Fraunhofer AAC codec.

License boilerplate update to follow.

Change-Id: I2810460c11a58b6d148d84673cc031f3685e79b5

1 files changed, 639 insertions, 0 deletions

diff --git a/libAACdec/src/rvlcconceal.cpp b/libAACdec/src/rvlcconceal.cpp
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+/****************************************************************************
+
+                     (C) Copyright Fraunhofer IIS (2004)
+                               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.
+
+ $Id$
+
+****************************************************************************/
+/*!
+  \file
+  \brief  rvlc concealment
+  \author Josef Hoepfl
+*/
+
+#include "rvlcconceal.h"
+
+
+#include "block.h"
+#include "rvlc.h"
+
+/*---------------------------------------------------------------------------------------------
+  function:      calcRefValFwd
+
+  description:   The function determines the scalefactor which is closed to the scalefactorband
+                 conceal_min. The same is done for intensity data and noise energies.
+-----------------------------------------------------------------------------------------------
+  output:        - reference value scf
+                 - reference value internsity data
+                 - reference value noise energy
+-----------------------------------------------------------------------------------------------
+  return:        -
+-------------------------------------------------------------------------------------------- */
+
+static
+void calcRefValFwd (CErRvlcInfo *pRvlc,
+                    CAacDecoderChannelInfo *pAacDecoderChannelInfo,
+                    int *refIsFwd,
+                    int *refNrgFwd,
+                    int *refScfFwd)
+{
+  int band,bnds,group,startBand;
+  int idIs,idNrg,idScf;
+  int conceal_min,conceal_group_min;
+  int MaximumScaleFactorBands;
+
+
+  if (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence)
+    MaximumScaleFactorBands = 16;
+  else
+    MaximumScaleFactorBands = 64;
+
+  conceal_min = pRvlc->conceal_min % MaximumScaleFactorBands;
+  conceal_group_min = pRvlc->conceal_min / MaximumScaleFactorBands;
+
+  /* calculate first reference value for approach in forward direction */
+  idIs = idNrg = idScf = 1;
+
+  /* set reference values */
+  *refIsFwd = - SF_OFFSET;
+  *refNrgFwd = pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain - SF_OFFSET - 90 - 256;
+  *refScfFwd = pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain - SF_OFFSET;
+
+  startBand = conceal_min-1;
+  for (group=conceal_group_min; group >= 0; group--) {
+    for (band=startBand; band >= 0; band--) {
+      bnds = 16*group+band;
+      switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {
+        case ZERO_HCB:
+          break;
+        case INTENSITY_HCB:
+        case INTENSITY_HCB2:
+          if (idIs) {
+            *refIsFwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+            idIs=0; /* reference value has been set */
+          }
+          break;
+        case NOISE_HCB:
+          if (idNrg) {
+            *refNrgFwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+            idNrg=0; /* reference value has been set */
+          }
+          break ;
+        default:
+          if (idScf) {
+            *refScfFwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+            idScf=0; /* reference value has been set */
+          }
+          break;
+      }
+    }
+    startBand = pRvlc->maxSfbTransmitted-1;
+  }
+
+}
+
+/*---------------------------------------------------------------------------------------------
+  function:      calcRefValBwd
+
+  description:   The function determines the scalefactor which is closed to the scalefactorband
+                 conceal_max. The same is done for intensity data and noise energies.
