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comparison spandsp-0.0.6pre17/src/oki_adpcm.c @ 4:26cd8f1ef0b1

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import spandsp-0.0.6pre17
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 15:50:58 +0200
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3:c6c5a16ce2f2 4:26cd8f1ef0b1
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 * All rights reserved.
13 *
14 * This program is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU Lesser General Public License version 2.1,
16 * as published by the Free Software Foundation.
17 *
18 * This program is distributed in the hope that it will be useful,
19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 * GNU Lesser General Public License for more details.
22 *
23 * You should have received a copy of the GNU Lesser General Public
24 * License along with this program; if not, write to the Free Software
25 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
26 *
27 * The actual OKI ADPCM encode and decode method is derived from freely
28 * available code, whose exact origins seem uncertain.
29 *
30 * $Id: oki_adpcm.c,v 1.32 2009/02/10 13:06:46 steveu Exp $
31 */
32
33 /*! \file */
34
35 #if defined(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 #include "spandsp/private/oki_adpcm.h"
46
47 /* Routines to convert 12 bit linear samples to the Oki ADPCM coding format,
48 widely used in CTI, because Dialogic use it. */
49
50 /* OKI ADPCM step variation table */
51 static const int16_t step_size[49] =
52 {
53 16, 17, 19, 21, 23, 25, 28, 31,
54 34, 37, 41, 45, 50, 55, 60, 66,
55 73, 80, 88, 97, 107, 118, 130, 143,
56 157, 173, 190, 209, 230, 253, 279, 307,
57 337, 371, 408, 449, 494, 544, 598, 658,
58 724, 796, 876, 963, 1060, 1166, 1282, 1411,
59 1552
60 };
61
62 static const int16_t step_adjustment[8] =
63 {
64 -1, -1, -1, -1, 2, 4, 6, 8
65 };
66
67 /* Band limiting filter, to allow sample rate conversion to and
68 from 6k samples/second. */
69 static const float cutoff_coeffs[] =
70 {
71 -3.648392e-4f,
72 5.062391e-4f,
73 1.206247e-3f,
74 1.804452e-3f,
75 1.691750e-3f,
76 4.083405e-4f,
77 -1.931085e-3f,
78 -4.452107e-3f,
79 -5.794821e-3f,
80 -4.778489e-3f,
81 -1.161266e-3f,
82 3.928504e-3f,
83 8.259786e-3f,
84 9.500425e-3f,
85 6.512800e-3f,
86 2.227856e-4f,
87 -6.531275e-3f,
88 -1.026843e-2f,
89 -8.718062e-3f,
90 -2.280487e-3f,
91 5.817733e-3f,
92 1.096777e-2f,
93 9.634404e-3f,
94 1.569301e-3f,
95 -9.522632e-3f,
96 -1.748273e-2f,
97 -1.684408e-2f,
98 -6.100054e-3f,
99 1.071206e-2f,
100 2.525209e-2f,
101 2.871779e-2f,
102 1.664411e-2f,
103 -7.706268e-3f,
104 -3.331083e-2f,
105 -4.521249e-2f,
106 -3.085962e-2f,
107 1.373653e-2f,
108 8.089593e-2f,
109 1.529060e-1f,
110 2.080487e-1f,
111 2.286834e-1f,
112 2.080487e-1f,
113 1.529060e-1f,
114 8.089593e-2f,
115 1.373653e-2f,
116 -3.085962e-2f,
117 -4.521249e-2f,
118 -3.331083e-2f,
119 -7.706268e-3f,
120 1.664411e-2f,
121 2.871779e-2f,
122 2.525209e-2f,
123 1.071206e-2f,
124 -6.100054e-3f,
125 -1.684408e-2f,
126 -1.748273e-2f,
127 -9.522632e-3f,
128 1.569301e-3f,
129 9.634404e-3f,
130 1.096777e-2f,
131 5.817733e-3f,
132 -2.280487e-3f,
133 -8.718062e-3f,
134 -1.026843e-2f,
135 -6.531275e-3f,
136 2.227856e-4f,
137 6.512800e-3f,
138 9.500425e-3f,
139 8.259786e-3f,
140 3.928504e-3f,
141 -1.161266e-3f,
142 -4.778489e-3f,
143 -5.794821e-3f,
144 -4.452107e-3f,
145 -1.931085e-3f,
146 4.083405e-4f,
147 1.691750e-3f,
148 1.804452e-3f,
149 1.206247e-3f,
150 5.062391e-4f,
151 -3.648392e-4f
152 };
153
154 static int16_t decode(oki_adpcm_state_t *s, uint8_t adpcm)
155 {
156 int16_t e;
157 int16_t ss;
158 int16_t linear;
159
160 /* Doing the next part as follows:
161 *
162 * x = adpcm & 0x07;
163 * e = (step_size[s->step_index]*(x + x + 1)) >> 3;
164 *
165 * Seems an obvious improvement on a modern machine, but remember
166 * the truncation errors do not come out the same. It would
167 * not, therefore, be an exact match for what this code is doing.
