path: root/libAACenc/src/intensity.cpp

/******************************** MPEG Audio Encoder **************************

                     (C) Copyright Fraunhofer IIS (2010)
                               All Rights Reserved

    Please be advised that this software and/or program delivery is
    Confidential Information of Fraunhofer and subject to and covered by the

    Fraunhofer IIS Software Evaluation Agreement
    between Google Inc. and  Fraunhofer
    effective and in full force since March 1, 2012.

    You may use this software and/or program only under the terms and
    conditions described in the above mentioned Fraunhofer IIS Software
    Evaluation Agreement. Any other and/or further use requires a separate agreement.


   This software and/or program is protected by copyright law and international
   treaties. Any reproduction or distribution of this software and/or program,
   or any portion of it, may result in severe civil and criminal penalties, and
   will be prosecuted to the maximum extent possible under law.

   $Id$

   Initial author:       A. Horndasch (code originally from lwr) / Josef Hoepfl (FDK)
   contents/description: intensity stereo processing

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

#include "intensity.h"
#include "interface.h"
#include "psy_configuration.h"
#include "psy_const.h"
#include "qc_main.h"
#include "bit_cnt.h"

/* only set an IS seed it left/right channel correlation is above IS_CORR_THRESH */
#define IS_CORR_THRESH                FL2FXCONST_DBL(0.95f)

/* when expanding the IS region to more SFBs only accept an error that is
 * not more than IS_TOTAL_ERROR_THRESH overall and
 * not more than IS_LOCAL_ERROR_THRESH for the current SFB */
#define IS_TOTAL_ERROR_THRESH         FL2FXCONST_DBL(0.04f)
#define IS_LOCAL_ERROR_THRESH         FL2FXCONST_DBL(0.01f)

/* the maximum allowed change of the intensity direction (unit: IS scale) - scaled with factor 0.25 - */
#define IS_DIRECTION_DEVIATION_THRESH_SF 2
#define IS_DIRECTION_DEVIATION_THRESH FL2FXCONST_DBL(2.0f/(1<<IS_DIRECTION_DEVIATION_THRESH_SF))

/* IS regions need to have a minimal percentage of the overall loudness, e.g. 0.06 == 6% */
#define IS_REGION_MIN_LOUDNESS        FL2FXCONST_DBL(0.1f)

/* only perform IS if IS_MIN_SFBS neighboring SFBs can be processed */
#define IS_MIN_SFBS                   6

/* only do IS if
 * if IS_LEFT_RIGHT_RATIO_THRESH < sfbEnergyLeft[sfb]/sfbEnergyRight[sfb] < 1 / IS_LEFT_RIGHT_RATIO_THRESH
 * -> no IS if the panning angle is not far from the middle, MS will do */
/* this is equivalent to a scale of +/-1.02914634566 */
#define IS_LEFT_RIGHT_RATIO_THRESH    FL2FXCONST_DBL(0.7f)

/* scalefactor of realScale */
#define REAL_SCALE_SF                    1

/* scalefactor overallLoudness */
#define OVERALL_LOUDNESS_SF              6

/* scalefactor for sum over max samples per goup */
#define MAX_SFB_PER_GROUP_SF             6

/* scalefactor for sum of mdct spectrum */
#define MDCT_SPEC_SF                     6


typedef struct
{

  FIXP_DBL corr_thresh;                 /*!< Only set an IS seed it left/right channel correlation is above corr_thresh */

  FIXP_DBL total_error_thresh;          /*!< When expanding the IS region to more SFBs only accept an error that is
                                             not more than 'total_error_thresh' overall. */

  FIXP_DBL local_error_thresh;          /*!< When expanding the IS region to more SFBs only accept an error that is
                                             not more than 'local_error_thresh' for the current SFB. */

  FIXP_DBL direction_deviation_thresh;  /*!< The maximum allowed change of the intensity direction (unit: IS scale) */

  FIXP_DBL is_region_min_loudness;      /*!< IS regions need to have a minimal percentage of the overall loudness, e.g. 0.06 == 6% */

  INT      min_is_sfbs;                 /*!< Only perform IS if 'min_is_sfbs' neighboring SFBs can be processed */

  FIXP_DBL left_right_ratio_threshold;  /*!< No IS if the panning angle is not far from the middle, MS will do */

} INTENSITY_PARAMETERS;


