/* Unified active matrix decoder for 2 channel matrix encoded surround
sources */
static inline void matrix_decode(short *in, const int k, const int il,
const int ir, const int decode_rear,
const int dlbuflen,
float l_fwr, float r_fwr,
float lpr_fwr, float lmr_fwr,
float *adapt_l_gain, float *adapt_r_gain,
float *adapt_lpr_gain, float *adapt_lmr_gain,
float *lf, float *rf, float *lr,
float *rr, float *cf)
{
const int kr = (k + MATREARDELAY) % dlbuflen;
float l_gain = (l_fwr + r_fwr) /
(1 + l_fwr + l_fwr);
float r_gain = (l_fwr + r_fwr) /
(1 + r_fwr + r_fwr);
/* The 2nd axis has strong gain fluctuations, and therefore require
limits. The factor corresponds to the 1 / amplification of (Lt
- Rt) when (Lt, Rt) is strongly correlated. (e.g. during
dialogues). It should be bigger than -12 dB to prevent
distortion. */
float lmr_lim_fwr = lmr_fwr > M9_03DB * lpr_fwr ?
lmr_fwr : M9_03DB * lpr_fwr;
float lpr_gain = (lpr_fwr + lmr_lim_fwr) /
(1 + lpr_fwr + lpr_fwr);
float lmr_gain = (lpr_fwr + lmr_lim_fwr) /
(1 + lmr_lim_fwr + lmr_lim_fwr);
float lmr_unlim_gain = (lpr_fwr + lmr_fwr) /
(1 + lmr_fwr + lmr_fwr);
float lpr, lmr;
float l_agc, r_agc, lpr_agc, lmr_agc;
float f, d_gain, c_gain, c_agc_cfk;
#if 0
static int counter = 0;
static FILE *fp_out;
if(counter == 0)
fp_out = fopen("af_hrtf.log", "w");
if(counter % 240 == 0)
fprintf(fp_out, "%g %g %g %g %g ", counter * (1.0 / 48000),
l_gain, r_gain, lpr_gain, lmr_gain);
#endif
/*** AXIS NO. 1: (Lt, Rt) -> (C, Ls, Rs) ***/
/* AGC adaption */
d_gain = (fabs(l_gain - *adapt_l_gain) +
fabs(r_gain - *adapt_r_gain)) * 0.5;
f = d_gain * (1.0 / MATAGCTRIG);
f = MATAGCDECAY - MATAGCDECAY / (1 + f * f);
*adapt_l_gain = (1 - f) * *adapt_l_gain + f * l_gain;
*adapt_r_gain = (1 - f) * *adapt_r_gain + f * r_gain;
/* Matrix */
l_agc = in[il] * passive_lock(*adapt_l_gain);
r_agc = in[ir] * passive_lock(*adapt_r_gain);
cf[k] = (l_agc + r_agc) * M_SQRT1_2;
if(decode_rear) {
lr[kr] = rr[kr] = (l_agc - r_agc) * M_SQRT1_2;
/* Stereo rear channel is steered with the same AGC steering as
the decoding matrix. Note this requires a fast updating AGC
at the order of 20 ms (which is the case here). */
lr[kr] *= (l_fwr + l_fwr) /
(1 + l_fwr + r_fwr);
rr[kr] *= (r_fwr + r_fwr) /
(1 + l_fwr + r_fwr);
}
/*** AXIS NO. 2: (Lt + Rt, Lt - Rt) -> (L, R) ***/
lpr = (in[il] + in[ir]) * M_SQRT1_2;
lmr = (in[il] - in[ir]) * M_SQRT1_2;
/* AGC adaption */
d_gain = fabs(lmr_unlim_gain - *adapt_lmr_gain);
f = d_gain * (1.0 / MATAGCTRIG);
f = MATAGCDECAY - MATAGCDECAY / (1 + f * f);
*adapt_lpr_gain = (1 - f) * *adapt_lpr_gain + f * lpr_gain;
*adapt_lmr_gain = (1 - f) * *adapt_lmr_gain + f * lmr_gain;
/* Matrix */
lpr_agc = lpr * passive_lock(*adapt_lpr_gain);
lmr_agc = lmr * passive_lock(*adapt_lmr_gain);
lf[k] = (lpr_agc + lmr_agc) * M_SQRT1_2;
rf[k] = (lpr_agc - lmr_agc) * M_SQRT1_2;
/*** CENTER FRONT CANCELLATION ***/
/* A heuristic approach exploits that Lt + Rt gain contains the
information about Lt, Rt correlation. This effectively reshapes
the front and rear "cones" to concentrate Lt + Rt to C and
introduce Lt - Rt in L, R. */
/* 0.67677 is the emprical lower bound for lpr_gain. */
c_gain = 8 * (*adapt_lpr_gain - 0.67677);
c_gain = c_gain > 0 ? c_gain : 0;
/* c_gain should not be too high, not even reaching full
cancellation (~ 0.50 - 0.55 at current AGC implementation), or
the center will s0und too narrow. */
c_gain = MATCOMPGAIN / (1 + c_gain * c_gain);
c_agc_cfk = c_gain * cf[k];
lf[k] -= c_agc_cfk;
rf[k] -= c_agc_cfk;
cf[k] += c_agc_cfk + c_agc_cfk;
#if 0
if(counter % 240 == 0)
fprintf(fp_out, "%g %g %g %g %g\n",
*adapt_l_gain, *adapt_r_gain,
*adapt_lpr_gain, *adapt_lmr_gain,
c_gain);
counter++;
#endif
}
void matrix_decode(const float *in, const int k, const int il,
const int ir, bool decode_rear,
const int _dlbuflen,
float _l_fwr, float _r_fwr,
float _lpr_fwr, float _lmr_fwr,
float *_adapt_l_gain, float *_adapt_r_gain,
float *_adapt_lpr_gain, float *_adapt_lmr_gain,
float *_lf, float *_rf, float *_lr,
float *_rr, float *_cf)
{
static const float M9_03DB = 0.3535533906f;
static const float MATAGCTRIG = 8.0f; /* (Fuzzy) AGC trigger */
static const float MATAGCDECAY = 1.0f; /* AGC baseline decay rate (1/samp.) */
static const float MATCOMPGAIN = 0.37f; /* Cross talk compensation gain, 0.50 - 0.55 is full cancellation. */
const int kr = (k + olddelay) % _dlbuflen;
float l_gain = (_l_fwr + _r_fwr) / (1 + _l_fwr + _l_fwr);
float r_gain = (_l_fwr + _r_fwr) / (1 + _r_fwr + _r_fwr);
// The 2nd axis has strong gain fluctuations, and therefore require
// limits. The factor corresponds to the 1 / amplification of (Lt
// - Rt) when (Lt, Rt) is strongly correlated. (e.g. during
// dialogues). It should be bigger than -12 dB to prevent
// distortion.
