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1 e5966052 Roman Shaposhnik
/*
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 library is free software; you can redistribute it and/or
9
 * modify it under the terms of the GNU Lesser General Public
10
 * License as published by the Free Software Foundation; either
11
 * version 2 of the License, or (at your option) any later version.
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 *
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 * This library is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16
 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
21
 */
22
#include <limits.h>
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#include "avcodec.h"
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#include "common.h"
25
26
/*
27
 * G.726 Standard uses rather odd 11bit floating point arithmentic for 
28
 * numerous occasions. It's a mistery to me why they did it this way
29
 * instead of simply using 32bit integer arithmetic.
30
 */
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typedef struct Float11 {
32
        int sign;   /* 1bit sign */
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        int exp;    /* 4bit exponent */
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        int mant;   /* 6bit mantissa */
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} Float11;
36
37
static inline Float11* i2f(int16_t i, Float11* f)
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{
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        f->sign = (i < 0);
40
        if (f->sign)
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                i = -i;
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        f->exp = av_log2_16bit(i) + !!i;
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        f->mant = i? (i<<6) >> f->exp : 
44
                         1<<5;
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        return f;
46
}
47
48
static inline int16_t mult(Float11* f1, Float11* f2)
49
{
50
        int res, exp;
51
52
        exp = f1->exp + f2->exp;
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        res = (((f1->mant * f2->mant) + 0x30) >> 4) << 7;
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        res = exp > 26 ? res << (exp - 26) : res >> (26 - exp);
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        return (f1->sign ^ f2->sign) ? -res : res;
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}
57
58
static inline int sgn(int value)
59
{
60
   return (value < 0) ? -1 : 1;
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}
62
63
typedef struct G726Tables {
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        int  bits;            /* bits per sample */
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        int* quant;           /* quantization table */
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        int* iquant;          /* inverse quantization table */
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        int* W;               /* special table #1 ;-) */
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        int* F;               /* special table #2 */
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} G726Tables;
70
71
typedef struct G726Context {
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         G726Tables* tbls;    /* static tables needed for computation */
73
         
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         Float11 sr[2];       /* prev. reconstructed samples */
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         Float11 dq[6];       /* prev. difference */
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         int a[2];            /* second order predictor coeffs */
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         int b[6];            /* sixth order predictor coeffs */
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         int pk[2];           /* signs of prev. 2 sez + dq */
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         int ap;              /* scale factor control */
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         int yu;              /* fast scale factor */
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         int yl;              /* slow scale factor */
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         int dms;             /* short average magnitude of F[i] */
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         int dml;             /* long average magnitude of F[i] */
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         int td;              /* tone detect */
86
87
         int se;              /* estimated signal for the next iteration */
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         int sez;             /* estimated second order prediction */
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         int y;               /* quantizer scaling factor for the next iteration */
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} G726Context;
91
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static int quant_tbl16[] =                       /* 16kbit/s 2bits per sample */
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           { 260, INT_MAX }; 
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static int iquant_tbl16[] =
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           { 116, 365, 365, 116 };
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static int W_tbl16[] = 
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           { -22, 439, 439, -22 };
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static int F_tbl16[] =
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           { 0, 7, 7, 0 };
100
           
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static int quant_tbl24[] =                       /* 24kbit/s 3bits per sample */
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           {  7, 217, 330, INT_MAX };
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static int iquant_tbl24[] =
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           { INT_MIN, 135, 273, 373, 373, 273, 135, INT_MIN };
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static int W_tbl24[] = 
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           { -4,  30, 137, 582, 582, 137,  30, -4 }; 
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static int F_tbl24[] =
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           { 0, 1, 2, 7, 7, 2, 1, 0 };
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static int quant_tbl32[] =                       /* 32kbit/s 4bits per sample */
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           { -125,  79, 177, 245, 299, 348, 399, INT_MAX };
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static int iquant_tbl32[] =
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           { INT_MIN,   4, 135, 213, 273, 323, 373, 425,  
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                 425, 373, 323, 273, 213, 135,   4, INT_MIN };
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static int W_tbl32[] = 
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           { -12,  18,  41,  64, 112, 198, 355, 1122,
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            1122, 355, 198, 112,  64,  41,  18, -12};
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static int F_tbl32[] = 
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           { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
120
           