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

    functionname: calcSfbMaxScale

    description:  Calc max value in scalefactor band

    input:        *mdctSpectrum
                   l1
                   l2

    output:       none

    returns:      scalefactor

*****************************************************************************/
static INT
calcSfbMaxScale(const FIXP_DBL *mdctSpectrum,
                const INT       l1,
                const INT       l2)
{
  INT i;
  INT sfbMaxScale;
  FIXP_DBL maxSpc;

  maxSpc = FL2FXCONST_DBL(0.0);
  for (i=l1; i<l2; i++) {
    FIXP_DBL tmp = fixp_abs((FIXP_DBL)mdctSpectrum[i]);
    maxSpc = fixMax(maxSpc, tmp);
  }
  sfbMaxScale = (maxSpc==FL2FXCONST_DBL(0.0)) ? (DFRACT_BITS-2) : CntLeadingZeros(maxSpc)-1;

  return sfbMaxScale;
 }


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

    functionname: FDKaacEnc_initIsParams

    description:  Initialization of intensity parameters

    input:        isParams

    output:       isParams

    returns:      none

*****************************************************************************/
static void
FDKaacEnc_initIsParams(INTENSITY_PARAMETERS *isParams)
{
  isParams->corr_thresh                = IS_CORR_THRESH;
  isParams->total_error_thresh         = IS_TOTAL_ERROR_THRESH;
  isParams->local_error_thresh         = IS_LOCAL_ERROR_THRESH;
  isParams->direction_deviation_thresh = IS_DIRECTION_DEVIATION_THRESH;
  isParams->is_region_min_loudness     = IS_REGION_MIN_LOUDNESS;
  isParams->min_is_sfbs                = IS_MIN_SFBS;
  isParams->left_right_ratio_threshold = IS_LEFT_RIGHT_RATIO_THRESH;
}


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

    functionname: FDKaacEnc_prepareIntensityDecision

    description:  Prepares intensity decision

    input:        sfbEnergyLeft
                  sfbEnergyRight
                  sfbEnergyLdDataLeft
                  sfbEnergyLdDataRight
                  mdctSpectrumLeft
                  sfbEnergyLdDataRight
                  isParams

    output:       hrrErr            scale: none
                  isMask            scale: none
                  realScale         scale: LD_DATA_SHIFT + REAL_SCALE_SF
                  normSfbLoudness   scale: none

    returns:      none

*****************************************************************************/
static void
FDKaacEnc_prepareIntensityDecision(const FIXP_DBL    *sfbEnergyLeft,
                                   const FIXP_DBL    *sfbEnergyRight,
                                   const FIXP_DBL    *sfbEnergyLdDataLeft,
                                   const FIXP_DBL    *sfbEnergyLdDataRight,
                                   const FIXP_DBL    *mdctSpectrumLeft,
                                   const FIXP_DBL    *mdctSpectrumRight,
                                   const INTENSITY_PARAMETERS *isParams,
                                   FIXP_DBL    *hrrErr,
                                   INT         *isMask,
                                   FIXP_DBL    *realScale,
                                   FIXP_DBL    *normSfbLoudness,
                                   const INT    sfbCnt,
                                   const INT    sfbPerGroup,
                                   const INT    maxSfbPerGroup,
                                   const INT   *sfbOffset)
{
  INT j,sfb,sfboffs;
  INT grpCounter;

  /* temporary variables to compute loudness */
  FIXP_DBL overallLoudness[MAX_NO_OF_GROUPS];

  /* temporary variables to compute correlation */
  FIXP_DBL channelCorr[MAX_GROUPED_SFB];
  FIXP_DBL ml, mr;
  FIXP_DBL prod_lr;
  FIXP_DBL square_l, square_r;
  FIXP_DBL tmp_l, tmp_r;
  FIXP_DBL inv_n;

  FDKmemclear(channelCorr,     MAX_GROUPED_SFB*sizeof(FIXP_DBL));
  FDKmemclear(normSfbLoudness, MAX_GROUPED_SFB*sizeof(FIXP_DBL));
  FDKmemclear(overallLoudness, MAX_NO_OF_GROUPS*sizeof(FIXP_DBL));
  FDKmemclear(realScale,       MAX_GROUPED_SFB*sizeof(FIXP_DBL));

  for (grpCounter = 0, sfboffs = 0; sfboffs < sfbCnt; sfboffs += sfbPerGroup, grpCounter++) {
    overallLoudness[grpCounter] = FL2FXCONST_DBL(0.0f);
    for (sfb = 0; sfb < maxSfbPerGroup; sfb++) {
      INT sL,sR,s;
      FIXP_DBL isValue = sfbEnergyLdDataLeft[sfb+sfboffs]-sfbEnergyLdDataRight[sfb+sfboffs];

