libavcodec/g726.c

   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 #include "avcodec.h"
  26 #include "get_bits.h"
  27 #include "put_bits.h"
  28
  29 /**
  30  * G.726 11bit float.
  31  * G.726 Standard uses rather odd 11bit floating point arithmentic for
  32  * numerous occasions. It's a mistery to me why they did it this way
  33  * instead of simply using 32bit integer arithmetic.
  34  */
  35 typedef struct Float11 {
  36     uint8_t sign;   /**< 1bit sign */
  37     uint8_t exp;    /**< 4bit exponent */
  38     uint8_t mant;   /**< 6bit mantissa */
  39 } Float11;
  40
  41 static inline Float11* i2f(int i, Float11* f)
  42 {
  43     f->sign = (i < 0);
  44     if (f->sign)
  45         i = -i;
  46     f->exp = av_log2_16bit(i) + !!i;
  47     f->mant = i? (i<<6) >> f->exp : 1<<5;
  48     return f;
  49 }
  50
  51 static inline int16_t mult(Float11* f1, Float11* f2)
  52 {
  53         int res, exp;
  54
  55         exp = f1->exp + f2->exp;
  56         res = (((f1->mant * f2->mant) + 0x30) >> 4);
  57         res = exp > 19 ? res << (exp - 19) : res >> (19 - exp);
  58         return (f1->sign ^ f2->sign) ? -res : res;
  59 }
  60
  61 static inline int sgn(int value)
  62 {
  63     return (value < 0) ? -1 : 1;
  64 }
  65
  66 typedef struct G726Tables {
  67     const int* quant;         /**< quantization table */
  68     const int16_t* iquant;    /**< inverse quantization table */
  69     const int16_t* W;         /**< special table #1 ;-) */
  70     const uint8_t* F;         /**< special table #2 */
  71 } G726Tables;
  72
  73 typedef struct G726Context {
  74     G726Tables tbls;    /**< static tables needed for computation */
  75
  76     Float11 sr[2];      /**< prev. reconstructed samples */
  77     Float11 dq[6];      /**< prev. difference */
  78     int a[2];           /**< second order predictor coeffs */
  79     int b[6];           /**< sixth order predictor coeffs */
  80     int pk[2];          /**< signs of prev. 2 sez + dq */
  81
  82     int ap;             /**< scale factor control */
  83     int yu;             /**< fast scale factor */
  84     int yl;             /**< slow scale factor */
  85     int dms;            /**< short average magnitude of F[i] */
  86     int dml;            /**< long average magnitude of F[i] */
  87     int td;             /**< tone detect */
  88
  89     int se;             /**< estimated signal for the next iteration */
  90     int sez;            /**< estimated second order prediction */
  91     int y;              /**< quantizer scaling factor for the next iteration */
  92     int code_size;
  93 } G726Context;
  94
  95 static const int quant_tbl16[] =                  /**< 16kbit/s 2bits per sample */
  96            { 260, INT_MAX };
  97 static const int16_t iquant_tbl16[] =
  98            { 116, 365, 365, 116 };
  99 static const int16_t W_tbl16[] =
 100            { -22, 439, 439, -22 };
 101 static const uint8_t F_tbl16[] =
 102            { 0, 7, 7, 0 };
 103
 104 static const int quant_tbl24[] =                  /**< 24kbit/s 3bits per sample */
 105            {  7, 217, 330, INT_MAX };
 106 static const int16_t iquant_tbl24[] =
 107            { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN };
 108 static const int16_t W_tbl24[] =
 109            { -4,  30, 137, 582, 582, 137,  30, -4 };
 110 static const uint8_t F_tbl24[] =
 111            { 0, 1, 2, 7, 7, 2, 1, 0 };
 112
 113 static const int quant_tbl32[] =                  /**< 32kbit/s 4bits per sample */
 114            { -125,  79, 177, 245, 299, 348, 399, INT_MAX };
 115 static const int16_t iquant_tbl32[] =
 116          { INT16_MIN,   4, 135, 213, 273, 323, 373, 425,
 117                  425, 373, 323, 273, 213, 135,   4, INT16_MIN };
 118 static const int16_t W_tbl32[] =
 119            { -12,  18,  41,  64, 112, 198, 355, 1122,
 120             1122, 355, 198, 112,  64,  41,  18, -12};
 121 static const uint8_t F_tbl32[] =
 122            { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
 123
 124 static const int quant_tbl40[] =                  /**< 40kbit/s 5bits per sample */
 125            { -122, -16,  67, 138, 197, 249, 297, 338,
 126               377, 412, 444, 474, 501, 527, 552, INT_MAX };
 127 static const int16_t iquant_tbl40[] =
 128          { INT16_MIN, -66,  28, 104, 169, 224, 274, 318,
 129                  358, 395, 429, 459, 488, 514, 539, 566,
 130                  566, 539, 514, 488, 459, 429, 395, 358,
 131                  318, 274, 224, 169, 104,  28, -66, INT16_MIN };
 132 static const int16_t W_tbl40[] =
 133            {   14,  14,  24,  39,  40,  41,   58,  100,
 134               141, 179, 219, 280, 358, 440,  529,  696,
 135               696, 529, 440, 358, 280, 219,  179,  141,
 136               100,  58,  41,  40,  39,  24,   14,   14 };
 137 static const uint8_t F_tbl40[] =
 138            { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
 139              6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
 140
 141 static const G726Tables G726Tables_pool[] =
 142            {{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
 143             { quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
 144             { quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
 145             { quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
 146
 147
 148 /**
 149  * Para 4.2.2 page 18: Adaptive quantizer.
