src/rate_poly_fir.h

   1 /* Effect: change sample rate  Copyright (c) 2008,12 robs@users.sourceforge.net
   2  *
   3  * This library is free software; you can redistribute it and/or modify it
   4  * under the terms of the GNU Lesser General Public License as published by
   5  * the Free Software Foundation; either version 2.1 of the License, or (at
   6  * your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  16  */
  17
  18 /* Resample using an interpolated poly-phase FIR with length LEN.*/
  19 /* Input must be followed by LEN-1 samples. */
  20
  21 #define a (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 0,j))
  22 #define b (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 1,j))
  23 #define c (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 2,j))
  24 #define d (coef(p->shared->poly_fir_coefs, COEF_INTERP, FIR_LENGTH, phase, 3,j))
  25 #if COEF_INTERP == 0
  26   #define _ sum += a *in[j], ++j;
  27 #elif COEF_INTERP == 1
  28   #define _ sum += (b *x + a)*in[j], ++j;
  29 #elif COEF_INTERP == 2
  30   #define _ sum += ((c *x + b)*x + a)*in[j], ++j;
  31 #elif COEF_INTERP == 3
  32   #define _ sum += (((d*x + c)*x + b)*x + a)*in[j], ++j;
  33 #else
  34   #error COEF_INTERP
  35 #endif
  36
  37 static void FUNCTION(stage_t * p, fifo_t * output_fifo)
  38 {
  39   sample_t const * input = stage_read_p(p);
  40   int i, num_in = stage_occupancy(p), max_num_out = 1 + num_in*p->out_in_ratio;
  41   sample_t * output = fifo_reserve(output_fifo, max_num_out);
  42
  43 #if defined HI_PREC_CLOCK
  44   if (p->use_hi_prec_clock) {
  45     hi_prec_clock_t at = p->at.hi_prec_clock;
  46     for (i = 0; (int)at < num_in; ++i, at += p->step.hi_prec_clock) {
  47       sample_t const * in = input + (int)at;
  48       hi_prec_clock_t fraction = at - (int)at;
  49       int phase = fraction * (1 << PHASE_BITS);
  50 #if COEF_INTERP > 0
  51       sample_t x = fraction * (1 << PHASE_BITS) - phase;
  52 #endif
  53       sample_t sum = 0;
  54       int j = 0;
  55       CONVOLVE
  56       output[i] = sum;
  57     }
  58     fifo_read(&p->fifo, (int)at, NULL);
  59     p->at.hi_prec_clock = at - (int)at;
  60   } else
  61 #endif
  62   {
  63     for (i = 0; p->at.parts.integer < num_in; ++i, p->at.all += p->step.all) {
  64       sample_t const * in = input + p->at.parts.integer;
  65       uint32_t fraction = p->at.parts.fraction;
  66       int phase = fraction >> (32 - PHASE_BITS); /* high-order bits */
  67 #if COEF_INTERP > 0              /* low-order bits, scaled to [0,1) */
  68       sample_t x = (sample_t) (fraction << PHASE_BITS) * (1 / MULT32);
  69 #endif
  70       sample_t sum = 0;
  71       int j = 0;
  72       CONVOLVE
  73       output[i] = sum;
  74     }
  75     fifo_read(&p->fifo, p->at.parts.integer, NULL);
  76     p->at.parts.integer = 0;
  77   }
  78   assert(max_num_out - i >= 0);
  79   fifo_trim_by(output_fifo, max_num_out - i);
  80 }
  81
  82 #undef _
  83 #undef a
  84 #undef b
  85 #undef c
  86 #undef d
  87 #undef COEF_INTERP
  88 #undef CONVOLVE
  89 #undef FIR_LENGTH
  90 #undef FUNCTION
  91 #undef PHASE_BITS