xref: /external/aac/libAACdec/src/rvlc.cpp

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

� Copyright  1995 - 2012 Fraunhofer-Gesellschaft zur F�rderung 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
----------------------------------------------------------------------------------------------------------- */

/*!
  \file
  \brief  RVLC Decoder
  \author Robert Weidner
*/

#include "rvlc.h"


#include "block.h"

#include "aac_rom.h"
#include "rvlcbit.h"
#include "rvlcconceal.h"
#include "aacdec_hcr.h"

/*---------------------------------------------------------------------------------------------
     function:     rvlcInit

     description:  init RVLC by data from channelinfo, which was decoded previously and
                   set up pointers
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - pointer channel info structure
                   - pointer bitstream structure
-----------------------------------------------------------------------------------------------
        return:    -
-------------------------------------------------------------------------------------------- */

static
void rvlcInit (CErRvlcInfo            *pRvlc,
               CAacDecoderChannelInfo *pAacDecoderChannelInfo,
               HANDLE_FDK_BITSTREAM    bs)
{
  /* RVLC common initialization part 2 of 2 */
  SHORT     *pScfEsc = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfEsc;
  SHORT     *pScfFwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd;
  SHORT     *pScfBwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd;
  SHORT     *pScaleFactor = pAacDecoderChannelInfo->pDynData->aScaleFactor;
  int bnds;

  pAacDecoderChannelInfo->pDynData->specificTo.aac.rvlcIntensityUsed = 0;

  pRvlc->numDecodedEscapeWordsEsc = 0;
  pRvlc->numDecodedEscapeWordsFwd = 0;
  pRvlc->numDecodedEscapeWordsBwd = 0;

  pRvlc->intensity_used = 0;
  pRvlc->errorLogRvlc   = 0;

  pRvlc->conceal_max = CONCEAL_MAX_INIT;
  pRvlc->conceal_min = CONCEAL_MIN_INIT;

  pRvlc->conceal_max_esc = CONCEAL_MAX_INIT;
  pRvlc->conceal_min_esc = CONCEAL_MIN_INIT;

  pRvlc->pHuffTreeRvlcEscape  = aHuffTreeRvlcEscape;
  pRvlc->pHuffTreeRvlCodewds  = aHuffTreeRvlCodewds;

  /* init scf arrays (for savety (in case of there are only zero codebooks)) */
  for (bnds = 0; bnds < RVLC_MAX_SFB; bnds++) {
    pScfFwd[bnds] = 0;
    pScfBwd[bnds] = 0;
    pScfEsc[bnds] = 0;
    pScaleFactor[bnds] = 0;
  }

  /* set base bitstream ptr to the RVL-coded part (start of RVLC data (ESC 2)) */
  FDKsyncCache (bs);

  pRvlc->bitstreamIndexRvlFwd = FDKgetBitCnt(bs); /* first bit within RVL coded block as start address for  forward decoding */
  pRvlc->bitstreamIndexRvlBwd = FDKgetBitCnt(bs) + pRvlc->length_of_rvlc_sf - 1; /* last bit within RVL coded block as start address for backward decoding */

  /* skip RVLC-bitstream-part -- pointing now to escapes (if present) or to TNS data (if present) */
  FDKpushFor (bs, pRvlc->length_of_rvlc_sf);

  if ( pRvlc->sf_escapes_present != 0 ) {

    /* locate internal bitstream ptr at escapes (which is the second part) */
    FDKsyncCache (bs);
    pRvlc->bitstreamIndexEsc = FDKgetBitCnt(bs);

    /* skip escapeRVLC-bitstream-part -- pointing to TNS data (if present)   to make decoder continue */
    /* decoding of RVLC should work despite this second pushFor during initialization because        */
    /* bitstream initialization is valid for both ESC2 data parts (RVL-coded values and ESC-coded values) */
    FDKpushFor (bs, pRvlc->length_of_rvlc_escapes);
  }

#if VERBOSE_RVLC_INIT
  DebugOutputInit(pRvlc,pAacDecoderChannelInfo);
#endif
}


/*---------------------------------------------------------------------------------------------
     function:     rvlcCheckIntensityCb

     description:  Check if a intensity codebook is used in the current channel.
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - pointer channel info structure
-----------------------------------------------------------------------------------------------
        output:    - intensity_used: 0 no intensity codebook is used
                                     1 intensity codebook is used
-----------------------------------------------------------------------------------------------
        return:    -
-------------------------------------------------------------------------------------------- */

static
void rvlcCheckIntensityCb (CErRvlcInfo            *pRvlc,
                           CAacDecoderChannelInfo *pAacDecoderChannelInfo)
{
  int group, band, bnds;

  pRvlc->intensity_used = 0;

  for (group=0; group < pRvlc->numWindowGroups; group++) {
    for (band=0; band < pRvlc->maxSfbTransmitted; band++) {
      bnds = 16*group+band;
      if ( (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds] == INTENSITY_HCB) || (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds] == INTENSITY_HCB2) ) {
        pRvlc->intensity_used = 1;
        break;
      }
    }
  }
}


/*---------------------------------------------------------------------------------------------
     function:     rvlcDecodeEscapeWord

     description:  Decode a huffman coded RVLC Escape-word. This value is part of a DPCM coded
                   scalefactor.
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
-----------------------------------------------------------------------------------------------
        return:    - a single RVLC-Escape value which had to be applied to a DPCM value (which
                     has a absolute value of 7)
-------------------------------------------------------------------------------------------- */

static
SCHAR rvlcDecodeEscapeWord (CErRvlcInfo          *pRvlc,
                            HANDLE_FDK_BITSTREAM  bs)
{
  int           i;
  SCHAR         value;
  UCHAR         carryBit;
  UINT          treeNode;
  UINT          branchValue;
  UINT          branchNode;

