libAACdec/src/stereo.cpp

   1
   2 /* -----------------------------------------------------------------------------------------------------------
   3 Software License for The Fraunhofer FDK AAC Codec Library for Android
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   9 The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software that implements
  10 the MPEG Advanced Audio Coding ("AAC") encoding and decoding scheme for digital audio.
  11 This FDK AAC Codec software is intended to be used on a wide variety of Android devices.
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  14 audio codecs. AAC-ELD is considered the best-performing full-bandwidth communications codec by
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  73 5.    CONTACT INFORMATION
  74
  75 Fraunhofer Institute for Integrated Circuits IIS
  76 Attention: Audio and Multimedia Departments - FDK AAC LL
  77 Am Wolfsmantel 33
  78 91058 Erlangen, Germany
  79
  80 www.iis.fraunhofer.de/amm
  81 amm-info@iis.fraunhofer.de
  82 ----------------------------------------------------------------------------------------------------------- */
  83
  84 /*****************************  MPEG-4 AAC Decoder  **************************
  85
  86    Author(s):   Josef Hoepfl
  87    Description: joint stereo processing
  88
  89 ******************************************************************************/
  90
  91 #include "stereo.h"
  92
  93
  94 #include "aac_rom.h"
  95 #include "FDK_bitstream.h"
  96 #include "channelinfo.h"
  97
  98 enum
  99 {
 100   L = 0,
 101   R = 1
 102 };
 103
 104
 105 int CJointStereo_Read(
 106         HANDLE_FDK_BITSTREAM bs,
 107         CJointStereoData *pJointStereoData,
 108         const int windowGroups,
 109         const int scaleFactorBandsTransmitted,
 110         const UINT flags
 111         )
 112 {
 113   int group,band;
 114
 115   pJointStereoData->MsMaskPresent = (UCHAR) FDKreadBits(bs,2);
 116
 117   FDKmemclear(pJointStereoData->MsUsed, scaleFactorBandsTransmitted*sizeof(UCHAR));
 118
 119   switch (pJointStereoData->MsMaskPresent)
 120   {
 121     case 0 : /* no M/S */
 122       /* all flags are already cleared */
 123       break ;
 124
 125     case 1 : /* read ms_used */
 126
 127       for (group=0; group<windowGroups; group++)
 128       {
 129         for (band=0; band<scaleFactorBandsTransmitted; band++)
 130         {
 131           pJointStereoData->MsUsed[band] |= (FDKreadBits(bs,1) << group);
 132         }
 133       }
 134       break ;
 135
 136     case 2 : /* full spectrum M/S */
 137
 138       for (band=0; band<scaleFactorBandsTransmitted; band++)
 139       {
 140         pJointStereoData->MsUsed[band] = 255 ;  /* set all flags to 1 */
 141       }
 142       break ;
 143   }
 144
 145   return 0;
 146 }
 147
 148 void CJointStereo_ApplyMS(
 149         CAacDecoderChannelInfo *pAacDecoderChannelInfo[2],
 150         const SHORT *pScaleFactorBandOffsets,
 151         const UCHAR *pWindowGroupLength,
 152         const int windowGroups,
 153         const int scaleFactorBandsTransmittedL,
 154         const int scaleFactorBandsTransmittedR
 155         )
 156 {
 157   CJointStereoData *pJointStereoData = &pAacDecoderChannelInfo[L]->pComData->jointStereoData;
 158   int window, group, scaleFactorBandsTransmitted;
 159
 160   FDK_ASSERT(scaleFactorBandsTransmittedL == scaleFactorBandsTransmittedR);
 161   scaleFactorBandsTransmitted = scaleFactorBandsTransmittedL;
 162   for (window = 0, group = 0; group < windowGroups; group++)
 163   {
 164     UCHAR groupMask = 1 << group;
 165
 166     for (int groupwin=0; groupwin<pWindowGroupLength[group]; groupwin++, window++)
 167     {
 168       int band;
 169       FIXP_DBL *leftSpectrum, *rightSpectrum;
 170       SHORT *leftScale = &pAacDecoderChannelInfo[L]->pDynData->aSfbScale[window*16];
 171       SHORT *rightScale = &pAacDecoderChannelInfo[R]->pDynData->aSfbScale[window*16];
 172
 173       leftSpectrum = SPEC(pAacDecoderChannelInfo[L]->pSpectralCoefficient, window, pAacDecoderChannelInfo[L]->granuleLength);
 174       rightSpectrum = SPEC(pAacDecoderChannelInfo[R]->pSpectralCoefficient, window, pAacDecoderChannelInfo[R]->granuleLength);
 175
 176       for (band=0; band<scaleFactorBandsTransmitted; band++)
 177       {
 178         if (pJointStereoData->MsUsed[band] & groupMask)
 179         {
 180           int lScale=leftScale[band];
 181           int rScale=rightScale[band];
 182           int commonScale=lScale > rScale ? lScale:rScale;
 183
 184           /* ISO/IEC 14496-3 Chapter 4.6.8.1.1 :
 185              M/S joint channel coding can only be used if common_window is \911\92. */
 186           FDK_ASSERT(GetWindowSequence(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowSequence(&pAacDecoderChannelInfo[R]->icsInfo));
 187           FDK_ASSERT(GetWindowShape(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowShape(&pAacDecoderChannelInfo[R]->icsInfo));
 188
 189           commonScale++;
 190           leftScale[band]=commonScale;
 191           rightScale[band]=commonScale;
 192
 193           lScale = fMin(DFRACT_BITS-1, commonScale - lScale);
 194           rScale = fMin(DFRACT_BITS-1, commonScale - rScale);
 195
 196           FDK_ASSERT(lScale >= 0 && rScale >= 0);
 197
 198           for (int index=pScaleFactorBandOffsets[band]; index<pScaleFactorBandOffsets[band+1]; index++)
 199           {
 200             FIXP_DBL leftCoefficient  = leftSpectrum [index] ;
 201             FIXP_DBL rightCoefficient = rightSpectrum [index] ;
 202
 203             leftCoefficient >>= lScale ;
 204             rightCoefficient >>= rScale ;
 205
 206             leftSpectrum [index] = leftCoefficient + rightCoefficient ;
 207             rightSpectrum [index] = leftCoefficient - rightCoefficient ;
 208           }
 209         }
 210       }
 211     }
 212   }
 213
 214   /* Reset MsUsed flags if no explicit signalling was transmitted. Necessary for intensity coding.
