libSBRdec/src/psbitdec.cpp

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

© Copyright  1995 - 2018 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
----------------------------------------------------------------------------- */

/**************************** SBR decoder library ******************************

   Author(s):

   Description:

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

#include "psbitdec.h"

#include "sbr_rom.h"
#include "huff_dec.h"

/* PS dec privat functions */
SBR_ERROR ResetPsDec(HANDLE_PS_DEC h_ps_d);

/***************************************************************************/
/*!
  \brief  huffman decoding by codebook table

  \return index of huffman codebook table

****************************************************************************/
static SCHAR decode_huff_cw(
    Huffman h,                    /*!< pointer to huffman codebook table */
    HANDLE_FDK_BITSTREAM hBitBuf, /*!< Handle to Bitbuffer */
    int *length)                  /*!< length of huffman codeword (or NULL) */
{
  UCHAR bit = 0;
  SCHAR index = 0;
  UCHAR bitCount = 0;

  while (index >= 0) {
    bit = FDKreadBits(hBitBuf, 1);
    bitCount++;
    index = h[index][bit];
  }
  if (length) {
    *length = bitCount;
  }
  return (index + 64); /* Add offset */
}

/***************************************************************************/
/*!
  \brief  helper function - limiting of value to min/max values

  \return limited value

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

static SCHAR limitMinMax(SCHAR i, SCHAR min, SCHAR max) {
  if (i < min)
    return min;
  else if (i > max)
    return max;
  else
    return i;
}

/***************************************************************************/
/*!
  \brief  Decodes delta values in-place and updates
          data buffers according to quantization classes.

  When delta coded in frequency the first element is deltacode from zero.
  aIndex buffer is decoded from delta values to actual values.

  \return none

****************************************************************************/
static void deltaDecodeArray(
    SCHAR enable, SCHAR *aIndex,  /*!< ICC/IID parameters */
    SCHAR *aPrevFrameIndex,       /*!< ICC/IID parameters  of previous frame */
    SCHAR DtDf, UCHAR nrElements, /*!< as conveyed in bitstream */
                                  /*!< output array size: nrElements*stride */
    UCHAR stride,                 /*!< 1=dflt, 2=half freq. resolution */
    SCHAR minIdx, SCHAR maxIdx) {
  int i;

  /* Delta decode */
  if (enable == 1) {
    if (DtDf == 0) { /* Delta coded in freq */
      aIndex[0] = 0 + aIndex[0];
      aIndex[0] = limitMinMax(aIndex[0], minIdx, maxIdx);
      for (i = 1; i < nrElements; i++) {
        aIndex[i] = aIndex[i - 1] + aIndex[i];
        aIndex[i] = limitMinMax(aIndex[i], minIdx, maxIdx);
      }
    } else { /* Delta time */
      for (i = 0; i < nrElements; i++) {
        aIndex[i] = aPrevFrameIndex[i * stride] + aIndex[i];
        aIndex[i] = limitMinMax(aIndex[i], minIdx, maxIdx);
      }
    }
  } else { /* No data is sent, set index to zero */
    for (i = 0; i < nrElements; i++) {
      aIndex[i] = 0;
    }
  }
  if (stride == 2) {
    for (i = nrElements * stride - 1; i > 0; i--) {
      aIndex[i] = aIndex[i >> 1];
    }
  }
}

/***************************************************************************/
/*!
  \brief Mapping of ICC/IID parameters to 20 stereo bands

  \return none

****************************************************************************/
static void map34IndexTo20(SCHAR *aIndex, /*!< decoded ICC/IID parameters */
                           UCHAR noBins)  /*!< number of stereo bands     */
{
  aIndex[0] = (2 * aIndex[0] + aIndex[1]) / 3;
  aIndex[1] = (aIndex[1] + 2 * aIndex[2]) / 3;
  aIndex[2] = (2 * aIndex[3] + aIndex[4]) / 3;
  aIndex[3] = (aIndex[4] + 2 * aIndex[5]) / 3;
  aIndex[4] = (aIndex[6] + aIndex[7]) / 2;
  aIndex[5] = (aIndex[8] + aIndex[9]) / 2;
  aIndex[6] = aIndex[10];
  aIndex[7] = aIndex[11];
  aIndex[8] = (aIndex[12] + aIndex[13]) / 2;
  aIndex[9] = (aIndex[14] + aIndex[15]) / 2;
  aIndex[10] = aIndex[16];
  /* For IPD/OPD it stops here */