  USHORT*       pBitstreamIndexEsc;
  const UINT*   pEscTree;

  pEscTree = pRvlc->pHuffTreeRvlcEscape;
  pBitstreamIndexEsc = &(pRvlc->bitstreamIndexEsc);
  treeNode = *pEscTree;                                             /* init at starting node */

  for (i=MAX_LEN_RVLC_ESCAPE_WORD-1; i >= 0; i--) {
    carryBit = rvlcReadBitFromBitstream(bs,                         /* get next bit */
                                        pBitstreamIndexEsc,
                                        FWD);

    CarryBitToBranchValue(carryBit,                                 /* huffman decoding, do a single step in huffman decoding tree */
                          treeNode,
                          &branchValue,
                          &branchNode);

    if ((branchNode & TEST_BIT_10) == TEST_BIT_10) {                /* test bit 10 ; if set --> a RVLC-escape-word is completely decoded */
      value = (SCHAR) branchNode & CLR_BIT_10;
      pRvlc->length_of_rvlc_escapes -= (MAX_LEN_RVLC_ESCAPE_WORD - i);

      if (pRvlc->length_of_rvlc_escapes < 0) {
        pRvlc->errorLogRvlc |= RVLC_ERROR_ALL_ESCAPE_WORDS_INVALID;
        value = -1;
      }

      return value;
    }
    else {
      treeNode = *(pEscTree + branchValue);                         /* update treeNode for further step in decoding tree */
    }
  }

  pRvlc->errorLogRvlc |= RVLC_ERROR_ALL_ESCAPE_WORDS_INVALID;

  return -1;                                                        /* should not be reached */
}


/*---------------------------------------------------------------------------------------------
     function:     rvlcDecodeEscapes

     description:  Decodes all huffman coded RVLC Escape Words.
                   Here a difference to the pseudo-code-implementation from standard can be
                   found. A while loop (and not two nested for loops) is used for two reasons:

                   1. The plain huffman encoded escapes are decoded before the RVL-coded
                      scalefactors. Therefore the escapes are present in the second step
                      when decoding the RVL-coded-scalefactor values in forward and
                      backward direction.

                      When the RVL-coded scalefactors are decoded and there a escape is
                      needed, then it is just taken out of the array in ascending order.

                   2. It's faster.
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - handle to FDK bitstream
-----------------------------------------------------------------------------------------------
        return:    - 0 ok     the decoded escapes seem to be valid
                   - 1 error  there was a error detected during decoding escapes
                              --> all escapes are invalid
-------------------------------------------------------------------------------------------- */

static
void rvlcDecodeEscapes (CErRvlcInfo          *pRvlc,
                        SHORT                *pEsc,
                        HANDLE_FDK_BITSTREAM  bs)
{
  SCHAR  escWord;
  SCHAR  escCnt=0;
  SHORT* pEscBitCntSum;

  pEscBitCntSum = &(pRvlc->length_of_rvlc_escapes);

  /* Decode all RVLC-Escape words with a plain Huffman-Decoder */
  while ( *pEscBitCntSum > 0 ) {
    escWord = rvlcDecodeEscapeWord(pRvlc, bs);

    if (escWord >= 0) {

      pEsc[escCnt] = escWord;
      escCnt++;
    }
    else {
      pRvlc->errorLogRvlc |= RVLC_ERROR_ALL_ESCAPE_WORDS_INVALID;
      pRvlc->numDecodedEscapeWordsEsc = escCnt;

      return;
    }
  } /* all RVLC escapes decoded */

  pRvlc->numDecodedEscapeWordsEsc = escCnt;
}


/*---------------------------------------------------------------------------------------------
     function:     decodeRVLCodeword

     description:  Decodes a RVL-coded dpcm-word (-part).
-----------------------------------------------------------------------------------------------
        input:     - FDK bitstream handle
                   - pointer rvlc structure
-----------------------------------------------------------------------------------------------
        return:    - a dpcm value which is within range [0,1,..,14] in case of no errors.
                     The offset of 7 must be subtracted to get a valid dpcm scalefactor value.
                     In case of errors a forbidden codeword is detected --> returning -1
-------------------------------------------------------------------------------------------- */

SCHAR decodeRVLCodeword (HANDLE_FDK_BITSTREAM  bs, CErRvlcInfo *pRvlc)
{
  int     i;
  SCHAR   value;
  UCHAR   carryBit;
  UINT    branchValue;
  UINT    branchNode;

  const UINT *pRvlCodeTree = pRvlc->pHuffTreeRvlCodewds;
  UCHAR   direction        = pRvlc->direction;
  USHORT *pBitstrIndxRvl   = pRvlc->pBitstrIndxRvl_RVL;
  UINT    treeNode         = *pRvlCodeTree;

  for (i=MAX_LEN_RVLC_CODE_WORD-1; i >= 0; i--) {
    carryBit = rvlcReadBitFromBitstream(bs,             /* get next bit */
                                        pBitstrIndxRvl,
                                        direction);

    CarryBitToBranchValue(carryBit,                     /* huffman decoding, do a single step in huffman decoding tree */
                          treeNode,
                          &branchValue,
                          &branchNode);

    if ((branchNode & TEST_BIT_10) == TEST_BIT_10) {    /* test bit 10 ; if set --> a RVLC-codeword is completely decoded */
      value = (SCHAR) (branchNode & CLR_BIT_10);
      *pRvlc->pRvlBitCnt_RVL -= (MAX_LEN_RVLC_CODE_WORD - i);

      /* check available bits for decoding */
      if (*pRvlc->pRvlBitCnt_RVL < 0) {
        if (direction ==  FWD) {
          pRvlc->errorLogRvlc |= RVLC_ERROR_RVL_SUM_BIT_COUNTER_BELOW_ZERO_FWD; }
        else {
          pRvlc->errorLogRvlc |= RVLC_ERROR_RVL_SUM_BIT_COUNTER_BELOW_ZERO_BWD; }
        value = -1;                                     /* signalize an error in return value, because too many bits was decoded */
      }

