1 /* libSoX Compander Transfer Function: (c) 2007 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 #include "sox_i.h"
19
20 #include "compandt.h"
21 #include <string.h>
22
23 #define LOG_TO_LOG10(x) ((x) * 20 / M_LN10)
24
lsx_compandt_show(sox_compandt_t * t,sox_plot_t plot)25 sox_bool lsx_compandt_show(sox_compandt_t * t, sox_plot_t plot)
26 {
27 int i;
28
29 for (i = 1; t->segments[i-1].x; ++i)
30 lsx_debug("TF: %g %g %g %g",
31 LOG_TO_LOG10(t->segments[i].x),
32 LOG_TO_LOG10(t->segments[i].y),
33 LOG_TO_LOG10(t->segments[i].a),
34 LOG_TO_LOG10(t->segments[i].b));
35
36 if (plot == sox_plot_octave) {
37 printf(
38 "%% GNU Octave file (may also work with MATLAB(R) )\n"
39 "in=linspace(-99.5,0,200);\n"
40 "out=[");
41 for (i = -199; i <= 0; ++i) {
42 double in = i/2.;
43 double in_lin = pow(10., in/20);
44 printf("%g ", in + 20 * log10(lsx_compandt(t, in_lin)));
45 }
46 printf(
47 "];\n"
48 "plot(in,out)\n"
49 "title('SoX effect: compand')\n"
50 "xlabel('Input level (dB)')\n"
51 "ylabel('Output level (dB)')\n"
52 "grid on\n"
53 "disp('Hit return to continue')\n"
54 "pause\n");
55 return sox_false;
56 }
57 if (plot == sox_plot_gnuplot) {
58 printf(
59 "# gnuplot file\n"
60 "set title 'SoX effect: compand'\n"
61 "set xlabel 'Input level (dB)'\n"
62 "set ylabel 'Output level (dB)'\n"
63 "set grid xtics ytics\n"
64 "set key off\n"
65 "plot '-' with lines\n");
66 for (i = -199; i <= 0; ++i) {
67 double in = i/2.;
68 double in_lin = pow(10., in/20);
69 printf("%g %g\n", in, in + 20 * log10(lsx_compandt(t, in_lin)));
70 }
71 printf(
72 "e\n"
73 "pause -1 'Hit return to continue'\n");
74 return sox_false;
75 }
76 return sox_true;
77 }
78
prepare_transfer_fn(sox_compandt_t * t)79 static void prepare_transfer_fn(sox_compandt_t * t)
80 {
81 int i;
82 double radius = t->curve_dB * M_LN10 / 20;
83
84 for (i = 0; !i || t->segments[i-2].x; i += 2) {
85 t->segments[i].y += t->outgain_dB;
86 t->segments[i].x *= M_LN10 / 20; /* Convert to natural logs */
87 t->segments[i].y *= M_LN10 / 20;
88 }
89
90 #define line1 t->segments[i - 4]
91 #define curve t->segments[i - 3]
92 #define line2 t->segments[i - 2]
93 #define line3 t->segments[i - 0]
94 for (i = 4; t->segments[i - 2].x; i += 2) {
95 double x, y, cx, cy, in1, in2, out1, out2, theta, len, r;
96
97 line1.a = 0;
98 line1.b = (line2.y - line1.y) / (line2.x - line1.x);
99
100 line2.a = 0;
101 line2.b = (line3.y - line2.y) / (line3.x - line2.x);
102
103 theta = atan2(line2.y - line1.y, line2.x - line1.x);
104 len = sqrt(pow(line2.x - line1.x, 2.) + pow(line2.y - line1.y, 2.));
105 r = min(radius, len);
106 curve.x = line2.x - r * cos(theta);
107 curve.y = line2.y - r * sin(theta);
108
109 theta = atan2(line3.y - line2.y, line3.x - line2.x);
110 len = sqrt(pow(line3.x - line2.x, 2.) + pow(line3.y - line2.y, 2.));
111 r = min(radius, len / 2);
112 x = line2.x + r * cos(theta);
113 y = line2.y + r * sin(theta);
114
115 cx = (curve.x + line2.x + x) / 3;
116 cy = (curve.y + line2.y + y) / 3;
117
118 line2.x = x;
119 line2.y = y;
120
121 in1 = cx - curve.x;
122 out1 = cy - curve.y;
123 in2 = line2.x - curve.x;
124 out2 = line2.y - curve.y;
125 curve.a = (out2/in2 - out1/in1) / (in2-in1);
126 curve.b = out1/in1 - curve.a*in1;