  if (noBins == NO_HI_RES_BINS) {
    aIndex[11] = aIndex[17];
    aIndex[12] = aIndex[18];
    aIndex[13] = aIndex[19];
    aIndex[14] = (aIndex[20] + aIndex[21]) / 2;
    aIndex[15] = (aIndex[22] + aIndex[23]) / 2;
    aIndex[16] = (aIndex[24] + aIndex[25]) / 2;
    aIndex[17] = (aIndex[26] + aIndex[27]) / 2;
    aIndex[18] = (aIndex[28] + aIndex[29] + aIndex[30] + aIndex[31]) / 4;
    aIndex[19] = (aIndex[32] + aIndex[33]) / 2;
  }
}

/***************************************************************************/
/*!
  \brief  Decodes delta coded IID, ICC, IPD and OPD indices

  \return PS processing flag. If set to 1

****************************************************************************/
int DecodePs(struct PS_DEC *h_ps_d,  /*!< PS handle */
             const UCHAR frameError, /*!< Flag telling that frame had errors */
             PS_DEC_COEFFICIENTS *pScratch) {
  MPEG_PS_BS_DATA *pBsData;
  UCHAR gr, env;
  int bPsHeaderValid, bPsDataAvail;

  /* Assign Scratch */
  h_ps_d->specificTo.mpeg.pCoef = pScratch;

  /* Shortcuts to avoid deferencing and keep the code readable */
  pBsData = &h_ps_d->bsData[h_ps_d->processSlot].mpeg;
  bPsHeaderValid = pBsData->bPsHeaderValid;
  bPsDataAvail =
      (h_ps_d->bPsDataAvail[h_ps_d->processSlot] == ppt_mpeg) ? 1 : 0;

  /***************************************************************************************
   * Decide whether to process or to conceal PS data or not. */

  if ((h_ps_d->psDecodedPrv && !frameError && !bPsDataAvail) ||
      (!h_ps_d->psDecodedPrv &&
       (frameError || !bPsDataAvail || !bPsHeaderValid))) {
    /* Don't apply PS processing.
     * Declare current PS header and bitstream data invalid. */
    pBsData->bPsHeaderValid = 0;
    h_ps_d->bPsDataAvail[h_ps_d->processSlot] = ppt_none;
    return (0);
  }

  if (frameError ||
      !bPsHeaderValid) { /* no new PS data available (e.g. frame loss) */
    /* => keep latest data constant (i.e. FIX with noEnv=0) */
    pBsData->noEnv = 0;
  }

  /***************************************************************************************
   * Decode bitstream payload or prepare parameter for concealment:
   */
  for (env = 0; env < pBsData->noEnv; env++) {
    SCHAR *aPrevIidIndex;
    SCHAR *aPrevIccIndex;

    UCHAR noIidSteps = pBsData->bFineIidQ ? NO_IID_STEPS_FINE : NO_IID_STEPS;

    if (env == 0) {
      aPrevIidIndex = h_ps_d->specificTo.mpeg.aIidPrevFrameIndex;
      aPrevIccIndex = h_ps_d->specificTo.mpeg.aIccPrevFrameIndex;
    } else {
      aPrevIidIndex = pBsData->aaIidIndex[env - 1];
      aPrevIccIndex = pBsData->aaIccIndex[env - 1];
    }

    deltaDecodeArray(pBsData->bEnableIid, pBsData->aaIidIndex[env],
                     aPrevIidIndex, pBsData->abIidDtFlag[env],
                     FDK_sbrDecoder_aNoIidBins[pBsData->freqResIid],
                     (pBsData->freqResIid) ? 1 : 2, -noIidSteps, noIidSteps);

    deltaDecodeArray(pBsData->bEnableIcc, pBsData->aaIccIndex[env],
                     aPrevIccIndex, pBsData->abIccDtFlag[env],
                     FDK_sbrDecoder_aNoIccBins[pBsData->freqResIcc],
                     (pBsData->freqResIcc) ? 1 : 2, 0, NO_ICC_STEPS - 1);
  } /* for (env=0; env<pBsData->noEnv; env++) */