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static int quant_tbl40[] =                      /* 40kbit/s 5bits per sample */
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           { -122, -16,  67, 138, 197, 249, 297, 338,
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              377, 412, 444, 474, 501, 527, 552, INT_MAX };
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static int iquant_tbl40[] =
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           { INT_MIN, -66,  28, 104, 169, 224, 274, 318,  
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                 358, 395, 429, 459, 488, 514, 539, 566,
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                 566, 539, 514, 488, 459, 429, 395, 358,
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                 318, 274, 224, 169, 104,  28, -66, INT_MIN };
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static int W_tbl40[] = 
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           {   14,  14,  24,  39,  40,  41,   58,  100,
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              141, 179, 219, 280, 358, 440,  529,  696, 
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              696, 529, 440, 358, 280, 219,  179,  141,
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              100,  58,  41,  40,  39,  24,   14,   14 };
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static int F_tbl40[] = 
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           { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
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             6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
137
138
static G726Tables G726Tables_pool[] = 
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           {{ 2, quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
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            { 3, quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
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            { 4, quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
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            { 5, quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
143
                                               
144
145
/*
146
 * Para 4.2.2 page 18: Adaptive quantizer. 
147
 */
148
static inline uint8_t quant(G726Context* c, int d)
149
{
150
   int sign, exp, i, dln;
151
   
152
   sign = i = 0;
153
   if (d < 0) {
154
       sign = 1;
155
       d = -d;
156
   }
157
   exp = av_log2_16bit(d);
158
   dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
159
   
160
   while (c->tbls->quant[i] < INT_MAX && c->tbls->quant[i] < dln)
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        ++i;
162
   
163
   if (sign)
164
       i = ~i;
165
   if (c->tbls->bits != 2 && i == 0) /* I'm not sure this is a good idea */
166
       i = 0xff;
167
168
   return i; 
169
}
170
171
/* 
172
 * Para 4.2.3 page 22: Inverse adaptive quantizer.
173
 */
174
static inline int16_t inverse_quant(G726Context* c, int i)
175
{
176
    int dql, dex, dqt;
177
        
178
    dql = c->tbls->iquant[i] + (c->y >> 2);
179
    dex = (dql>>7) & 0xf;        /* 4bit exponent */
180
    dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
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    return (dql < 0) ? 0 : ((dqt<<7) >> (14-dex)); 
182
}
183
184
static inline int16_t g726_iterate(G726Context* c, int16_t I)
185
{
186
    int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
187
    Float11 f;
188
    
189
    dq = inverse_quant(c, I);
190
    if (I >> (c->tbls->bits - 1))  /* get the sign */
191
        dq = -dq;
192
    re_signal = c->se + dq;
193
194
    /* Transition detect */
195
    ylint = (c->yl >> 15);
196
    ylfrac = (c->yl >> 10) & 0x1f;
197
    thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
198
    if (c->td == 1 && abs(dq) > ((thr2+(thr2>>1))>>1))
199
        tr = 1;
200
    else
201
        tr = 0;
202
    
203
    /* Update second order predictor coefficient A2 and A1 */
204
    pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
205
    dq0 = dq ? sgn(dq) : 0;
206
    if (tr) {
207
        c->a[0] = 0;
208
        c->a[1] = 0;
209
        for (i=0; i<6; i++)
210
           c->b[i] = 0;
211
    } else {
212
        /* This is a bit crazy, but it really is +255 not +256 */
213 eb5b0422 Michael Niedermayer
        fa1 = clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
214 e5966052 Roman Shaposhnik
        