float lmr_lim_fwr = _lmr_fwr > M9_03DB * _lpr_fwr ? _lmr_fwr : M9_03DB * _lpr_fwr;
float lpr_gain = (_lpr_fwr + lmr_lim_fwr) / (1 + _lpr_fwr + _lpr_fwr);
float lmr_gain = (_lpr_fwr + lmr_lim_fwr) / (1 + lmr_lim_fwr + lmr_lim_fwr);
float lmr_unlim_gain = (_lpr_fwr + _lmr_fwr) / (1 + _lmr_fwr + _lmr_fwr);
float lpr, lmr;
float l_agc, r_agc, lpr_agc, lmr_agc;
float f, d_gain, c_gain, c_agc_cfk;
/*** AXIS NO. 1: (Lt, Rt) -> (C, Ls, Rs) ***/
/* AGC adaption */
d_gain = (fabs(l_gain - *_adapt_l_gain) + fabs(r_gain - *_adapt_r_gain)) * 0.5f;
f = d_gain * (1.0f / MATAGCTRIG);
f = MATAGCDECAY - MATAGCDECAY / (1 + f * f);
*_adapt_l_gain = (1 - f) * *_adapt_l_gain + f * l_gain;
*_adapt_r_gain = (1 - f) * *_adapt_r_gain + f * r_gain;
/* Matrix */
l_agc = in[il] * passive_lock(*_adapt_l_gain);
r_agc = in[ir] * passive_lock(*_adapt_r_gain);
_cf[k] = (l_agc + r_agc) * (float)M_SQRT1_2;
if (decode_rear)
{
_lr[kr] = _rr[kr] = (l_agc - r_agc) * (float)M_SQRT1_2;
// Stereo rear channel is steered with the same AGC steering as
// the decoding matrix. Note this requires a fast updating AGC
// at the order of 20 ms (which is the case here).
_lr[kr] *= (_l_fwr + _l_fwr) / (1 + _l_fwr + _r_fwr);
_rr[kr] *= (_r_fwr + _r_fwr) / (1 + _l_fwr + _r_fwr);
}
/*** AXIS NO. 2: (Lt + Rt, Lt - Rt) -> (L, R) ***/
lpr = (in[il] + in[ir]) * (float)M_SQRT1_2;
lmr = (in[il] - in[ir]) * (float)M_SQRT1_2;
/* AGC adaption */
d_gain = fabs(lmr_unlim_gain - *_adapt_lmr_gain);
f = d_gain * (1.0f / MATAGCTRIG);
f = MATAGCDECAY - MATAGCDECAY / (1 + f * f);
*_adapt_lpr_gain = (1 - f) * *_adapt_lpr_gain + f * lpr_gain;
*_adapt_lmr_gain = (1 - f) * *_adapt_lmr_gain + f * lmr_gain;
/* Matrix */
lpr_agc = lpr * passive_lock(*_adapt_lpr_gain);
lmr_agc = lmr * passive_lock(*_adapt_lmr_gain);
_lf[k] = (lpr_agc + lmr_agc) * (float)M_SQRT1_2;
_rf[k] = (lpr_agc - lmr_agc) * (float)M_SQRT1_2;
/*** CENTER FRONT CANCELLATION ***/
// A heuristic approach exploits that Lt + Rt gain contains the
// information about Lt, Rt correlation. This effectively reshapes
// the front and rear "cones" to concentrate Lt + Rt to C and
// introduce Lt - Rt in L, R.
/* 0.67677 is the empirical lower bound for lpr_gain. */
c_gain = 8 * (*_adapt_lpr_gain - 0.67677f);
c_gain = c_gain > 0 ? c_gain : 0;
// c_gain should not be too high, not even reaching full
// cancellation (~ 0.50 - 0.55 at current AGC implementation), or
// the center will sound too narrow. */
c_gain = MATCOMPGAIN / (1 + c_gain * c_gain);
c_agc_cfk = c_gain * _cf[k];
_lf[k] -= c_agc_cfk;
_rf[k] -= c_agc_cfk;
_cf[k] += c_agc_cfk + c_agc_cfk;
}