1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License"). You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22 /*
23 * Copyright (c) 1992-2001 by Sun Microsystems, Inc.
24 * All rights reserved.
25 */
26
27 #pragma ident "%Z%%M% %I% %E% SMI"
28
29 /*
30 * This is a impementation of sampling rate conversion for low-passed signals.
31 *
32 * To convert the input signal of sampling rate of fi to another rate of fo,
33 * the least common multiple of fi and fo is derived first:
34 * fm = L * fi = M * fo.
35 * Then the input signal is up-sampled to fm by inserting (L -1) zero valued
36 * samples after each input sample, low-pass filtered, and down-smapled by
37 * saving one sample for every M samples. The implementation takes advantages
38 * of the (L - 1) zero values in the filter input and the (M - 1) output
39 * samples to be disregarded.
40 *
41 * If L = 1 or M = 1, a simpler decimation or interpolation is used.
42 */
43 #include <memory.h>
44 #include <math.h>
45
46 #include <Resample.h>
47
48 extern "C" {
49 char *bcopy(char *, char *, int);
50 char *memmove(char *, char *, int);
51 }
52
53 #define BCOPY(src, dest, num) memmove(dest, src, num)
54
55 // convolve(), short2double() and double2short() are defined in Fir.cc.
56 extern double convolve(double *, double *, int);
57 extern void short2double(double *, short *, int);
58 extern short double2short(double);
59
60 // generate truncated ideal LPF
sinc_coef(int fold,int order,double * coef)61 static void sinc_coef(int fold, // sample rate change
62 int order, // LP FIR filter order
63 double *coef) // filter coefficients
64 {
65 int i;
66 float alpha;
67 double bandwidth = M_PI / fold; // digital bandwidth of pass band
68
69 int half = order >> 1;
70 if (order & 1) { // order is odd, center = half + 0.5
71 float center = half + 0.5;
72 for (i = 0; i <= half; i++) {
73 alpha = center - i;
74 coef[i] = sin(bandwidth * alpha) / (M_PI * alpha);
75 }
76 } else { // order is even, center = half
77 for (i = 0; i < half; i++) {
78 alpha = half - i;
79 coef[i] = sin(bandwidth * alpha) / (M_PI * alpha);
80 }
81 coef[i++] = bandwidth / M_PI;
82 }
83 for (; i <= order; i++) // symmetric FIR
84 coef[i] = coef[order - i];
85 }
86
87 /*
88 * poly_conv() = coef[0] * data[length - 1] +
89 * coef[inc_coef] * data[length - 2] +
90 * ...
91 * coef[(length - 1) * inc_coef] * data[0] +
92 *
93 * convolution of coef[order + 1] and data[length] up-sampled by a factor
94 * of inc_coef. The terms of coef[1, 2, ... inc_coef - 1] multiplying 0
95 * are ignored.
96 */
97 // polyphase filter convolution
98 double
poly_conv(double * coef,int order,int inc_coef,double * data,int length)99 poly_conv(double *coef, // filter coef array
100 int order, // filter order
101 int inc_coef, // 1-to-L up-sample for data[length]
102 double *data, // data array
103 int length) // data array length
104 {
105 if ((order < 0) || (inc_coef < 1) || (length < 1))
106 return (0.0);
107 else {
108 double sum = 0.0;
109 double *coef_end = coef + order;
110 double *data_end = data + length;
111 while ((coef <= coef_end) && (data < data_end)) {
112 sum += *coef * *--data_end;
113 coef += inc_coef;
114 }
115 return (sum);
116 }
117 }
118
119 int
gcf(int a,int b)120 gcf(int a, int b) // greatest common factor between a and b
121 {
122 int remainder = a % b;
123 return (remainder == 0)? b : gcf(b, remainder);
124 }
125
126 void ResampleFilter::
updateState(double * in,int size)127 updateState(
128 double *in,
129 int size)
130 {
131 if (up <= 1)
132 Fir::updateState(in, size);
133 else if (size >= num_state)
134 memcpy(state, in + size - num_state,
135 num_state * sizeof (double));
136 else {
137 int old = num_state - size;
138 BCOPY((char *)(state + size), (char *)state,
139 old * sizeof (double));
140 memcpy(state + old, in, size * sizeof (double));
141 }
142 }
143
144 ResampleFilter:: // constructor
ResampleFilter(int rate_in,int rate_out)145 ResampleFilter(
146 int rate_in, // sampling rate of input signal
147 int rate_out) // sampling rate of output signal
148 {
149 // filter sampling rate = common multiple of rate_in and rate_out
150 int commonfactor = gcf(rate_in, rate_out);
