psdec_hybrid.cpp - Android社区 - https://www.androidos.net.cn/

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

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This FDK AAC Codec software is intended to be used on a wide variety of Android devices.

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Fraunhofer Institute for Integrated Circuits IIS
Attention: Audio and Multimedia Departments - FDK AAC LL
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91058 Erlangen, Germany

www.iis.fraunhofer.de/amm
amm-info@iis.fraunhofer.de
----------------------------------------------------------------------------------------------------------- */

#include "psdec_hybrid.h"

#include "fft.h"
#include "sbr_ram.h"

#include "FDK_tools_rom.h"
#include "sbr_rom.h"

/*******************************************************************************
 Functionname:  InitHybridFilterBank
 *******************************************************************************

Description:   Init one instance of HANDLE_HYBRID stuct

Arguments:

Return:        none

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

SBR_ERROR
InitHybridFilterBank ( HANDLE_HYBRID hs,          /*!< Handle to HYBRID struct. */
                       SCHAR frameSize,           /*!< Framesize (in Qmf s�bband samples). */
                       SCHAR noBands,             /*!< Number of Qmf bands for hybrid filtering. */
                       const UCHAR *pResolution ) /*!< Resolution in Qmf bands (length noBands). */
{
  SCHAR i;
  UCHAR maxNoChannels = 0;

for (i = 0; i < noBands; i++) {
    hs->pResolution[i] = pResolution[i];
    if(pResolution[i] > maxNoChannels)
      maxNoChannels = pResolution[i];
  }

hs->nQmfBands     = noBands;
  hs->frameSize     = frameSize;
  hs->qmfBufferMove = HYBRID_FILTER_LENGTH - 1;

hs->sf_mQmfBuffer = 0;

return SBRDEC_OK;
}

/*******************************************************************************
 Functionname:  dualChannelFiltering
 *******************************************************************************

Description:   fast 2-channel real-valued filtering with 6-tap delay.

Arguments:

Return:        none

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

/*!
2 channel filter
<pre>
   Filter Coefs:
   0.0,
   0.01899487526049,
   0.0,
   -0.07293139167538,
   0.0,
   0.30596630545168,
   0.5,
   0.30596630545168,
   0.0,
   -0.07293139167538,
   0.0,
   0.01899487526049,
   0.0

Filter design:
   h[q,n] = g[n] * cos(2pi/2 * q * (n-6) );  n = 0..12,  q = 0,1;

->  h[0,n] = g[n] * 1;
   ->  h[1,n] = g[n] * pow(-1,n);
</pre>
*/

static void slotBasedDualChannelFiltering( const FIXP_DBL *pQmfReal,
                                           const FIXP_DBL *pQmfImag,

FIXP_DBL       *mHybridReal,
                                           FIXP_DBL       *mHybridImag)
{

FIXP_DBL  t1, t3, t5, t6;

/* symmetric filter coefficients */

/*  you don't have to shift the result after fMult because of p2_13_20 <= 0.5 */
  t1 = fMultDiv2(p2_13_20[1] , ( (pQmfReal[1] >> 1) + (pQmfReal[11] >> 1)));
  t3 = fMultDiv2(p2_13_20[3] , ( (pQmfReal[3] >> 1) + (pQmfReal[ 9] >> 1)));
  t5 = fMultDiv2(p2_13_20[5] , ( (pQmfReal[5] >> 1) + (pQmfReal[ 7] >> 1)));
  t6 = fMultDiv2(p2_13_20[6] ,   (pQmfReal[6] >> 1) );

mHybridReal[0] = (t1 + t3 + t5 + t6) << 2;
  mHybridReal[1] = (- t1 - t3 - t5 + t6) << 2;

t1 = fMultDiv2(p2_13_20[1] , ( (pQmfImag[1] >> 1) + (pQmfImag[11] >> 1)));
  t3 = fMultDiv2(p2_13_20[3] , ( (pQmfImag[3] >> 1) + (pQmfImag[ 9] >> 1)));
  t5 = fMultDiv2(p2_13_20[5] , ( (pQmfImag[5] >> 1) + (pQmfImag[ 7] >> 1)));
  t6 = fMultDiv2(p2_13_20[6] ,    pQmfImag[6] >> 1 );

mHybridImag[0] = (t1 + t3 + t5 + t6) << 2;
  mHybridImag[1] = (- t1 - t3 - t5 + t6) << 2;
}

