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1
/*
2
 * G.726 ADPCM audio codec 
3
 * Copyright (c) 2004 Roman Shaposhnik.
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 *
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 * This is a very straightforward rendition of the G.726
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 * Section 4 "Computational Details". 
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 *
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 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * 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
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 * 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
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 */
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#include <limits.h>
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#include "avcodec.h"
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#include "common.h"
25

    
26
/*
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 * G.726 Standard uses rather odd 11bit floating point arithmentic for 
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 * numerous occasions. It's a mistery to me why they did it this way
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 * instead of simply using 32bit integer arithmetic.
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 */
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typedef struct Float11 {
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        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;
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static inline Float11* i2f(int16_t i, Float11* f)
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{
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        f->sign = (i < 0);
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        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 : 
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                         1<<5;
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        return f;
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}
47

    
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static inline int16_t mult(Float11* f1, Float11* f2)
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{
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        int res, exp;
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        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

    
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static inline int clamp(int value, int min, int max)
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{
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   if (value < min)
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       return min;
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   else if (value > max)
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       return max;
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   else 
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       return value;
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}
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static inline int sgn(int value)
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{
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   return (value < 0) ? -1 : 1;
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}
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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;
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typedef struct G726Context {
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         G726Tables* tbls;    /* static tables needed for computation */
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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 */
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         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;
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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 };
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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 };
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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 };
147

    
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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 }};
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;
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   if (d < 0) {
164
       sign = 1;
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       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->tbls->bits != 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 */
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    return (dql < 0) ? 0 : ((dqt<<7) >> (14-dex)); 
192
}
193

    
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static inline int16_t g726_iterate(G726Context* c, int16_t I)
195
{
196
    int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
197
    Float11 f;
198
    
199
    dq = inverse_quant(c, I);
200
    if (I >> (c->tbls->bits - 1))  /* get the sign */
201
        dq = -dq;
202
    re_signal = c->se + dq;
203

    
204
    /* Transition detect */
205
    ylint = (c->yl >> 15);
206
    ylfrac = (c->yl >> 10) & 0x1f;
207
    thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
208
    if (c->td == 1 && abs(dq) > ((thr2+(thr2>>1))>>1))
209
        tr = 1;
210
    else
211
        tr = 0;
212
    
213
    /* Update second order predictor coefficient A2 and A1 */
214
    pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
215
    dq0 = dq ? sgn(dq) : 0;
216
    if (tr) {
217
        c->a[0] = 0;
218
        c->a[1] = 0;
219
        for (i=0; i<6; i++)
220
           c->b[i] = 0;
221
    } else {
222
        /* This is a bit crazy, but it really is +255 not +256 */
223
        fa1 = clamp((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
224
        
225
        c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
226
        c->a[1] = clamp(c->a[1], -12288, 12288);
227
        c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
228
        c->a[0] = clamp(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
229

    
230
        for (i=0; i<6; i++)
231
             c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
232
    }
233

    
234
    /* Update Dq and Sr and Pk */
235
    c->pk[1] = c->pk[0];
236
    c->pk[0] = pk0 ? pk0 : 1;
237
    c->sr[1] = c->sr[0];
238
    i2f(re_signal, &c->sr[0]);
239
    for (i=5; i>0; i--)
240
       c->dq[i] = c->dq[i-1];
241
    i2f(dq, &c->dq[0]);
242
    c->dq[0].sign = I >> (c->tbls->bits - 1); /* Isn't it crazy ?!?! */
243
    
244
    /* Update tone detect [I'm not sure 'tr == 0' is really needed] */
245
    c->td = (tr == 0 && c->a[1] < -11776); 
246
       
247
    /* Update Ap */
248
    c->dms += ((c->tbls->F[I]<<9) - c->dms) >> 5;
249
    c->dml += ((c->tbls->F[I]<<11) - c->dml) >> 7;
250
    if (tr) 
251
       c->ap = 256;
252
    else if (c->y > 1535 && !c->td && (abs((c->dms << 2) - c->dml) < (c->dml >> 3)))
253
       c->ap += (-c->ap) >> 4;
254
    else
255
       c->ap += (0x200 - c->ap) >> 4; 
256

    
257
    /* Update Yu and Yl */
258
    c->yu = clamp(c->y + (((c->tbls->W[I] << 5) - c->y) >> 5), 544, 5120);
259
    c->yl += c->yu + ((-c->yl)>>6);
260
 
261
    /* Next iteration for Y */
262
    al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
263
    c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
264
        
265
    /* Next iteration for SE and SEZ */
266
    c->se = 0;
267
    for (i=0; i<6; i++)
268
       c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
269
    c->sez = c->se >> 1;
270
    for (i=0; i<2; i++)
271
       c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
272
    c->se >>= 1;
273