151 up = rate_out / commonfactor;
152 down = rate_in / commonfactor;
153
154 int fold = (up > down)? up : down; // take the bigger rate change
155 order = (fold << 4) - 2; // filter order = fold * 16 - 2
156 coef = new double[order + 1];
157 sinc_coef(fold, order, coef); // required bandwidth = PI/fold
158
159 if (up > 1) { // need (order/up) states
160 num_state = (order + up - 1) / up;
161 state = new double[num_state];
162 for (int i = 0; i < num_state; i++) // reset states
163 state[i] = 0.0;
164 } else {
165 num_state = order;
166 state = new double[order]; // need order states
167 resetState();
168 }
169 delay = (order + 1) >> 1; // assuming symmetric FIR
170 down_offset = 0;
171 up_offset = 0;
172 }
173
174 // down-to-1 decimation
175 int ResampleFilter::
decimate_noadjust(short * in,int size,short * out)176 decimate_noadjust(short *in,
177 int size,
178 short *out)
179 {
180 int i;
181
182 if (size <= 0)
183 return (0);
184 else if (down <= 1) // normal filter
185 return (Fir::filter_noadjust(in, size, out));
186 else if (size <= down_offset) { // just update states
187 update_short(in, size);
188 down_offset -= size;
189 return (0);
190 }
191
192 double *in_buf = new double[size];
193 short2double(in_buf, in, size);
194
195 // filter and decimate and output
196 short *out_ptr = out;
197 int init_size = (size <= order)? size : order;
198 for (i = down_offset; i < init_size; i += down)
199 *out_ptr++ = double2short(convolve(coef, in_buf, i + 1) +
200 convolve(coef + i + 1, state + i, order - i));
201 for (; i < size; i += down)
202 *out_ptr++ = double2short(convolve(coef, in_buf + i - order,
203 order + 1));
204 down_offset = i - size;
205
206 updateState(in_buf, size);
207 delete in_buf;
208 return (out_ptr - out);
209 }
210
211 // decimate with group delay adjusted to 0
212 int ResampleFilter::
decimate(short * in,int size,short * out)213 decimate(short *in,
214 int size,
215 short *out)
216 {
217 if (delay <= 0)
218 return (decimate_noadjust(in, size, out));
219 else if (size <= delay) {
220 update_short(in, size);
221 delay -= size;
222 return (0);
223 } else {
224 update_short(in, delay);
225 in += delay;
226 size -= delay;
227 delay = 0;
228 return (decimate_noadjust(in, size, out));
229 }
230 }
231
232 // flush decimate filter
233 int ResampleFilter::
decimate_flush(short * out)234 decimate_flush(short *out)
235 {
236 int num_in = Fir::getFlushSize();
237 short *in = new short[num_in];
238 memset(in, 0, num_in * sizeof (short));
239 int num_out = decimate_noadjust(in, num_in, out);
240 delay += num_in;
241 delete in;
242 return (num_out);
243 }
244
245 // 1-to-up interpolation
246 int ResampleFilter::
interpolate_noadjust(short * in,int size,short * out)247 interpolate_noadjust(short *in,
248 int size,
249 short *out)
250 {
251 int i, j;
252
253 if (size <= 0)
254 return (0);
255 else if (up <= 1) // regular filter
256 return (Fir::filter_noadjust(in, size, out));
257
258 double *in_buf = new double[size];
259 short2double(in_buf, in, size);
260 short *out_ptr = out;
261 // befor the 1st input sample, generate "-up_offset" output samples
262 int coef_offset = up + up_offset;
263 for (j = up_offset; j < 0; j++) {
264 *out_ptr++ = double2short(up * poly_conv(coef + coef_offset,
265 order - coef_offset, up, state, num_state));
266 coef_offset++;
267 }
268 // for each of the rest input samples, generate up output samples
269 for (i = 1; i < size; i++) {
270 for (j = 0; j < up; j++) {
271 *out_ptr++ = double2short(up * (poly_conv(coef + j,
272 order - j, up, in_buf, i) + poly_conv(
273 coef + coef_offset, order - coef_offset, up, state,
274 num_state)));
275 coef_offset++;
276 }
277 }
278
279 // for the last input samples, generate "up_offset + up" output samples
280 for (j = 0; j < (up_offset + up); j++) {
281 *out_ptr++ = double2short(up * (poly_conv(coef + j,
282 order - j, up, in_buf, size) + poly_conv(
283 coef + coef_offset, order - coef_offset, up, state,
284 num_state)));
285 coef_offset++;
286 }
287 updateState(in_buf, size);
288 delete in_buf;
289 return (out_ptr - out);
290 }
291
292 // flush interpolate filter
293 int ResampleFilter::