/*******************************************************************************
 Functionname:  eightChannelFiltering
 *******************************************************************************

Description:   fast 8-channel complex-valued filtering with 6-tap delay.

Arguments:

Return:        none

*******************************************************************************/
/*!
   8 channel filter

Implementation using a FFT of length 8
<pre>
   prototype filter coefficients:
   0.00746082949812   0.02270420949825   0.04546865930473   0.07266113929591   0.09885108575264   0.11793710567217
   0.125
   0.11793710567217   0.09885108575264   0.07266113929591   0.04546865930473   0.02270420949825   0.00746082949812

Filter design:
   N = 13; Q = 8;
   h[q,n]       = g[n] * exp(j * 2 * pi / Q * (q + .5) * (n - 6));  n = 0..(N-1),  q = 0..(Q-1);

Time Signal:   x[t];
   Filter Bank Output
   y[q,t] = conv(x[t],h[q,t]) = conv(h[q,t],x[t]) = sum(x[k] * h[q, t - k] ) = sum(h[q, k] * x[t - k] ); k = 0..(N-1);

y[q,t] =   x[t - 12]*h[q, 12]  +  x[t - 11]*h[q, 11]  +  x[t - 10]*h[q, 10]  +  x[t -  9]*h[q,  9]
           +  x[t -  8]*h[q,  8]  +  x[t -  7]*h[q,  7]
           +  x[t -  6]*h[q,  6]
           +  x[t -  5]*h[q,  5]  +  x[t -  4]*h[q,  4]
           +  x[t -  3]*h[q,  3]  +  x[t -  2]*h[q,  2]  +  x[t -  1]*h[q,  1]  +  x[t -  0]*h[q,  0];

h'[q, n] = h[q,(N-1)-n] = g[n] * exp(j * 2 * pi / Q * (q + .5) * (6 - n));  n = 0..(N-1),  q = 0..(Q-1);

y[q,t] =   x[t - 12]*h'[q,  0]  +  x[t - 11]*h'[q,  1]  +  x[t - 10]*h'[q,  2]  +  x[t -  9]*h'[q,  3]
           +  x[t -  8]*h'[q,  4]  +  x[t -  7]*h'[q,  5]
           +  x[t -  6]*h'[q,  6]
           +  x[t -  5]*h'[q,  7]  +  x[t -  4]*h'[q,  8]
           +  x[t -  3]*h'[q,  9]  +  x[t -  2]*h'[q, 10]  +  x[t -  1]*h'[q, 11]  +  x[t -  0]*h'[q, 12];

Try to split off FFT Modulation Term:
   FFT(x[t], q) = sum(x[t+k]*exp(-j*2*pi/N *q * k))
                                           c                                           m
   Step 1:  h'[q,n] = g[n] * ( exp(j * 2 * pi / 8 * .5 * (6 - n)) ) * ( exp (j * 2 * pi / 8 * q * (6 - n)) );

h'[q,n] = g[n] *c[n] * m[q,n]; (see above)
    c[n]    = exp( j * 2 * pi / 8 * .5 * (6 - n) );
    m[q,n]  = exp( j * 2 * pi / 8 *  q * (6 - n) );

y[q,t] = x[t -  0]*g[0]*c[0]*m[q,0]  +  x[t -  1]*g[1]*c[ 1]*m[q, 1]  + ...
             ...                         +  x[t - 12]*g[2]*c[12]*m[q,12];

