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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 } G726Context;
100 
101 static const int quant_tbl16[] = /**< 16kbit/s 2bits per sample */
102  { 260, INT_MAX };
103 static const int16_t iquant_tbl16[] =
104  { 116, 365, 365, 116 };
105 static const int16_t W_tbl16[] =
106  { -22, 439, 439, -22 };
107 static const uint8_t F_tbl16[] =
108  { 0, 7, 7, 0 };
109 
110 static const int quant_tbl24[] = /**< 24kbit/s 3bits per sample */
111  { 7, 217, 330, INT_MAX };
112 static const int16_t iquant_tbl24[] =
113  { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN };
114 static const int16_t W_tbl24[] =
115  { -4, 30, 137, 582, 582, 137, 30, -4 };
116 static const uint8_t F_tbl24[] =
117  { 0, 1, 2, 7, 7, 2, 1, 0 };
118 
119 static const int quant_tbl32[] = /**< 32kbit/s 4bits per sample */
120  { -125, 79, 177, 245, 299, 348, 399, INT_MAX };
121 static const int16_t iquant_tbl32[] =
122  { INT16_MIN, 4, 135, 213, 273, 323, 373, 425,
123  425, 373, 323, 273, 213, 135, 4, INT16_MIN };
124 static const int16_t W_tbl32[] =
125  { -12, 18, 41, 64, 112, 198, 355, 1122,
126  1122, 355, 198, 112, 64, 41, 18, -12};
127 static const uint8_t F_tbl32[] =
128  { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
129 
130 static const int quant_tbl40[] = /**< 40kbit/s 5bits per sample */
131  { -122, -16, 67, 138, 197, 249, 297, 338,
132  377, 412, 444, 474, 501, 527, 552, INT_MAX };
133 static const int16_t iquant_tbl40[] =
134  { INT16_MIN, -66, 28, 104, 169, 224, 274, 318,
135  358, 395, 429, 459, 488, 514, 539, 566,
136  566, 539, 514, 488, 459, 429, 395, 358,
137  318, 274, 224, 169, 104, 28, -66, INT16_MIN };
138 static const int16_t W_tbl40[] =
139  { 14, 14, 24, 39, 40, 41, 58, 100,
140  141, 179, 219, 280, 358, 440, 529, 696,
141  696, 529, 440, 358, 280, 219, 179, 141,
142  100, 58, 41, 40, 39, 24, 14, 14 };
143 static const uint8_t F_tbl40[] =
144  { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
145  6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
146 
147 static const G726Tables G726Tables_pool[] =
152 
153 
154 /**
155  * Para 4.2.2 page 18: Adaptive quantizer.
156  */
157 static inline uint8_t quant(G726Context* c, int d)
158 {
159  int sign, exp, i, dln;
160 
161  sign = i = 0;
162  if (d < 0) {
163  sign = 1;
164  d = -d;
165  }
166  exp = av_log2_16bit(d);
167  dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
168 
169  while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln)
170  ++i;
171 
172  if (sign)
173  i = ~i;
174  if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */
175  i = 0xff;
176 
177  return i;
178 }
179 
180 /**
181  * Para 4.2.3 page 22: Inverse adaptive quantizer.
