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comparison spandsp-0.0.3/spandsp-0.0.3/src/oki_adpcm.c @ 5:f762bf195c4b

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import spandsp-0.0.3
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 16:00:21 +0200
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4:26cd8f1ef0b1 5:f762bf195c4b
1 /*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * oki_adpcm.c - Conversion routines between linear 16 bit PCM data and
5 * OKI (Dialogic) ADPCM format. Supports with the 32kbps
6 * and 24kbps variants used by Dialogic.
7 *
8 * Written by Steve Underwood <steveu@coppice.org>
9 *
10 * Copyright (C) 2001, 2004 Steve Underwood
11 *
12 * The actual OKI ADPCM encode and decode method is derived from freely
13 * available code, whose exact origins seem uncertain.
14 *
15 * All rights reserved.
16 *
17 * This program is free software; you can redistribute it and/or modify
18 * it under the terms of the GNU General Public License version 2, as
19 * published by the Free Software Foundation.
20 *
21 * This program is distributed in the hope that it will be useful,
22 * but WITHOUT ANY WARRANTY; without even the implied warranty of
23 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24 * GNU General Public License for more details.
25 *
26 * You should have received a copy of the GNU General Public License
27 * along with this program; if not, write to the Free Software
28 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
29 *
30 * $Id: oki_adpcm.c,v 1.22 2006/11/28 16:59:56 steveu Exp $
31 */
32
33 /*! \file */
34
35 #ifdef HAVE_CONFIG_H
36 #include <config.h>
37 #endif
38
39 #include <stdlib.h>
40 #include <inttypes.h>
41 #include <string.h>
42
43 #include "spandsp/telephony.h"
44 #include "spandsp/oki_adpcm.h"
45
46 /* Routines to convert 12 bit linear samples to the Oki ADPCM coding format,
47 widely used in CTI, because Dialogic use it. */
48
49 static const int16_t step_size[49] =
50 {
51 16, 17, 19, 21, 23, 25, 28, 31,
52 34, 37, 41, 45, 50, 55, 60, 66,
53 73, 80, 88, 97, 107, 118, 130, 143,
54 157, 173, 190, 209, 230, 253, 279, 307,
55 337, 371, 408, 449, 494, 544, 598, 658,
56 724, 796, 876, 963, 1060, 1166, 1282, 1408,
57 1552
58 };
59
60 static const int16_t step_adjustment[8] =
61 {
62 -1, -1, -1, -1, 2, 4, 6, 8
63 };
64
65 /* Band limiting filter, to allow sample rate conversion to and
66 from 6k samples/second. */
67 static const float cutoff_coeffs[] =
68 {
69 -3.648392e-4f,
70 5.062391e-4f,
71 1.206247e-3f,
72 1.804452e-3f,
73 1.691750e-3f,
74 4.083405e-4f,
75 -1.931085e-3f,
76 -4.452107e-3f,
77 -5.794821e-3f,
78 -4.778489e-3f,
79 -1.161266e-3f,
80 3.928504e-3f,
81 8.259786e-3f,
82 9.500425e-3f,
83 6.512800e-3f,
84 2.227856e-4f,
85 -6.531275e-3f,
86 -1.026843e-2f,
87 -8.718062e-3f,
88 -2.280487e-3f,
89 5.817733e-3f,
90 1.096777e-2f,
91 9.634404e-3f,
92 1.569301e-3f,
93 -9.522632e-3f,
94 -1.748273e-2f,
95 -1.684408e-2f,
96 -6.100054e-3f,
97 1.071206e-2f,
98 2.525209e-2f,
99 2.871779e-2f,
100 1.664411e-2f,
101 -7.706268e-3f,
102 -3.331083e-2f,