      /* check max value of dpcm value */
      if (value > MAX_ALLOWED_DPCM_INDEX) {
        if (direction ==  FWD) {
          pRvlc->errorLogRvlc |= RVLC_ERROR_FORBIDDEN_CW_DETECTED_FWD;
        }
        else {
          pRvlc->errorLogRvlc |= RVLC_ERROR_FORBIDDEN_CW_DETECTED_BWD;
        }
        value = -1;                                     /* signalize an error in return value, because a forbidden cw was detected*/
      }

      return value;                                     /* return a dpcm value with offset +7 or an error status */
    }
    else {
      treeNode = *(pRvlCodeTree + branchValue);         /* update treeNode for further step in decoding tree */
    }
  }

  return -1;
}


/*---------------------------------------------------------------------------------------------
     function:     rvlcDecodeForward

     description:  Decode RVL-coded codewords in forward direction.
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - pointer channel info structure
                   - handle to FDK bitstream
-----------------------------------------------------------------------------------------------
        return:    -
-------------------------------------------------------------------------------------------- */

static
void rvlcDecodeForward (CErRvlcInfo            *pRvlc,
                        CAacDecoderChannelInfo *pAacDecoderChannelInfo,
                        HANDLE_FDK_BITSTREAM    bs)
{
  int band  = 0;
  int group = 0;
  int bnds  = 0;

  SHORT dpcm;

  SHORT  factor   = pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain - SF_OFFSET;
  SHORT  position = - SF_OFFSET;
  SHORT  noisenrg = pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain - SF_OFFSET - 90 - 256;

  SHORT* pScfFwd = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd;
  SHORT* pScfEsc = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfEsc;
  UCHAR* pEscFwdCnt = &(pRvlc->numDecodedEscapeWordsFwd);

  pRvlc->pRvlBitCnt_RVL = &(pRvlc->length_of_rvlc_sf_fwd);
  pRvlc->pBitstrIndxRvl_RVL = &(pRvlc->bitstreamIndexRvlFwd);

  *pEscFwdCnt       = 0;
  pRvlc->direction  = FWD;
  pRvlc->noise_used = 0;
  pRvlc->sf_used    = 0;
  pRvlc->lastScf    = 0;
  pRvlc->lastNrg    = 0;
  pRvlc->lastIs     = 0;

  rvlcCheckIntensityCb(pRvlc,pAacDecoderChannelInfo);

  /* main loop fwd long */
  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 :
        pScfFwd[bnds] = 0;
        break;

      case INTENSITY_HCB2 :
      case INTENSITY_HCB  :
        /* store dpcm_is_position */
        dpcm = decodeRVLCodeword(bs, pRvlc);
        if ( dpcm < 0 ) {
          pRvlc->conceal_max = bnds;
          return;
        }
        dpcm -= TABLE_OFFSET;
        if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
          if (pRvlc->length_of_rvlc_escapes) {
            pRvlc->conceal_max = bnds;
            return;
          }
          else {
            if (dpcm == MIN_RVL) {
              dpcm -= *pScfEsc++;
            }
            else {
              dpcm += *pScfEsc++;
            }
            (*pEscFwdCnt)++;
            if (pRvlc->conceal_max_esc == CONCEAL_MAX_INIT) {
              pRvlc->conceal_max_esc = bnds;
            }
          }
        }
        position += dpcm;
        pScfFwd[bnds] = position;
        pRvlc->lastIs = position;
        break;

      case NOISE_HCB :
        if (pRvlc->noise_used == 0) {
          pRvlc->noise_used = 1;
          pRvlc->first_noise_band = bnds;
          noisenrg += pRvlc->dpcm_noise_nrg;
          pScfFwd[bnds] = 100 + noisenrg;
          pRvlc->lastNrg = noisenrg;
        }
        else {
          dpcm = decodeRVLCodeword(bs, pRvlc);
          if ( dpcm < 0 ) {
            pRvlc->conceal_max = bnds;
            return;
          }
          dpcm -= TABLE_OFFSET;
          if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
            if (pRvlc->length_of_rvlc_escapes) {
              pRvlc->conceal_max = bnds;
              return;
            }
            else {
              if (dpcm == MIN_RVL) {
                dpcm -= *pScfEsc++;
              }
              else {
                dpcm += *pScfEsc++;
              }
              (*pEscFwdCnt)++;
              if (pRvlc->conceal_max_esc == CONCEAL_MAX_INIT) {
                pRvlc->conceal_max_esc = bnds;
              }
            }
          }
          noisenrg += dpcm;
          pScfFwd[bnds] = 100 + noisenrg;
          pRvlc->lastNrg = noisenrg;
        }
        pAacDecoderChannelInfo->data.aac.PnsData.pnsUsed[bnds] = 1;
        break ;

      default :
        pRvlc->sf_used = 1;
        dpcm = decodeRVLCodeword(bs, pRvlc);
        if ( dpcm < 0 ) {
          pRvlc->conceal_max = bnds;
          return;
        }
        dpcm -= TABLE_OFFSET;
        if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
          if (pRvlc->length_of_rvlc_escapes) {
            pRvlc->conceal_max = bnds;
            return;
          }
          else {
            if (dpcm == MIN_RVL) {
              dpcm -= *pScfEsc++; }
            else {
              dpcm += *pScfEsc++;
            }
            (*pEscFwdCnt)++;
            if (pRvlc->conceal_max_esc == CONCEAL_MAX_INIT) {
              pRvlc->conceal_max_esc = bnds;
            }
          }
        }
        factor += dpcm;
        pScfFwd[bnds] = factor;
        pRvlc->lastScf = factor;
        break;
      }
    }
  }