    
274
    return clamp(re_signal << 2, -0xffff, 0xffff);
275
}
276

    
277
static int g726_reset(G726Context* c, int bit_rate)
278
{
279
    int i;
280

    
281
    c->tbls = &G726Tables_pool[bit_rate/8000 - 2];
282
    for (i=0; i<2; i++) {
283
       i2f(0, &c->sr[i]);
284
       c->a[i] = 0;
285
       c->pk[i] = 1;
286
    }
287
    for (i=0; i<6; i++) {
288
       i2f(0, &c->dq[i]);
289
       c->b[i] = 0;
290
    }
291
    c->ap = 0;
292
    c->dms = 0;
293
    c->dml = 0;
294
    c->yu = 544;
295
    c->yl = 34816;
296
    c->td = 0;
297

    
298
    c->se = 0;
299
    c->sez = 0;
300
    c->y = 544;
301

    
302
    return 0;
303
}
304

    
305
static int16_t g726_decode(G726Context* c, int16_t i)
306
{
307
    return g726_iterate(c, i);
308
}
309

    
310
static int16_t g726_encode(G726Context* c, int16_t sig)
311
{
312
   uint8_t i;
313
   
314
   i = quant(c, sig/4 - c->se) & ((1<<c->tbls->bits) - 1);
315
   g726_iterate(c, i);
316
   return i;
317
}
318

    
319
/* Interfacing to the libavcodec */
320

    
321
typedef struct AVG726Context {
322
   G726Context c;
323
   int bits_left;
324
   int bit_buffer;
325
   int code_size;
326
} AVG726Context;
327

    
328
static int g726_init(AVCodecContext * avctx)
329
{
330
    AVG726Context* c = (AVG726Context*)avctx->priv_data;
331
    
332
    if (avctx->sample_rate != 8000 || avctx->channels != 1 ||
333
        (avctx->bit_rate != 16000 && avctx->bit_rate != 24000 &&
334
         avctx->bit_rate != 32000 && avctx->bit_rate != 40000)) {
335
        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
336
        return -1;
337
    }
338
    g726_reset(&c->c, avctx->bit_rate);
339
    c->code_size = c->c.tbls->bits;
340
    c->bit_buffer = 0;
341
    c->bits_left = 0;
342

    
343
    return 0;
344
}
345

    
346
static int g726_encode_frame(AVCodecContext *avctx,
347
                            uint8_t *dst, int buf_size, void *data)
348
{
349
    AVG726Context *c = avctx->priv_data;
350
    short *samples = data;
351
    PutBitContext pb;
352

    
353
    init_put_bits(&pb, dst, 1024*1024);
354

    
355
    for (; buf_size; buf_size--)
356
       put_bits(&pb, c->code_size, g726_encode(&c->c, *samples++));
357

    
358
    flush_put_bits(&pb);
359

    
360
    return put_bits_count(&pb)>>3; 
361
}                
362

    
363
static int g726_decode_frame(AVCodecContext *avctx,
364
                             void *data, int *data_size,
365
                             uint8_t *buf, int buf_size)
366
{
367
    AVG726Context *c = avctx->priv_data;
368
    short *samples = data;
369
    uint8_t code;
370
    uint8_t mask;
371
    GetBitContext gb; 
372
   
373
    if (!buf_size)
374
        goto out;
375
    
376
    mask = (1<<c->code_size) - 1;
377
    init_get_bits(&gb, buf, buf_size * 8);
378
    if (c->bits_left) {
379
        int s = c->code_size - c->bits_left;;
380
        code = (c->bit_buffer << s) | get_bits(&gb, s);
381
        *samples++ = g726_decode(&c->c, code & mask);
382
    }
383
    
384
    while (get_bits_count(&gb) + c->code_size <= buf_size*8)
385
        *samples++ = g726_decode(&c->c, get_bits(&gb, c->code_size) & mask);
386
    
387
    c->bits_left = buf_size*8 - get_bits_count(&gb);
388
    c->bit_buffer = get_bits(&gb, c->bits_left);
389
    
390
out:
391
    *data_size = (uint8_t*)samples - (uint8_t*)data;
392
    return buf_size;
393
}
394

    
395
#ifdef CONFIG_ENCODERS
396
AVCodec adpcm_g726_encoder = {
397
    "g726",
398
    CODEC_TYPE_AUDIO,
399
    CODEC_ID_ADPCM_G726,
400
    sizeof(AVG726Context),
401
    g726_init,
402
    g726_encode_frame,
403
    NULL,
404
    NULL,
405
};
406
#endif //CONFIG_ENCODERS
407

    
408
AVCodec adpcm_g726_decoder = {
409
    "g726",
410
    CODEC_TYPE_AUDIO,
411
    CODEC_ID_ADPCM_G726,
412
    sizeof(AVG726Context),
413
    g726_init,
414
    NULL,
415
    NULL,
416
    g726_decode_frame,
417
};