|
    n                   m                            *exp(-j*2*pi)            |   n'                   fft
-------------------------------------------------------------------------------------------------------------------------
    0       exp( j * 2 * pi / 8 * q * 6) ->  exp(-j * 2 * pi / 8 * q * 2)     |   2         exp(-j * 2 * pi / 8 * q * 0)
    1       exp( j * 2 * pi / 8 * q * 5) ->  exp(-j * 2 * pi / 8 * q * 3)     |   3         exp(-j * 2 * pi / 8 * q * 1)
    2       exp( j * 2 * pi / 8 * q * 4) ->  exp(-j * 2 * pi / 8 * q * 4)     |   4         exp(-j * 2 * pi / 8 * q * 2)
    3       exp( j * 2 * pi / 8 * q * 3) ->  exp(-j * 2 * pi / 8 * q * 5)     |   5         exp(-j * 2 * pi / 8 * q * 3)
    4       exp( j * 2 * pi / 8 * q * 2) ->  exp(-j * 2 * pi / 8 * q * 6)     |   6         exp(-j * 2 * pi / 8 * q * 4)
    5       exp( j * 2 * pi / 8 * q * 1) ->  exp(-j * 2 * pi / 8 * q * 7)     |   7         exp(-j * 2 * pi / 8 * q * 5)
    6       exp( j * 2 * pi / 8 * q * 0)                                      |   0         exp(-j * 2 * pi / 8 * q * 6)
    7       exp(-j * 2 * pi / 8 * q * 1)                                      |   1         exp(-j * 2 * pi / 8 * q * 7)
    8       exp(-j * 2 * pi / 8 * q * 2)                                      |   2
    9       exp(-j * 2 * pi / 8 * q * 3)                                      |   3
    10      exp(-j * 2 * pi / 8 * q * 4)                                      |   4
    11      exp(-j * 2 * pi / 8 * q * 5)                                      |   5
    12      exp(-j * 2 * pi / 8 * q * 6)                                      |   6

now use fft modulation coefficients
    m[6]  =       = fft[0]
    m[7]  =       = fft[1]
    m[8]  = m[ 0] = fft[2]
    m[9]  = m[ 1] = fft[3]
    m[10] = m[ 2] = fft[4]
    m[11] = m[ 3] = fft[5]
    m[12] = m[ 4] = fft[6]
            m[ 5] = fft[7]

y[q,t] = (                       x[t- 6]*g[ 6]*c[ 6] ) * fft[q,0]  +
             (                       x[t- 7]*g[ 7]*c[ 7] ) * fft[q,1]  +
             ( x[t- 0]*g[ 0]*c[ 0] + x[t- 8]*g[ 8]*c[ 8] ) * fft[q,2]  +
             ( x[t- 1]*g[ 1]*c[ 1] + x[t- 9]*g[ 9]*c[ 9] ) * fft[q,3]  +
             ( x[t- 2]*g[ 2]*c[ 2] + x[t-10]*g[10]*c[10] ) * fft[q,4]  +
             ( x[t- 3]*g[ 3]*c[ 3] + x[t-11]*g[11]*c[11] ) * fft[q,5]  +
             ( x[t- 4]*g[ 4]*c[ 4] + x[t-12]*g[12]*c[12] ) * fft[q,6]  +
             ( x[t- 5]*g[ 5]*c[ 5]                       ) * fft[q,7];

pre twiddle factors c[n] = exp(j * 2 * pi / 8 * .5 * (6 - n));
    n                c]           |  n                c[n]         |  n                c[n]
---------------------------------------------------------------------------------------------------
    0       exp( j * 6 * pi / 8)  |  1       exp( j * 5 * pi / 8)  |  2       exp( j * 4 * pi / 8)
    3       exp( j * 3 * pi / 8)  |  4       exp( j * 2 * pi / 8)  |  5       exp( j * 1 * pi / 8)
    6       exp( j * 0 * pi / 8)  |  7       exp(-j * 1 * pi / 8)  |  8       exp(-j * 2 * pi / 8)
    9       exp(-j * 3 * pi / 8)  | 10       exp(-j * 4 * pi / 8)  | 11       exp(-j * 5 * pi / 8)
   12       exp(-j * 6 * pi / 8)  |                                |
</pre>
*/