      /* delimitate intensity scale value to representable range */
      realScale[sfb + sfboffs] = fixMin(FL2FXCONST_DBL(60.f/(1<<(REAL_SCALE_SF+LD_DATA_SHIFT))), fixMax(FL2FXCONST_DBL(-60.f/(1<<(REAL_SCALE_SF+LD_DATA_SHIFT))), isValue));

      sL = fixMax(0,(CntLeadingZeros(sfbEnergyLeft[sfb + sfboffs])-1));
      sR = fixMax(0,(CntLeadingZeros(sfbEnergyRight[sfb + sfboffs])-1));
      s  = (fixMin(sL,sR)>>2)<<2;
      normSfbLoudness[sfb + sfboffs] = sqrtFixp(sqrtFixp(((sfbEnergyLeft[sfb + sfboffs]<<s) >> 1) + ((sfbEnergyRight[sfb + sfboffs]<<s) >> 1))) >> (s>>2);

      overallLoudness[grpCounter] += normSfbLoudness[sfb + sfboffs] >> OVERALL_LOUDNESS_SF;
      /* don't do intensity if
       * - panning angle is too close to the middle or
       * - one channel is non-existent or
       * - if it is dual mono */
      if(   (sfbEnergyLeft[sfb + sfboffs] >= fMult(isParams->left_right_ratio_threshold,sfbEnergyRight[sfb + sfboffs]))
         && (fMult(isParams->left_right_ratio_threshold,sfbEnergyLeft[sfb + sfboffs]) <= sfbEnergyRight[sfb + sfboffs]) ) {

        /* this will prevent post processing from considering this SFB for merging */
        hrrErr[sfb + sfboffs] = FL2FXCONST_DBL(1.0/8.0);
      }
    }
  }

  for (grpCounter = 0, sfboffs = 0; sfboffs < sfbCnt; sfboffs += sfbPerGroup, grpCounter++) {
    INT invOverallLoudnessSF;
    FIXP_DBL invOverallLoudness;

    if (overallLoudness[grpCounter] == FL2FXCONST_DBL(0.0)) {
      invOverallLoudness = FL2FXCONST_DBL(0.0);
      invOverallLoudnessSF = 0;
    }
    else {
      invOverallLoudness = fDivNorm((FIXP_DBL)MAXVAL_DBL, overallLoudness[grpCounter],&invOverallLoudnessSF);
      invOverallLoudnessSF = invOverallLoudnessSF - OVERALL_LOUDNESS_SF + 1; /* +1: compensate fMultDiv2() in subsequent loop */
    }
    invOverallLoudnessSF = fixMin(fixMax(invOverallLoudnessSF,-(DFRACT_BITS-1)),DFRACT_BITS-1);

    for (sfb = 0; sfb < maxSfbPerGroup; sfb++) {
      FIXP_DBL tmp;

      tmp = fMultDiv2((normSfbLoudness[sfb + sfboffs]>>OVERALL_LOUDNESS_SF)<<OVERALL_LOUDNESS_SF,invOverallLoudness);

      normSfbLoudness[sfb + sfboffs] = scaleValue(tmp, invOverallLoudnessSF);

      channelCorr[sfb + sfboffs] = FL2FXCONST_DBL(0.0f);

      FDK_ASSERT(50 >= 49);
      /* max width of scalefactorband is 96; width's are always even */
      /* inv_n is scaled with factor 2 to compensate fMultDiv2() in subsequent loops */
      inv_n = GetInvInt((sfbOffset[sfb + sfboffs + 1] - sfbOffset[sfb + sfboffs])>>1);

      if (inv_n > FL2FXCONST_DBL(0.0f)) {
        INT s,sL,sR;

