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https://github.com/cookiengineer/audacity
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Move library tree where it belongs
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ra
256
lib-src/libnyquist/nyquist/tran/pluck.c
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256
lib-src/libnyquist/nyquist/tran/pluck.c
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#include "stdio.h"
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#ifndef mips
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#include "stdlib.h"
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#endif
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#include "xlisp.h"
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#include "sound.h"
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#include "falloc.h"
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#include "cext.h"
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#include "pluck.h"
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void pluck_free();
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typedef struct pluck_susp_struct {
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snd_susp_node susp;
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long terminate_cnt;
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double stretch;
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double cons;
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double loss;
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long len;
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double x2;
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double x3;
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sample_type *shiftreg;
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sample_type *i1;
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sample_type *i2;
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sample_type *i3;
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sample_type *i4;
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sample_type *endptr;
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} pluck_susp_node, *pluck_susp_type;
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#define MAXLENGTH 20000
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long pluck_parameters(double hz, double sr, double final, double dur,
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double *stretch, double *cons, double *rho)
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{
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double t = PI * (hz / sr);
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double y = fabs(cos(t));
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/* original m4c code used ratio of initial amp to final amp in dB
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and then converted to a ratio, e.g. you specify 60 and the
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parameter Final is 1000.0. This is counterintuitive to me (RBD)
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because I would expect the value to be -60dB or 0.001. That is
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what I implemented, so to get this back into correspondence
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with the m4c algorithm, I take the NEGATIVE log to get lf,
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whereas m4c takes the positive log:
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*/
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double lf = -log(final);
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double tdecay = -lf / (hz * log(y));
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double st;
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long len;
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double x;
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if (hz <= sr / MAXLENGTH) {
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xlfail("pluck hz is too low");
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} else if (hz >= sr / 3) {
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xlfail("pluck hz is too high");
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}
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/*
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* if desired decay time is shorter than the natural decay time,
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* then introduce a loss factor. Otherwise, stretch note out.
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*/
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st = hz * dur;
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if (dur < tdecay) {
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*rho = exp(-lf / st) / y;
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*stretch = 0.5;
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} else {
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*rho = 1;
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*stretch = 0.5 + sqrt(0.25 -
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(1 - exp(2 * lf * (hz - sr) / (st * sr))) /
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(2 - 2 * cos(2 * t)));
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}
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/* delay line length is */
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len = (int) ((sr / hz) - *stretch - 0.001);
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/* tuning constant is */
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x = (sr / hz) - len - *stretch;
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*cons = (1.0 - x) / (1.0 + x);
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if (len <= 1) {
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xlfail("internal error: pluck delay line length too short");
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}
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return len;
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}
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static unsigned int rnext = 1;
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int krand()
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{
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rnext = rnext * 1103515245 + 12345;
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return (rnext >> 16) & 0x7fff;
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}
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void pluck_initialize(sample_type *shiftreg, sample_type *array,
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long len, double cons)
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{
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sample_type suma = 0.0F;
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long k;
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sample_type avea;
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array[1] = 0;
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for (k = len; k > 0; k--, array--) {
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/* note: the m4c code has a bug. It claims to filter
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the initial values, but it really just sets the
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values to +1 or -1. The following does the same
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thing with much less code:
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*/
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*array = (krand() & 2) - 1;
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suma += *array; /* compute sum for the average */
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}
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avea = suma / len;
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/* zero the average */
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for (k = 0; k <= len + 1; k++) shiftreg[k] -= avea;
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shiftreg[len] = 0;
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shiftreg[len + 1] = 0;
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}
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void pluck__fetch(register pluck_susp_type susp, snd_list_type snd_list)
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{
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int cnt = 0; /* how many samples computed */
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int togo;
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int n;
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sample_block_type out;
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register sample_block_values_type out_ptr;
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register sample_block_values_type out_ptr_reg;
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register double stretch_reg;
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register double cons_reg;
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register double loss_reg;
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register double x2_reg;
