ref: dd06c89010a81f089c7395887bb5c4fa0054b65b
dir: /src/rate_poly_fir.h/
/* Effect: change sample rate Copyright (c) 2008 robs@users.sourceforge.net
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at
* your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/* Up-sample by step in (0,1) using a poly-phase FIR with length LEN.*/
/* Input must be preceded by LEN >> 1 samples. */
/* Input must be followed by (LEN-1) >> 1 samples. */
#define a (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 0,j))
#define b (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 1,j))
#define c (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 2,j))
#define d (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 3,j))
#if COEF_INTERP == 0
#define _ sum += a *at[j], ++j;
#elif COEF_INTERP == 1
#define _ sum += (b *x + a)*at[j], ++j;
#elif COEF_INTERP == 2
#define _ sum += ((c *x + b)*x + a)*at[j], ++j;
#elif COEF_INTERP == 3
#define _ sum += (((d*x + c)*x + b)*x + a)*at[j], ++j;
#else
#error COEF_INTERP
#endif
static void FUNCTION(stage_t * p, fifo_t * output_fifo)
{
sample_t const * input = stage_read_p(p);
int i, num_in = stage_occupancy(p), max_num_out = 1 + num_in*p->out_in_ratio;
sample_t * output = fifo_reserve(output_fifo, max_num_out);
for (i = 0; p->at.parts.integer < num_in; ++i, p->at.all += p->step.all) {
sample_t const * at = input + p->at.parts.integer;
uint32_t fraction = p->at.parts.fraction;
int phase = fraction >> (32 - PHASE_BITS); /* high-order bits */
#if COEF_INTERP > 0 /* low-order bits, scaled to [0,1) */
sample_t x = (sample_t) (fraction << PHASE_BITS) * (1 / MULT32);
#endif
sample_t sum = 0;
int j = 0;
CONVOLVE
assert(j == FIR_LENGTH);
output[i] = sum;
}
assert(max_num_out - i >= 0);
fifo_trim_by(output_fifo, max_num_out - i);
fifo_read(&p->fifo, p->at.parts.integer, NULL);
p->at.parts.integer = 0;
}
#undef _
#undef a
#undef b
#undef c
#undef d
#undef COEF_INTERP
#undef CONVOLVE
#undef FIR_LENGTH
#undef FUNCTION
#undef PHASE_BITS