ref: 381a7bd0e2bbe4838cc59f9220eaecaa46b6a303
dir: /src/rate_half_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
*/
/* Down-sample by a factor of 2 using a FIR with odd length (LEN).*/
/* Input must be preceded and followed by LEN >> 1 samples. */
#define _ sum += (input[-j] + input[j]) * COEFS[j], ++j;
static void FUNCTION(stage_t * p, fifo_t * output_fifo)
{
sample_t const * input = stage_read_p(p);
int i, num_out = (stage_occupancy(p) + 1) / 2;
sample_t * output = fifo_reserve(output_fifo, num_out);
for (i = 0; i < num_out; ++i, input += 2) {
int j = 1;
sample_t sum = input[0] * COEFS[0];
CONVOLVE
assert(j == array_length(COEFS));
output[i] = sum;
}
fifo_read(&p->fifo, 2 * num_out, NULL);
}
#undef _
#undef COEFS
#undef CONVOLVE
#undef FUNCTION