        /* correlation := Pearson's product-moment coefficient */
        /* compute correlation between channels and check if it is over threshold */
        ml       = FL2FXCONST_DBL(0.0f);
        mr       = FL2FXCONST_DBL(0.0f);
        prod_lr  = FL2FXCONST_DBL(0.0f);
        square_l = FL2FXCONST_DBL(0.0f);
        square_r = FL2FXCONST_DBL(0.0f);

        sL = calcSfbMaxScale(mdctSpectrumLeft,sfbOffset[sfb+sfboffs],sfbOffset[sfb+sfboffs+1]);
        sR = calcSfbMaxScale(mdctSpectrumRight,sfbOffset[sfb+sfboffs],sfbOffset[sfb+sfboffs+1]);
        s = fixMin(sL,sR);

        for (j = sfbOffset[sfb + sfboffs]; j < sfbOffset[sfb + sfboffs + 1]; j++) {
          ml += fMultDiv2((mdctSpectrumLeft[j]  << s),inv_n);             // scaled with mdctScale - s + inv_n
          mr += fMultDiv2((mdctSpectrumRight[j] << s),inv_n);             // scaled with mdctScale - s + inv_n
        }
        ml = fMultDiv2(ml,inv_n);                                         // scaled with mdctScale - s + inv_n
        mr = fMultDiv2(mr,inv_n);                                         // scaled with mdctScale - s + inv_n

        for (j = sfbOffset[sfb + sfboffs]; j < sfbOffset[sfb + sfboffs + 1]; j++) {
          tmp_l = fMultDiv2((mdctSpectrumLeft[j]  << s),inv_n) - ml;      // scaled with mdctScale - s + inv_n
          tmp_r = fMultDiv2((mdctSpectrumRight[j] << s),inv_n) - mr;      // scaled with mdctScale - s + inv_n

          prod_lr  += fMultDiv2(tmp_l,tmp_r);                             // scaled with 2*(mdctScale - s + inv_n) + 1
          square_l += fPow2Div2(tmp_l);                                   // scaled with 2*(mdctScale - s + inv_n) + 1
          square_r += fPow2Div2(tmp_r);                                   // scaled with 2*(mdctScale - s + inv_n) + 1
        }
        prod_lr  = prod_lr  << 1;                                         // scaled with 2*(mdctScale - s + inv_n)
        square_l = square_l << 1;                                         // scaled with 2*(mdctScale - s + inv_n)
        square_r = square_r << 1;                                         // scaled with 2*(mdctScale - s + inv_n)

        if (square_l > FL2FXCONST_DBL(0.0f) && square_r > FL2FXCONST_DBL(0.0f)) {
          INT channelCorrSF = 0;

          /* local scaling of square_l and square_r is compensated after sqrt calculation */
          sL  = fixMax(0,(CntLeadingZeros(square_l)-1));
          sR  = fixMax(0,(CntLeadingZeros(square_r)-1));
          s   = ((sL + sR)>>1)<<1;
          sL  = fixMin(sL,s);
          sR  = s-sL;
          tmp = fMult(square_l<<sL,square_r<<sR);
          tmp = sqrtFixp(tmp);

          FDK_ASSERT(tmp > FL2FXCONST_DBL(0.0f));

          /* numerator and denominator have the same scaling */
          if (prod_lr < FL2FXCONST_DBL(0.0f) ) {
            channelCorr[sfb + sfboffs] = -(fDivNorm(-prod_lr,tmp,&channelCorrSF));

          }
          else {
            channelCorr[sfb + sfboffs] =  (fDivNorm( prod_lr,tmp,&channelCorrSF));
          }
          channelCorrSF = fixMin(fixMax(( channelCorrSF + ((sL+sR)>>1)),-(DFRACT_BITS-1)),DFRACT_BITS-1);

          if (channelCorrSF < 0) {
            channelCorr[sfb + sfboffs] = channelCorr[sfb + sfboffs] >> (-channelCorrSF);
          }
          else {
            /* avoid overflows due to limited computational accuracy */
            if ( fAbs(channelCorr[sfb + sfboffs]) > (((FIXP_DBL)MAXVAL_DBL)>>channelCorrSF) ) {
              if (channelCorr[sfb + sfboffs] < FL2FXCONST_DBL(0.0f))
                channelCorr[sfb + sfboffs] = -(FIXP_DBL) MAXVAL_DBL;
              else
                channelCorr[sfb + sfboffs] =  (FIXP_DBL) MAXVAL_DBL;
            }
            else {
              channelCorr[sfb + sfboffs] = channelCorr[sfb + sfboffs] << channelCorrSF;
            }
          }
        }
      }