182  */
183 static inline int16_t inverse_quant(G726Context* c, int i)
184 {
185  int dql, dex, dqt;
186 
187  dql = c->tbls.iquant[i] + (c->y >> 2);
188  dex = (dql>>7) & 0xf; /* 4bit exponent */
189  dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
190  return (dql < 0) ? 0 : ((dqt<<dex) >> 7);
191 }
192 
193 static int16_t g726_decode(G726Context* c, int I)
194 {
195  int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
196  Float11 f;
197  int I_sig= I >> (c->code_size - 1);
198 
199  dq = inverse_quant(c, I);
200 
201  /* Transition detect */
202  ylint = (c->yl >> 15);
203  ylfrac = (c->yl >> 10) & 0x1f;
204  thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
205  tr= (c->td == 1 && dq > ((3*thr2)>>2));
206 
207  if (I_sig) /* get the sign */
208  dq = -dq;
209  re_signal = c->se + dq;
210 
211  /* Update second order predictor coefficient A2 and A1 */
212  pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
213  dq0 = dq ? sgn(dq) : 0;
214  if (tr) {
215  c->a[0] = 0;
216  c->a[1] = 0;
217  for (i=0; i<6; i++)
218  c->b[i] = 0;
219  } else {
220  /* This is a bit crazy, but it really is +255 not +256 */
221  fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
222 
223  c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
224  c->a[1] = av_clip(c->a[1], -12288, 12288);
225  c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
226  c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
227 
228  for (i=0; i<6; i++)
229  c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
230  }
231 
232  /* Update Dq and Sr and Pk */
233  c->pk[1] = c->pk[0];
234  c->pk[0] = pk0 ? pk0 : 1;
235  c->sr[1] = c->sr[0];
236  i2f(re_signal, &c->sr[0]);
237  for (i=5; i>0; i--)
238  c->dq[i] = c->dq[i-1];
239  i2f(dq, &c->dq[0]);
240  c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */
241 
242  c->td = c->a[1] < -11776;
243 
244  /* Update Ap */
245  c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5);
246  c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7);
247  if (tr)
248  c->ap = 256;
249  else {
250  c->ap += (-c->ap) >> 4;
251  if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3))
252  c->ap += 0x20;
253  }
254 
255  /* Update Yu and Yl */
256  c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120);
257  c->yl += c->yu + ((-c->yl)>>6);
258 
259  /* Next iteration for Y */
260  al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
261  c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
262 
263  /* Next iteration for SE and SEZ */
264  c->se = 0;
265  for (i=0; i<6; i++)
266  c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
267  c->sez = c->se >> 1;
268  for (i=0; i<2; i++)
269  c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
270  c->se >>= 1;
271 
272  return av_clip(re_signal << 2, -0xffff, 0xffff);
273 }
274 
276 {
277  int i;
278 
279  c->tbls = G726Tables_pool[c->code_size - 2];
280  for (i=0; i<2; i++) {
281  c->sr[i].mant = 1<<5;
282  c->pk[i] = 1;
283  }
284  for (i=0; i<6; i++) {
285  c->dq[i].mant = 1<<5;
286  }
287  c->yu = 544;
288  c->yl = 34816;
289 
290  c->y = 544;
291 
292  return 0;
293 }
294 
295 #if CONFIG_ADPCM_G726_ENCODER
296 static int16_t g726_encode(G726Context* c, int16_t sig)
297 {
298  uint8_t i;
299 
300  i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1);
301  g726_decode(c, i);
302  return i;
303 }
304 
305 /* Interfacing to the libavcodec */
306 
307 static av_cold int g726_encode_init(AVCodecContext *avctx)
308 {
309  G726Context* c = avctx->priv_data;
310 
312  avctx->sample_rate != 8000) {
313  av_log(avctx, AV_LOG_ERROR, "Sample rates other than 8kHz are not "
314  "allowed when the compliance level is higher than unofficial. "
315  "Resample or reduce the compliance level.\n");
316  return AVERROR(EINVAL);
317  }
318  av_assert0(avctx->sample_rate > 0);
319 
320  if(avctx->channels != 1){
321  av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
322  return AVERROR(EINVAL);
323  }
324 
325  if (avctx->bit_rate)
326  c->code_size = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate;