  /* postfetch fwd long */
  if (pRvlc->intensity_used) {
    dpcm = decodeRVLCodeword(bs, pRvlc);      /* dpcm_is_last_position */
    if ( dpcm < 0 ) {
      pRvlc->conceal_max = bnds;
      return;
    }
    dpcm -= TABLE_OFFSET;
    if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
      if (pRvlc->length_of_rvlc_escapes) {
        pRvlc->conceal_max = bnds;
        return;
      }
      else {
        if (dpcm == MIN_RVL) {
          dpcm -= *pScfEsc++;
        }
        else {
          dpcm += *pScfEsc++;
        }
        (*pEscFwdCnt)++;
        if (pRvlc->conceal_max_esc == CONCEAL_MAX_INIT) {
          pRvlc->conceal_max_esc = bnds;
        }
      }
    }
    pRvlc->dpcm_is_last_position = dpcm;
  }
}


/*---------------------------------------------------------------------------------------------
     function:     rvlcDecodeBackward

     description:  Decode RVL-coded codewords in backward direction.
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - pointer channel info structure
                   - handle FDK bitstream
-----------------------------------------------------------------------------------------------
        return:    -
-------------------------------------------------------------------------------------------- */

static
void rvlcDecodeBackward (CErRvlcInfo            *pRvlc,
                         CAacDecoderChannelInfo *pAacDecoderChannelInfo,
                         HANDLE_FDK_BITSTREAM    bs)
{
  SHORT  band, group, dpcm, offset;
  SHORT  bnds = pRvlc->maxSfbTransmitted-1;

  SHORT  factor     = pRvlc->rev_global_gain - SF_OFFSET;
  SHORT  position   = pRvlc->dpcm_is_last_position - SF_OFFSET;
  SHORT  noisenrg   = pRvlc->rev_global_gain + pRvlc->dpcm_noise_last_position - SF_OFFSET - 90 - 256;

  SHORT *pScfBwd    = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfBwd;
  SHORT *pScfEsc    = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfEsc;
  UCHAR *pEscEscCnt = &(pRvlc->numDecodedEscapeWordsEsc);
  UCHAR *pEscBwdCnt = &(pRvlc->numDecodedEscapeWordsBwd);

  pRvlc->pRvlBitCnt_RVL = &(pRvlc->length_of_rvlc_sf_bwd);
  pRvlc->pBitstrIndxRvl_RVL = &(pRvlc->bitstreamIndexRvlBwd);

  *pEscBwdCnt = 0;
  pRvlc->direction = BWD;
  pScfEsc += *pEscEscCnt - 1;             /* set pScfEsc to last entry */
  pRvlc->firstScf = 0;
  pRvlc->firstNrg = 0;
  pRvlc->firstIs = 0;

  /* prefetch long BWD */
  if (pRvlc->intensity_used) {
    dpcm = decodeRVLCodeword(bs, pRvlc);      /* dpcm_is_last_position */
    if ( dpcm < 0 ) {
      pRvlc->dpcm_is_last_position = 0;
      pRvlc->conceal_min = bnds;
      return;
    }
    dpcm -= TABLE_OFFSET;
    if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
      if (pRvlc->length_of_rvlc_escapes) {
        pRvlc->conceal_min = bnds;
        return;
      }
      else {
        if (dpcm == MIN_RVL) {
          dpcm -= *pScfEsc--;
        }
        else {
          dpcm += *pScfEsc--;
        }
        (*pEscBwdCnt)++;
        if (pRvlc->conceal_min_esc == CONCEAL_MIN_INIT) {
          pRvlc->conceal_min_esc = bnds;
        }
      }
    }
    pRvlc->dpcm_is_last_position = dpcm;
  }

  /* main loop long BWD */
  for (group=pRvlc->numWindowGroups-1; group >= 0; group--) {
    for (band=pRvlc->maxSfbTransmitted-1; band >= 0; band--) {
      bnds = 16*group+band;
      if ((band == 0) && (pRvlc->numWindowGroups != 1))
        offset = 16 - pRvlc->maxSfbTransmitted + 1;
      else
        offset = 1;

      switch (pAacDecoderChannelInfo->pDynData->aCodeBook[bnds]) {

      case ZERO_HCB :
        pScfBwd[bnds] = 0;
        break;

      case INTENSITY_HCB2 :
      case INTENSITY_HCB  :
        /* store dpcm_is_position */
        dpcm = decodeRVLCodeword(bs, pRvlc);
        if ( dpcm < 0 ) {
          pScfBwd[bnds] = position;
          pRvlc->conceal_min = FDKmax(0,bnds-offset);
          return;
        }
        dpcm -= TABLE_OFFSET;
        if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
          if (pRvlc->length_of_rvlc_escapes) {
            pScfBwd[bnds] = position;
            pRvlc->conceal_min = FDKmax(0,bnds-offset);
            return;
          }
          else {
            if (dpcm == MIN_RVL) {
              dpcm -= *pScfEsc--;
            }
            else {
              dpcm += *pScfEsc--;
            }
            (*pEscBwdCnt)++;
            if (pRvlc->conceal_min_esc == CONCEAL_MIN_INIT) {
              pRvlc->conceal_min_esc = FDKmax(0,bnds-offset);
            }
          }
        }
        pScfBwd[bnds] = position;
        position -= dpcm;
        pRvlc->firstIs = position;
        break;

      case NOISE_HCB :
        if ( bnds == pRvlc->first_noise_band ) {
          pScfBwd[bnds] = pRvlc->dpcm_noise_nrg + pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain - SF_OFFSET - 90 - 256;
          pRvlc->firstNrg = pScfBwd[bnds];
        }
        else {
          dpcm = decodeRVLCodeword(bs, pRvlc);
          if ( dpcm < 0 ) {
            pScfBwd[bnds] = noisenrg;
            pRvlc->conceal_min = FDKmax(0,bnds-offset);
            return;
          }
          dpcm -= TABLE_OFFSET;
          if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
            if (pRvlc->length_of_rvlc_escapes) {
              pScfBwd[bnds] = noisenrg;
              pRvlc->conceal_min = FDKmax(0,bnds-offset);
              return;
            }
            else {
              if (dpcm == MIN_RVL) {
                dpcm -= *pScfEsc--;
              }
              else {
                dpcm += *pScfEsc--;
              }
              (*pEscBwdCnt)++;
              if (pRvlc->conceal_min_esc == CONCEAL_MIN_INIT) {
                pRvlc->conceal_min_esc = FDKmax(0,bnds-offset);
              }
            }
          }
          pScfBwd[bnds] = noisenrg;
          noisenrg -= dpcm;
          pRvlc->firstNrg = noisenrg;
        }
        break ;