168 *
169 * Just what a Dialogic card does, I do not know!
170 */
171
172 ss = step_size[s->step_index];
173 e = ss >> 3;
174 if (adpcm & 0x01)
175 e += (ss >> 2);
176 /*endif*/
177 if (adpcm & 0x02)
178 e += (ss >> 1);
179 /*endif*/
180 if (adpcm & 0x04)
181 e += ss;
182 /*endif*/
183 if (adpcm & 0x08)
184 e = -e;
185 /*endif*/
186 linear = s->last + e;
187
188 /* Saturate the values to +/- 2^11 (supposed to be 12 bits) */
189 if (linear > 2047)
190 linear = 2047;
191 else if (linear < -2048)
192 linear = -2048;
193 /*endif*/
194
195 s->last = linear;
196 s->step_index += step_adjustment[adpcm & 0x07];
197 if (s->step_index < 0)
198 s->step_index = 0;
199 else if (s->step_index > 48)
200 s->step_index = 48;
201 /*endif*/
202 /* Note: the result here is a 12 bit value */
203 return linear;
204 }
205 /*- End of function --------------------------------------------------------*/
206
207 static uint8_t encode(oki_adpcm_state_t *s, int16_t linear)
208 {
209 int16_t e;
210 int16_t ss;
211 uint8_t adpcm;
212
213 ss = step_size[s->step_index];
214 e = (linear >> 4) - s->last;
215 adpcm = (uint8_t) 0x00;
216 if (e < 0)
217 {
218 adpcm = (uint8_t) 0x08;
219 e = -e;
220 }
221 /*endif*/
222 if (e >= ss)
223 {
224 adpcm |= (uint8_t) 0x04;
225 e -= ss;
226 }
227 /*endif*/
228 if (e >= (ss >> 1))
229 {
230 adpcm |= (uint8_t) 0x02;
231 e -= ss;
232 }
233 /*endif*/
234 if (e >= (ss >> 2))
235 adpcm |= (uint8_t) 0x01;
236 /*endif*/
237
238 /* Use the decoder to set the estimate of the last sample. */
239 /* It also will adjust the step_index for us. */
240 s->last = decode(s, adpcm);
241 return adpcm;
242 }
243 /*- End of function --------------------------------------------------------*/
244
245 SPAN_DECLARE(oki_adpcm_state_t *) oki_adpcm_init(oki_adpcm_state_t *s, int bit_rate)
246 {
247 if (bit_rate != 32000 && bit_rate != 24000)
248 return NULL;
249 if (s == NULL)
250 {
251 if ((s = (oki_adpcm_state_t *) malloc(sizeof(*s))) == NULL)
252 return NULL;
253 }
254 memset(s, 0, sizeof(*s));
255 s->bit_rate = bit_rate;
256
257 return s;
258 }
259 /*- End of function --------------------------------------------------------*/
260
261 SPAN_DECLARE(int) oki_adpcm_release(oki_adpcm_state_t *s)
262 {
263 return 0;
264 }
265 /*- End of function --------------------------------------------------------*/
266
267 SPAN_DECLARE(int) oki_adpcm_free(oki_adpcm_state_t *s)
268 {
269 free(s);
270 return 0;
271 }
272 /*- End of function --------------------------------------------------------*/
273
274 SPAN_DECLARE(int) oki_adpcm_decode(oki_adpcm_state_t *s,
