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g726.c
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1 /*
2  * G.726 ADPCM audio codec
3  * Copyright (c) 2004 Roman Shaposhnik
4  *
5  * This is a very straightforward rendition of the G.726
6  * Section 4 "Computational Details".
7  *
8  * This file is part of FFmpeg.
9  *
10  * FFmpeg is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU Lesser General Public
12  * License as published by the Free Software Foundation; either
13  * version 2.1 of the License, or (at your option) any later version.
14  *
15  * FFmpeg is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18  * Lesser General Public License for more details.
19  *
20  * You should have received a copy of the GNU Lesser General Public
21  * License along with FFmpeg; if not, write to the Free Software
22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23  */
24 #include <limits.h>
25 
26 #include "libavutil/avassert.h"
28 #include "libavutil/opt.h"
29 #include "avcodec.h"
30 #include "internal.h"
31 #include "get_bits.h"
32 #include "put_bits.h"
33 
34 /**
35  * G.726 11bit float.
36  * G.726 Standard uses rather odd 11bit floating point arithmentic for
37  * numerous occasions. It's a mystery to me why they did it this way
38  * instead of simply using 32bit integer arithmetic.
39  */
40 typedef struct Float11 {
41  uint8_t sign; /**< 1bit sign */
42  uint8_t exp; /**< 4bit exponent */
43  uint8_t mant; /**< 6bit mantissa */
44 } Float11;
45 
46 static inline Float11* i2f(int i, Float11* f)
47 {
48  f->sign = (i < 0);
49  if (f->sign)
50  i = -i;
51  f->exp = av_log2_16bit(i) + !!i;
52  f->mant = i? (i<<6) >> f->exp : 1<<5;
53  return f;
54 }
55 
56 static inline int16_t mult(Float11* f1, Float11* f2)
57 {
58  int res, exp;
59 
60  exp = f1->exp + f2->exp;
61  res = (((f1->mant * f2->mant) + 0x30) >> 4);
62  res = exp > 19 ? res << (exp - 19) : res >> (19 - exp);
63  return (f1->sign ^ f2->sign) ? -res : res;
64 }
65 
66 static inline int sgn(int value)
67 {
68  return (value < 0) ? -1 : 1;
69 }
70 
71 typedef struct G726Tables {
72  const int* quant; /**< quantization table */
73  const int16_t* iquant; /**< inverse quantization table */
74  const int16_t* W; /**< special table #1 ;-) */
75  const uint8_t* F; /**< special table #2 */
76 } G726Tables;
77 
78 typedef struct G726Context {
79  AVClass *class;
80  G726Tables tbls; /**< static tables needed for computation */
81 
82  Float11 sr[2]; /**< prev. reconstructed samples */
83  Float11 dq[6]; /**< prev. difference */
84  int a[2]; /**< second order predictor coeffs */
85  int b[6]; /**< sixth order predictor coeffs */
86  int pk[2]; /**< signs of prev. 2 sez + dq */
87 
88  int ap; /**< scale factor control */
89  int yu; /**< fast scale factor */
90  int yl; /**< slow scale factor */
91  int dms; /**< short average magnitude of F[i] */
92  int dml; /**< long average magnitude of F[i] */
93  int td; /**< tone detect */
94 
95  int se; /**< estimated signal for the next iteration */
96  int sez; /**< estimated second order prediction */
97  int y; /**< quantizer scaling factor for the next iteration */
98  int code_size;
99  int little_endian; /**< little-endian bitstream as used in aiff and Sun AU */
100 } G726Context;
101 
102 static const int quant_tbl16[] = /**< 16kbit/s 2bits per sample */
103  { 260, INT_MAX };
104 static const int16_t iquant_tbl16[] =
105  { 116, 365, 365, 116 };
106 static const int16_t W_tbl16[] =
107  { -22, 439, 439, -22 };
108 static const uint8_t F_tbl16[] =
109  { 0, 7, 7, 0 };
110 
111 static const int quant_tbl24[] = /**< 24kbit/s 3bits per sample */
112  { 7, 217, 330, INT_MAX };