      /* for post processing: hrrErr is the error in terms of (too little) correlation
       * weighted with the loudness of the SFB; SFBs with small hrrErr can be merged */
      if (hrrErr[sfb + sfboffs] == FL2FXCONST_DBL(1.0/8.0)) {
        continue;
      }

      hrrErr[sfb + sfboffs] = fMultDiv2((FL2FXCONST_DBL(0.25f)-(channelCorr[sfb + sfboffs]>>2)),normSfbLoudness[sfb + sfboffs]);

      /* set IS mask/vector to 1, if correlation is high enough */
      if (fAbs(channelCorr[sfb + sfboffs]) >= isParams->corr_thresh) {
        isMask[sfb + sfboffs] = 1;
      }
    }
  }
}


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

    functionname: FDKaacEnc_finalizeIntensityDecision

    description:  Finalizes intensity decision

    input:        isParams          scale: none
                  hrrErr            scale: none
                  realIsScale       scale: LD_DATA_SHIFT + REAL_SCALE_SF
                  normSfbLoudness   scale: none

    output:       isMask            scale: none

    returns:      none

*****************************************************************************/
static void
FDKaacEnc_finalizeIntensityDecision(const FIXP_DBL *hrrErr,
                                    INT            *isMask,
                                    const FIXP_DBL *realIsScale,
                                    const FIXP_DBL *normSfbLoudness,
                                    const INTENSITY_PARAMETERS *isParams,
                                    const INT       sfbCnt,
                                    const INT       sfbPerGroup,
                                    const INT       maxSfbPerGroup)
{
  INT sfb,sfboffs, j;
  INT startIsSfb = 0;
  INT inIsBlock;
  INT currentIsSfbCount;
  FIXP_DBL overallHrrError;
  FIXP_DBL isScaleLast = FL2FXCONST_DBL(0.0f);
  FIXP_DBL isRegionLoudness;

  for (sfboffs = 0; sfboffs < sfbCnt; sfboffs += sfbPerGroup) {
    inIsBlock = 0;
    currentIsSfbCount = 0;
    overallHrrError = FL2FXCONST_DBL(0.0f);
    isRegionLoudness = FL2FXCONST_DBL(0.0f);
    for (sfb = 0; sfb < maxSfbPerGroup; sfb++) {
      if (isMask[sfboffs + sfb] == 1) {
        if (currentIsSfbCount == 0) {
          startIsSfb = sfboffs + sfb;
          isScaleLast = realIsScale[sfboffs + sfb];
        }
        inIsBlock = 1;
        currentIsSfbCount++;
        overallHrrError  += hrrErr[sfboffs + sfb] >> (MAX_SFB_PER_GROUP_SF-3);
        isRegionLoudness += normSfbLoudness[sfboffs + sfb] >> MAX_SFB_PER_GROUP_SF;
      }
      else {
        /* based on correlation, IS should not be used
         * -> use it anyway, if overall error is below threshold
         *    and if local error does not exceed threshold
         * otherwise: check if there are enough IS SFBs
         */
        if (inIsBlock) {
          overallHrrError  += hrrErr[sfboffs + sfb] >> (MAX_SFB_PER_GROUP_SF-3);
          isRegionLoudness += normSfbLoudness[sfboffs + sfb] >> MAX_SFB_PER_GROUP_SF;

          if ( (hrrErr[sfboffs + sfb] < (isParams->local_error_thresh>>3)) && (overallHrrError < (isParams->total_error_thresh>>MAX_SFB_PER_GROUP_SF)) ) {
            currentIsSfbCount++;
            /* overwrite correlation based decision */
            isMask[sfboffs + sfb] = 1;
          } else {
            inIsBlock = 0;
          }
        }
      }
      /* check for large direction deviation */
      if (inIsBlock) {
        if( fAbs(isScaleLast-realIsScale[sfboffs + sfb]) < (isParams->direction_deviation_thresh>>(REAL_SCALE_SF+LD_DATA_SHIFT-IS_DIRECTION_DEVIATION_THRESH_SF)) ) {
          isScaleLast = realIsScale[sfboffs + sfb];
        }
        else{
          isMask[sfboffs + sfb] = 0;
          inIsBlock = 0;
          currentIsSfbCount--;
        }
      }