 150  */
 151 static inline uint8_t quant(G726Context* c, int d)
 152 {
 153     int sign, exp, i, dln;
 154
 155     sign = i = 0;
 156     if (d < 0) {
 157         sign = 1;
 158         d = -d;
 159     }
 160     exp = av_log2_16bit(d);
 161     dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
 162
 163     while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln)
 164         ++i;
 165
 166     if (sign)
 167         i = ~i;
 168     if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */
 169         i = 0xff;
 170
 171     return i;
 172 }
 173
 174 /**
 175  * Para 4.2.3 page 22: Inverse adaptive quantizer.
 176  */
 177 static inline int16_t inverse_quant(G726Context* c, int i)
 178 {
 179     int dql, dex, dqt;
 180
 181     dql = c->tbls.iquant[i] + (c->y >> 2);
 182     dex = (dql>>7) & 0xf;        /* 4bit exponent */
 183     dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
 184     return (dql < 0) ? 0 : ((dqt<<dex) >> 7);
 185 }
 186
 187 static int16_t g726_decode(G726Context* c, int I)
 188 {
 189     int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
 190     Float11 f;
 191     int I_sig= I >> (c->code_size - 1);
 192
 193     dq = inverse_quant(c, I);
 194
 195     /* Transition detect */
 196     ylint = (c->yl >> 15);
 197     ylfrac = (c->yl >> 10) & 0x1f;
 198     thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
 199     tr= (c->td == 1 && dq > ((3*thr2)>>2));
 200
 201     if (I_sig)  /* get the sign */
 202         dq = -dq;
 203     re_signal = c->se + dq;
 204
 205     /* Update second order predictor coefficient A2 and A1 */
 206     pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
 207     dq0 = dq ? sgn(dq) : 0;
 208     if (tr) {
 209         c->a[0] = 0;
 210         c->a[1] = 0;
 211         for (i=0; i<6; i++)
 212             c->b[i] = 0;
 213     } else {
 214         /* This is a bit crazy, but it really is +255 not +256 */
 215         fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
 216
 217         c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
 218         c->a[1] = av_clip(c->a[1], -12288, 12288);
 219         c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
 220         c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
 221
 222         for (i=0; i<6; i++)
 223             c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
 224     }
 225
 226     /* Update Dq and Sr and Pk */
 227     c->pk[1] = c->pk[0];
 228     c->pk[0] = pk0 ? pk0 : 1;
 229     c->sr[1] = c->sr[0];
 230     i2f(re_signal, &c->sr[0]);
 231     for (i=5; i>0; i--)
 232         c->dq[i] = c->dq[i-1];
 233     i2f(dq, &c->dq[0]);
 234     c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */
 235
 236     c->td = c->a[1] < -11776;
 237
 238     /* Update Ap */
 239     c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5);
 240     c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7);
 241     if (tr)
 242         c->ap = 256;
 243     else {
 244         c->ap += (-c->ap) >> 4;
 245         if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3))
 246             c->ap += 0x20;
 247     }
 248
 249     /* Update Yu and Yl */
 250     c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120);
 251     c->yl += c->yu + ((-c->yl)>>6);
 252
 253     /* Next iteration for Y */
 254     al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
 255     c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
 256
 257     /* Next iteration for SE and SEZ */
 258     c->se = 0;
 259     for (i=0; i<6; i++)
 260         c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
 261     c->sez = c->se >> 1;
 262     for (i=0; i<2; i++)
 263         c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
 264     c->se >>= 1;
 265
 266     return av_clip(re_signal << 2, -0xffff, 0xffff);
 267 }
 268
 269 static av_cold int g726_reset(G726Context* c, int index)
 270 {
 271     int i;
 272
 273     c->tbls = G726Tables_pool[index];