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register double x3_reg;
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register sample_type * i1_reg;
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register sample_type * i2_reg;
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register sample_type * i3_reg;
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register sample_type * i4_reg;
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register sample_type * endptr_reg;
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falloc_sample_block(out, "pluck__fetch");
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out_ptr = out->samples;
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snd_list->block = out;
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while (cnt < max_sample_block_len) { /* outer loop */
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/* first compute how many samples to generate in inner loop: */
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/* don't overflow the output sample block: */
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togo = max_sample_block_len - cnt;
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/* don't run past terminate time */
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if (susp->terminate_cnt != UNKNOWN &&
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susp->terminate_cnt <= susp->susp.current + cnt + togo) {
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togo = susp->terminate_cnt - (susp->susp.current + cnt);
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if (togo == 0) break;
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}
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n = togo;
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stretch_reg = susp->stretch;
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cons_reg = susp->cons;
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loss_reg = susp->loss;
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x2_reg = susp->x2;
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x3_reg = susp->x3;
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i1_reg = susp->i1;
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i2_reg = susp->i2;
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i3_reg = susp->i3;
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i4_reg = susp->i4;
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endptr_reg = susp->endptr;
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out_ptr_reg = out_ptr;
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if (n) do { /* the inner sample computation loop */
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sample_type sum = (sample_type)
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((*i1_reg++ * x2_reg) + (*i2_reg++ * x3_reg) +
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(*i3_reg++ * stretch_reg) - (*i4_reg++ * cons_reg));
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/* wrap pointers around shift register if necessary */
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if (i1_reg == endptr_reg) i1_reg = susp->shiftreg;
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if (i2_reg == endptr_reg) i2_reg = susp->shiftreg;
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if (i3_reg == endptr_reg) i3_reg = susp->shiftreg;
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if (i4_reg == endptr_reg) i4_reg = susp->shiftreg;
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/* store new value in shift register */
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*i4_reg = (sample_type) (sum * loss_reg);
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/* deliver sample */
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*out_ptr_reg++ = sum;
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;
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} while (--n); /* inner loop */
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susp->i1 = i1_reg;
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susp->i2 = i2_reg;
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susp->i3 = i3_reg;
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susp->i4 = i4_reg;
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out_ptr += togo;
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cnt += togo;
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} /* outer loop */
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/* test for termination */
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if (togo == 0 && cnt == 0) {
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snd_list_terminate(snd_list);
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} else {
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snd_list->block_len = cnt;
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susp->susp.current += cnt;
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}
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} /* pluck__fetch */
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void pluck_free(pluck_susp_type susp)
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{
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free(susp->shiftreg);
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ffree_generic(susp, sizeof(pluck_susp_node), "pluck_free");
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}
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void pluck_print_tree(pluck_susp_type susp, int n)
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{
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}
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sound_type snd_make_pluck(rate_type sr, double hz, time_type t0, time_type d, double final_amp)
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{
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register pluck_susp_type susp;
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/* sr specified as input parameter */
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/* t0 specified as input parameter */
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sample_type scale_factor = 1.0F;
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falloc_generic(susp, pluck_susp_node, "snd_make_pluck");
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susp->stretch = 0;
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susp->cons = 0;
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susp->loss = 0;
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susp->len = pluck_parameters(hz, sr, final_amp, d,
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&susp->stretch, &susp->cons,
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&susp->loss);
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susp->x2 = -susp->cons * (susp->stretch - 1);
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susp->x3 = susp->cons * susp->stretch - susp->stretch + 1;
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susp->shiftreg = (sample_type *) calloc (susp->len + 4, sizeof(sample_type));
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susp->i1 = susp->shiftreg + susp->len + 1;
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susp->i2 = susp->shiftreg + susp->len;
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susp->i3 = susp->shiftreg + susp->len - 1;
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susp->i4 = susp->shiftreg + susp->len - 2;
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susp->endptr = susp->shiftreg + susp->len + 2;
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pluck_initialize(susp->shiftreg, susp->i3,
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susp->len, susp->cons);
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susp->susp.fetch = pluck__fetch;
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susp->terminate_cnt = round((d) * sr);
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/* initialize susp state */
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susp->susp.free = pluck_free;
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susp->susp.sr = sr;
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susp->susp.t0 = t0;
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susp->susp.mark = NULL;
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susp->susp.print_tree = pluck_print_tree;
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susp->susp.name = "pluck";
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susp->susp.log_stop_cnt = UNKNOWN;
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susp->susp.current = 0;
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return sound_create((snd_susp_type)susp, t0, sr, scale_factor);
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}
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sound_type snd_pluck(rate_type sr, double hz, time_type t0, time_type d, double final_amp)
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{
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return snd_make_pluck(sr, hz, t0, d, final_amp);
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}
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