  /* handling of FIX noEnv=0 */
  if (pBsData->noEnv == 0) {
    /* set noEnv=1, keep last parameters or force 0 if not enabled */
    pBsData->noEnv = 1;

    if (pBsData->bEnableIid) {
      pBsData->bFineIidQ = h_ps_d->specificTo.mpeg.bPrevFrameFineIidQ;
      pBsData->freqResIid = h_ps_d->specificTo.mpeg.prevFreqResIid;
      for (gr = 0; gr < NO_HI_RES_IID_BINS; gr++) {
        pBsData->aaIidIndex[pBsData->noEnv - 1][gr] =
            h_ps_d->specificTo.mpeg.aIidPrevFrameIndex[gr];
      }
    } else {
      for (gr = 0; gr < NO_HI_RES_IID_BINS; gr++) {
        pBsData->aaIidIndex[pBsData->noEnv - 1][gr] = 0;
      }
    }

    if (pBsData->bEnableIcc) {
      pBsData->freqResIcc = h_ps_d->specificTo.mpeg.prevFreqResIcc;
      for (gr = 0; gr < NO_HI_RES_ICC_BINS; gr++) {
        pBsData->aaIccIndex[pBsData->noEnv - 1][gr] =
            h_ps_d->specificTo.mpeg.aIccPrevFrameIndex[gr];
      }
    } else {
      for (gr = 0; gr < NO_HI_RES_ICC_BINS; gr++) {
        pBsData->aaIccIndex[pBsData->noEnv - 1][gr] = 0;
      }
    }
  }

  /* Update previous frame Iid quantization */
  h_ps_d->specificTo.mpeg.bPrevFrameFineIidQ = pBsData->bFineIidQ;

  /* Update previous frequency resolution for IID */
  h_ps_d->specificTo.mpeg.prevFreqResIid = pBsData->freqResIid;

  /* Update previous frequency resolution for ICC */
  h_ps_d->specificTo.mpeg.prevFreqResIcc = pBsData->freqResIcc;

  /* Update previous frame index buffers */
  for (gr = 0; gr < NO_HI_RES_IID_BINS; gr++) {
    h_ps_d->specificTo.mpeg.aIidPrevFrameIndex[gr] =
        pBsData->aaIidIndex[pBsData->noEnv - 1][gr];
  }
  for (gr = 0; gr < NO_HI_RES_ICC_BINS; gr++) {
    h_ps_d->specificTo.mpeg.aIccPrevFrameIndex[gr] =
        pBsData->aaIccIndex[pBsData->noEnv - 1][gr];
  }

  /* PS data from bitstream (if avail) was decoded now */
  h_ps_d->bPsDataAvail[h_ps_d->processSlot] = ppt_none;

  /* handling of env borders for FIX & VAR */
  if (pBsData->bFrameClass == 0) {
    /* FIX_BORDERS NoEnv=0,1,2,4 */
    pBsData->aEnvStartStop[0] = 0;
    for (env = 1; env < pBsData->noEnv; env++) {
      pBsData->aEnvStartStop[env] =
          (env * h_ps_d->noSubSamples) / pBsData->noEnv;
    }
    pBsData->aEnvStartStop[pBsData->noEnv] = h_ps_d->noSubSamples;
    /* 1024 (32 slots) env borders:  0, 8, 16, 24, 32 */
    /*  960 (30 slots) env borders:  0, 7, 15, 22, 30 */
  } else { /* if (h_ps_d->bFrameClass == 0) */
    /* VAR_BORDERS NoEnv=1,2,3,4 */
    pBsData->aEnvStartStop[0] = 0;

    /* handle case aEnvStartStop[noEnv]<noSubSample for VAR_BORDERS by
       duplicating last PS parameters and incrementing noEnv */
    if (pBsData->aEnvStartStop[pBsData->noEnv] < h_ps_d->noSubSamples) {
      for (gr = 0; gr < NO_HI_RES_IID_BINS; gr++) {
        pBsData->aaIidIndex[pBsData->noEnv][gr] =
            pBsData->aaIidIndex[pBsData->noEnv - 1][gr];
      }
      for (gr = 0; gr < NO_HI_RES_ICC_BINS; gr++) {
        pBsData->aaIccIndex[pBsData->noEnv][gr] =
            pBsData->aaIccIndex[pBsData->noEnv - 1][gr];
      }
      pBsData->noEnv++;
      pBsData->aEnvStartStop[pBsData->noEnv] = h_ps_d->noSubSamples;
    }

