FDK AAC Codec software is provided by Fraunhofer on behalf of the copyright holders and contributors
	"AS IS" and WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, including but not limited to the implied warranties
	of merchantability and fitness for a particular purpose. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
	CONTRIBUTORS BE LIABLE for any direct, indirect, incidental, special, exemplary, or consequential damages,
	including but not limited to procurement of substitute goods or services; loss of use, data, or profits,
	or business interruption, however caused and on any theory of liability, whether in contract, strict
	liability, or tort (including negligence), arising in any way out of the use of this software, even if
	advised of the possibility of such damage.

	5. CONTACT INFORMATION

	Fraunhofer Institute for Integrated Circuits IIS
	Attention: Audio and Multimedia Departments - FDK AAC LL
	Am Wolfsmantel 33
	91058 Erlangen, Germany

	www.iis.fraunhofer.de/amm
	amm-info@iis.fraunhofer.de
	----------------------------------------------------------------------------------------------------------- */

	/********************** FDK PCM postprocessor module *******************

	Author(s): Matthias Neusinger
	Description: Hard limiter for clipping prevention

	*******************************************************************************/

	#include "limiter.h"


	struct TDLimiter {
	unsigned int attack;
	FIXP_DBL attackConst, releaseConst;
	unsigned int attackMs, releaseMs, maxAttackMs;
	FIXP_PCM threshold;
	unsigned int channels, maxChannels;
	unsigned int sampleRate, maxSampleRate;
	FIXP_DBL cor, max;
	FIXP_DBL* maxBuf;
	FIXP_DBL* delayBuf;
	unsigned int maxBufIdx, delayBufIdx;
	FIXP_DBL smoothState0;
	FIXP_DBL minGain;

	FIXP_DBL additionalGainPrev;
	FIXP_DBL additionalGainFilterState;
	FIXP_DBL additionalGainFilterState1;
	};

	/* create limiter */
	TDLimiterPtr createLimiter(
	unsigned int maxAttackMs,
	unsigned int releaseMs,
	INT_PCM threshold,
	unsigned int maxChannels,
	unsigned int maxSampleRate
	)
	{
	TDLimiterPtr limiter = NULL;
	unsigned int attack, release;
	FIXP_DBL attackConst, releaseConst, exponent;
	INT e_ans;

	/* calc attack and release time in samples */
	attack = (unsigned int)(maxAttackMs * maxSampleRate / 1000);
	release = (unsigned int)(releaseMs * maxSampleRate / 1000);

	/* alloc limiter struct */
	limiter = (TDLimiterPtr)FDKcalloc(1, sizeof(struct TDLimiter));
	if (!limiter) return NULL;

	/* alloc max and delay buffers */
	limiter->maxBuf = (FIXP_DBL*)FDKcalloc(attack + 1, sizeof(FIXP_DBL));
	limiter->delayBuf = (FIXP_DBL)FDKcalloc(attack maxChannels, sizeof(FIXP_DBL));

	if (!limiter->maxBuf \|\| !limiter->delayBuf) {
	destroyLimiter(limiter);
	return NULL;
	}

	/* attackConst = pow(0.1, 1.0 / (attack + 1)) */
	exponent = invFixp(attack+1);
	attackConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
	attackConst = scaleValue(attackConst, e_ans);

	/* releaseConst = (float)pow(0.1, 1.0 / (release + 1)) */
	exponent = invFixp(release + 1);
	releaseConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
	releaseConst = scaleValue(releaseConst, e_ans);

	/* init parameters */
	limiter->attackMs = maxAttackMs;
	limiter->maxAttackMs = maxAttackMs;
	limiter->releaseMs = releaseMs;
	limiter->attack = attack;
	limiter->attackConst = attackConst;
	limiter->releaseConst = releaseConst;
	limiter->threshold = (FIXP_PCM)threshold;
	limiter->channels = maxChannels;
	limiter->maxChannels = maxChannels;
	limiter->sampleRate = maxSampleRate;
	limiter->maxSampleRate = maxSampleRate;

	resetLimiter(limiter);

	return limiter;
	}


	/* reset limiter */
	TDLIMITER_ERROR resetLimiter(TDLimiterPtr limiter)
	{
	if (limiter != NULL) {