327 
328  c->code_size = av_clip(c->code_size, 2, 5);
329  avctx->bit_rate = c->code_size * avctx->sample_rate;
330  avctx->bits_per_coded_sample = c->code_size;
331 
332  g726_reset(c);
333 
334  /* select a frame size that will end on a byte boundary and have a size of
335  approximately 1024 bytes */
336  avctx->frame_size = ((int[]){ 4096, 2736, 2048, 1640 })[c->code_size - 2];
337 
338  return 0;
339 }
340 
341 static int g726_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
342  const AVFrame *frame, int *got_packet_ptr)
343 {
344  G726Context *c = avctx->priv_data;
345  const int16_t *samples = (const int16_t *)frame->data[0];
346  PutBitContext pb;
347  int i, ret, out_size;
348 
349  out_size = (frame->nb_samples * c->code_size + 7) / 8;
350  if ((ret = ff_alloc_packet2(avctx, avpkt, out_size)) < 0)
351  return ret;
352  init_put_bits(&pb, avpkt->data, avpkt->size);
353 
354  for (i = 0; i < frame->nb_samples; i++)
355  put_bits(&pb, c->code_size, g726_encode(c, *samples++));
356 
357  flush_put_bits(&pb);
358 
359  avpkt->size = out_size;
360  *got_packet_ptr = 1;
361  return 0;
362 }
363 
364 #define OFFSET(x) offsetof(G726Context, x)
365 #define AE AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
366 static const AVOption options[] = {
367  { "code_size", "Bits per code", OFFSET(code_size), AV_OPT_TYPE_INT, { .i64 = 4 }, 2, 5, AE },
368  { NULL },
369 };
370 
371 static const AVClass g726_class = {
372  .class_name = "g726",
373  .item_name = av_default_item_name,
374  .option = options,
375  .version = LIBAVUTIL_VERSION_INT,
376 };
377 
378 static const AVCodecDefault defaults[] = {
379  { "b", "0" },
380  { NULL },
381 };
382 
383 AVCodec ff_adpcm_g726_encoder = {
384  .name = "g726",
385  .type = AVMEDIA_TYPE_AUDIO,
387  .priv_data_size = sizeof(G726Context),
388  .init = g726_encode_init,
389  .encode2 = g726_encode_frame,
390  .capabilities = CODEC_CAP_SMALL_LAST_FRAME,
391  .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
393  .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
394  .priv_class = &g726_class,
395  .defaults = defaults,
396 };
397 #endif
398 
399 #if CONFIG_ADPCM_G726_DECODER
400 static av_cold int g726_decode_init(AVCodecContext *avctx)
401 {
402  G726Context* c = avctx->priv_data;
403 
404  avctx->channels = 1;
406 
407  c->code_size = avctx->bits_per_coded_sample;
408  if (c->code_size < 2 || c->code_size > 5) {
409  av_log(avctx, AV_LOG_ERROR, "Invalid number of bits %d\n", c->code_size);
410  return AVERROR(EINVAL);
411  }
412  g726_reset(c);
413 
414  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
415 
416  return 0;
417 }
418 
419 static int g726_decode_frame(AVCodecContext *avctx, void *data,
420  int *got_frame_ptr, AVPacket *avpkt)
421 {
422  AVFrame *frame = data;
423  const uint8_t *buf = avpkt->data;
424  int buf_size = avpkt->size;
425  G726Context *c = avctx->priv_data;
426  int16_t *samples;
427  GetBitContext gb;
428  int out_samples, ret;
429 
430  out_samples = buf_size * 8 / c->code_size;
431 
432  /* get output buffer */
433  frame->nb_samples = out_samples;
434  if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
435  return ret;
436  samples = (int16_t *)frame->data[0];
437 
438  init_get_bits(&gb, buf, buf_size * 8);
439 
440  while (out_samples--)
441  *samples++ = g726_decode(c, get_bits(&gb, c->code_size));
442 
443  if (get_bits_left(&gb) > 0)
444  av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");
445 
446  *got_frame_ptr = 1;
447 
448  return buf_size;
449 }
450 
451 static void g726_decode_flush(AVCodecContext *avctx)
452 {
453  G726Context *c = avctx->priv_data;
454  g726_reset(c);
455 }
456 
457 AVCodec ff_adpcm_g726_decoder = {
458  .name = "g726",
459  .type = AVMEDIA_TYPE_AUDIO,
461  .priv_data_size = sizeof(G726Context),
462  .init = g726_decode_init,
463  .decode = g726_decode_frame,
464  .flush = g726_decode_flush,
465  .capabilities = CODEC_CAP_DR1,
466  .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
467 };
468 #endif