      if (currentIsSfbCount > 0 && (!inIsBlock || sfb == maxSfbPerGroup - 1)) {
        /* not enough SFBs -> do not use IS */
        if (currentIsSfbCount < isParams->min_is_sfbs || (isRegionLoudness < isParams->is_region_min_loudness>>MAX_SFB_PER_GROUP_SF)) {
          for(j = startIsSfb; j <= sfboffs + sfb; j++) {
            isMask[j] = 0;
          }
        }
        currentIsSfbCount = 0;
        overallHrrError = FL2FXCONST_DBL(0.0f);
        isRegionLoudness = FL2FXCONST_DBL(0.0f);
      }
    }
  }
}


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

    functionname: FDKaacEnc_IntensityStereoProcessing

    description:  Intensity stereo processing tool

    input:        sfbEnergyLeft
                  sfbEnergyRight
                  mdctSpectrumLeft
                  mdctSpectrumRight
                  sfbThresholdLeft
                  sfbThresholdRight
                  sfbSpreadEnLeft
                  sfbSpreadEnRight
                  sfbEnergyLdDataLeft
                  sfbEnergyLdDataRight

    output:       isBook
                  isScale
                  pnsData->pnsFlag
                  msDigest                 zeroed from start to sfbCnt
                  msMask                   zeroed from start to sfbCnt
                  mdctSpectrumRight        zeroed where isBook!=0
                  sfbEnergyRight           zeroed where isBook!=0
                  sfbSpreadEnRight       zeroed where isBook!=0
                  sfbThresholdRight        zeroed where isBook!=0
                  sfbEnergyLdDataRight     FL2FXCONST_DBL(-1.0) where isBook!=0
                  sfbThresholdLdDataRight  FL2FXCONST_DBL(-0.515625f) where isBook!=0

    returns:      none

*****************************************************************************/
void FDKaacEnc_IntensityStereoProcessing(
        FIXP_DBL                  *sfbEnergyLeft,
        FIXP_DBL                  *sfbEnergyRight,
        FIXP_DBL                  *mdctSpectrumLeft,
        FIXP_DBL                  *mdctSpectrumRight,
        FIXP_DBL                  *sfbThresholdLeft,
        FIXP_DBL                  *sfbThresholdRight,
        FIXP_DBL                  *sfbThresholdLdDataRight,
        FIXP_DBL                  *sfbSpreadEnLeft,
        FIXP_DBL                  *sfbSpreadEnRight,
        FIXP_DBL                  *sfbEnergyLdDataLeft,
        FIXP_DBL                  *sfbEnergyLdDataRight,
        INT                       *msDigest,
        INT                       *msMask,
        const INT                  sfbCnt,
        const INT                  sfbPerGroup,
        const INT                  maxSfbPerGroup,
        const INT                 *sfbOffset,
        const INT                  allowIS,
        INT                       *isBook,
        INT                       *isScale,
        PNS_DATA         *RESTRICT pnsData[2]
        )
{
  INT sfb,sfboffs, j;
  FIXP_DBL scale;
  FIXP_DBL lr;
  FIXP_DBL hrrErr[MAX_GROUPED_SFB];
  FIXP_DBL normSfbLoudness[MAX_GROUPED_SFB];
  FIXP_DBL realIsScale[MAX_GROUPED_SFB];
  INTENSITY_PARAMETERS isParams;
  INT isMask[MAX_GROUPED_SFB];

  FDKmemclear((void*)isBook,sfbCnt*sizeof(INT));
  FDKmemclear((void*)isMask,sfbCnt*sizeof(INT));
  FDKmemclear((void*)realIsScale,sfbCnt*sizeof(FIXP_DBL));
  FDKmemclear((void*)isScale,sfbCnt*sizeof(INT));
  FDKmemclear((void*)hrrErr,sfbCnt*sizeof(FIXP_DBL));

  if (!allowIS)
    return;

  FDKaacEnc_initIsParams(&isParams);