/* defining rotation factors for *ChannelFiltering */

#define cos0Pi    FL2FXCONST_DBL( 1.f)
#define sin0Pi    FL2FXCONST_DBL( 0.f)

#define cos1Pi    FL2FXCONST_DBL(-1.f)
#define sin1Pi    FL2FXCONST_DBL( 0.f)

#define cos1Pi_2  FL2FXCONST_DBL( 0.f)
#define sin1Pi_2  FL2FXCONST_DBL( 1.f)

#define cos1Pi_3  FL2FXCONST_DBL( 0.5f)
#define sin1Pi_3  FL2FXCONST_DBL( 0.86602540378444f)

#define cos0Pi_4  cos0Pi
#define cos1Pi_4  FL2FXCONST_DBL(0.70710678118655f)
#define cos2Pi_4  cos1Pi_2
#define cos3Pi_4  (-cos1Pi_4)
#define cos4Pi_4  (-cos0Pi_4)
#define cos5Pi_4  cos3Pi_4
#define cos6Pi_4  cos2Pi_4

#define sin0Pi_4  sin0Pi
#define sin1Pi_4  FL2FXCONST_DBL(0.70710678118655f)
#define sin2Pi_4  sin1Pi_2
#define sin3Pi_4  sin1Pi_4
#define sin4Pi_4  sin0Pi_4
#define sin5Pi_4  (-sin3Pi_4)
#define sin6Pi_4  (-sin2Pi_4)

#define cos0Pi_8  cos0Pi
#define cos1Pi_8  FL2FXCONST_DBL(0.92387953251129f)
#define cos2Pi_8  cos1Pi_4
#define cos3Pi_8  FL2FXCONST_DBL(0.38268343236509f)
#define cos4Pi_8  cos2Pi_4
#define cos5Pi_8  (-cos3Pi_8)
#define cos6Pi_8  (-cos2Pi_8)

#define sin0Pi_8  sin0Pi
#define sin1Pi_8  cos3Pi_8
#define sin2Pi_8  sin1Pi_4
#define sin3Pi_8  cos1Pi_8
#define sin4Pi_8  sin2Pi_4
#define sin5Pi_8  sin3Pi_8
#define sin6Pi_8  sin1Pi_4

#if defined(ARCH_PREFER_MULT_32x16)
  #define FIXP_HYB FIXP_SGL
  #define FIXP_CAST FX_DBL2FX_SGL
#else
  #define FIXP_HYB FIXP_DBL
  #define FIXP_CAST
#endif

static const FIXP_HYB  cr[13] =
{
   FIXP_CAST(cos6Pi_8), FIXP_CAST(cos5Pi_8), FIXP_CAST(cos4Pi_8),
   FIXP_CAST(cos3Pi_8), FIXP_CAST(cos2Pi_8), FIXP_CAST(cos1Pi_8),
   FIXP_CAST(cos0Pi_8),
   FIXP_CAST(cos1Pi_8), FIXP_CAST(cos2Pi_8), FIXP_CAST(cos3Pi_8),
   FIXP_CAST(cos4Pi_8), FIXP_CAST(cos5Pi_8), FIXP_CAST(cos6Pi_8)
};

static const FIXP_HYB  ci[13] =
{
   FIXP_CAST( sin6Pi_8), FIXP_CAST( sin5Pi_8), FIXP_CAST( sin4Pi_8),
   FIXP_CAST( sin3Pi_8), FIXP_CAST( sin2Pi_8), FIXP_CAST( sin1Pi_8),
   FIXP_CAST( sin0Pi_8) ,
   FIXP_CAST(-sin1Pi_8), FIXP_CAST(-sin2Pi_8), FIXP_CAST(-sin3Pi_8),
   FIXP_CAST(-sin4Pi_8), FIXP_CAST(-sin5Pi_8), FIXP_CAST(-sin6Pi_8)
};

static void slotBasedEightChannelFiltering( const FIXP_DBL *pQmfReal,
                                            const FIXP_DBL *pQmfImag,