103 -4.521249e-2f,
104 -3.085962e-2f,
105 1.373653e-2f,
106 8.089593e-2f,
107 1.529060e-1f,
108 2.080487e-1f,
109 2.286834e-1f,
110 2.080487e-1f,
111 1.529060e-1f,
112 8.089593e-2f,
113 1.373653e-2f,
114 -3.085962e-2f,
115 -4.521249e-2f,
116 -3.331083e-2f,
117 -7.706268e-3f,
118 1.664411e-2f,
119 2.871779e-2f,
120 2.525209e-2f,
121 1.071206e-2f,
122 -6.100054e-3f,
123 -1.684408e-2f,
124 -1.748273e-2f,
125 -9.522632e-3f,
126 1.569301e-3f,
127 9.634404e-3f,
128 1.096777e-2f,
129 5.817733e-3f,
130 -2.280487e-3f,
131 -8.718062e-3f,
132 -1.026843e-2f,
133 -6.531275e-3f,
134 2.227856e-4f,
135 6.512800e-3f,
136 9.500425e-3f,
137 8.259786e-3f,
138 3.928504e-3f,
139 -1.161266e-3f,
140 -4.778489e-3f,
141 -5.794821e-3f,
142 -4.452107e-3f,
143 -1.931085e-3f,
144 4.083405e-4f,
145 1.691750e-3f,
146 1.804452e-3f,
147 1.206247e-3f,
148 5.062391e-4f,
149 -3.648392e-4f
150 };
151
152 static int16_t decode(oki_adpcm_state_t *s, uint8_t adpcm)
153 {
154 int16_t e;
155 int16_t ss;
156 int16_t linear;
157
158 /* Doing the next part as follows:
159 *
160 * x = adpcm & 0x07;
161 * e = (step_size[s->step_index]*(x + x + 1)) >> 3;
162 *
163 * Seems an obvious improvement on a modern machine, but remember
164 * the truncation errors do not come out the same. It would
165 * not, therefore, be an exact match for what this code is doing.
166 *
167 * Just what a Dialogic card does, I do not know!
168 */
169
170 ss = step_size[s->step_index];
171 e = ss >> 3;
172 if (adpcm & 0x01)
173 e += (ss >> 2);
174 /*endif*/
175 if (adpcm & 0x02)
176 e += (ss >> 1);
177 /*endif*/
178 if (adpcm & 0x04)
179 e += ss;
180 /*endif*/
181 if (adpcm & 0x08)
182 e = -e;
183 /*endif*/
184 linear = s->last + e;
185
186 /* Saturate the values to +/- 2^11 (supposed to be 12 bits) */
187 if (linear > 2047)
188 linear = 2047;
189 else if (linear < -2048)
190 linear = -2048;
191 /*endif*/
192
193 s->last = linear;
194 s->step_index += step_adjustment[adpcm & 0x07];
195 if (s->step_index < 0)
196 s->step_index = 0;
197 else if (s->step_index > 48)
198 s->step_index = 48;
199 /*endif*/
200 /* Note: the result here is a 12 bit value */
201 return linear;
202 }
203 /*- End of function --------------------------------------------------------*/
204
205 static uint8_t encode(oki_adpcm_state_t *s, int16_t linear)
206 {
207 int16_t e;
208 int16_t ss;
209 uint8_t adpcm;
210
211 ss = step_size[s->step_index];
212 e = (linear >> 4) - s->last;
213 adpcm = (uint8_t) 0x00;
214 if (e < 0)
215 {
216 adpcm = (uint8_t) 0x08;
217 e = -e;
218 }
219 /*endif*/
220 if (e >= ss)
221 {
222 adpcm |= (uint8_t) 0x04;
223 e -= ss;
224 }
225 /*endif*/
226 if (e >= (ss >> 1))
227 {
228 adpcm |= (uint8_t) 0x02;
229 e -= ss;
230 }
231 /*endif*/
232 if (e >= (ss >> 2))
233 adpcm |= (uint8_t) 0x01;
234 /*endif*/
235
236 /* Use the decoder to set the estimate of the last sample. */
237 /* It also will adjust the step_index for us. */
238 s->last = decode(s, adpcm);
239 return adpcm;
240 }
241 /*- End of function --------------------------------------------------------*/
242
243 oki_adpcm_state_t *oki_adpcm_init(oki_adpcm_state_t *s, int bit_rate)