  /* compute / set the following values per SFB:
   * - left/right ratio between channels
   * - normalized loudness
   *   + loudness == average of energy in channels to 0.25
   *   + normalization: division by sum of all SFB loudnesses
   * - isMask (is set to 0 if channels are the same or one is 0)
   */
   FDKaacEnc_prepareIntensityDecision(sfbEnergyLeft,
                                      sfbEnergyRight,
                                      sfbEnergyLdDataLeft,
                                      sfbEnergyLdDataRight,
                                      mdctSpectrumLeft,
                                      mdctSpectrumRight,
                                      &isParams,
                                      hrrErr,
                                      isMask,
                                      realIsScale,
                                      normSfbLoudness,
                                      sfbCnt,
                                      sfbPerGroup,
                                      maxSfbPerGroup,
                                      sfbOffset);

  FDKaacEnc_finalizeIntensityDecision(hrrErr,
                                      isMask,
                                      realIsScale,
                                      normSfbLoudness,
                                      &isParams,
                                      sfbCnt,
                                      sfbPerGroup,
                                      maxSfbPerGroup);

  for (sfb=0; sfb<sfbCnt; sfb+=sfbPerGroup) {
    for (sfboffs=0; sfboffs<maxSfbPerGroup; sfboffs++) {
      INT sL, sR;
      FIXP_DBL inv_n;

      msMask[sfb+sfboffs] = 0;
      if (isMask[sfb+sfboffs] == 0) {
        continue;
      }

      if (   (sfbEnergyLeft[sfb+sfboffs] < sfbThresholdLeft[sfb+sfboffs])
          &&(fMult(FL2FXCONST_DBL(1.0f/1.5f),sfbEnergyRight[sfb+sfboffs]) > sfbThresholdRight[sfb+sfboffs]) ) {
        continue;
      }
      /* NEW: if there is a big-enough IS region, switch off PNS */
      if (pnsData[0]) {
        if(pnsData[0]->pnsFlag[sfb+sfboffs]) {
          pnsData[0]->pnsFlag[sfb+sfboffs] = 0;
        }
        if(pnsData[1]->pnsFlag[sfb+sfboffs]) {
          pnsData[1]->pnsFlag[sfb+sfboffs] = 0;
        }
      }

      inv_n = GetInvInt((sfbOffset[sfb + sfboffs + 1] - sfbOffset[sfb + sfboffs])>>1);  // scaled with 2 to compensate fMultDiv2() in subsequent loop
      sL = calcSfbMaxScale(mdctSpectrumLeft,sfbOffset[sfb+sfboffs],sfbOffset[sfb+sfboffs+1]);
      sR = calcSfbMaxScale(mdctSpectrumRight,sfbOffset[sfb+sfboffs],sfbOffset[sfb+sfboffs+1]);

      lr = FL2FXCONST_DBL(0.0f);
      for (j=sfbOffset[sfb+sfboffs]; j<sfbOffset[sfb+sfboffs+1]; j++)
        lr += fMultDiv2(fMultDiv2(mdctSpectrumLeft[j]<<sL,mdctSpectrumRight[j]<<sR),inv_n);
      lr = lr<<1;

      if (lr < FL2FXCONST_DBL(0.0f)) {
        /* This means OUT OF phase intensity stereo, cf. standard */
        INT s0, s1, s2;
        FIXP_DBL tmp, d, ed = FL2FXCONST_DBL(0.0f);

        s0 = fixMin(sL,sR);
        for (j=sfbOffset[sfb+sfboffs]; j<sfbOffset[sfb+sfboffs+1]; j++) {
          d = ((mdctSpectrumLeft[j]<<s0)>>1) - ((mdctSpectrumRight[j]<<s0)>>1);
          ed += fMultDiv2(d,d)>>(MDCT_SPEC_SF-1);
        }
        msMask[sfb+sfboffs] = 1;
        tmp = fDivNorm(sfbEnergyLeft[sfb+sfboffs],ed,&s1);
        s2 = (s1) + (2*s0) - 2 - MDCT_SPEC_SF;
        if (s2 & 1) {
          tmp = tmp>>1;
          s2 = s2+1;
        }
        s2 = (s2>>1) + 1;  // +1 compensate fMultDiv2() in subsequent loop
        s2 = fixMin(fixMax(s2,-(DFRACT_BITS-1)),(DFRACT_BITS-1));
        scale = sqrtFixp(tmp);
        if (s2 < 0) {
          s2 = -s2;
          for (j=sfbOffset[sfb+sfboffs]; j<sfbOffset[sfb+sfboffs+1]; j++) {
            mdctSpectrumLeft[j] = (fMultDiv2(mdctSpectrumLeft[j],scale) - fMultDiv2(mdctSpectrumRight[j],scale)) >> s2;
            mdctSpectrumRight[j] = FL2FXCONST_DBL(0.0f);
          }
        }
        else {
          for (j=sfbOffset[sfb+sfboffs]; j<sfbOffset[sfb+sfboffs+1]; j++) {
            mdctSpectrumLeft[j] = (fMultDiv2(mdctSpectrumLeft[j],scale) - fMultDiv2(mdctSpectrumRight[j],scale)) << s2;
            mdctSpectrumRight[j] = FL2FXCONST_DBL(0.0f);
          }
        }
      }
      else {
        /* This means IN phase intensity stereo, cf. standard */
        INT s0,s1,s2;
        FIXP_DBL tmp, s, es = FL2FXCONST_DBL(0.0f);