FIXP_DBL  *mHybridReal,
                                            FIXP_DBL  *mHybridImag)
{

int bin;
  FIXP_DBL _fft[128 + ALIGNMENT_DEFAULT - 1];
  FIXP_DBL *fft = (FIXP_DBL *)ALIGN_PTR(_fft);

#if defined(ARCH_PREFER_MULT_32x16)
  const FIXP_SGL *p = p8_13_20; /* BASELINE_PS */
#else
  const FIXP_DBL *p = p8_13_20; /* BASELINE_PS */
#endif

/* pre twiddeling */

/*   x*(a*b + c*d) = fMultDiv2(x, fMultAddDiv2(fMultDiv2(a, b), c, d)) */
  /*   x*(a*b - c*d) = fMultDiv2(x, fMultSubDiv2(fMultDiv2(a, b), c, d)) */
  FIXP_DBL accu1, accu2, accu3, accu4;

#define TWIDDLE_1(n_0,n_1,n_2)                                                        \
         cplxMultDiv2(&accu1, &accu2, pQmfReal[n_0], pQmfImag[n_0], cr[n_0], ci[n_0]);  \
         accu1 = fMultDiv2(p[n_0], accu1);                                              \
         accu2 = fMultDiv2(p[n_0], accu2);                                              \
         cplxMultDiv2(&accu3, &accu4, pQmfReal[n_1], pQmfImag[n_1], cr[n_1], ci[n_1]);  \
         accu3 = fMultDiv2(p[n_1], accu3);                                              \
         accu4 = fMultDiv2(p[n_1], accu4);                                              \
         fft[FIXP_FFT_IDX_R(n_2)] = accu1 + accu3;                                      \
         fft[FIXP_FFT_IDX_I(n_2)] = accu2 + accu4;

#define TWIDDLE_0(n_0,n_1)                                                            \
         cplxMultDiv2(&accu1, &accu2, pQmfReal[n_0], pQmfImag[n_0], cr[n_0], ci[n_0]);  \
         fft[FIXP_FFT_IDX_R(n_1)] = fMultDiv2(p[n_0], accu1);                           \
         fft[FIXP_FFT_IDX_I(n_1)] = fMultDiv2(p[n_0], accu2);

TWIDDLE_0( 6, 0)
  TWIDDLE_0( 7, 1)

TWIDDLE_1( 0, 8, 2)
  TWIDDLE_1( 1, 9, 3)
  TWIDDLE_1( 2,10, 4)
  TWIDDLE_1( 3,11, 5)
  TWIDDLE_1( 4,12, 6)

TWIDDLE_0( 5, 7)

fft_8 (fft);

/* resort fft data into output array*/
  for(bin=0; bin<8;bin++ ) {
    mHybridReal[bin] = fft[FIXP_FFT_IDX_R(bin)] << 4;
    mHybridImag[bin] = fft[FIXP_FFT_IDX_I(bin)] << 4;
  }
}

/*******************************************************************************
 Functionname:  fillHybridDelayLine
 *******************************************************************************

Description:   The delay line of the hybrid filter is filled and copied from
                left to right.

Return:        none

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

void
fillHybridDelayLine( FIXP_DBL **fixpQmfReal,          /*!< Qmf real Values    */
                     FIXP_DBL **fixpQmfImag,          /*!< Qmf imag Values    */
                     FIXP_DBL   fixpHybridLeftR[12],  /*!< Hybrid real Values left channel  */
                     FIXP_DBL   fixpHybridLeftI[12],  /*!< Hybrid imag Values left channel  */
                     FIXP_DBL   fixpHybridRightR[12], /*!< Hybrid real Values right channel */
                     FIXP_DBL   fixpHybridRightI[12], /*!< Hybrid imag Values right channel */
                     HANDLE_HYBRID hHybrid )
{
  int i;

for (i = 0; i < HYBRID_FILTER_DELAY; i++) {
    slotBasedHybridAnalysis ( fixpQmfReal[i],
                              fixpQmfReal[i],
                              fixpHybridLeftR,
                              fixpHybridLeftI,
                              hHybrid );
  }