    /* enforce strictly monotonic increasing borders */
    for (env = 1; env < pBsData->noEnv; env++) {
      UCHAR thr;
      thr = (UCHAR)h_ps_d->noSubSamples - (pBsData->noEnv - env);
      if (pBsData->aEnvStartStop[env] > thr) {
        pBsData->aEnvStartStop[env] = thr;
      } else {
        thr = pBsData->aEnvStartStop[env - 1] + 1;
        if (pBsData->aEnvStartStop[env] < thr) {
          pBsData->aEnvStartStop[env] = thr;
        }
      }
    }
  } /* if (h_ps_d->bFrameClass == 0) ... else */

  /* copy data prior to possible 20<->34 in-place mapping */
  for (env = 0; env < pBsData->noEnv; env++) {
    UCHAR i;
    for (i = 0; i < NO_HI_RES_IID_BINS; i++) {
      h_ps_d->specificTo.mpeg.pCoef->aaIidIndexMapped[env][i] =
          pBsData->aaIidIndex[env][i];
    }
    for (i = 0; i < NO_HI_RES_ICC_BINS; i++) {
      h_ps_d->specificTo.mpeg.pCoef->aaIccIndexMapped[env][i] =
          pBsData->aaIccIndex[env][i];
    }
  }

  /* MPEG baseline PS */
  /* Baseline version of PS always uses the hybrid filter structure with 20
   * stereo bands. */
  /* If ICC/IID parameters for 34 stereo bands are decoded they have to be
   * mapped to 20   */
  /* stereo bands. */
  /* Additionaly the IPD/OPD parameters won't be used. */

  for (env = 0; env < pBsData->noEnv; env++) {
    if (pBsData->freqResIid == 2)
      map34IndexTo20(h_ps_d->specificTo.mpeg.pCoef->aaIidIndexMapped[env],
                     NO_HI_RES_IID_BINS);
    if (pBsData->freqResIcc == 2)
      map34IndexTo20(h_ps_d->specificTo.mpeg.pCoef->aaIccIndexMapped[env],
                     NO_HI_RES_ICC_BINS);

    /* IPD/OPD is disabled in baseline version and thus was removed here */
  }

  return (1);
}

/***************************************************************************/
/*!

  \brief  Reads parametric stereo data from bitstream

  \return

****************************************************************************/
unsigned int ReadPsData(
    HANDLE_PS_DEC h_ps_d,         /*!< handle to struct PS_DEC */
    HANDLE_FDK_BITSTREAM hBitBuf, /*!< handle to struct BIT_BUF */
    int nBitsLeft                 /*!< max number of bits available */
) {
  MPEG_PS_BS_DATA *pBsData;

  UCHAR gr, env;
  SCHAR dtFlag;
  INT startbits;
  Huffman CurrentTable;
  SCHAR bEnableHeader;

  if (!h_ps_d) return 0;

  pBsData = &h_ps_d->bsData[h_ps_d->bsReadSlot].mpeg;

  if (h_ps_d->bsReadSlot != h_ps_d->bsLastSlot) {
    /* Copy last header data */
    FDKmemcpy(pBsData, &h_ps_d->bsData[h_ps_d->bsLastSlot].mpeg,
              sizeof(MPEG_PS_BS_DATA));
  }

  startbits = (INT)FDKgetValidBits(hBitBuf);

  bEnableHeader = (SCHAR)FDKreadBits(hBitBuf, 1);

  /* Read header */
  if (bEnableHeader) {
    pBsData->bPsHeaderValid = 1;
    pBsData->bEnableIid = (UCHAR)FDKreadBits(hBitBuf, 1);
    if (pBsData->bEnableIid) {
      pBsData->modeIid = (UCHAR)FDKreadBits(hBitBuf, 3);
    }

    pBsData->bEnableIcc = (UCHAR)FDKreadBits(hBitBuf, 1);
    if (pBsData->bEnableIcc) {
      pBsData->modeIcc = (UCHAR)FDKreadBits(hBitBuf, 3);
    }

    pBsData->bEnableExt = (UCHAR)FDKreadBits(hBitBuf, 1);
  }

  pBsData->bFrameClass = (UCHAR)FDKreadBits(hBitBuf, 1);
  if (pBsData->bFrameClass == 0) {
    /* FIX_BORDERS NoEnv=0,1,2,4 */
    pBsData->noEnv =
        FDK_sbrDecoder_aFixNoEnvDecode[(UCHAR)FDKreadBits(hBitBuf, 2)];
    /* all additional handling of env borders is now in DecodePs() */
  } else {
    /* VAR_BORDERS NoEnv=1,2,3,4 */
    pBsData->noEnv = 1 + (UCHAR)FDKreadBits(hBitBuf, 2);
    for (env = 1; env < pBsData->noEnv + 1; env++)
      pBsData->aEnvStartStop[env] = ((UCHAR)FDKreadBits(hBitBuf, 5)) + 1;
    /* all additional handling of env borders is now in DecodePs() */
  }