      default :
        dpcm = decodeRVLCodeword(bs, pRvlc);
        if ( dpcm < 0 ) {
          pScfBwd[bnds] = factor;
          pRvlc->conceal_min = FDKmax(0,bnds-offset);
          return;
        }
        dpcm -= TABLE_OFFSET;
        if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {
          if (pRvlc->length_of_rvlc_escapes) {
            pScfBwd[bnds] = factor;
            pRvlc->conceal_min = FDKmax(0,bnds-offset);
            return;
          }
          else {
            if (dpcm == MIN_RVL) {
              dpcm -= *pScfEsc--;
            }
            else {
              dpcm += *pScfEsc--;
            }
            (*pEscBwdCnt)++;
            if (pRvlc->conceal_min_esc == CONCEAL_MIN_INIT) {
              pRvlc->conceal_min_esc = FDKmax(0,bnds-offset);
            }
          }
        }
        pScfBwd[bnds] = factor;
        factor -= dpcm;
        pRvlc->firstScf = factor;
        break;
      }
    }
  }
}


/*---------------------------------------------------------------------------------------------
     function:     rvlcFinalErrorDetection

     description:  Call RVLC concealment if error was detected in decoding process
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - pointer channel info structure
-----------------------------------------------------------------------------------------------
        return:    -
-------------------------------------------------------------------------------------------- */

static
void rvlcFinalErrorDetection (CAacDecoderChannelInfo  *pAacDecoderChannelInfo,
                              CAacDecoderStaticChannelInfo *pAacDecoderStaticChannelInfo)
{
  CErRvlcInfo *pRvlc = &pAacDecoderChannelInfo->pComData->overlay.aac.erRvlcInfo;
  UCHAR ErrorStatusComplete       = 0;
  UCHAR ErrorStatusLengthFwd      = 0;
  UCHAR ErrorStatusLengthBwd      = 0;
  UCHAR ErrorStatusLengthEscapes  = 0;
  UCHAR ErrorStatusFirstScf       = 0;
  UCHAR ErrorStatusLastScf        = 0;
  UCHAR ErrorStatusFirstNrg       = 0;
  UCHAR ErrorStatusLastNrg        = 0;
  UCHAR ErrorStatusFirstIs        = 0;
  UCHAR ErrorStatusLastIs         = 0;
  UCHAR ErrorStatusForbiddenCwFwd = 0;
  UCHAR ErrorStatusForbiddenCwBwd = 0;
  UCHAR ErrorStatusNumEscapesFwd  = 0;
  UCHAR ErrorStatusNumEscapesBwd  = 0;
  UCHAR ConcealStatus             = 1;
  UCHAR currentBlockType;  /* short: 0, not short: 1*/

#if VERBOSE_RVLC_OUTPUT
  CHAR  Strategy[60]="No";
  SHORT conceal_max;
  SHORT conceal_min;
#endif

  pAacDecoderChannelInfo->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK = 1;

  /* invalid escape words, bit counter unequal zero, forbidden codeword detected */
  if (pRvlc->errorLogRvlc & RVLC_ERROR_FORBIDDEN_CW_DETECTED_FWD)
    ErrorStatusForbiddenCwFwd = 1;

  if (pRvlc->errorLogRvlc & RVLC_ERROR_FORBIDDEN_CW_DETECTED_BWD)
    ErrorStatusForbiddenCwBwd = 1;

  /* bit counter forward unequal zero */
  if (pRvlc->length_of_rvlc_sf_fwd)
    ErrorStatusLengthFwd = 1;

  /* bit counter backward unequal zero */
  if (pRvlc->length_of_rvlc_sf_bwd)
    ErrorStatusLengthBwd = 1;

  /* bit counter escape sequences unequal zero */
  if (pRvlc->sf_escapes_present)
    if (pRvlc->length_of_rvlc_escapes)
      ErrorStatusLengthEscapes = 1;

  if (pRvlc->sf_used) {
    /* first decoded scf does not match to global gain in backward direction */
    if (pRvlc->firstScf != (pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain - SF_OFFSET) )
      ErrorStatusFirstScf = 1;

    /* last decoded scf does not match to rev global gain in forward direction */
    if (pRvlc->lastScf != (pRvlc->rev_global_gain - SF_OFFSET) )
      ErrorStatusLastScf = 1;
  }

  if (pRvlc->noise_used) {
    /* first decoded nrg does not match to dpcm_noise_nrg in backward direction */
    if (pRvlc->firstNrg != (pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain + pRvlc->dpcm_noise_nrg - SF_OFFSET -90 - 256) )
      ErrorStatusFirstNrg = 1;

    /* last decoded nrg does not match to dpcm_noise_last_position in forward direction */
    if (pRvlc->lastNrg != (pRvlc->rev_global_gain + pRvlc->dpcm_noise_last_position - SF_OFFSET - 90 - 256) )
      ErrorStatusLastNrg = 1;
  }

  if (pRvlc->intensity_used) {
    /* first decoded is position does not match in backward direction */
    if (pRvlc->firstIs != (-SF_OFFSET) )
      ErrorStatusFirstIs = 1;

    /* last decoded is position does not match in forward direction */
    if (pRvlc->lastIs != (pRvlc->dpcm_is_last_position - SF_OFFSET) )
      ErrorStatusLastIs = 1;
  }