FDKmemcpy(fixpHybridRightR, fixpHybridLeftR, sizeof(FIXP_DBL)*NO_SUB_QMF_CHANNELS);
  FDKmemcpy(fixpHybridRightI, fixpHybridLeftI, sizeof(FIXP_DBL)*NO_SUB_QMF_CHANNELS);
}

/*******************************************************************************
 Functionname:  slotBasedHybridAnalysis
 *******************************************************************************

Description:   The lower QMF subbands are further split to provide better
                frequency resolution for PS processing.

Return:        none

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

void
slotBasedHybridAnalysis ( FIXP_DBL *fixpQmfReal,      /*!< Qmf real Values */
                          FIXP_DBL *fixpQmfImag,      /*!< Qmf imag Values */

FIXP_DBL  fixpHybridReal[12],   /*!< Hybrid real Values */
                          FIXP_DBL  fixpHybridImag[12],   /*!< Hybrid imag Values */

HANDLE_HYBRID hHybrid)
{
  int  k, band;
  HYBRID_RES hybridRes;
  int  chOffset = 0;

C_ALLOC_SCRATCH_START(pTempRealSlot, FIXP_DBL, 4*HYBRID_FILTER_LENGTH);

FIXP_DBL *pTempImagSlot = pTempRealSlot + HYBRID_FILTER_LENGTH;
  FIXP_DBL *pWorkRealSlot = pTempImagSlot + HYBRID_FILTER_LENGTH;
  FIXP_DBL *pWorkImagSlot = pWorkRealSlot + HYBRID_FILTER_LENGTH;

/*!
  Hybrid filtering is applied to the first hHybrid->nQmfBands QMF bands (3 when 10 or 20 stereo bands
  are used, 5 when 34 stereo bands are used). For the remaining QMF bands a delay would be necessary.
  But there is no need to implement a delay because there is a look-ahead of HYBRID_FILTER_DELAY = 6
  QMF samples in the low-band buffer.
  */

for(band = 0; band < hHybrid->nQmfBands; band++) {

/*  get hybrid resolution per qmf band                */
    /*  in case of baseline ps 10/20 band stereo mode :   */
    /*                                                    */
    /*             qmfBand[0] : 8 ( HYBRID_8_CPLX )       */
    /*             qmfBand[1] : 2 ( HYBRID_2_REAL )       */
    /*             qmfBand[2] : 2 ( HYBRID_2_REAL )       */
    /*                                                    */
    /*  (split the 3 lower qmf band to 12 hybrid bands)   */

hybridRes = (HYBRID_RES)hHybrid->pResolution[band];

FDKmemcpy(pWorkRealSlot, hHybrid->mQmfBufferRealSlot[band], hHybrid->qmfBufferMove * sizeof(FIXP_DBL));
    FDKmemcpy(pWorkImagSlot, hHybrid->mQmfBufferImagSlot[band], hHybrid->qmfBufferMove * sizeof(FIXP_DBL));

pWorkRealSlot[hHybrid->qmfBufferMove] = fixpQmfReal[band];
    pWorkImagSlot[hHybrid->qmfBufferMove] = fixpQmfImag[band];

FDKmemcpy(hHybrid->mQmfBufferRealSlot[band], pWorkRealSlot + 1, hHybrid->qmfBufferMove * sizeof(FIXP_DBL));
    FDKmemcpy(hHybrid->mQmfBufferImagSlot[band], pWorkImagSlot + 1, hHybrid->qmfBufferMove * sizeof(FIXP_DBL));

if (fixpQmfReal) {

/* actual filtering only if output signal requested */
      switch( hybridRes ) {

