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

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

� Copyright  1995 - 2013 Fraunhofer-Gesellschaft zur F�rderung der angewandten Forschung e.V.
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 1.    INTRODUCTION
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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)
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Commercially-licensed AAC software libraries, including floating-point versions with enhanced sound quality,
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Fraunhofer Institute for Integrated Circuits IIS
Attention: Audio and Multimedia Departments - FDK AAC LL
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----------------------------------------------------------------------------------------------------------- */

/*****************************  MPEG-4 AAC Decoder  **************************

   Author(s):   Josef Hoepfl
   Description: joint stereo processing

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

#include "stereo.h"


#include "aac_rom.h"
#include "FDK_bitstream.h"
#include "channelinfo.h"

enum
{
  L = 0,
  R = 1
};


int CJointStereo_Read(
        HANDLE_FDK_BITSTREAM bs,
        CJointStereoData *pJointStereoData,
        const int windowGroups,
        const int scaleFactorBandsTransmitted,
        const UINT flags
        )
{
  int group,band;

  pJointStereoData->MsMaskPresent = (UCHAR) FDKreadBits(bs,2);

  FDKmemclear(pJointStereoData->MsUsed, scaleFactorBandsTransmitted*sizeof(UCHAR));

  switch (pJointStereoData->MsMaskPresent)
  {
    case 0 : /* no M/S */
      /* all flags are already cleared */
      break ;

    case 1 : /* read ms_used */

      for (group=0; group<windowGroups; group++)
      {
        for (band=0; band<scaleFactorBandsTransmitted; band++)
        {
          pJointStereoData->MsUsed[band] |= (FDKreadBits(bs,1) << group);
        }
      }
      break ;

    case 2 : /* full spectrum M/S */

      for (band=0; band<scaleFactorBandsTransmitted; band++)
      {
        pJointStereoData->MsUsed[band] = 255 ;  /* set all flags to 1 */
      }
      break ;
  }

  return 0;
}

void CJointStereo_ApplyMS(
        CAacDecoderChannelInfo *pAacDecoderChannelInfo[2],
        const SHORT *pScaleFactorBandOffsets,
        const UCHAR *pWindowGroupLength,
        const int windowGroups,
        const int scaleFactorBandsTransmittedL,
        const int scaleFactorBandsTransmittedR
        )
{
  CJointStereoData *pJointStereoData = &pAacDecoderChannelInfo[L]->pComData->jointStereoData;
  int window, group, scaleFactorBandsTransmitted;

  FDK_ASSERT(scaleFactorBandsTransmittedL == scaleFactorBandsTransmittedR);
  scaleFactorBandsTransmitted = scaleFactorBandsTransmittedL;
  for (window = 0, group = 0; group < windowGroups; group++)
  {
    UCHAR groupMask = 1 << group;

    for (int groupwin=0; groupwin<pWindowGroupLength[group]; groupwin++, window++)
    {
      int band;
      FIXP_DBL *leftSpectrum, *rightSpectrum;
      SHORT *leftScale = &pAacDecoderChannelInfo[L]->pDynData->aSfbScale[window*16];
      SHORT *rightScale = &pAacDecoderChannelInfo[R]->pDynData->aSfbScale[window*16];

      leftSpectrum = SPEC(pAacDecoderChannelInfo[L]->pSpectralCoefficient, window, pAacDecoderChannelInfo[L]->granuleLength);
      rightSpectrum = SPEC(pAacDecoderChannelInfo[R]->pSpectralCoefficient, window, pAacDecoderChannelInfo[R]->granuleLength);

      for (band=0; band<scaleFactorBandsTransmitted; band++)
      {
        if (pJointStereoData->MsUsed[band] & groupMask)
        {
          int lScale=leftScale[band];
          int rScale=rightScale[band];
          int commonScale=lScale > rScale ? lScale:rScale;

          /* ISO/IEC 14496-3 Chapter 4.6.8.1.1 :
             M/S joint channel coding can only be used if common_window is �1�. */
          FDK_ASSERT(GetWindowSequence(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowSequence(&pAacDecoderChannelInfo[R]->icsInfo));
          FDK_ASSERT(GetWindowShape(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowShape(&pAacDecoderChannelInfo[R]->icsInfo));

          commonScale++;
          leftScale[band]=commonScale;
          rightScale[band]=commonScale;

          lScale = fMin(DFRACT_BITS-1, commonScale - lScale);
          rScale = fMin(DFRACT_BITS-1, commonScale - rScale);

