/* -----------------------------------------------------------------------------

Software License for The Fraunhofer FDK AAC Codec Library for Android

© Copyright  1995 - 2021 Fraunhofer-Gesellschaft zur Förderung der angewandten

Forschung e.V. All rights reserved.

 1.    INTRODUCTION

The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software

that implements the MPEG Advanced Audio Coding ("AAC") encoding and decoding

scheme for digital audio. This FDK AAC Codec software is intended to be used on

a wide variety of Android devices.

AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient

general perceptual audio codecs. AAC-ELD is considered the best-performing

full-bandwidth communications codec by independent studies and is widely

deployed. AAC has been standardized by ISO and IEC as part of the MPEG

specifications.

Patent licenses for necessary patent claims for the FDK AAC Codec (including

those of Fraunhofer) may be obtained through Via Licensing

(www.vialicensing.com) or through the respective patent owners individually for

the purpose of encoding or decoding bit streams in products that are compliant

with the ISO/IEC MPEG audio standards. Please note that most manufacturers of

Android devices already license these patent claims through Via Licensing or

directly from the patent owners, and therefore FDK AAC Codec software may

already be covered under those patent licenses when it is used for those

licensed purposes only.

Commercially-licensed AAC software libraries, including floating-point versions

with enhanced sound quality, are also available from Fraunhofer. Users are

encouraged to check the Fraunhofer website for additional applications

information and documentation.

2.    COPYRIGHT LICENSE

Redistribution and use in source and binary forms, with or without modification,

are permitted without payment of copyright license fees provided that you

satisfy the following conditions:

You must retain the complete text of this software license in redistributions of

the FDK AAC Codec or your modifications thereto in source code form.

You must retain the complete text of this software license in the documentation

and/or other materials provided with redistributions of the FDK AAC Codec or

your modifications thereto in binary form. You must make available free of

charge copies of the complete source code of the FDK AAC Codec and your

modifications thereto to recipients of copies in binary form.

The name of Fraunhofer may not be used to endorse or promote products derived

from this library without prior written permission.

You may not charge copyright license fees for anyone to use, copy or distribute

the FDK AAC Codec software or your modifications thereto.

Your modified versions of the FDK AAC Codec must carry prominent notices stating

that you changed the software and the date of any change. For modified versions

of the FDK AAC Codec, the term "Fraunhofer FDK AAC Codec Library for Android"

must be replaced by the term "Third-Party Modified Version of the Fraunhofer FDK

AAC Codec Library for Android."

3.    NO PATENT LICENSE

NO EXPRESS OR IMPLIED LICENSES TO ANY PATENT CLAIMS, including without

limitation the patents of Fraunhofer, ARE GRANTED BY THIS SOFTWARE LICENSE.

Fraunhofer provides no warranty of patent non-infringement with respect to this

software.

You may use this FDK AAC Codec software or modifications thereto only for

purposes that are authorized by appropriate patent licenses.

4.    DISCLAIMER

This FDK AAC Codec software is provided by Fraunhofer on behalf of the copyright

holders and contributors "AS IS" and WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,

including but not limited to the implied warranties of merchantability and

fitness for a particular purpose. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR

CONTRIBUTORS BE LIABLE for any direct, indirect, incidental, special, exemplary,

or consequential damages, including but not limited to procurement of substitute

goods or services; loss of use, data, or profits, or business interruption,

however caused and on any theory of liability, whether in contract, strict

liability, or tort (including negligence), arising in any way out of the use of

this software, even if advised of the possibility of such damage.

5.    CONTACT INFORMATION

Fraunhofer Institute for Integrated Circuits IIS

Attention: Audio and Multimedia Departments - FDK AAC LL

Am Wolfsmantel 33

91058 Erlangen, Germany

www.iis.fraunhofer.de/amm

amm-info@iis.fraunhofer.de

----------------------------------------------------------------------------- */

/**************************** AAC decoder library ******************************

   Author(s):

   Description:

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

/*!

  \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->bsAnchor = (INT)FDKgetValidBits(bs);

  pRvlc->bitstreamIndexRvlFwd =

      0; /* first bit within RVL coded block as start address for  forward

            decoding */

  pRvlc->bitstreamIndexRvlBwd =

      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 = pRvlc->bsAnchor - (INT)FDKgetValidBits(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);

  }

}

/*---------------------------------------------------------------------------------------------

     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;

  INT *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 */

                                 pRvlc->bsAnchor, 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;

  INT *pBitstrIndxRvl = pRvlc->pBitstrIndxRvl_RVL;

  UINT treeNode = *pRvlCodeTree;

  for (i = MAX_LEN_RVLC_CODE_WORD - 1; i >= 0; i--) {

    carryBit =

        rvlcReadBitFromBitstream(bs, /* get next bit */

                                 pRvlc->bsAnchor, 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 escEscCnt = 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 += escEscCnt - 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) || (*pEscBwdCnt >= escEscCnt)) {

        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 = fMax(0, bnds - offset);

            return;

          }

          dpcm -= TABLE_OFFSET;

          if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {

            if ((pRvlc->length_of_rvlc_escapes) || (*pEscBwdCnt >= escEscCnt)) {

              pScfBwd[bnds] = position;

              pRvlc->conceal_min = fMax(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 = fMax(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 = fMax(0, bnds - offset);

              return;

            }

            dpcm -= TABLE_OFFSET;

            if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {

              if ((pRvlc->length_of_rvlc_escapes) ||

                  (*pEscBwdCnt >= escEscCnt)) {

                pScfBwd[bnds] = noisenrg;

                pRvlc->conceal_min = fMax(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 = fMax(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 = fMax(0, bnds - offset);

            return;

          }

          dpcm -= TABLE_OFFSET;

          if ((dpcm == MIN_RVL) || (dpcm == MAX_RVL)) {

            if ((pRvlc->length_of_rvlc_escapes) || (*pEscBwdCnt >= escEscCnt)) {

              pScfBwd[bnds] = factor;

              pRvlc->conceal_min = fMax(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 = fMax(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*/

  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 (ErrorStatusLengthEscapes ||

      (((pRvlc->conceal_max == CONCEAL_MAX_INIT) &&

        (pRvlc->numDecodedEscapeWordsFwd != pRvlc->numDecodedEscapeWordsEsc) &&

        (ErrorStatusLastScf || ErrorStatusLastNrg || ErrorStatusLastIs))

       &&

       ((pRvlc->conceal_min == CONCEAL_MIN_INIT) &&