/* HYBRID_2_REAL & HYBRID_8_CPLX are only needful for baseline ps */
      case HYBRID_2_REAL:

slotBasedDualChannelFiltering( pWorkRealSlot,
                                       pWorkImagSlot,
                                       pTempRealSlot,
                                       pTempImagSlot);
        break;

case HYBRID_8_CPLX:

slotBasedEightChannelFiltering( pWorkRealSlot,
                                        pWorkImagSlot,
                                        pTempRealSlot,
                                        pTempImagSlot);
        break;

default:
        FDK_ASSERT(0);
      }

for(k = 0; k < (SCHAR)hybridRes; k++) {
        fixpHybridReal [chOffset + k] = pTempRealSlot[k];
        fixpHybridImag [chOffset + k] = pTempImagSlot[k];
      }
      chOffset += hybridRes;
    } /* if (mHybridReal) */
  }

/* group hybrid channels 3+4 -> 3 and 2+5 -> 2 */
  fixpHybridReal[3] += fixpHybridReal[4];
  fixpHybridImag[3] += fixpHybridImag[4];
  fixpHybridReal[4] = (FIXP_DBL)0;
  fixpHybridImag[4] = (FIXP_DBL)0;

fixpHybridReal[2] += fixpHybridReal[5];
  fixpHybridImag[2] += fixpHybridImag[5];
  fixpHybridReal[5] = (FIXP_DBL)0;
  fixpHybridImag[5] = (FIXP_DBL)0;

/* free memory on scratch */
  C_ALLOC_SCRATCH_END(pTempRealSlot, FIXP_DBL, 4*HYBRID_FILTER_LENGTH);

}

/*******************************************************************************
 Functionname:  slotBasedHybridSynthesis
 *******************************************************************************

Description:  The coefficients offering higher resolution for the lower QMF
               channel are simply added prior to the synthesis with the 54
               subbands QMF.

Arguments:

Return:        none

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

/*! <pre>
      l,r0(n) ---\
      l,r1(n) ---- + --\
      l,r2(n) ---/      \
                         + --> F0(w)
      l,r3(n) ---\      /
      l,r4(n) ---- + --/
      l,r5(n) ---/

l,r6(n) ---\
                  + ---------> F1(w)
      l,r7(n) ---/

l,r8(n) ---\
                  + ---------> F2(w)
      l,r9(n) ---/

</pre>
      Hybrid QMF synthesis filterbank for the 10 and 20 stereo-bands configurations. The
      coefficients offering higher resolution for the lower QMF channel are simply added
      prior to the synthesis with the 54 subbands QMF.

[see ISO/IEC 14496-3:2001/FDAM 2:2004(E) - Page 52]
*/

void
slotBasedHybridSynthesis ( FIXP_DBL  *fixpHybridReal,  /*!< Hybrid real Values */
                           FIXP_DBL  *fixpHybridImag,  /*!< Hybrid imag Values */
                           FIXP_DBL  *fixpQmfReal,     /*!< Qmf real Values */
                           FIXP_DBL  *fixpQmfImag,     /*!< Qmf imag Values */
                           HANDLE_HYBRID hHybrid )     /*!< Handle to HYBRID struct. */
{
  int  k, band;

HYBRID_RES hybridRes;
  int  chOffset = 0;

for(band = 0; band < hHybrid->nQmfBands; band++) {

FIXP_DBL qmfReal = FL2FXCONST_DBL(0.f);
    FIXP_DBL qmfImag = FL2FXCONST_DBL(0.f);
    hybridRes = (HYBRID_RES)hHybrid->pResolution[band];

for(k = 0; k < (SCHAR)hybridRes; k++) {
      qmfReal += fixpHybridReal[chOffset + k];
      qmfImag += fixpHybridImag[chOffset + k];
    }

fixpQmfReal[band] = qmfReal;
    fixpQmfImag[band] = qmfImag;

chOffset += hybridRes;
  }
}

C++程序 | 653行 | 25.03 KB

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