interpolate_flush(short * out)294 interpolate_flush(short *out)
295 {
296 int num = (Fir::getFlushSize() + up - 1) / up;
297
298 short *in = new short[num];
299 memset(in, 0, num * sizeof (short));
300 int out_num = interpolate_noadjust(in, num, out);
301 delay += num * up;
302 delete in;
303 return (out_num);
304 }
305
306 // interpolate with delay adjusted
307 int ResampleFilter::
interpolate(short * in,int size,short * out)308 interpolate(short *in,
309 int size,
310 short *out)
311 {
312 if (size <= 0)
313 return (interpolate_flush(out));
314 else if (delay <= 0)
315 return (interpolate_noadjust(in, size, out));
316 else {
317 int delay_in = (delay + up - 1) / up;
318 if (size < delay_in)
319 delay_in = size;
320 double *in_buf = new double[delay_in];
321 short2double(in_buf, in, delay_in);
322 updateState(in_buf, delay_in);
323 delete in_buf;
324 delay -= delay_in * up;
325 up_offset = delay;
326 return (interpolate_noadjust(in + delay_in, size -
327 delay_in, out));
328 }
329 }
330
331 int ResampleFilter::
filter_noadjust(short * in,int size,short * out)332 filter_noadjust(short *in, // non-integer sampling rate conversion
333 int size,
334 short *out)
335 {
336 int i, j;
337
338 if (size <= 0)
339 return (0);
340 else if (up <= 1)
341 return (decimate_noadjust(in, size, out));
342 else if (down <= 1)
343 return (interpolate_noadjust(in, size, out));
344
345 double *in_buf = new double[size];
346 short2double(in_buf, in, size);
347 short *init_out = out;
348 int coef_offset = up_offset + down_offset + up;
349
350 /*
351 * before the 1st input sample,
352 * start from "up_offset + down_offset"th up-sampled sample
353 */
354 for (j = up_offset + down_offset; j < 0; j += down) {
355 *out++ = double2short(up * poly_conv(coef + coef_offset,
356 order - coef_offset, up, state, num_state));
357 coef_offset += down;
358 }
359
360 // process the input samples until the last one
361 for (i = 1; i < size; i++) {
362 for (; j < up; j += down) {
363 *out++ = double2short(up * (poly_conv(coef + j,
364 order - j, up, in_buf, i) + poly_conv(
365 coef + coef_offset, order - coef_offset, up, state,
366 num_state)));
367 coef_offset += down;
368 }
369 j -= up;
370 }
371
372 // for the last input sample, end at the "up + up_offset"th
373 for (; j < (up + up_offset); j += down) {
374 *out++ = double2short(up * (poly_conv(coef + j, order - j, up,
375 in_buf, size) + poly_conv(coef + coef_offset,
376 order - coef_offset, up, state, num_state)));
377 coef_offset += down;
378 }
379 down_offset = j - (up + up_offset);
380
381 updateState(in_buf, size);
382 delete in_buf;
383 return (out - init_out);
384 }
385
386 int ResampleFilter::
getFlushSize(void)387 getFlushSize(void)
388 {
389 int num_in = (Fir::getFlushSize() + up - 1) / up;
390 return ((num_in * up + down - 1 - down_offset) / down);
391 }
392
393 int ResampleFilter::
flush(short * out)394 flush(short *out) // flush resampling filter
395
396 {
397 if (down <= 1)
398 return (interpolate_flush(out));
399 else if (up <= 1)
400 return (decimate_flush(out));
401
402 int num = (Fir::getFlushSize() + up - 1) / up;
403
404 short *in = new short[num];
405 memset(in, 0, num * sizeof (short));
406 int out_num = filter_noadjust(in, num, out);
407 delete in;
408 delay += num * up;
409 return (out_num);
410 }
411
412 /*
413 * sampling rate conversion with filter delay adjusted
414 */
415 int ResampleFilter::
filter(short * in,int size,short * out)416 filter(
417 short *in,
418 int size,
419 short *out)
420 {
421 if (size <= 0)
422 return (flush(out));
423 else if (up <= 1)
424 return (decimate(in, size, out));
425 else if (down <= 1)
426 return (interpolate(in, size, out));
427 else if (delay <= 0)
428 return (filter_noadjust(in, size, out));
429 else {
430 int delay_in = (delay + up - 1) / up;
431 if (size < delay_in)
432 delay_in = size;
433 double *in_buf = new double[delay_in];
434 short2double(in_buf, in, delay_in);
435 updateState(in_buf, delay_in);
436 delete in_buf;
437 delay -= up * delay_in;
438 if (delay <= 0) {
439 up_offset = delay;
440 down_offset = 0;
441 }
442 return (filter_noadjust(in + delay_in, size - delay_in, out));
443 }
444 }
445