  /* decoded escapes and used escapes in forward direction do not fit */
  if ((pRvlc->numDecodedEscapeWordsFwd != pRvlc->numDecodedEscapeWordsEsc) && (pRvlc->conceal_max == CONCEAL_MAX_INIT)) {
    ErrorStatusNumEscapesFwd = 1;
  }

  /* decoded escapes and used escapes in backward direction do not fit */
  if ((pRvlc->numDecodedEscapeWordsBwd != pRvlc->numDecodedEscapeWordsEsc) && (pRvlc->conceal_min == CONCEAL_MIN_INIT)) {
    ErrorStatusNumEscapesBwd = 1;
  }

#if VERBOSE_RVLC_OUTPUT
  conceal_max = pRvlc->conceal_max;
  conceal_min = pRvlc->conceal_min;
#endif

  if (    ErrorStatusLengthEscapes
      || (
           (   (pRvlc->conceal_max == CONCEAL_MAX_INIT)
            && (pRvlc->numDecodedEscapeWordsFwd != pRvlc->numDecodedEscapeWordsEsc)
            && (ErrorStatusLastScf || ErrorStatusLastNrg || ErrorStatusLastIs) )

            &&

           (   (pRvlc->conceal_min == CONCEAL_MIN_INIT)
            && (pRvlc->numDecodedEscapeWordsBwd != pRvlc->numDecodedEscapeWordsEsc)
            && (ErrorStatusFirstScf || ErrorStatusFirstNrg || ErrorStatusFirstIs) )
         )
      || (   (pRvlc->conceal_max == CONCEAL_MAX_INIT)
          && ((pRvlc->rev_global_gain - SF_OFFSET - pRvlc->lastScf) < -15)
         )
      || (   (pRvlc->conceal_min == CONCEAL_MIN_INIT)
          && ((pAacDecoderChannelInfo->pDynData->RawDataInfo.GlobalGain - SF_OFFSET - pRvlc->firstScf) < -15)
         )
     ) {
    if ((pRvlc->conceal_max == CONCEAL_MAX_INIT) || (pRvlc->conceal_min == CONCEAL_MIN_INIT)) {
      pRvlc->conceal_max = 0;
      pRvlc->conceal_min = FDKmax(0, (pRvlc->numWindowGroups-1)*16+pRvlc->maxSfbTransmitted-1);
    }
    else {
      pRvlc->conceal_max = FDKmin(pRvlc->conceal_max,pRvlc->conceal_max_esc);
      pRvlc->conceal_min = FDKmax(pRvlc->conceal_min,pRvlc->conceal_min_esc);
    }
  }

  ErrorStatusComplete =    ErrorStatusLastScf || ErrorStatusFirstScf || ErrorStatusLastNrg || ErrorStatusFirstNrg
                        || ErrorStatusLastIs || ErrorStatusFirstIs || ErrorStatusForbiddenCwFwd || ErrorStatusForbiddenCwBwd
                        || ErrorStatusLengthFwd || ErrorStatusLengthBwd || ErrorStatusLengthEscapes || ErrorStatusNumEscapesFwd
                        || ErrorStatusNumEscapesBwd;

  currentBlockType = (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence) ? 0 : 1;


  if (!ErrorStatusComplete) {
    int band;
    int group;
    int bnds;
    int lastSfbIndex;

    lastSfbIndex = (pRvlc->numWindowGroups > 1) ? 16 : 64;

    for (group=0; group < pRvlc->numWindowGroups; group++) {
      for (band=0; band<pRvlc->maxSfbTransmitted; band++) {
        bnds = 16*group+band;
        pAacDecoderChannelInfo->pDynData->aScaleFactor[bnds] = pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousScaleFactor[bnds] = pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfFwd[bnds];
      }
    }

    for (group=0; group < pRvlc->numWindowGroups; group++)
    {
      for (band=0; band<pRvlc->maxSfbTransmitted; band++) {
        bnds = 16*group+band;
        pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds] = pAacDecoderChannelInfo->pDynData->aCodeBook[bnds];
      }
      for (; band <lastSfbIndex; band++) {
        bnds = 16*group+band;
        FDK_ASSERT(bnds >= 0 && bnds < RVLC_MAX_SFB);
        pAacDecoderStaticChannelInfo->concealmentInfo.aRvlcPreviousCodebook[bnds] = ZERO_HCB;
      }
    }
  }
  else {
    int band;
    int group;

    /* A single bit error was detected in decoding of dpcm values. It also could be an error with more bits in decoding
       of escapes and dpcm values whereby an illegal codeword followed not directly after the corrupted bits but just
       after decoding some more (wrong) scalefactors. Use the smaller scalefactor from forward decoding, backward decoding
       and previous frame. */
    if (   ((pRvlc->conceal_min != CONCEAL_MIN_INIT) || (pRvlc->conceal_max != CONCEAL_MAX_INIT)) && (pRvlc->conceal_min <= pRvlc->conceal_max)
        && (pAacDecoderStaticChannelInfo->concealmentInfo.rvlcPreviousBlockType == currentBlockType) && pAacDecoderStaticChannelInfo->concealmentInfo.rvlcPreviousScaleFactorOK
        && pRvlc->sf_concealment && ConcealStatus )
    {
      BidirectionalEstimation_UseScfOfPrevFrameAsReference (pAacDecoderChannelInfo, pAacDecoderStaticChannelInfo);
      ConcealStatus=0;
#if VERBOSE_RVLC_OUTPUT
      FDKstrcpy(Strategy,"Yes (BidirectionalEstimation_UseScfOfPrevFrameAsReference)");
#endif
    }