	limiter->maxBufIdx = 0;
	limiter->delayBufIdx = 0;
	limiter->max = (FIXP_DBL)0;
	limiter->cor = FL2FXCONST_DBL(1.0f/(1<<1));
	limiter->smoothState0 = FL2FXCONST_DBL(1.0f/(1<<1));
	limiter->minGain = FL2FXCONST_DBL(1.0f/(1<<1));

	limiter->additionalGainPrev = FL2FXCONST_DBL(1.0f/(1<<TDL_GAIN_SCALING));
	limiter->additionalGainFilterState = FL2FXCONST_DBL(1.0f/(1<<TDL_GAIN_SCALING));
	limiter->additionalGainFilterState1 = FL2FXCONST_DBL(1.0f/(1<<TDL_GAIN_SCALING));

	FDKmemset(limiter->maxBuf, 0, (limiter->attack + 1) * sizeof(FIXP_DBL) );
	FDKmemset(limiter->delayBuf, 0, limiter->attack * limiter->channels * sizeof(FIXP_DBL) );
	}
	else {
	return TDLIMIT_INVALID_HANDLE;
	}

	return TDLIMIT_OK;
	}


	/* destroy limiter */
	TDLIMITER_ERROR destroyLimiter(TDLimiterPtr limiter)
	{
	if (limiter != NULL) {
	FDKfree(limiter->maxBuf);
	FDKfree(limiter->delayBuf);

	FDKfree(limiter);
	}
	else {
	return TDLIMIT_INVALID_HANDLE;
	}
	return TDLIMIT_OK;
	}

	/* apply limiter */
	TDLIMITER_ERROR applyLimiter(TDLimiterPtr limiter,
	INT_PCM* samples,
	FIXP_DBL* pGain,
	const INT* gain_scale,
	const UINT gain_size,
	const UINT gain_delay,
	const UINT nSamples)
	{
	unsigned int i, j;
	FIXP_PCM tmp1, tmp2;
	FIXP_DBL tmp, old, gain, additionalGain, additionalGainUnfiltered;
	FIXP_DBL minGain = FL2FXCONST_DBL(1.0f/(1<<1));

	FDK_ASSERT(gain_size == 1);
	FDK_ASSERT(gain_delay <= nSamples);

	if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

	{
	unsigned int channels = limiter->channels;
	unsigned int attack = limiter->attack;
	FIXP_DBL attackConst = limiter->attackConst;
	FIXP_DBL releaseConst = limiter->releaseConst;
	FIXP_DBL threshold = FX_PCM2FX_DBL(limiter->threshold)>>TDL_GAIN_SCALING;

	FIXP_DBL max = limiter->max;
	FIXP_DBL* maxBuf = limiter->maxBuf;
	unsigned int maxBufIdx = limiter->maxBufIdx;
	FIXP_DBL cor = limiter->cor;
	FIXP_DBL* delayBuf = limiter->delayBuf;
	unsigned int delayBufIdx = limiter->delayBufIdx;

	FIXP_DBL smoothState0 = limiter->smoothState0;
	FIXP_DBL additionalGainSmoothState = limiter->additionalGainFilterState;
	FIXP_DBL additionalGainSmoothState1 = limiter->additionalGainFilterState1;

	for (i = 0; i < nSamples; i++) {

	if (i < gain_delay) {
	additionalGainUnfiltered = limiter->additionalGainPrev;
	} else {
	additionalGainUnfiltered = pGain[0];
	}

	/* Smooth additionalGain */
	/* [b,a] = butter(1, 0.01) */
	static const FIXP_SGL b[] = { FL2FXCONST_SGL(0.0154662.0), FL2FXCONST_SGL( 0.0154662.0) };
	static const FIXP_SGL a[] = { FL2FXCONST_SGL(1.000000), FL2FXCONST_SGL(-0.96907) };
	/* [b,a] = butter(1, 0.001) */
	//static const FIXP_SGL b[] = { FL2FXCONST_SGL(0.00156832.0), FL2FXCONST_SGL( 0.00156832.0) };
	//static const FIXP_SGL a[] = { FL2FXCONST_SGL(1.0000000), FL2FXCONST_SGL(-0.99686) };
	additionalGain = - fMult(additionalGainSmoothState, a[1]) + fMultDiv2( additionalGainUnfiltered, b[0]) + fMultDiv2(additionalGainSmoothState1, b[1]);
	additionalGainSmoothState1 = additionalGainUnfiltered;
	additionalGainSmoothState = additionalGain;

