imdct.cpp

ac3的解码程序

#include "imdct.h"

/*
const sample_t imdct_window[] = 
{
  0.00014, 0.00024, 0.00037, 0.00051, 0.00067, 0.00086, 0.00107, 0.00130,
  0.00157, 0.00187, 0.00220, 0.00256, 0.00297, 0.00341, 0.00390, 0.00443,
  0.00501, 0.00564, 0.00632, 0.00706, 0.00785, 0.00871, 0.00962, 0.01061,
  0.01166, 0.01279, 0.01399, 0.01526, 0.01662, 0.01806, 0.01959, 0.02121,
  0.02292, 0.02472, 0.02662, 0.02863, 0.03073, 0.03294, 0.03527, 0.03770,
  0.04025, 0.04292, 0.04571, 0.04862, 0.05165, 0.05481, 0.05810, 0.06153,
  0.06508, 0.06878, 0.07261, 0.07658, 0.08069, 0.08495, 0.08935, 0.09389,
  0.09859, 0.10343, 0.10842, 0.11356, 0.11885, 0.12429, 0.12988, 0.13563,
  0.14152, 0.14757, 0.15376, 0.16011, 0.16661, 0.17325, 0.18005, 0.18699,
  0.19407, 0.20130, 0.20867, 0.21618, 0.22382, 0.23161, 0.23952, 0.24757,
  0.25574, 0.26404, 0.27246, 0.28100, 0.28965, 0.29841, 0.30729, 0.31626,
  0.32533, 0.33450, 0.34376, 0.35311, 0.36253, 0.37204, 0.38161, 0.39126,
  0.40096, 0.41072, 0.42054, 0.43040, 0.44030, 0.45023, 0.46020, 0.47019,
  0.48020, 0.49022, 0.50025, 0.51028, 0.52031, 0.53033, 0.54033, 0.55031,
  0.56026, 0.57019, 0.58007, 0.58991, 0.59970, 0.60944, 0.61912, 0.62873,
  0.63827, 0.64774, 0.65713, 0.66643, 0.67564, 0.68476, 0.69377, 0.70269,
  0.71150, 0.72019, 0.72877, 0.73723, 0.74557, 0.75378, 0.76186, 0.76981,
  0.77762, 0.78530, 0.79283, 0.80022, 0.80747, 0.81457, 0.82151, 0.82831,
  0.83496, 0.84145, 0.84779, 0.85398, 0.86001, 0.86588, 0.87160, 0.87716,
  0.88257, 0.88782, 0.89291, 0.89785, 0.90264, 0.90728, 0.91176, 0.91610,
  0.92028, 0.92432, 0.92822, 0.93197, 0.93558, 0.93906, 0.94240, 0.94560,
  0.94867, 0.95162, 0.95444, 0.95713, 0.95971, 0.96217, 0.96451, 0.96674,
  0.96887, 0.97089, 0.97281, 0.97463, 0.97635, 0.97799, 0.97953, 0.98099,
  0.98236, 0.98366, 0.98488, 0.98602, 0.98710, 0.98811, 0.98905, 0.98994,
  0.99076, 0.99153, 0.99225, 0.99291, 0.99353, 0.99411, 0.99464, 0.99513,
  0.99558, 0.99600, 0.99639, 0.99674, 0.99706, 0.99736, 0.99763, 0.99788,
  0.99811, 0.99831, 0.99850, 0.99867, 0.99882, 0.99895, 0.99908, 0.99919,
  0.99929, 0.99938, 0.99946, 0.99953, 0.99959, 0.99965, 0.99969, 0.99974,
  0.99978, 0.99981, 0.99984, 0.99986, 0.99988, 0.99990, 0.99992, 0.99993,
  0.99994, 0.99995, 0.99996, 0.99997, 0.99998, 0.99998, 0.99998, 0.99999,
  0.99999, 0.99999, 0.99999, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000,
  1.00000, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000
};
*/
const uint8_t fftorder[] = 
{
      0,128, 64,192, 32,160,224, 96, 16,144, 80,208,240,112, 48,176,
      8,136, 72,200, 40,168,232,104,248,120, 56,184, 24,152,216, 88,
      4,132, 68,196, 36,164,228,100, 20,148, 84,212,244,116, 52,180,
    252,124, 60,188, 28,156,220, 92, 12,140, 76,204,236,108, 44,172,
      2,130, 66,194, 34,162,226, 98, 18,146, 82,210,242,114, 50,178,
     10,138, 74,202, 42,170,234,106,250,122, 58,186, 26,154,218, 90,
    254,126, 62,190, 30,158,222, 94, 14,142, 78,206,238,110, 46,174,
      6,134, 70,198, 38,166,230,102,246,118, 54,182, 22,150,214, 86
};