215
        c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
216 eb5b0422 Michael Niedermayer
        c->a[1] = clip(c->a[1], -12288, 12288);
217 e5966052 Roman Shaposhnik
        c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
218 eb5b0422 Michael Niedermayer
        c->a[0] = clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
219 e5966052 Roman Shaposhnik
220
        for (i=0; i<6; i++)
221
             c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
222
    }
223
224
    /* Update Dq and Sr and Pk */
225
    c->pk[1] = c->pk[0];
226
    c->pk[0] = pk0 ? pk0 : 1;
227
    c->sr[1] = c->sr[0];
228
    i2f(re_signal, &c->sr[0]);
229
    for (i=5; i>0; i--)
230
       c->dq[i] = c->dq[i-1];
231
    i2f(dq, &c->dq[0]);
232
    c->dq[0].sign = I >> (c->tbls->bits - 1); /* Isn't it crazy ?!?! */
233
    
234
    /* Update tone detect [I'm not sure 'tr == 0' is really needed] */
235
    c->td = (tr == 0 && c->a[1] < -11776); 
236
       
237
    /* Update Ap */
238
    c->dms += ((c->tbls->F[I]<<9) - c->dms) >> 5;
239
    c->dml += ((c->tbls->F[I]<<11) - c->dml) >> 7;
240
    if (tr) 
241
       c->ap = 256;
242
    else if (c->y > 1535 && !c->td && (abs((c->dms << 2) - c->dml) < (c->dml >> 3)))
243
       c->ap += (-c->ap) >> 4;
244
    else
245
       c->ap += (0x200 - c->ap) >> 4; 
246
247
    /* Update Yu and Yl */
248 eb5b0422 Michael Niedermayer
    c->yu = clip(c->y + (((c->tbls->W[I] << 5) - c->y) >> 5), 544, 5120);
249 e5966052 Roman Shaposhnik
    c->yl += c->yu + ((-c->yl)>>6);
250
 
251
    /* Next iteration for Y */
252
    al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
253
    c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
254
        
255
    /* Next iteration for SE and SEZ */
256
    c->se = 0;
257
    for (i=0; i<6; i++)
258
       c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
259
    c->sez = c->se >> 1;
260
    for (i=0; i<2; i++)
261
       c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
262
    c->se >>= 1;
263
264 eb5b0422 Michael Niedermayer
    return clip(re_signal << 2, -0xffff, 0xffff);
265 e5966052 Roman Shaposhnik
}
266
267
static int g726_reset(G726Context* c, int bit_rate)
268
{
269
    int i;
270
271
    c->tbls = &G726Tables_pool[bit_rate/8000 - 2];
272
    for (i=0; i<2; i++) {
273
       i2f(0, &c->sr[i]);
274
       c->a[i] = 0;
275
       c->pk[i] = 1;
276
    }
277
    for (i=0; i<6; i++) {
278
       i2f(0, &c->dq[i]);
279
       c->b[i] = 0;
280
    }
281
    c->ap = 0;
282
    c->dms = 0;
283
    c->dml = 0;
284
    c->yu = 544;
285
    c->yl = 34816;
286
    c->td = 0;
287
288
    c->se = 0;
289
    c->sez = 0;
290
    c->y = 544;
291
292
    return 0;
293
}
294
295
static int16_t g726_decode(G726Context* c, int16_t i)
296
{
297
    return g726_iterate(c, i);
298
}
299
300
static int16_t g726_encode(G726Context* c, int16_t sig)
301
{
302
   uint8_t i;
303
   
304
   i = quant(c, sig/4 - c->se) & ((1<<c->tbls->bits) - 1);
305
   g726_iterate(c, i);
306
   return i;
307
}
308
309
/* Interfacing to the libavcodec */
310
311
typedef struct AVG726Context {
312
   G726Context c;
313
   int bits_left;
314
   int bit_buffer;
315
   int code_size;
316
} AVG726Context;
317
318
static int g726_init(AVCodecContext * avctx)
319
{
320
    AVG726Context* c = (AVG726Context*)avctx->priv_data;
321
    