    /* A single bit error was detected in decoding of dpcm values. It also could be an error with more bits in decoding
       of escapes and dpcm values whereby an illegal codeword followed not directly after the corrupted bits but just
       after decoding some more (wrong) scalefactors. Use the smaller scalefactor from forward and backward decoding. */
    if (   (pRvlc->conceal_min <= pRvlc->conceal_max)  && ((pRvlc->conceal_min != CONCEAL_MIN_INIT) || (pRvlc->conceal_max != CONCEAL_MAX_INIT))
        && !(pAacDecoderStaticChannelInfo->concealmentInfo.rvlcPreviousScaleFactorOK && pRvlc->sf_concealment && (pAacDecoderStaticChannelInfo->concealmentInfo.rvlcPreviousBlockType == currentBlockType))
        && ConcealStatus )
    {
      BidirectionalEstimation_UseLowerScfOfCurrentFrame (pAacDecoderChannelInfo);
      ConcealStatus=0;
#if VERBOSE_RVLC_OUTPUT
      FDKstrcpy(Strategy,"Yes (BidirectionalEstimation_UseLowerScfOfCurrentFrame)");
#endif
    }

    /* No errors were detected in decoding of escapes and dpcm values however the first and last value
       of a group (is,nrg,sf) is incorrect */
    if (   (pRvlc->conceal_min <= pRvlc->conceal_max)  && ((ErrorStatusLastScf && ErrorStatusFirstScf)
        || (ErrorStatusLastNrg && ErrorStatusFirstNrg) || (ErrorStatusLastIs && ErrorStatusFirstIs))
        && !(ErrorStatusForbiddenCwFwd || ErrorStatusForbiddenCwBwd || ErrorStatusLengthEscapes ) && ConcealStatus)
    {
      StatisticalEstimation (pAacDecoderChannelInfo);
      ConcealStatus=0;
#if VERBOSE_RVLC_OUTPUT
      FDKstrcpy(Strategy,"Yes (StatisticalEstimation)");
#endif
    }

    /* A error with more bits in decoding of escapes and dpcm values was detected. Use the smaller scalefactor from forward
       decoding, backward decoding and previous frame. */
    if (   (pRvlc->conceal_min <= pRvlc->conceal_max) && pAacDecoderStaticChannelInfo->concealmentInfo.rvlcPreviousScaleFactorOK && pRvlc->sf_concealment
        && (pAacDecoderStaticChannelInfo->concealmentInfo.rvlcPreviousBlockType == currentBlockType) && ConcealStatus )
    {
      PredictiveInterpolation(pAacDecoderChannelInfo, pAacDecoderStaticChannelInfo);
      ConcealStatus=0;
#if VERBOSE_RVLC_OUTPUT
      FDKstrcpy(Strategy,"Yes (PredictiveInterpolation)");
#endif
    }

    /* Call frame concealment, because no better strategy was found. Setting the scalefactors to zero is done for debugging
       purposes */
    if (ConcealStatus) {
      for (group=0; group < pRvlc->numWindowGroups; group++) {
        for (band=0; band<pRvlc->maxSfbTransmitted; band++) {
          pAacDecoderChannelInfo->pDynData->aScaleFactor[16*group+band] = 0;
        }
      }
      pAacDecoderChannelInfo->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK = 0;
#if VERBOSE_RVLC_OUTPUT
      FDKstrcpy(Strategy,"Yes (FrameConcealment)");
#endif
    }
  }

#if VERBOSE_RVLC_OUTPUT
  DebugOutputDistortedBitstreams(pRvlc,pAacDecoderChannelInfo,ErrorStatusLengthFwd,ErrorStatusLengthBwd,
                                 ErrorStatusLengthEscapes,ErrorStatusFirstScf,ErrorStatusLastScf,
                                 ErrorStatusFirstNrg,ErrorStatusLastNrg,ErrorStatusFirstIs,ErrorStatusLastIs,
                                 ErrorStatusForbiddenCwFwd,ErrorStatusForbiddenCwBwd,ErrorStatusNumEscapesFwd,
                                 ErrorStatusNumEscapesBwd,conceal_max,conceal_min,Strategy);
#endif
}


/*---------------------------------------------------------------------------------------------
     function:     CRvlc_Read

     description:  Read RVLC ESC1 data (side info) from bitstream.
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - pointer channel info structure
                   - pointer bitstream structure
-----------------------------------------------------------------------------------------------
        return:    -
-------------------------------------------------------------------------------------------- */

void CRvlc_Read (
                 CAacDecoderChannelInfo *pAacDecoderChannelInfo,
                 HANDLE_FDK_BITSTREAM    bs)
{
  CErRvlcInfo *pRvlc = &pAacDecoderChannelInfo->pComData->overlay.aac.erRvlcInfo;

  int  group,band;

  /* RVLC long specific initialization  Init part 1 of 2 */
  pRvlc->numWindowGroups   = GetWindowGroups(&pAacDecoderChannelInfo->icsInfo);
  pRvlc->maxSfbTransmitted = GetScaleFactorBandsTransmitted(&pAacDecoderChannelInfo->icsInfo);
  pRvlc->noise_used               =  0;                  /* noise detection */
  pRvlc->dpcm_noise_nrg           =  0;                  /* only for debugging */
  pRvlc->dpcm_noise_last_position =  0;                  /* only for debugging */
  pRvlc->length_of_rvlc_escapes   = -1; /* default value is used for error detection and concealment */

  /* read only error sensitivity class 1 data (ESC 1 - data) */
  pRvlc->sf_concealment    = FDKreadBits(bs,1);                    /* #1 */
  pRvlc->rev_global_gain   = FDKreadBits(bs,8);                    /* #2 */

  if (GetWindowSequence(&pAacDecoderChannelInfo->icsInfo) == EightShortSequence) {
    pRvlc->length_of_rvlc_sf = FDKreadBits(bs,11);                 /* #3 */
  }
  else {
    pRvlc->length_of_rvlc_sf = FDKreadBits(bs,9);                  /* #3 */
  }