113 static const int16_t iquant_tbl24[] =
114  { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN };
115 static const int16_t W_tbl24[] =
116  { -4, 30, 137, 582, 582, 137, 30, -4 };
117 static const uint8_t F_tbl24[] =
118  { 0, 1, 2, 7, 7, 2, 1, 0 };
119 
120 static const int quant_tbl32[] = /**< 32kbit/s 4bits per sample */
121  { -125, 79, 177, 245, 299, 348, 399, INT_MAX };
122 static const int16_t iquant_tbl32[] =
123  { INT16_MIN, 4, 135, 213, 273, 323, 373, 425,
124  425, 373, 323, 273, 213, 135, 4, INT16_MIN };
125 static const int16_t W_tbl32[] =
126  { -12, 18, 41, 64, 112, 198, 355, 1122,
127  1122, 355, 198, 112, 64, 41, 18, -12};
128 static const uint8_t F_tbl32[] =
129  { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
130 
131 static const int quant_tbl40[] = /**< 40kbit/s 5bits per sample */
132  { -122, -16, 67, 138, 197, 249, 297, 338,
133  377, 412, 444, 474, 501, 527, 552, INT_MAX };
134 static const int16_t iquant_tbl40[] =
135  { INT16_MIN, -66, 28, 104, 169, 224, 274, 318,
136  358, 395, 429, 459, 488, 514, 539, 566,
137  566, 539, 514, 488, 459, 429, 395, 358,
138  318, 274, 224, 169, 104, 28, -66, INT16_MIN };
139 static const int16_t W_tbl40[] =
140  { 14, 14, 24, 39, 40, 41, 58, 100,
141  141, 179, 219, 280, 358, 440, 529, 696,
142  696, 529, 440, 358, 280, 219, 179, 141,
143  100, 58, 41, 40, 39, 24, 14, 14 };
144 static const uint8_t F_tbl40[] =
145  { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
146  6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
147 
148 static const G726Tables G726Tables_pool[] =
153 
154 
155 /**
156  * Para 4.2.2 page 18: Adaptive quantizer.
157  */
158 static inline uint8_t quant(G726Context* c, int d)
159 {
160  int sign, exp, i, dln;
161 
162  sign = i = 0;
163  if (d < 0) {
164  sign = 1;
165  d = -d;
166  }
167  exp = av_log2_16bit(d);
168  dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
169 
170  while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln)
171  ++i;
172 
173  if (sign)
174  i = ~i;
175  if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */
176  i = 0xff;
177 
178  return i;
179 }
180 
181 /**
182  * Para 4.2.3 page 22: Inverse adaptive quantizer.
183  */
184 static inline int16_t inverse_quant(G726Context* c, int i)
185 {
186  int dql, dex, dqt;
187 
188  dql = c->tbls.iquant[i] + (c->y >> 2);
189  dex = (dql>>7) & 0xf; /* 4bit exponent */
190  dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
191  return (dql < 0) ? 0 : ((dqt<<dex) >> 7);
192 }
193 
194 static int16_t g726_decode(G726Context* c, int I)
195 {
196  int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
197  Float11 f;
198  int I_sig= I >> (c->code_size - 1);
199 
200  dq = inverse_quant(c, I);
201 
202  /* Transition detect */
203  ylint = (c->yl >> 15);
204  ylfrac = (c->yl >> 10) & 0x1f;
205  thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
206  tr= (c->td == 1 && dq > ((3*thr2)>>2));
207 
208  if (I_sig) /* get the sign */
209  dq = -dq;
210  re_signal = c->se + dq;
211 
212  /* Update second order predictor coefficient A2 and A1 */
213  pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
214  dq0 = dq ? sgn(dq) : 0;
215  if (tr) {
216  c->a[0] = 0;
217  c->a[1] = 0;
218  for (i=0; i<6; i++)
219  c->b[i] = 0;
220  } else {
221  /* This is a bit crazy, but it really is +255 not +256 */
222  fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
223 
224  c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
225  c->a[1] = av_clip(c->a[1], -12288, 12288);
226  c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
227  c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
228 
229  for (i=0; i<6; i++)