          FDK_ASSERT(lScale >= 0 && rScale >= 0);

          for (int index=pScaleFactorBandOffsets[band]; index<pScaleFactorBandOffsets[band+1]; index++)
          {
            FIXP_DBL leftCoefficient  = leftSpectrum [index] ;
            FIXP_DBL rightCoefficient = rightSpectrum [index] ;

            leftCoefficient >>= lScale ;
            rightCoefficient >>= rScale ;

            leftSpectrum [index] = leftCoefficient + rightCoefficient ;
            rightSpectrum [index] = leftCoefficient - rightCoefficient ;
          }
        }
      }
    }
  }

  /* Reset MsUsed flags if no explicit signalling was transmitted. Necessary for intensity coding.
     PNS correlation signalling was mapped before calling CJointStereo_ApplyMS(). */
  if (pJointStereoData->MsMaskPresent == 2) {
    FDKmemclear(pJointStereoData->MsUsed, JointStereoMaximumBands * sizeof(UCHAR));
  }
}

void CJointStereo_ApplyIS(
        CAacDecoderChannelInfo *pAacDecoderChannelInfo[2],
        const SHORT *pScaleFactorBandOffsets,
        const UCHAR *pWindowGroupLength,
        const int windowGroups,
        const int scaleFactorBandsTransmitted,
        const UINT CommonWindow
        )
{
  CJointStereoData *pJointStereoData = &pAacDecoderChannelInfo[L]->pComData->jointStereoData;

  for (int window=0,group=0; group<windowGroups; group++)
  {
    UCHAR *CodeBook;
    SHORT *ScaleFactor;
    UCHAR groupMask = 1 << group;

    CodeBook = &pAacDecoderChannelInfo[R]->pDynData->aCodeBook[group*16];
    ScaleFactor = &pAacDecoderChannelInfo[R]->pDynData->aScaleFactor[group*16];

    for (int groupwin=0; groupwin<pWindowGroupLength[group]; groupwin++, window++)
    {
      FIXP_DBL *leftSpectrum, *rightSpectrum;
      SHORT *leftScale = &pAacDecoderChannelInfo[L]->pDynData->aSfbScale[window*16];
      SHORT *rightScale = &pAacDecoderChannelInfo[R]->pDynData->aSfbScale[window*16];
      int band;

      leftSpectrum = SPEC(pAacDecoderChannelInfo[L]->pSpectralCoefficient, window, pAacDecoderChannelInfo[L]->granuleLength);
      rightSpectrum = SPEC(pAacDecoderChannelInfo[R]->pSpectralCoefficient, window, pAacDecoderChannelInfo[R]->granuleLength);

      for (band=0; band<scaleFactorBandsTransmitted; band++)
      {
        if ((CodeBook [band] == INTENSITY_HCB) ||
            (CodeBook [band] == INTENSITY_HCB2))
        {
          int bandScale = -(ScaleFactor [band] + 100) ;

          int msb = bandScale >> 2 ;
          int lsb = bandScale & 0x03 ;

          /* exponent of MantissaTable[lsb][0] is 1, thus msb+1 below. */
          FIXP_DBL scale = MantissaTable[lsb][0];

          /* ISO/IEC 14496-3 Chapter 4.6.8.2.3 :
             The use of intensity stereo coding is signaled by the use of the pseudo codebooks
             INTENSITY_HCB and INTENSITY_HCB2 (15 and 14) only in the right channel of a
             channel_pair_element() having a common ics_info() (common_window == 1). */
          FDK_ASSERT(GetWindowSequence(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowSequence(&pAacDecoderChannelInfo[R]->icsInfo));
          FDK_ASSERT(GetWindowShape(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowShape(&pAacDecoderChannelInfo[R]->icsInfo));

          rightScale[band] = leftScale[band]+msb+1;

          if (CommonWindow && (pJointStereoData->MsUsed[band] & groupMask))
          {

            if (CodeBook[band] == INTENSITY_HCB) /* _NOT_ in-phase */
            {
              scale = -scale ;
            }
          }
          else
          {
            if (CodeBook[band] == INTENSITY_HCB2) /* out-of-phase */
            {
              scale = -scale ;
            }
          }

          for (int index=pScaleFactorBandOffsets[band]; index<pScaleFactorBandOffsets[band+1]; index++)
          {
            rightSpectrum[index] = fMult(leftSpectrum[index],scale);
          }
        }
      }
    }
  }
}