 215      PNS correlation signalling was mapped before calling CJointStereo_ApplyMS(). */
 216   if (pJointStereoData->MsMaskPresent == 2) {
 217     FDKmemclear(pJointStereoData->MsUsed, JointStereoMaximumBands * sizeof(UCHAR));
 218   }
 219 }
 220
 221 void CJointStereo_ApplyIS(
 222         CAacDecoderChannelInfo *pAacDecoderChannelInfo[2],
 223         const SHORT *pScaleFactorBandOffsets,
 224         const UCHAR *pWindowGroupLength,
 225         const int windowGroups,
 226         const int scaleFactorBandsTransmitted,
 227         const UINT CommonWindow
 228         )
 229 {
 230   CJointStereoData *pJointStereoData = &pAacDecoderChannelInfo[L]->pComData->jointStereoData;
 231
 232   for (int window=0,group=0; group<windowGroups; group++)
 233   {
 234     UCHAR *CodeBook;
 235     SHORT *ScaleFactor;
 236     UCHAR groupMask = 1 << group;
 237
 238     CodeBook = &pAacDecoderChannelInfo[R]->pDynData->aCodeBook[group*16];
 239     ScaleFactor = &pAacDecoderChannelInfo[R]->pDynData->aScaleFactor[group*16];
 240
 241     for (int groupwin=0; groupwin<pWindowGroupLength[group]; groupwin++, window++)
 242     {
 243       FIXP_DBL *leftSpectrum, *rightSpectrum;
 244       SHORT *leftScale = &pAacDecoderChannelInfo[L]->pDynData->aSfbScale[window*16];
 245       SHORT *rightScale = &pAacDecoderChannelInfo[R]->pDynData->aSfbScale[window*16];
 246       int band;
 247
 248       leftSpectrum = SPEC(pAacDecoderChannelInfo[L]->pSpectralCoefficient, window, pAacDecoderChannelInfo[L]->granuleLength);
 249       rightSpectrum = SPEC(pAacDecoderChannelInfo[R]->pSpectralCoefficient, window, pAacDecoderChannelInfo[R]->granuleLength);
 250
 251       for (band=0; band<scaleFactorBandsTransmitted; band++)
 252       {
 253         if ((CodeBook [band] == INTENSITY_HCB) ||
 254             (CodeBook [band] == INTENSITY_HCB2))
 255         {
 256           int bandScale = -(ScaleFactor [band] + 100) ;
 257
 258           int msb = bandScale >> 2 ;
 259           int lsb = bandScale & 0x03 ;
 260
 261           /* exponent of MantissaTable[lsb][0] is 1, thus msb+1 below. */
 262           FIXP_DBL scale = MantissaTable[lsb][0];
 263
 264           /* ISO/IEC 14496-3 Chapter 4.6.8.2.3 :
 265              The use of intensity stereo coding is signaled by the use of the pseudo codebooks
 266              INTENSITY_HCB and INTENSITY_HCB2 (15 and 14) only in the right channel of a
 267              channel_pair_element() having a common ics_info() (common_window == 1). */
 268           FDK_ASSERT(GetWindowSequence(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowSequence(&pAacDecoderChannelInfo[R]->icsInfo));
 269           FDK_ASSERT(GetWindowShape(&pAacDecoderChannelInfo[L]->icsInfo) == GetWindowShape(&pAacDecoderChannelInfo[R]->icsInfo));
 270
 271           rightScale[band] = leftScale[band]+msb+1;
 272
 273           if (CommonWindow && (pJointStereoData->MsUsed[band] & groupMask))
 274           {
 275
 276             if (CodeBook[band] == INTENSITY_HCB) /* _NOT_ in-phase */
 277             {
 278               scale = -scale ;
 279             }
 280           }
 281           else
 282           {
 283             if (CodeBook[band] == INTENSITY_HCB2) /* out-of-phase */
 284             {
 285               scale = -scale ;
 286             }
 287           }
 288
 289           for (int index=pScaleFactorBandOffsets[band]; index<pScaleFactorBandOffsets[band+1]; index++)
 290           {
 291             rightSpectrum[index] = fMult(leftSpectrum[index],scale);
 292           }
 293         }
 294       }
 295     }
 296   }
 297 }