        s0 = fixMin(sL,sR);
        for (j=sfbOffset[sfb+sfboffs]; j<sfbOffset[sfb+sfboffs+1]; j++) {
          s   = ((mdctSpectrumLeft[j]<<s0)>>1) + ((mdctSpectrumRight[j]<<s0)>>1);
          es += fMultDiv2(s,s)>>(MDCT_SPEC_SF-1);     // scaled 2*(mdctScale - s0 + 1) + MDCT_SPEC_SF
        }
        msMask[sfb+sfboffs] = 0;
        tmp = fDivNorm(sfbEnergyLeft[sfb+sfboffs],es,&s1);
        s2 = (s1) + (2*s0) - 2 - MDCT_SPEC_SF;
        if (s2 & 1) {
          tmp = tmp>>1;
          s2 = s2 + 1;
        }
        s2 = (s2>>1) + 1; // +1 compensate fMultDiv2() in subsequent loop
        s2 = fixMin(fixMax(s2,-(DFRACT_BITS-1)),(DFRACT_BITS-1));
        scale = sqrtFixp(tmp);
        if (s2 < 0) {
          s2 = -s2;
          for (j=sfbOffset[sfb+sfboffs]; j<sfbOffset[sfb+sfboffs+1]; j++) {
            mdctSpectrumLeft[j] = (fMultDiv2(mdctSpectrumLeft[j],scale) + fMultDiv2(mdctSpectrumRight[j],scale)) >> s2;
            mdctSpectrumRight[j] = FL2FXCONST_DBL(0.0f);
          }
        }
        else {
          for (j=sfbOffset[sfb+sfboffs]; j<sfbOffset[sfb+sfboffs+1]; j++) {
            mdctSpectrumLeft[j] = (fMultDiv2(mdctSpectrumLeft[j],scale) + fMultDiv2(mdctSpectrumRight[j],scale)) << s2;
            mdctSpectrumRight[j] = FL2FXCONST_DBL(0.0f);
          }
        }
      }

      isBook[sfb+sfboffs] = CODE_BOOK_IS_IN_PHASE_NO;

      if ( realIsScale[sfb+sfboffs] < FL2FXCONST_DBL(0.0f) ) {
        isScale[sfb+sfboffs] = (INT)(((realIsScale[sfb+sfboffs]>>1)-FL2FXCONST_DBL(0.5f/(1<<(REAL_SCALE_SF+LD_DATA_SHIFT+1))))>>(DFRACT_BITS-1-REAL_SCALE_SF-LD_DATA_SHIFT-1)) + 1;
      }
      else {
        isScale[sfb+sfboffs] = (INT)(((realIsScale[sfb+sfboffs]>>1)+FL2FXCONST_DBL(0.5f/(1<<(REAL_SCALE_SF+LD_DATA_SHIFT+1))))>>(DFRACT_BITS-1-REAL_SCALE_SF-LD_DATA_SHIFT-1));
      }

      sfbEnergyRight[sfb+sfboffs] = FL2FXCONST_DBL(0.0f);
      sfbEnergyLdDataRight[sfb+sfboffs] = FL2FXCONST_DBL(-1.0f);
      sfbThresholdRight[sfb+sfboffs] = FL2FXCONST_DBL(0.0f);
      sfbThresholdLdDataRight[sfb+sfboffs] = FL2FXCONST_DBL(-0.515625f);
      sfbSpreadEnRight[sfb+sfboffs] = FL2FXCONST_DBL(0.0f);

      *msDigest = MS_SOME;
    }
  }
}