230  c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
231  }
232 
233  /* Update Dq and Sr and Pk */
234  c->pk[1] = c->pk[0];
235  c->pk[0] = pk0 ? pk0 : 1;
236  c->sr[1] = c->sr[0];
237  i2f(re_signal, &c->sr[0]);
238  for (i=5; i>0; i--)
239  c->dq[i] = c->dq[i-1];
240  i2f(dq, &c->dq[0]);
241  c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */
242 
243  c->td = c->a[1] < -11776;
244 
245  /* Update Ap */
246  c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5);
247  c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7);
248  if (tr)
249  c->ap = 256;
250  else {
251  c->ap += (-c->ap) >> 4;
252  if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3))
253  c->ap += 0x20;
254  }
255 
256  /* Update Yu and Yl */
257  c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120);
258  c->yl += c->yu + ((-c->yl)>>6);
259 
260  /* Next iteration for Y */
261  al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
262  c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
263 
264  /* Next iteration for SE and SEZ */
265  c->se = 0;
266  for (i=0; i<6; i++)
267  c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
268  c->sez = c->se >> 1;
269  for (i=0; i<2; i++)
270  c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
271  c->se >>= 1;
272 
273  return av_clip(re_signal << 2, -0xffff, 0xffff);
274 }
275 
277 {
278  int i;
279 
280  c->tbls = G726Tables_pool[c->code_size - 2];
281  for (i=0; i<2; i++) {
282  c->sr[i].mant = 1<<5;
283  c->pk[i] = 1;
284  }
285  for (i=0; i<6; i++) {
286  c->dq[i].mant = 1<<5;
287  }
288  c->yu = 544;
289  c->yl = 34816;
290 
291  c->y = 544;
292 
293  return 0;
294 }
295 
296 #if CONFIG_ADPCM_G726_ENCODER
297 static int16_t g726_encode(G726Context* c, int16_t sig)
298 {
299  uint8_t i;
300 
301  i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1);
302  g726_decode(c, i);
303  return i;
304 }
305 
306 /* Interfacing to the libavcodec */
307 
308 static av_cold int g726_encode_init(AVCodecContext *avctx)
309 {
310  G726Context* c = avctx->priv_data;
311 
313  avctx->sample_rate != 8000) {
314  av_log(avctx, AV_LOG_ERROR, "Sample rates other than 8kHz are not "
315  "allowed when the compliance level is higher than unofficial. "
316  "Resample or reduce the compliance level.\n");
317  return AVERROR(EINVAL);
318  }
319  av_assert0(avctx->sample_rate > 0);
320 
321  if(avctx->channels != 1){
322  av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
323  return AVERROR(EINVAL);
324  }
325 
326  if (avctx->bit_rate)
327  c->code_size = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate;
328 
329  c->code_size = av_clip(c->code_size, 2, 5);
330  avctx->bit_rate = c->code_size * avctx->sample_rate;
331  avctx->bits_per_coded_sample = c->code_size;
332 
333  g726_reset(c);
334 
335  /* select a frame size that will end on a byte boundary and have a size of
336  approximately 1024 bytes */
337  avctx->frame_size = ((int[]){ 4096, 2736, 2048, 1640 })[c->code_size - 2];
338 
339  return 0;
340 }
341 
342 static int g726_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
343  const AVFrame *frame, int *got_packet_ptr)
344 {
345  G726Context *c = avctx->priv_data;
346  const int16_t *samples = (const int16_t *)frame->data[0];
347  PutBitContext pb;
348  int i, ret, out_size;
349 
350  out_size = (frame->nb_samples * c->code_size + 7) / 8;
351  if ((ret = ff_alloc_packet2(avctx, avpkt, out_size)) < 0)
352  return ret;
353  init_put_bits(&pb, avpkt->data, avpkt->size);
354 
355  for (i = 0; i < frame->nb_samples; i++)
356  put_bits(&pb, c->code_size, g726_encode(c, *samples++));
357 
358  flush_put_bits(&pb);
359 
360  avpkt->size = out_size;
361  *got_packet_ptr = 1;