// the basic split-radix ifft butterfly
#define BUTTERFLY(a0,a1,a2,a3,wr,wi) do {       \
    tmp5 = a2.real * wr + a2.imag * wi;         \
    tmp6 = a2.imag * wr - a2.real * wi;         \
    tmp7 = a3.real * wr - a3.imag * wi;         \
    tmp8 = a3.imag * wr + a3.real * wi;         \
    tmp1 = tmp5 + tmp7;                         \
    tmp2 = tmp6 + tmp8;                         \
    tmp3 = tmp6 - tmp8;                         \
    tmp4 = tmp7 - tmp5;                         \
    a2.real = a0.real - tmp1;                   \
    a2.imag = a0.imag - tmp2;                   \
    a3.real = a1.real - tmp3;                   \
    a3.imag = a1.imag - tmp4;                   \
    a0.real += tmp1;                            \
    a0.imag += tmp2;                            \
    a1.real += tmp3;                            \
    a1.imag += tmp4;                            \
} while (0)

// split-radix ifft butterfly, specialized for wr=1 wi=0
#define BUTTERFLY_ZERO(a0,a1,a2,a3) do {        \
    tmp1 = a2.real + a3.real;                   \
    tmp2 = a2.imag + a3.imag;                   \
    tmp3 = a2.imag - a3.imag;                   \
    tmp4 = a3.real - a2.real;                   \
    a2.real = a0.real - tmp1;                   \
    a2.imag = a0.imag - tmp2;                   \
    a3.real = a1.real - tmp3;                   \
    a3.imag = a1.imag - tmp4;                   \
    a0.real += tmp1;                            \
    a0.imag += tmp2;                            \
    a1.real += tmp3;                            \
    a1.imag += tmp4;                            \
} while (0)

/* split-radix ifft butterfly, specialized for wr=wi */
#define BUTTERFLY_HALF(a0,a1,a2,a3,w) do {      \
    tmp5 = (a2.real + a2.imag) * w;             \
    tmp6 = (a2.imag - a2.real) * w;             \
    tmp7 = (a3.real - a3.imag) * w;             \
    tmp8 = (a3.imag + a3.real) * w;             \
    tmp1 = tmp5 + tmp7;                         \
    tmp2 = tmp6 + tmp8;                         \
    tmp3 = tmp6 - tmp8;                         \
    tmp4 = tmp7 - tmp5;                         \
    a2.real = a0.real - tmp1;                   \
    a2.imag = a0.imag - tmp2;                   \
    a3.real = a1.real - tmp3;                   \
    a3.imag = a1.imag - tmp4;                   \
    a0.real += tmp1;                            \
    a0.imag += tmp2;                            \
    a1.real += tmp3;                            \
    a1.imag += tmp4;                            \
} while (0)




IMDCT::IMDCT()
{
  int i, k;

  for (i = 0; i < 3; i++)
    roots16[i] = cos ((M_PI / 8) * (i + 1));

  for (i = 0; i < 7; i++)
    roots32[i] = cos ((M_PI / 16) * (i + 1));

  for (i = 0; i < 15; i++)
    roots64[i] = cos ((M_PI / 32) * (i + 1));

  for (i = 0; i < 31; i++)
    roots128[i] = cos ((M_PI / 64) * (i + 1));

  for (i = 0; i < 64; i++) 
  {
    k = fftorder[i] / 2 + 64;
    pre1[i].real = cos ((M_PI / 256) * (k - 0.25));
    pre1[i].imag = sin ((M_PI / 256) * (k - 0.25));
  }

  for (i = 64; i < 128; i++) 
  {
    k = fftorder[i] / 2 + 64;
    pre1[i].real = -cos ((M_PI / 256) * (k - 0.25));
    pre1[i].imag = -sin ((M_PI / 256) * (k - 0.25));
  }

  for (i = 0; i < 64; i++) 
  {
    post1[i].real = cos ((M_PI / 256) * (i + 0.5));
    post1[i].imag = sin ((M_PI / 256) * (i + 0.5));
  }

  for (i = 0; i < 64; i++) 
  {
    k = fftorder[i] / 4;
    pre2[i].real = cos ((M_PI / 128) * (k - 0.25));
    pre2[i].imag = sin ((M_PI / 128) * (k - 0.25));
  }

  for (i = 0; i < 32; i++) 
  {
    post2[i].real = cos ((M_PI / 128) * (i + 0.5));
    post2[i].imag = sin ((M_PI / 128) * (i + 0.5));
  }