+-----------------------------------------------------------------------------------------------
+  output:        - reference value scf
+                 - reference value internsity data
+                 - reference value noise energy
+-----------------------------------------------------------------------------------------------
+  return:        -
+-------------------------------------------------------------------------------------------- */
+
+static
+void calcRefValBwd (CErRvlcInfo *pRvlc,
+                    CAacDecoderChannelInfo *pAacDecoderChannelInfo,
+                    int *refIsBwd,
+                    int *refNrgBwd,
+                    int *refScfBwd)
+{
+  int band,bnds,group,startBand;
+  int idIs,idNrg,idScf;
+  int conceal_max,conceal_group_max;
+  int MaximumScaleFactorBands;
+
+  if (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence)
+    MaximumScaleFactorBands = 16;
+  else
+    MaximumScaleFactorBands = 64;
+
+  conceal_max = pRvlc->conceal_max % MaximumScaleFactorBands;
+  conceal_group_max = pRvlc->conceal_max / MaximumScaleFactorBands;
+
+  /* calculate first reference value for approach in backward direction */
+  idIs = idNrg = idScf = 1;
+
+  /* set reference values */
+  *refIsBwd = pRvlc->dpcm_is_last_position - SF_OFFSET;
+  *refNrgBwd = pRvlc->rev_global_gain + pRvlc->dpcm_noise_last_position - SF_OFFSET - 90 - 256 + pRvlc->dpcm_noise_nrg;
+  *refScfBwd = pRvlc->rev_global_gain - SF_OFFSET;
+
+  startBand=conceal_max+1;
+
+  /* if needed, re-set reference values */
+  for (group=conceal_group_max; group < pRvlc->numWindowGroups; group++) {
+    for (band=startBand; band < pRvlc->maxSfbTransmitted; band++) {
+      bnds = 16*group+band;
+      switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {
+        case ZERO_HCB:
+          break;
+        case INTENSITY_HCB:
+        case INTENSITY_HCB2:
+          if (idIs) {
+            *refIsBwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+            idIs=0; /* reference value has been set */
+          }
+          break;
+        case NOISE_HCB:
+          if (idNrg) {
+            *refNrgBwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+            idNrg=0;  /* reference value has been set */
+          }
+          break ;
+        default:
+          if (idScf) {
+            *refScfBwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+            idScf=0; /* reference value has been set */
+          }
+          break;
+      }
+    }
+    startBand=0;
+  }
+
+}
+
+
+/*---------------------------------------------------------------------------------------------
+  function:      BidirectionalEstimation_UseLowerScfOfCurrentFrame
+
+  description:   This approach by means of bidirectional estimation is generally performed when
+                 a single bit error has been detected, the bit error can be isolated between
+                 'conceal_min' and 'conceal_max' and the 'sf_concealment' flag is not set. The
+                 sets of scalefactors decoded in forward and backward direction are compared
+                 with each other. The smaller scalefactor will be considered as the correct one
+                 respectively. The reconstruction of the scalefactors with this approach archieve
+                 good results in audio quality. The strategy must be applied to scalefactors,
+                 intensity data and noise energy seperately.
+-----------------------------------------------------------------------------------------------
+  output:        Concealed scalefactor, noise energy and intensity data between conceal_min and
+                 conceal_max
+-----------------------------------------------------------------------------------------------
+  return:        -
+-------------------------------------------------------------------------------------------- */
+
+void BidirectionalEstimation_UseLowerScfOfCurrentFrame (CAacDecoderChannelInfo *pAacDecoderChannelInfo)
+{
+  CErRvlcInfo *pRvlc = &pAacDecoderChannelInfo->pComData->overlay.aac.erRvlcInfo;
+  int band,bnds,startBand,endBand,group;
+  int conceal_min,conceal_max;
+  int conceal_group_min,conceal_group_max;
+  int MaximumScaleFactorBands;
+
+  if (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence) {
+    MaximumScaleFactorBands = 16;
+  }
+  else {
+    MaximumScaleFactorBands = 64;
+  }
+  
+  /* If an error was detected just in forward or backward direction, set the corresponding border for concealment to a
+     appropriate scalefactor band. The border is set to first or last sfb respectively, because the error will possibly 
+     not follow directly after the corrupt bit but just after decoding some more (wrong) scalefactors. */
+  if (pRvlc->conceal_min == CONCEAL_MIN_INIT)
+    pRvlc->conceal_min = 0;
+
+  if (pRvlc->conceal_max == CONCEAL_MAX_INIT)
+    pRvlc->conceal_max = (pRvlc->numWindowGroups-1)*16+pRvlc->maxSfbTransmitted-1;
+
+  conceal_min = pRvlc->conceal_min % MaximumScaleFactorBands;
+  conceal_group_min = pRvlc->conceal_min / MaximumScaleFactorBands;
+  conceal_max = pRvlc->conceal_max % MaximumScaleFactorBands;
+  conceal_group_max = pRvlc->conceal_max / MaximumScaleFactorBands;
+
+  if (pRvlc->conceal_min == pRvlc->conceal_max) {
+
+    int refIsFwd,refNrgFwd,refScfFwd;
+    int refIsBwd,refNrgBwd,refScfBwd;