244 {
245 if (bit_rate != 32000 && bit_rate != 24000)
246 return NULL;
247 if (s == NULL)
248 {
249 if ((s = (oki_adpcm_state_t *) malloc(sizeof(*s))) == NULL)
250 return NULL;
251 }
252 memset(s, 0, sizeof(*s));
253 s->bit_rate = bit_rate;
254
255 return s;
256 }
257 /*- End of function --------------------------------------------------------*/
258
259 int oki_adpcm_release(oki_adpcm_state_t *s)
260 {
261 free(s);
262 return 0;
263 }
264 /*- End of function --------------------------------------------------------*/
265
266 int oki_adpcm_decode(oki_adpcm_state_t *s,
267 int16_t amp[],
268 const uint8_t oki_data[],
269 int oki_bytes)
270 {
271 int i;
272 int x;
273 int l;
274 int n;
275 int samples;
276 float z;
277
278 samples = 0;
279 if (s->bit_rate == 32000)
280 {
281 for (i = 0; i < oki_bytes; i++)
282 {
283 amp[samples++] = decode(s, (oki_data[i] >> 4) & 0xF) << 4;
284 amp[samples++] = decode(s, oki_data[i] & 0xF) << 4;
285 }
286 /*endwhile*/
287 }
288 else
289 {
290 n = 0;
291 for (i = 0; i < oki_bytes; )
292 {
293 /* 6k to 8k sample/second conversion */
294 if (s->phase)
295 {
296 s->history[s->ptr++] =
297 decode(s, (n++ & 1) ? (oki_data[i++] & 0xF) : ((oki_data[i] >> 4) & 0xF)) << 4;
298 s->ptr &= (32 - 1);
299 }
300 /*endif*/
301 z = 0.0f;
302 for (l = 80 - 3 + s->phase, x = s->ptr - 1; l >= 0; l -= 4, x--)
303 z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
304 amp[samples++] = (int16_t) (z*4.0f);
305 if (++s->phase > 3)
306 s->phase = 0;
307 /*endif*/
308 }
309 /*endfor*/
310 }
311 /*endif*/
312 return samples;
313 }
314 /*- End of function --------------------------------------------------------*/
315
316 int oki_adpcm_encode(oki_adpcm_state_t *s,
317 uint8_t oki_data[],
318 const int16_t amp[],
319 int len)
320 {
321 int x;
322 int l;
323 int n;
324 int bytes;
325 float z;
326
327 bytes = 0;
328 if (s->bit_rate == 32000)
329 {
330 for (n = 0; n < len; n++)
331 {
332 s->oki_byte = (s->oki_byte << 4) | encode(s, amp[n]);
333 if ((s->mark++ & 1))
334 oki_data[bytes++] = s->oki_byte;
335 /*endif*/
336 }
337 /*endfor*/
338 }
339 else
340 {
341 n = 0;
342 for (;;)
343 {
344 /* 8k to 6k sample/second conversion */
345 if (s->phase > 2)
346 {
347 s->history[s->ptr++] = amp[n];
348 s->ptr &= (32 - 1);
349 s->phase = 0;
350 if (++n >= len)
351 break;
352 /*endif*/
353 }
354 /*endif*/
355 s->history[s->ptr++] = amp[n];
356 s->ptr &= (32 - 1);
357 z = 0.0f;
358 for (l = 80 - s->phase, x = s->ptr - 1; l >= 0; l -= 3, x--)
359 z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
360 /*endfor*/
361 s->oki_byte = (s->oki_byte << 4) | encode(s, (int16_t) (z*3.0f));
362 if ((s->mark++ & 1))
363 oki_data[bytes++] = s->oki_byte;
364 /*endif*/
365 s->phase++;
366 if (++n >= len)
367 break;
368 /*endif*/
369 }
370 /*endfor*/
371 }
372 /*endif*/
373 return bytes;
374 }
375 /*- End of function --------------------------------------------------------*/
376 /*- End of file ------------------------------------------------------------*/

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