}


void 
IMDCT::imdct_512 (sample_t *data, sample_t *delay)
{
  int i, k;
//  sample_t t_r, t_i, a_r, a_i, b_r, b_i, w_1, w_2;
//  const sample_t *window = imdct_window;
  sample_t t_r, t_i, a_r, a_i, b_r, b_i;
        
  for (i = 0; i < 128; i++) 
  {
    k = fftorder[i];
    t_r = pre1[i].real;
    t_i = pre1[i].imag;

    buf[i].real = t_i * data[255-k] + t_r * data[k];
    buf[i].imag = t_r * data[255-k] - t_i * data[k];
  }

  ifft128 (buf);

  // Post IFFT complex multiply plus IFFT complex conjugate
  // Window and convert to real valued signal
  for (i = 0; i < 64; i++) 
  {
    // y[n] = z[n] * (xcos1[n] + j * xsin1[n]) ;
    t_r = post1[i].real;
    t_i = post1[i].imag;

    a_r = t_r * buf[i].real     + t_i * buf[i].imag;
    a_i = t_i * buf[i].real     - t_r * buf[i].imag;
    b_r = t_i * buf[127-i].real + t_r * buf[127-i].imag;
    b_i = t_r * buf[127-i].real - t_i * buf[127-i].imag;

//    w_1 = window[2*i];
//    w_2 = window[255-2*i];
//    data[2*i]     = delay[2*i] * w_2 - a_r * w_1 + bias;
//    data[255-2*i] = delay[2*i] * w_1 + a_r * w_2 + bias;
    data[2*i]     = -a_r;
    data[255-2*i] = +a_r;
    delay[2*i] = a_i;
    delay[255-2*i] = a_i;

//    w_1 = window[2*i+1];
//    w_2 = window[254-2*i];
//    data[2*i+1]   = delay[2*i+1] * w_2 + b_r * w_1 + bias;
//    data[254-2*i] = delay[2*i+1] * w_1 - b_r * w_2 + bias;
    data[2*i+1]   = +b_r;
    data[254-2*i] = -b_r;
    delay[2*i+1] = b_i;
    delay[254-2*i] = b_i;
  }
}

void 
IMDCT::imdct_256(sample_t *data, sample_t *delay)
{
  int i, k;
  complex_t * buf1, * buf2;
//  sample_t t_r, t_i, a_r, a_i, b_r, b_i, c_r, c_i, d_r, d_i, w_1, w_2;
//  const sample_t * window = imdct_window;
  sample_t t_r, t_i, a_r, a_i, b_r, b_i, c_r, c_i, d_r, d_i;

  buf1 = &buf[0];
  buf2 = &buf[64];

  // Pre IFFT complex multiply plus IFFT cmplx conjugate
  for (i = 0; i < 64; i++) 
  {
    k = fftorder[i];
    t_r = pre2[i].real;
    t_i = pre2[i].imag;

    buf1[i].real = t_i * data[254-k] + t_r * data[k];
    buf1[i].imag = t_r * data[254-k] - t_i * data[k];

    buf2[i].real = t_i * data[255-k] + t_r * data[k+1];
    buf2[i].imag = t_r * data[255-k] - t_i * data[k+1];
  }

  ifft64 (buf1);
  ifft64 (buf2);

  // Post IFFT complex multiply
  // Window and convert to real valued signal
  for (i = 0; i < 32; i++) 
  {
    // y1[n] = z1[n] * (xcos2[n] + j * xs in2[n]) ;
    t_r = post2[i].real;
    t_i = post2[i].imag;

    a_r = t_r * buf1[i].real    + t_i * buf1[i].imag;
    a_i = t_i * buf1[i].real    - t_r * buf1[i].imag;
    b_r = t_i * buf1[63-i].real + t_r * buf1[63-i].imag;
    b_i = t_r * buf1[63-i].real - t_i * buf1[63-i].imag;

    c_r = t_r * buf2[i].real    + t_i * buf2[i].imag;
    c_i = t_i * buf2[i].real    - t_r * buf2[i].imag;
    d_r = t_i * buf2[63-i].real + t_r * buf2[63-i].imag;
    d_i = t_r * buf2[63-i].real - t_i * buf2[63-i].imag;