322 eb5b0422 Michael Niedermayer
    if (avctx->channels != 1 ||
323 e5966052 Roman Shaposhnik
        (avctx->bit_rate != 16000 && avctx->bit_rate != 24000 &&
324
         avctx->bit_rate != 32000 && avctx->bit_rate != 40000)) {
325
        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
326
        return -1;
327
    }
328 eb5b0422 Michael Niedermayer
    if (avctx->sample_rate != 8000 && avctx->strict_std_compliance>=0) {
329
        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
330
        return -1;
331
    }
332 e5966052 Roman Shaposhnik
    g726_reset(&c->c, avctx->bit_rate);
333
    c->code_size = c->c.tbls->bits;
334
    c->bit_buffer = 0;
335
    c->bits_left = 0;
336
337 826ca104 Roman Shaposhnik
    avctx->coded_frame = avcodec_alloc_frame();
338
    if (!avctx->coded_frame)
339
        return -ENOMEM;
340
    avctx->coded_frame->key_frame = 1;
341
342
    return 0;
343
}
344
345
static int g726_close(AVCodecContext *avctx)
346
{
347
    av_freep(&avctx->coded_frame);
348 e5966052 Roman Shaposhnik
    return 0;
349
}
350
351
static int g726_encode_frame(AVCodecContext *avctx,
352
                            uint8_t *dst, int buf_size, void *data)
353
{
354
    AVG726Context *c = avctx->priv_data;
355
    short *samples = data;
356
    PutBitContext pb;
357
358
    init_put_bits(&pb, dst, 1024*1024);
359
360
    for (; buf_size; buf_size--)
361
       put_bits(&pb, c->code_size, g726_encode(&c->c, *samples++));
362
363
    flush_put_bits(&pb);
364
365
    return put_bits_count(&pb)>>3; 
366
}                
367
368
static int g726_decode_frame(AVCodecContext *avctx,
369
                             void *data, int *data_size,
370
                             uint8_t *buf, int buf_size)
371
{
372
    AVG726Context *c = avctx->priv_data;
373
    short *samples = data;
374
    uint8_t code;
375
    uint8_t mask;
376
    GetBitContext gb; 
377
   
378
    if (!buf_size)
379
        goto out;
380
    
381
    mask = (1<<c->code_size) - 1;
382
    init_get_bits(&gb, buf, buf_size * 8);
383
    if (c->bits_left) {
384
        int s = c->code_size - c->bits_left;;
385
        code = (c->bit_buffer << s) | get_bits(&gb, s);
386
        *samples++ = g726_decode(&c->c, code & mask);
387
    }
388
    
389
    while (get_bits_count(&gb) + c->code_size <= buf_size*8)
390
        *samples++ = g726_decode(&c->c, get_bits(&gb, c->code_size) & mask);
391
    
392
    c->bits_left = buf_size*8 - get_bits_count(&gb);
393
    c->bit_buffer = get_bits(&gb, c->bits_left);
394
    
395
out:
396
    *data_size = (uint8_t*)samples - (uint8_t*)data;
397
    return buf_size;
398
}
399
400
#ifdef CONFIG_ENCODERS
401
AVCodec adpcm_g726_encoder = {
402
    "g726",
403
    CODEC_TYPE_AUDIO,
404
    CODEC_ID_ADPCM_G726,
405
    sizeof(AVG726Context),
406
    g726_init,
407
    g726_encode_frame,
408 826ca104 Roman Shaposhnik
    g726_close,
409 e5966052 Roman Shaposhnik
    NULL,
410
};
411
#endif //CONFIG_ENCODERS
412
413
AVCodec adpcm_g726_decoder = {
414
    "g726",
415
    CODEC_TYPE_AUDIO,
416
    CODEC_ID_ADPCM_G726,
417
    sizeof(AVG726Context),
418
    g726_init,
419
    NULL,
420 826ca104 Roman Shaposhnik
    g726_close,
421 e5966052 Roman Shaposhnik
    g726_decode_frame,
422
};