+
+    bnds = pRvlc->conceal_min;
+    calcRefValFwd(pRvlc,pAacDecoderChannelInfo,&refIsFwd,&refNrgFwd,&refScfFwd);
+    calcRefValBwd(pRvlc,pAacDecoderChannelInfo,&refIsBwd,&refNrgBwd,&refScfBwd);
+
+    switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {
+      case ZERO_HCB:
+        break;
+      case INTENSITY_HCB:
+      case INTENSITY_HCB2:
+        if (refIsFwd < refIsBwd) 
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = refIsFwd;
+        else
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = refIsBwd;
+        break;
+      case NOISE_HCB:
+        if (refNrgFwd < refNrgBwd)
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = refNrgFwd;
+        else
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = refNrgBwd;
+        break;
+      default:
+        if (refScfFwd < refScfBwd)
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = refScfFwd;
+        else 
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = refScfBwd;
+        break;
+    }
+  }
+  else {
+    pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[pRvlc->conceal_max] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[pRvlc->conceal_max];
+    pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[pRvlc->conceal_min] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[pRvlc->conceal_min];
+
+    /* consider the smaller of the forward and backward decoded value as the correct one */  
+    startBand = conceal_min;      
+    if (conceal_group_min == conceal_group_max)   
+      endBand = conceal_max;      
+    else          
+      endBand = pRvlc->maxSfbTransmitted-1;       
+
+    for (group=conceal_group_min; group <= conceal_group_max; group++) {  
+      for (band=startBand; band <= endBand; band++) {  
+        bnds = 16*group+band;  
+        if (pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds] < pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds])  
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+        else
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+      }  
+      startBand = 0;   
+      if ((group+1) == conceal_group_max)  
+        endBand = conceal_max;  
+    }  
+  }
+
+  /* now copy all data to the output buffer which needs not to be concealed */
+  if (conceal_group_min == 0) 
+    endBand = conceal_min;    
+  else        
+    endBand = pRvlc->maxSfbTransmitted;     
+  for (group=0; group <= conceal_group_min; group++) {
+    for (band=0; band < endBand; band++) {
+      bnds = 16*group+band;
+      pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+    }
+    if ((group+1) == conceal_group_min) 
+      endBand = conceal_min;    
+  }
+
+  startBand = conceal_max+1;    
+  for (group=conceal_group_max; group < pRvlc->numWindowGroups; group++) {
+    for (band=startBand; band < pRvlc->maxSfbTransmitted; band++) {
+      bnds = 16*group+band;
+      pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+    }
+    startBand = 0;
+  }
+}
+
+/*---------------------------------------------------------------------------------------------
+  function:      BidirectionalEstimation_UseScfOfPrevFrameAsReference
+
+  description:   This approach by means of bidirectional estimation is generally performed when
+                 a single bit error has been detected, the bit error can be isolated between 
+                 'conceal_min' and 'conceal_max', the 'sf_concealment' flag is set and the 
+                 previous frame has the same block type as the current frame. The scalefactor 
+                 decoded in forward and backward direction and the scalefactor of the previous 
+                 frame are compared with each other. The smaller scalefactor will be considered 
+                 as the correct one. At this the codebook of the previous and current frame must 
+                 be of the same set (scf, nrg, is) in each scalefactorband. Otherwise the 
+                 scalefactor of the previous frame is not considered in the minimum calculation. 
+                 The reconstruction of the scalefactors with this approach archieve good results 
+                 in audio quality. The strategy must be applied to scalefactors, intensity data 
+                 and noise energy seperately.
+-----------------------------------------------------------------------------------------------
+  output:        Concealed scalefactor, noise energy and intensity data between conceal_min and 
+                 conceal_max
+-----------------------------------------------------------------------------------------------
+  return:        -
+-------------------------------------------------------------------------------------------- */
+
+void BidirectionalEstimation_UseScfOfPrevFrameAsReference (
+        CAacDecoderChannelInfo *pAacDecoderChannelInfo,
+        CAacDecoderStaticChannelInfo *pAacDecoderStaticChannelInfo
+        )
+{
+  CErRvlcInfo *pRvlc = &pAacDecoderChannelInfo->pComData->overlay.aac.erRvlcInfo;
+  int band,bnds,startBand,endBand,group;
+  int conceal_min,conceal_max;
+  int conceal_group_min,conceal_group_max;
+  int MaximumScaleFactorBands;
+  int commonMin;
+
+  if (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence) {
+    MaximumScaleFactorBands = 16;
+  }
+  else {
+    MaximumScaleFactorBands = 64;
+  }
+