275 int16_t amp[],
276 const uint8_t oki_data[],
277 int oki_bytes)
278 {
279 int i;
280 int x;
281 int l;
282 int n;
283 int samples;
284 float z;
285
286 #if (_MSC_VER >= 1400)
287 __analysis_assume(s->phase >= 0 && s->phase <= 4);
288 #endif
289 samples = 0;
290 if (s->bit_rate == 32000)
291 {
292 for (i = 0; i < oki_bytes; i++)
293 {
294 amp[samples++] = decode(s, (oki_data[i] >> 4) & 0xF) << 4;
295 amp[samples++] = decode(s, oki_data[i] & 0xF) << 4;
296 }
297 /*endwhile*/
298 }
299 else
300 {
301 n = 0;
302 for (i = 0; i < oki_bytes; )
303 {
304 /* 6k to 8k sample/second conversion */
305 if (s->phase)
306 {
307 s->history[s->ptr++] =
308 decode(s, (n++ & 1) ? (oki_data[i++] & 0xF) : ((oki_data[i] >> 4) & 0xF)) << 4;
309 s->ptr &= (32 - 1);
310 }
311 /*endif*/
312 z = 0.0f;
313 for (l = 80 - 3 + s->phase, x = s->ptr - 1; l >= 0; l -= 4, x--)
314 z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
315 amp[samples++] = (int16_t) (z*4.0f);
316 if (++s->phase > 3)
317 s->phase = 0;
318 /*endif*/
319 }
320 /*endfor*/
321 }
322 /*endif*/
323 return samples;
324 }
325 /*- End of function --------------------------------------------------------*/
326
327 SPAN_DECLARE(int) oki_adpcm_encode(oki_adpcm_state_t *s,
328 uint8_t oki_data[],
329 const int16_t amp[],
330 int len)
331 {
332 int x;
333 int l;
334 int n;
335 int bytes;
336 float z;
337
338 bytes = 0;
339 if (s->bit_rate == 32000)
340 {
341 for (n = 0; n < len; n++)
342 {
343 s->oki_byte = (s->oki_byte << 4) | encode(s, amp[n]);
344 if ((s->mark++ & 1))
345 oki_data[bytes++] = s->oki_byte;
346 /*endif*/
347 }
348 /*endfor*/
349 }
350 else
351 {
352 n = 0;
353 for (;;)
354 {
355 /* 8k to 6k sample/second conversion */
356 if (s->phase > 2)
357 {
358 s->history[s->ptr++] = amp[n];
359 s->ptr &= (32 - 1);
360 s->phase = 0;
361 if (++n >= len)
362 break;
363 /*endif*/
364 }
365 /*endif*/
366 s->history[s->ptr++] = amp[n];
367 s->ptr &= (32 - 1);
368 z = 0.0f;
369 for (l = 80 - s->phase, x = s->ptr - 1; l >= 0; l -= 3, x--)
370 z += cutoff_coeffs[l]*s->history[x & (32 - 1)];
371 /*endfor*/
372 s->oki_byte = (s->oki_byte << 4) | encode(s, (int16_t) (z*3.0f));
373 if ((s->mark++ & 1))
374 oki_data[bytes++] = s->oki_byte;
375 /*endif*/
376 s->phase++;
377 if (++n >= len)
378 break;
379 /*endif*/
380 }
381 /*endfor*/
382 }
383 /*endif*/
384 return bytes;
385 }
386 /*- End of function --------------------------------------------------------*/
387 /*- End of file ------------------------------------------------------------*/

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