void is_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,
uint16_t frame_len)
{
uint8_t g, sfb, b;
uint16_t i;
#ifndef FIXED_POINT
real_t scale;
#else
int32_t exp, frac;
#endif
uint16_t nshort = frame_len/8;
uint8_t group = 0;
for (g = 0; g < icsr->num_window_groups; g++)
{
/* Do intensity stereo decoding */
for (b = 0; b < icsr->window_group_length[g]; b++)
{
for (sfb = 0; sfb < icsr->max_sfb; sfb++)
{
if (is_intensity(icsr, g, sfb))
{
/* For scalefactor bands coded in intensity stereo the
corresponding predictors in the right channel are
switched to "off".
*/
ics->pred.prediction_used[sfb] = 0;
icsr->pred.prediction_used[sfb] = 0;
#ifndef FIXED_POINT
scale = (real_t)pow(0.5, (0.25*icsr->scale_factors[g][sfb]));
#else
exp = icsr->scale_factors[g][sfb] >> 2;
frac = icsr->scale_factors[g][sfb] & 3;
#endif
/* Scale from left to right channel,
do not touch left channel */
for (i = icsr->swb_offset[sfb]; i < icsr->swb_offset[sfb+1]; i++)
{
#ifndef FIXED_POINT
r_spec[(group*nshort)+i] = MUL_R(l_spec[(group*nshort)+i], scale);
#else
if (exp < 0)
r_spec[(group*nshort)+i] = l_spec[(group*nshort)+i] << -exp;
else
r_spec[(group*nshort)+i] = l_spec[(group*nshort)+i] >> exp;
r_spec[(group*nshort)+i] = MUL_C(r_spec[(group*nshort)+i], pow05_table[frac + 3]);
#endif
if (is_intensity(icsr, g, sfb) != invert_intensity(ics, g, sfb))
r_spec[(group*nshort)+i] = -r_spec[(group*nshort)+i];
}
}
}
group++;
}
}
}
void ms_decode(ic_stream *ics, ic_stream *icsr, real_t *l_spec, real_t *r_spec,
uint16_t frame_len)
{
uint8_t g, b, sfb;
uint8_t group = 0;
uint16_t nshort = frame_len/8;
uint16_t i, k;
real_t tmp;
if (ics->ms_mask_present >= 1)
{
for (g = 0; g < ics->num_window_groups; g++)
{
for (b = 0; b < ics->window_group_length[g]; b++)
{
for (sfb = 0; sfb < ics->max_sfb; sfb++)
{
/* If intensity stereo coding or noise substitution is on
for a particular scalefactor band, no M/S stereo decoding
is carried out.
*/
if ((ics->ms_used[g][sfb] || ics->ms_mask_present == 2) &&
!is_intensity(icsr, g, sfb) && !is_noise(ics, g, sfb))
{
for (i = ics->swb_offset[sfb]; i < ics->swb_offset[sfb+1]; i++)
{
k = (group*nshort) + i;
tmp = l_spec[k] - r_spec[k];
l_spec[k] = l_spec[k] + r_spec[k];
r_spec[k] = tmp;
}
}
}
group++;
}
}
}
}