+  /* If an error was detected just in forward or backward direction, set the corresponding border for concealment to a
+     appropriate scalefactor band. The border is set to first or last sfb respectively, because the error will possibly 
+     not follow directly after the corrupt bit but just after decoding some more (wrong) scalefactors. */
+  if (pRvlc->conceal_min == CONCEAL_MIN_INIT)
+    pRvlc->conceal_min = 0;
+
+  if (pRvlc->conceal_max == CONCEAL_MAX_INIT)
+    pRvlc->conceal_max = (pRvlc->numWindowGroups-1)*16+pRvlc->maxSfbTransmitted-1;
+
+  conceal_min = pRvlc->conceal_min % MaximumScaleFactorBands;
+  conceal_group_min = pRvlc->conceal_min / MaximumScaleFactorBands;
+  conceal_max = pRvlc->conceal_max % MaximumScaleFactorBands;
+  conceal_group_max = pRvlc->conceal_max / MaximumScaleFactorBands;
+
+  pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[pRvlc->conceal_max] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[pRvlc->conceal_max];  
+  pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[pRvlc->conceal_min] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[pRvlc->conceal_min];  
+
+  /* consider the smaller of the forward and backward decoded value as the correct one */
+  startBand = conceal_min;    
+  if (conceal_group_min == conceal_group_max) 
+    endBand = conceal_max;    
+  else        
+    endBand = pRvlc->maxSfbTransmitted-1;     
+
+  for (group=conceal_group_min; group <= conceal_group_max; group++) {
+    for (band=startBand; band <= endBand; band++) {
+      bnds = 16*group+band;
+      switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {
+        case ZERO_HCB:
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = 0;
+          break;
+
+        case INTENSITY_HCB:
+        case INTENSITY_HCB2:
+          if ( (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]==INTENSITY_HCB) || (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]==INTENSITY_HCB2) ) {
+            commonMin = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(commonMin, pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousScaleFactor[bnds]);
+          }
+          else {
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+          }
+          break;
+
+        case NOISE_HCB:
+          if ( (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]==NOISE_HCB) ) {
+            commonMin = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(commonMin, pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousScaleFactor[bnds]);
+          } else {
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+          }
+          break;
+
+        default:
+          if (   (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=ZERO_HCB)
+              && (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=NOISE_HCB)
+              && (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=INTENSITY_HCB) 
+              && (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=INTENSITY_HCB2) )
+          {
+            commonMin = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds], pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(commonMin, pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousScaleFactor[bnds]);
+          } else {
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+          }
+          break;
+      }
+    }
+    startBand = 0; 
+    if ((group+1) == conceal_group_max)
+      endBand = conceal_max;
+  }
+
+  /* now copy all data to the output buffer which needs not to be concealed */
+  if (conceal_group_min == 0) 
+    endBand = conceal_min;    
+  else        
+    endBand = pRvlc->maxSfbTransmitted;     
+  for (group=0; group <= conceal_group_min; group++) {
+    for (band=0; band < endBand; band++) {
+      bnds = 16*group+band;
+      pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+    }
+    if ((group+1) == conceal_group_min) 
+      endBand = conceal_min;    
+  }
+
+  startBand = conceal_max+1;    
+  for (group=conceal_group_max; group < pRvlc->numWindowGroups; group++) {
+    for (band=startBand; band < pRvlc->maxSfbTransmitted; band++) {
+      bnds = 16*group+band;
+      pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+    }
+    startBand = 0;
+  }
+}
+
+/*---------------------------------------------------------------------------------------------
+  function:      StatisticalEstimation
+
+  description:   This approach by means of statistical estimation is generally performed when 
+                 both the start value and the end value are different and no further errors have 
+                 been detected. Considering the forward and backward decoded scalefactors, the 
+                 set with the lower scalefactors in sum will be considered as the correct one. 
+                 The scalefactors are differentially encoded. Normally it would reach to compare 
+                 one pair of the forward and backward decoded scalefactors to specify the lower 
+                 set. But having detected no further errors does not necessarily mean the absence
+                 of errors. Therefore all scalefactors decoded in forward and backward direction 
+                 are summed up seperately. The set with the lower sum will be used. The strategy 
+                 must be applied to scalefactors, intensity data and noise energy seperately.