  /* verify that IID & ICC modes (quant grid, freq res) are supported */
  if ((pBsData->modeIid > 5) || (pBsData->modeIcc > 5)) {
    /* no useful PS data could be read from bitstream */
    h_ps_d->bPsDataAvail[h_ps_d->bsReadSlot] = ppt_none;
    /* discard all remaining bits */
    nBitsLeft -= startbits - (INT)FDKgetValidBits(hBitBuf);
    while (nBitsLeft > 0) {
      int i = nBitsLeft;
      if (i > 8) {
        i = 8;
      }
      FDKreadBits(hBitBuf, i);
      nBitsLeft -= i;
    }
    return (UINT)(startbits - (INT)FDKgetValidBits(hBitBuf));
  }

  if (pBsData->modeIid > 2) {
    pBsData->freqResIid = pBsData->modeIid - 3;
    pBsData->bFineIidQ = 1;
  } else {
    pBsData->freqResIid = pBsData->modeIid;
    pBsData->bFineIidQ = 0;
  }

  if (pBsData->modeIcc > 2) {
    pBsData->freqResIcc = pBsData->modeIcc - 3;
  } else {
    pBsData->freqResIcc = pBsData->modeIcc;
  }

  /* Extract IID data */
  if (pBsData->bEnableIid) {
    for (env = 0; env < pBsData->noEnv; env++) {
      dtFlag = (SCHAR)FDKreadBits(hBitBuf, 1);
      if (!dtFlag) {
        if (pBsData->bFineIidQ)
          CurrentTable = (Huffman)&aBookPsIidFineFreqDecode;
        else
          CurrentTable = (Huffman)&aBookPsIidFreqDecode;
      } else {
        if (pBsData->bFineIidQ)
          CurrentTable = (Huffman)&aBookPsIidFineTimeDecode;
        else
          CurrentTable = (Huffman)&aBookPsIidTimeDecode;
      }

      for (gr = 0; gr < FDK_sbrDecoder_aNoIidBins[pBsData->freqResIid]; gr++)
        pBsData->aaIidIndex[env][gr] =
            decode_huff_cw(CurrentTable, hBitBuf, NULL);
      pBsData->abIidDtFlag[env] = dtFlag;
    }
  }

  /* Extract ICC data */
  if (pBsData->bEnableIcc) {
    for (env = 0; env < pBsData->noEnv; env++) {
      dtFlag = (SCHAR)FDKreadBits(hBitBuf, 1);
      if (!dtFlag)
        CurrentTable = (Huffman)&aBookPsIccFreqDecode;
      else
        CurrentTable = (Huffman)&aBookPsIccTimeDecode;

      for (gr = 0; gr < FDK_sbrDecoder_aNoIccBins[pBsData->freqResIcc]; gr++)
        pBsData->aaIccIndex[env][gr] =
            decode_huff_cw(CurrentTable, hBitBuf, NULL);
      pBsData->abIccDtFlag[env] = dtFlag;
    }
  }

  if (pBsData->bEnableExt) {
    /*!
    Decoders that support only the baseline version of the PS tool are allowed
    to ignore the IPD/OPD data, but according header data has to be parsed.
    ISO/IEC 14496-3 Subpart 8 Annex 4
    */

    int cnt = FDKreadBits(hBitBuf, PS_EXTENSION_SIZE_BITS);
    if (cnt == (1 << PS_EXTENSION_SIZE_BITS) - 1) {
      cnt += FDKreadBits(hBitBuf, PS_EXTENSION_ESC_COUNT_BITS);
    }
    while (cnt--) FDKreadBits(hBitBuf, 8);
  }

  /* new PS data was read from bitstream */
  h_ps_d->bPsDataAvail[h_ps_d->bsReadSlot] = ppt_mpeg;

  return (startbits - (INT)FDKgetValidBits(hBitBuf));
}