	/* Apply the additional scaling that has no delay and no smoothing */
	if (gain_scale[0] > 0) {
	additionalGain <<= gain_scale[0];
	} else {
	additionalGain >>= gain_scale[0];
	}

	/* get maximum absolute sample value of all channels, including the additional gain. */
	tmp1 = (FIXP_PCM)0;
	for (j = 0; j < channels; j++) {
	tmp2 = (FIXP_PCM)samples[i * channels + j];
	if (tmp2 == (FIXP_PCM)SAMPLE_MIN) /* protect fAbs from -1.0 value */
	tmp2 = (FIXP_PCM)(SAMPLE_MIN+1);
	tmp1 = fMax(tmp1, fAbs(tmp2));
	}
	tmp = SATURATE_LEFT_SHIFT(fMultDiv2(tmp1, additionalGain), 1, DFRACT_BITS);

	/* set threshold as lower border to save calculations in running maximum algorithm */
	tmp = fMax(tmp, threshold);

	/* running maximum */
	old = maxBuf[maxBufIdx];
	maxBuf[maxBufIdx] = tmp;

	if (tmp >= max) {
	/* new sample is greater than old maximum, so it is the new maximum */
	max = tmp;
	}
	else if (old < max) {
	/* maximum does not change, as the sample, which has left the window was
	not the maximum */
	}
	else {
	/* the old maximum has left the window, we have to search the complete
	buffer for the new max */
	max = maxBuf[0];
	for (j = 1; j <= attack; j++) {
	if (maxBuf[j] > max) max = maxBuf[j];
	}
	}
	maxBufIdx++;
	if (maxBufIdx >= attack+1) maxBufIdx = 0;

	/* calc gain */
	/* gain is downscaled by one, so that gain = 1.0 can be represented */
	if (max > threshold) {
	gain = fDivNorm(threshold, max)>>1;
	}
	else {
	gain = FL2FXCONST_DBL(1.0f/(1<<1));
	}

	/* gain smoothing, method: TDL_EXPONENTIAL */
	/* first order IIR filter with attack correction to avoid overshoots */

	/* correct the 'aiming' value of the exponential attack to avoid the remaining overshoot */
	if (gain < smoothState0) {
	cor = fMin(cor, fMultDiv2((gain - fMultDiv2(FL2FXCONST_SGL(0.1f*(1<<1)),smoothState0)), FL2FXCONST_SGL(1.11111111f/(1<<1)))<<2);
	}
	else {
	cor = gain;
	}

	/* smoothing filter */
	if (cor < smoothState0) {
	smoothState0 = fMult(attackConst,(smoothState0 - cor)) + cor; /* attack */
	smoothState0 = fMax(smoothState0, gain); /* avoid overshooting target */
	}
	else {
	/* sign inversion twice to round towards +infinity,
	so that gain can converge to 1.0 again,
	for bit-identical output when limiter is not active */
	smoothState0 = -fMult(releaseConst,-(smoothState0 - cor)) + cor; /* release */
	}

	gain = smoothState0;

	/* lookahead delay, apply gain */
	for (j = 0; j < channels; j++) {

	tmp = delayBuf[delayBufIdx * channels + j];
	delayBuf[delayBufIdx * channels + j] = fMult((FIXP_PCM)samples[i * channels + j], additionalGain);

	/* Apply gain to delayed signal */
	if (gain < FL2FXCONST_DBL(1.0f/(1<<1)))
	tmp = fMult(tmp,gain<<1);

	samples[i * channels + j] = FX_DBL2FX_PCM((FIXP_DBL)SATURATE_LEFT_SHIFT(tmp,TDL_GAIN_SCALING,DFRACT_BITS));
	}
	delayBufIdx++;
	if (delayBufIdx >= attack) delayBufIdx = 0;