+-----------------------------------------------------------------------------------------------
+  output:        Concealed scalefactor, noise energy and intensity data
+-----------------------------------------------------------------------------------------------
+  return:        -
+-------------------------------------------------------------------------------------------- */
+
+void StatisticalEstimation (CAacDecoderChannelInfo *pAacDecoderChannelInfo)
+{
+  CErRvlcInfo *pRvlc = &pAacDecoderChannelInfo->pComData->overlay.aac.erRvlcInfo;
+  int band,bnds,group;
+  int sumIsFwd,sumIsBwd;            /* sum of intensity data forward/backward */
+  int sumNrgFwd,sumNrgBwd;          /* sum of noise energy data forward/backward */
+  int sumScfFwd,sumScfBwd;          /* sum of scalefactor data forward/backward */
+  int useIsFwd,useNrgFwd,useScfFwd; /* the flags signals the elements which are used for the final result */
+  int MaximumScaleFactorBands;
+
+  if (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence)
+    MaximumScaleFactorBands = 16;
+  else
+    MaximumScaleFactorBands = 64;
+
+  sumIsFwd = sumIsBwd = sumNrgFwd = sumNrgBwd = sumScfFwd = sumScfBwd = 0;
+  useIsFwd = useNrgFwd = useScfFwd = 0;
+
+  /* calculate sum of each group (scf,nrg,is) of forward and backward direction */
+  for (group=0; group<pRvlc->numWindowGroups; group++) {
+    for (band=0; band < pRvlc->maxSfbTransmitted; band++) {
+      bnds = 16*group+band;
+      switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {
+        case ZERO_HCB:
+          break;
+
+        case INTENSITY_HCB:
+        case INTENSITY_HCB2:
+          sumIsFwd += pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+          sumIsBwd += pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+          break;
+
+        case NOISE_HCB:
+          sumNrgFwd += pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+          sumNrgBwd += pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+          break ;
+
+        default:
+          sumScfFwd += pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+          sumScfBwd += pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+          break;
+      }
+    }
+  }
+
+  /* find for each group (scf,nrg,is) the correct direction */
+  if ( sumIsFwd < sumIsBwd )
+    useIsFwd = 1;
+
+  if ( sumNrgFwd < sumNrgBwd )
+    useNrgFwd = 1;
+
+  if ( sumScfFwd < sumScfBwd )
+    useScfFwd = 1;
+
+  /* conceal each group (scf,nrg,is) */
+  for (group=0; group<pRvlc->numWindowGroups; group++) {
+    for (band=0; band < pRvlc->maxSfbTransmitted; band++) {
+      bnds = 16*group+band;
+      switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {
+        case ZERO_HCB:
+          break;
+
+        case INTENSITY_HCB:
+        case INTENSITY_HCB2:
+          if (useIsFwd)
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+          else
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+          break;
+
+        case NOISE_HCB:
+          if (useNrgFwd)
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+          else
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+          break ;
+
+        default:
+          if (useScfFwd)
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
+          else
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds];
+          break;
+      }
+    }
+  }
+}
+
+
+/*---------------------------------------------------------------------------------------------
+  description:   Approach by means of predictive interpolation
+                 This approach by means of predictive estimation is generally performed when 
+                 the error cannot be isolated between 'conceal_min' and 'conceal_max', the 
+                 'sf_concealment' flag is set and the previous frame has the same block type 
+                 as the current frame. Check for each scalefactorband if the same type of data 
+                 (scalefactor, internsity data, noise energies) is transmitted. If so use the 
+                 scalefactor (intensity data, noise energy) in the current frame. Otherwise set 
+                 the scalefactor (intensity data, noise energy) for this scalefactorband to zero.
+-----------------------------------------------------------------------------------------------
+  output:        Concealed scalefactor, noise energy and intensity data
+-----------------------------------------------------------------------------------------------
+  return:        -
+-------------------------------------------------------------------------------------------- */
+
+void PredictiveInterpolation (
+        CAacDecoderChannelInfo *pAacDecoderChannelInfo,
+        CAacDecoderStaticChannelInfo *pAacDecoderStaticChannelInfo
+        )
+{
+  CErRvlcInfo *pRvlc = &pAacDecoderChannelInfo->pComData->overlay.aac.erRvlcInfo;
+  int band,bnds,group;
+  int MaximumScaleFactorBands;
+  int commonMin;
+
+  if (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence)
+    MaximumScaleFactorBands = 16;
+  else
+    MaximumScaleFactorBands = 64;
+
+  for (group=0; group<pRvlc->numWindowGroups; group++) {
+    for (band=0; band < pRvlc->maxSfbTransmitted; band++) {
+      bnds = 16*group+band;
+      switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {
+        case ZERO_HCB:
+          pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = 0;
+          break;
+
+        case INTENSITY_HCB:
+        case INTENSITY_HCB2:
+          if ( (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]==INTENSITY_HCB) || (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]==INTENSITY_HCB2) ) {
+            commonMin = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(commonMin, pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousScaleFactor[bnds]);
+          }
+          else {
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = -110;
+          }
+          break;
+
+        case NOISE_HCB:
+          if ( (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]==NOISE_HCB) ) {
+            commonMin = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(commonMin, pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousScaleFactor[bnds]);
+          }
+          else {
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = -110;
+          }
+          break;
+
+        default:
+          if (   (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=ZERO_HCB)
+              && (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=NOISE_HCB) 
+              && (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=INTENSITY_HCB) 
+              && (pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds]!=INTENSITY_HCB2) ) {
+            commonMin = FDKmin(pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds],pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd[bnds]);
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = FDKmin(commonMin, pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousScaleFactor[bnds]);
+          }
+          else {
+            pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = 0;
+          }
+          break;
+      }
+    }
+  }
+}
+