362  return 0;
363 }
364 
365 #define OFFSET(x) offsetof(G726Context, x)
366 #define AE AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
367 static const AVOption options[] = {
368  { "code_size", "Bits per code", OFFSET(code_size), AV_OPT_TYPE_INT, { .i64 = 4 }, 2, 5, AE },
369  { NULL },
370 };
371 
372 static const AVClass g726_class = {
373  .class_name = "g726",
374  .item_name = av_default_item_name,
375  .option = options,
376  .version = LIBAVUTIL_VERSION_INT,
377 };
378 
379 static const AVCodecDefault defaults[] = {
380  { "b", "0" },
381  { NULL },
382 };
383 
384 AVCodec ff_adpcm_g726_encoder = {
385  .name = "g726",
386  .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
387  .type = AVMEDIA_TYPE_AUDIO,
389  .priv_data_size = sizeof(G726Context),
390  .init = g726_encode_init,
391  .encode2 = g726_encode_frame,
392  .capabilities = CODEC_CAP_SMALL_LAST_FRAME,
393  .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
395  .priv_class = &g726_class,
396  .defaults = defaults,
397 };
398 #endif
399 
400 #if CONFIG_ADPCM_G726_DECODER || CONFIG_ADPCM_G726LE_DECODER
401 static av_cold int g726_decode_init(AVCodecContext *avctx)
402 {
403  G726Context* c = avctx->priv_data;
404 
405  if(avctx->channels > 1){
406  avpriv_request_sample(avctx, "Decoding more than one channel");
407  return AVERROR_PATCHWELCOME;
408  }
409  avctx->channels = 1;
411 
412  c->little_endian = !strcmp(avctx->codec->name, "g726le");
413 
414  c->code_size = avctx->bits_per_coded_sample;
415  if (c->code_size < 2 || c->code_size > 5) {
416  av_log(avctx, AV_LOG_ERROR, "Invalid number of bits %d\n", c->code_size);
417  return AVERROR(EINVAL);
418  }
419  g726_reset(c);
420 
421  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
422 
423  return 0;
424 }
425 
426 static int g726_decode_frame(AVCodecContext *avctx, void *data,
427  int *got_frame_ptr, AVPacket *avpkt)
428 {
429  AVFrame *frame = data;
430  const uint8_t *buf = avpkt->data;
431  int buf_size = avpkt->size;
432  G726Context *c = avctx->priv_data;
433  int16_t *samples;
434  GetBitContext gb;
435  int out_samples, ret;
436 
437  out_samples = buf_size * 8 / c->code_size;
438 
439  /* get output buffer */
440  frame->nb_samples = out_samples;
441  if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
442  return ret;
443  samples = (int16_t *)frame->data[0];
444 
445  init_get_bits(&gb, buf, buf_size * 8);
446 
447  while (out_samples--)
448  *samples++ = g726_decode(c, c->little_endian ?
449  get_bits_le(&gb, c->code_size) :
450  get_bits(&gb, c->code_size));
451 
452  if (get_bits_left(&gb) > 0)
453  av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");
454 
455  *got_frame_ptr = 1;
456 
457  return buf_size;
458 }
459 
460 static void g726_decode_flush(AVCodecContext *avctx)
461 {
462  G726Context *c = avctx->priv_data;
463  g726_reset(c);
464 }
465 #endif
466 
467 #if CONFIG_ADPCM_G726_DECODER
468 AVCodec ff_adpcm_g726_decoder = {
469  .name = "g726",
470  .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
471  .type = AVMEDIA_TYPE_AUDIO,
473  .priv_data_size = sizeof(G726Context),
474  .init = g726_decode_init,
475  .decode = g726_decode_frame,
476  .flush = g726_decode_flush,
477  .capabilities = CODEC_CAP_DR1,
478 };
479 #endif
480 
481 #if CONFIG_ADPCM_G726LE_DECODER
482 AVCodec ff_adpcm_g726le_decoder = {
483  .name = "g726le",
484  .type = AVMEDIA_TYPE_AUDIO,
486  .priv_data_size = sizeof(G726Context),
487  .init = g726_decode_init,
488  .decode = g726_decode_frame,
489  .flush = g726_decode_flush,
490  .capabilities = CODEC_CAP_DR1,
491  .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM little-endian"),
492 };
493 #endif