	/* save minimum gain factor */
	if (gain < minGain) minGain = gain;
	}


	limiter->max = max;
	limiter->maxBufIdx = maxBufIdx;
	limiter->cor = cor;
	limiter->delayBufIdx = delayBufIdx;

	limiter->smoothState0 = smoothState0;
	limiter->additionalGainFilterState = additionalGainSmoothState;
	limiter->additionalGainFilterState1 = additionalGainSmoothState1;

	limiter->minGain = minGain;

	limiter->additionalGainPrev = pGain[0];

	return TDLIMIT_OK;
	}
	}

	/* get delay in samples */
	unsigned int getLimiterDelay(TDLimiterPtr limiter)
	{
	FDK_ASSERT(limiter != NULL);
	return limiter->attack;
	}

	/* set number of channels */
	TDLIMITER_ERROR setLimiterNChannels(TDLimiterPtr limiter, unsigned int nChannels)
	{
	if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

	if (nChannels > limiter->maxChannels) return TDLIMIT_INVALID_PARAMETER;

	limiter->channels = nChannels;
	//resetLimiter(limiter);

	return TDLIMIT_OK;
	}

	/* set sampling rate */
	TDLIMITER_ERROR setLimiterSampleRate(TDLimiterPtr limiter, unsigned int sampleRate)
	{
	unsigned int attack, release;
	FIXP_DBL attackConst, releaseConst, exponent;
	INT e_ans;

	if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

	if (sampleRate > limiter->maxSampleRate) return TDLIMIT_INVALID_PARAMETER;

	/* update attack and release time in samples */
	attack = (unsigned int)(limiter->attackMs * sampleRate / 1000);
	release = (unsigned int)(limiter->releaseMs * sampleRate / 1000);

	/* attackConst = pow(0.1, 1.0 / (attack + 1)) */
	exponent = invFixp(attack+1);
	attackConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
	attackConst = scaleValue(attackConst, e_ans);

	/* releaseConst = (float)pow(0.1, 1.0 / (release + 1)) */
	exponent = invFixp(release + 1);
	releaseConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
	releaseConst = scaleValue(releaseConst, e_ans);

	limiter->attack = attack;
	limiter->attackConst = attackConst;
	limiter->releaseConst = releaseConst;
	limiter->sampleRate = sampleRate;

	/* reset */
	//resetLimiter(limiter);

	return TDLIMIT_OK;
	}

	/* set attack time */
	TDLIMITER_ERROR setLimiterAttack(TDLimiterPtr limiter, unsigned int attackMs)
	{
	unsigned int attack;
	FIXP_DBL attackConst, exponent;
	INT e_ans;

	if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

	if (attackMs > limiter->maxAttackMs) return TDLIMIT_INVALID_PARAMETER;

	/* calculate attack time in samples */
	attack = (unsigned int)(attackMs * limiter->sampleRate / 1000);

	/* attackConst = pow(0.1, 1.0 / (attack + 1)) */
	exponent = invFixp(attack+1);
	attackConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
	attackConst = scaleValue(attackConst, e_ans);

	limiter->attack = attack;
	limiter->attackConst = attackConst;
	limiter->attackMs = attackMs;

	return TDLIMIT_OK;
	}

	/* set release time */
	TDLIMITER_ERROR setLimiterRelease(TDLimiterPtr limiter, unsigned int releaseMs)
	{
	unsigned int release;
	FIXP_DBL releaseConst, exponent;
	INT e_ans;

	if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

	/* calculate release time in samples */
	release = (unsigned int)(releaseMs * limiter->sampleRate / 1000);

	/* releaseConst = (float)pow(0.1, 1.0 / (release + 1)) */
	exponent = invFixp(release + 1);
	releaseConst = fPow(FL2FXCONST_DBL(0.1f), 0, exponent, 0, &e_ans);
	releaseConst = scaleValue(releaseConst, e_ans);

	limiter->releaseConst = releaseConst;
	limiter->releaseMs = releaseMs;

	return TDLIMIT_OK;
	}

	/* set limiter threshold */
	TDLIMITER_ERROR setLimiterThreshold(TDLimiterPtr limiter, INT_PCM threshold)
	{
	if ( limiter == NULL ) return TDLIMIT_INVALID_HANDLE;

	limiter->threshold = (FIXP_PCM)threshold;

	return TDLIMIT_OK;
	}