  /* check if noise codebook is used */
  for (group = 0; group < pRvlc->numWindowGroups; group++) {
    for (band=0; band < pRvlc->maxSfbTransmitted; band++) {
      if (pAacDecoderChannelInfo->pDynData->aCodeBook[16*group+band] == NOISE_HCB) {
        pRvlc->noise_used = 1;
        break;
      }
    }
  }

  if (pRvlc->noise_used)
    pRvlc->dpcm_noise_nrg = FDKreadBits(bs, 9);              /* #4  PNS */

  pRvlc->sf_escapes_present = FDKreadBits(bs, 1);            /* #5      */

  if ( pRvlc->sf_escapes_present) {
    pRvlc->length_of_rvlc_escapes = FDKreadBits(bs, 8);      /* #6      */
  }

  if (pRvlc->noise_used) {
    pRvlc->dpcm_noise_last_position = FDKreadBits(bs, 9);    /* #7  PNS */
    pRvlc->length_of_rvlc_sf -= 9;
  }

  pRvlc->length_of_rvlc_sf_fwd = pRvlc->length_of_rvlc_sf;
  pRvlc->length_of_rvlc_sf_bwd = pRvlc->length_of_rvlc_sf;
}


/*---------------------------------------------------------------------------------------------
     function:     CRvlc_Decode

     description:  Decode rvlc data
                   The function reads both the escape sequences and the scalefactors in forward
                   and backward direction. If an error occured during decoding process which can
                   not be concealed with the rvlc concealment frame concealment will be initiated.
                   Then the element "rvlcCurrentScaleFactorOK" in the decoder channel info is set
                   to 0 otherwise it is set to 1.
-----------------------------------------------------------------------------------------------
        input:     - pointer rvlc structure
                   - pointer channel info structure
                   - pointer to persistent channel info structure
                   - pointer bitstream structure
-----------------------------------------------------------------------------------------------
        return:    ErrorStatus = AAC_DEC_OK
-------------------------------------------------------------------------------------------- */

void CRvlc_Decode (
        CAacDecoderChannelInfo  *pAacDecoderChannelInfo,
        CAacDecoderStaticChannelInfo *pAacDecoderStaticChannelInfo,
        HANDLE_FDK_BITSTREAM     bs
        )
{
  CErRvlcInfo *pRvlc = &pAacDecoderChannelInfo->pComData->overlay.aac.erRvlcInfo;
  INT  bitCntOffst;
  UINT saveBitCnt;

  rvlcInit(pRvlc,pAacDecoderChannelInfo,bs);

  /* save bitstream position */
  saveBitCnt = FDKgetBitCnt(bs);

#if RVLC_ADVANCED_BITSTREAM_ERROR_GENERATOR_SF
  GenerateSingleBitError(pRvlc,
                         &(pRvlc->bitstreamIndexRvlFwd),
                         pRvlc->length_of_rvlc_sf,
                         0);
#endif

#if RVLC_ADVANCED_BITSTREAM_ERROR_GENERATOR_ESC
  if (pRvlc->sf_escapes_present)
    GenerateSingleBitError(pRvlc,
                           &(pRvlc->bitstreamIndexEsc),
                           pRvlc->length_of_rvlc_escapes,
                           1);
#endif

  if ( pRvlc->sf_escapes_present)
    rvlcDecodeEscapes(pRvlc, pAacDecoderChannelInfo->pComData->overlay.aac.aRvlcScfEsc, bs);

  rvlcDecodeForward(pRvlc,pAacDecoderChannelInfo, bs);
  rvlcDecodeBackward(pRvlc,pAacDecoderChannelInfo, bs);
  rvlcFinalErrorDetection(pAacDecoderChannelInfo, pAacDecoderStaticChannelInfo);

  pAacDecoderChannelInfo->pDynData->specificTo.aac.rvlcIntensityUsed = pRvlc->intensity_used;
  pAacDecoderChannelInfo->data.aac.PnsData.PnsActive = pRvlc->noise_used;

  /* restore bitstream position */
  bitCntOffst = saveBitCnt - FDKgetBitCnt(bs);
  if( bitCntOffst ) {
    FDKpushBiDirectional(bs, bitCntOffst);
  }
}

void CRvlc_ElementCheck (
        CAacDecoderChannelInfo *pAacDecoderChannelInfo[],
        CAacDecoderStaticChannelInfo *pAacDecoderStaticChannelInfo[],
        const UINT flags,
        const INT elChannels
        )
{
  int ch;

  /* Required for MPS residuals. */
  if (pAacDecoderStaticChannelInfo == NULL) {
    return;
  }

  /* RVLC specific sanity checks */
  if ( (flags & AC_ER_RVLC) && (elChannels == 2)) { /* to be reviewed */
    if ( ( (pAacDecoderChannelInfo[0]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK == 0) ||
           (pAacDecoderChannelInfo[1]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK == 0) )
        &&  pAacDecoderChannelInfo[0]->pComData->jointStereoData.MsMaskPresent  ) {
      pAacDecoderChannelInfo[0]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK = 0;
      pAacDecoderChannelInfo[1]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK = 0;
    }

    if (   (pAacDecoderChannelInfo[0]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK == 0)
        && (pAacDecoderChannelInfo[1]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK == 1)
        && (pAacDecoderChannelInfo[1]->pDynData->specificTo.aac.rvlcIntensityUsed == 1) ){
      pAacDecoderChannelInfo[1]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK = 0;
    }
  }

  for (ch = 0; ch < elChannels; ch ++)
  {
    pAacDecoderStaticChannelInfo[ch]->concealmentInfo.rvlcPreviousBlockType = (GetWindowSequence(&pAacDecoderChannelInfo[ch]->icsInfo) == EightShortSequence) ? 0 : 1;
    if (flags & AC_ER_RVLC) {
      pAacDecoderStaticChannelInfo[ch]->concealmentInfo.rvlcPreviousScaleFactorOK = pAacDecoderChannelInfo[ch]->pDynData->specificTo.aac.rvlcCurrentScaleFactorOK;
    }
    else {
      pAacDecoderStaticChannelInfo[ch]->concealmentInfo.rvlcPreviousScaleFactorOK = 0;
    }
  }
}