//    w_1 = window[2*i];
//    w_2 = window[255-2*i];
//    data[2*i]     = delay[2*i] * w_2 - a_r * w_1 + bias;
//    data[255-2*i] = delay[2*i] * w_1 + a_r * w_2 + bias;
    data[2*i]     = -a_r;
    data[255-2*i] = +a_r;
    delay[2*i] = c_i;
    delay[255-2*i] = c_i;

//    w_1 = window[128+2*i];
//    w_2 = window[127-2*i];
//    data[128+2*i] = delay[127-2*i] * w_2 + a_i * w_1 + bias;
//    data[127-2*i] = delay[127-2*i] * w_1 - a_i * w_2 + bias;
    data[128+2*i] = +a_i;
    data[127-2*i] = -a_i;
    delay[127-2*i] = c_r;
    delay[128+2*i] = c_r;

//    w_1 = window[2*i+1];
//    w_2 = window[254-2*i];
//    data[2*i+1]   = delay[2*i+1] * w_2 - b_i * w_1 + bias;
//    data[254-2*i] = delay[2*i+1] * w_1 + b_i * w_2 + bias;
    data[2*i+1]   = -b_i;
    data[254-2*i] = +b_i;
    delay[2*i+1] = d_r;
    delay[254-2*i] = d_r;

//    w_1 = window[129+2*i];
//    w_2 = window[126-2*i];
//    data[129+2*i] = delay[126-2*i] * w_2 + b_r * w_1 + bias;
//    data[126-2*i] = delay[126-2*i] * w_1 - b_r * w_2 + bias;
    data[129+2*i] = +b_r;
    data[126-2*i] = -b_r;
    delay[126-2*i] = d_i;
    delay[129+2*i] = d_i;
  }
}

void 
IMDCT::ifft128 (complex_t * buf)
{
  ifft32 (buf);
  ifft16 (buf + 32);
  ifft16 (buf + 48);
  ifft_pass (buf, roots64 - 16, 16);

  ifft32 (buf + 64);
  ifft32 (buf + 96);
  ifft_pass (buf, roots128 - 32, 32);
}

void 
IMDCT::ifft64 (complex_t * buf)
{
  ifft32 (buf);
  ifft16 (buf + 32);
  ifft16 (buf + 48);
  ifft_pass (buf, roots64 - 16, 16);
}

void 
IMDCT::ifft32 (complex_t * buf)
{
  ifft16 (buf);
  ifft8 (buf + 16);
  ifft8 (buf + 24);
  ifft_pass (buf, roots32 - 8, 8);
}

void 
IMDCT::ifft16 (complex_t * buf)
{
  ifft8 (buf);
  ifft4 (buf + 8);
  ifft4 (buf + 12);
  ifft_pass (buf, roots16 - 4, 4);
}

void 
IMDCT::ifft8 (complex_t * buf)
{
  double tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7, tmp8;

  ifft4 (buf);
  ifft2 (buf + 4);
  ifft2 (buf + 6);
  BUTTERFLY_ZERO (buf[0], buf[2], buf[4], buf[6]);
  BUTTERFLY_HALF (buf[1], buf[3], buf[5], buf[7], roots16[1]);
}

void 
IMDCT::ifft_pass (complex_t * buf, sample_t * weight, int n)
{
  complex_t * buf1;
  complex_t * buf2;
  complex_t * buf3;
  double tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7, tmp8;
  int i;
  buf++;
  buf1 = buf + n;
  buf2 = buf + 2 * n;
  buf3 = buf + 3 * n;

  BUTTERFLY_ZERO (buf[-1], buf1[-1], buf2[-1], buf3[-1]);

  i = n - 1;

  do 
  {
    BUTTERFLY (buf[0], buf1[0], buf2[0], buf3[0], weight[n], weight[2*i]);
    buf++;
    buf1++;
    buf2++;
    buf3++;
    weight++;
  } while (--i);
}