 274     for (i=0; i<2; i++) {
 275         c->sr[i].mant = 1<<5;
 276         c->pk[i] = 1;
 277     }
 278     for (i=0; i<6; i++) {
 279         c->dq[i].mant = 1<<5;
 280     }
 281     c->yu = 544;
 282     c->yl = 34816;
 283
 284     c->y = 544;
 285
 286     return 0;
 287 }
 288
 289 #if CONFIG_ADPCM_G726_ENCODER
 290 static int16_t g726_encode(G726Context* c, int16_t sig)
 291 {
 292     uint8_t i;
 293
 294     i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1);
 295     g726_decode(c, i);
 296     return i;
 297 }
 298 #endif
 299
 300 /* Interfacing to the libavcodec */
 301
 302 static av_cold int g726_init(AVCodecContext * avctx)
 303 {
 304     G726Context* c = avctx->priv_data;
 305     unsigned int index;
 306
 307     if (avctx->sample_rate <= 0) {
 308         av_log(avctx, AV_LOG_ERROR, "Samplerate is invalid\n");
 309         return -1;
 310     }
 311
 312     index = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate - 2;
 313
 314     if (avctx->bit_rate % avctx->sample_rate && avctx->codec->encode) {
 315         av_log(avctx, AV_LOG_ERROR, "Bitrate - Samplerate combination is invalid\n");
 316         return -1;
 317     }
 318     if(avctx->channels != 1){
 319         av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
 320         return -1;
 321     }
 322     if(index>3){
 323         av_log(avctx, AV_LOG_ERROR, "Unsupported number of bits %d\n", index+2);
 324         return -1;
 325     }
 326     g726_reset(c, index);
 327     c->code_size = index+2;
 328
 329     avctx->coded_frame = avcodec_alloc_frame();
 330     if (!avctx->coded_frame)
 331         return AVERROR(ENOMEM);
 332     avctx->coded_frame->key_frame = 1;
 333
 334     if (avctx->codec->decode)
 335         avctx->sample_fmt = SAMPLE_FMT_S16;
 336
 337     return 0;
 338 }
 339
 340 static av_cold int g726_close(AVCodecContext *avctx)
 341 {
 342     av_freep(&avctx->coded_frame);
 343     return 0;
 344 }
 345
 346 #if CONFIG_ADPCM_G726_ENCODER
 347 static int g726_encode_frame(AVCodecContext *avctx,
 348                             uint8_t *dst, int buf_size, void *data)
 349 {
 350     G726Context *c = avctx->priv_data;
 351     short *samples = data;
 352     PutBitContext pb;
 353
 354     init_put_bits(&pb, dst, 1024*1024);
 355
 356     for (; buf_size; buf_size--)
 357         put_bits(&pb, c->code_size, g726_encode(c, *samples++));
 358
 359     flush_put_bits(&pb);
 360
 361     return put_bits_count(&pb)>>3;
 362 }
 363 #endif
 364
 365 static int g726_decode_frame(AVCodecContext *avctx,
 366                              void *data, int *data_size,
 367                              AVPacket *avpkt)
 368 {
 369     const uint8_t *buf = avpkt->data;
 370     int buf_size = avpkt->size;
 371     G726Context *c = avctx->priv_data;
 372     short *samples = data;
 373     GetBitContext gb;
 374
 375     init_get_bits(&gb, buf, buf_size * 8);
 376
 377     while (get_bits_count(&gb) + c->code_size <= buf_size*8)
 378         *samples++ = g726_decode(c, get_bits(&gb, c->code_size));
 379
 380     if(buf_size*8 != get_bits_count(&gb))
 381         av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");
 382
 383     *data_size = (uint8_t*)samples - (uint8_t*)data;
 384     return buf_size;
 385 }
 386
 387 #if CONFIG_ADPCM_G726_ENCODER
 388 AVCodec adpcm_g726_encoder = {
 389     "g726",
 390     CODEC_TYPE_AUDIO,
 391     CODEC_ID_ADPCM_G726,
 392     sizeof(G726Context),
 393     g726_init,
 394     g726_encode_frame,
 395     g726_close,
 396     NULL,
 397     .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
 398     .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
 399 };
 400 #endif
 401
 402 AVCodec adpcm_g726_decoder = {
 403     "g726",
 404     CODEC_TYPE_AUDIO,
 405     CODEC_ID_ADPCM_G726,
 406     sizeof(G726Context),
 407     g726_init,
 408     NULL,
 409     g726_close,
 410     g726_decode_frame,
 411     .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
 412 };