127 }
128 #undef line1
129 #undef curve
130 #undef line2
131 #undef line3
132 t->segments[i - 3].x = 0;
133 t->segments[i - 3].y = t->segments[i - 2].y;
134
135 t->in_min_lin = exp(t->segments[1].x);
136 t->out_min_lin= exp(t->segments[1].y);
137 }
138
parse_transfer_value(char const * text,double * value)139 static sox_bool parse_transfer_value(char const * text, double * value)
140 {
141 char dummy; /* To check for extraneous chars. */
142
143 if (!text) {
144 lsx_fail("syntax error trying to read transfer function value");
145 return sox_false;
146 }
147 if (!strcmp(text, "-inf"))
148 *value = -20 * log10(-(double)SOX_SAMPLE_MIN);
149 else if (sscanf(text, "%lf %c", value, &dummy) != 1) {
150 lsx_fail("syntax error trying to read transfer function value");
151 return sox_false;
152 }
153 else if (*value > 0) {
154 lsx_fail("transfer function values are relative to maximum volume so can't exceed 0dB");
155 return sox_false;
156 }
157 return sox_true;
158 }
159
lsx_compandt_parse(sox_compandt_t * t,char * points,char * gain)160 sox_bool lsx_compandt_parse(sox_compandt_t * t, char * points, char * gain)
161 {
162 char const * text = points;
163 unsigned i, j, num, pairs, commas = 0;
164 char dummy; /* To check for extraneous chars. */
165
166 if (sscanf(points, "%lf %c", &t->curve_dB, &dummy) == 2 && dummy == ':')
167 points = strchr(points, ':') + 1;
168 else t->curve_dB = 0;
169 t->curve_dB = max(t->curve_dB, .01);
170
171 while (*text) commas += *text++ == ',';
172 pairs = 1 + commas / 2;
173 ++pairs; /* allow room for extra pair at the beginning */
174 pairs *= 2; /* allow room for the auto-curves */
175 ++pairs; /* allow room for 0,0 at end */
176 t->segments = lsx_calloc(pairs, sizeof(*t->segments));
177
178 #define s(n) t->segments[2*((n)+1)]
179 for (i = 0, text = strtok(points, ","); text != NULL; ++i) {
180 if (!parse_transfer_value(text, &s(i).x))
181 return sox_false;
182 if (i && s(i-1).x > s(i).x) {
183 lsx_fail("transfer function input values must be strictly increasing");
184 return sox_false;
185 }
186 if (i || (commas & 1)) {
187 text = strtok(NULL, ",");
188 if (!parse_transfer_value(text, &s(i).y))
189 return sox_false;
190 s(i).y -= s(i).x;
191 }
192 text = strtok(NULL, ",");
193 }
194 num = i;
195
196 if (num == 0 || s(num-1).x) /* Add 0,0 if necessary */
197 ++num;
198 #undef s
199
200 if (gain && sscanf(gain, "%lf %c", &t->outgain_dB, &dummy) != 1) {
201 lsx_fail("syntax error trying to read post-processing gain value");
202 return sox_false;
203 }
204
205 #define s(n) t->segments[2*(n)]
206 s(0).x = s(1).x - 2 * t->curve_dB; /* Add a tail off segment at the start */
207 s(0).y = s(1).y;
208 ++num;
209
210 for (i = 2; i < num; ++i) { /* Join adjacent colinear segments */
211 double g1 = (s(i-1).y - s(i-2).y) * (s(i-0).x - s(i-1).x);
212 double g2 = (s(i-0).y - s(i-1).y) * (s(i-1).x - s(i-2).x);
213 if (fabs(g1 - g2)) /* fabs stops epsilon problems */
214 continue;
215 --num;
216 for (j = --i; j < num; ++j)
217 s(j) = s(j+1);
218 }
219 #undef s
220
221 prepare_transfer_fn(t);
222 return sox_true;
223 }
224
lsx_compandt_kill(sox_compandt_t * p)225 void lsx_compandt_kill(sox_compandt_t * p)
226 {
227 free(p->segments);
228 }
229
230