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1
/*
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 * G.726 ADPCM audio codec
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 * 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 file is part of FFmpeg.
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 *
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 * FFmpeg 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 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg 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 FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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"
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#include "bitstream.h"
28

    
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/**
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 * G.726 11bit float.
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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 : 1<<5;
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    return f;
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}
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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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}
60

    
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static inline int sgn(int value)
62
{
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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 };
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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 }};
146

    
147

    
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/**
149
 * Para 4.2.2 page 18: Adaptive quantizer.
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 */
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static inline uint8_t quant(G726Context* c, int d)
152
{
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    int sign, exp, i, dln;
154

    
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    sign = i = 0;
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    if (d < 0) {
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        sign = 1;
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        d = -d;
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    }
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    exp = av_log2_16bit(d);
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    dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
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    while (c->tbls->quant[i] < INT_MAX && c->tbls->quant[i] < dln)
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        ++i;
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166
    if (sign)
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        i = ~i;
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    if (c->tbls->bits != 2 && i == 0) /* I'm not sure this is a good idea */
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        i = 0xff;
170

    
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    return i;
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}
173

    
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/**
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 * Para 4.2.3 page 22: Inverse adaptive quantizer.
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 */
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static inline int16_t inverse_quant(G726Context* c, int i)
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{
179
    int dql, dex, dqt;
180

    
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    dql = c->tbls->iquant[i] + (c->y >> 2);
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    dex = (dql>>7) & 0xf;        /* 4bit exponent */
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    dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
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    return (dql < 0) ? 0 : ((dqt<<7) >> (14-dex));
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}
186

    
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static inline int16_t g726_iterate(G726Context* c, int16_t I)
188
{
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    int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
190
    Float11 f;
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    dq = inverse_quant(c, I);
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    if (I >> (c->tbls->bits - 1))  /* get the sign */
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        dq = -dq;
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    re_signal = c->se + dq;
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    /* Transition detect */
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    ylint = (c->yl >> 15);
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    ylfrac = (c->yl >> 10) & 0x1f;
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    thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
201
    if (c->td == 1 && abs(dq) > ((thr2+(thr2>>1))>>1))
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        tr = 1;
203
    else
204
        tr = 0;
205

    
206
    /* Update second order predictor coefficient A2 and A1 */
207
    pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
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    dq0 = dq ? sgn(dq) : 0;
209
    if (tr) {
210
        c->a[0] = 0;
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        c->a[1] = 0;
212
        for (i=0; i<6; i++)
213
            c->b[i] = 0;
214
    } else {
215
        /* This is a bit crazy, but it really is +255 not +256 */
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        fa1 = clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
217

    
218
        c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
219
        c->a[1] = clip(c->a[1], -12288, 12288);
220
        c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
221
        c->a[0] = clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
222

    
223
        for (i=0; i<6; i++)
224
            c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
225
    }
226

    
227
    /* Update Dq and Sr and Pk */
228
    c->pk[1] = c->pk[0];
229
    c->pk[0] = pk0 ? pk0 : 1;
230
    c->sr[1] = c->sr[0];
231
    i2f(re_signal, &c->sr[0]);
232
    for (i=5; i>0; i--)
233
        c->dq[i] = c->dq[i-1];
234
    i2f(dq, &c->dq[0]);
235
    c->dq[0].sign = I >> (c->tbls->bits - 1); /* Isn't it crazy ?!?! */
236

    
237
    /* Update tone detect [I'm not sure 'tr == 0' is really needed] */
238
    c->td = (tr == 0 && c->a[1] < -11776);
239

    
240
    /* Update Ap */
241
    c->dms += ((c->tbls->F[I]<<9) - c->dms) >> 5;
242
    c->dml += ((c->tbls->F[I]<<11) - c->dml) >> 7;
243
    if (tr)
244
        c->ap = 256;
245
    else if (c->y > 1535 && !c->td && (abs((c->dms << 2) - c->dml) < (c->dml >> 3)))
246
        c->ap += (-c->ap) >> 4;
247
    else
248
        c->ap += (0x200 - c->ap) >> 4;
249

    
250
    /* Update Yu and Yl */
251
    c->yu = clip(c->y + (((c->tbls->W[I] << 5) - c->y) >> 5), 544, 5120);
252
    c->yl += c->yu + ((-c->yl)>>6);
253

    
254
    /* Next iteration for Y */
255
    al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
256
    c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
257

    
258
    /* Next iteration for SE and SEZ */
259
    c->se = 0;
260
    for (i=0; i<6; i++)
261
        c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
262
    c->sez = c->se >> 1;
263
    for (i=0; i<2; i++)
264
        c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
265
    c->se >>= 1;
266

    
267
    return clip(re_signal << 2, -0xffff, 0xffff);
268
}
269

    
270
static int g726_reset(G726Context* c, int bit_rate)
271
{
272
    int i;
273

    
274
    c->tbls = &G726Tables_pool[bit_rate/8000 - 2];
275
    for (i=0; i<2; i++) {
276
        i2f(0, &c->sr[i]);
277
        c->a[i] = 0;
278
        c->pk[i] = 1;
279
    }
280
    for (i=0; i<6; i++) {
281
        i2f(0, &c->dq[i]);
282
        c->b[i] = 0;
283
    }
284
    c->ap = 0;
285
    c->dms = 0;
286
    c->dml = 0;
287
    c->yu = 544;
288
    c->yl = 34816;
289
    c->td = 0;
290

    
291
    c->se = 0;
292
    c->sez = 0;
293
    c->y = 544;
294

    
295
    return 0;
296
}
297

    
298
static int16_t g726_decode(G726Context* c, int16_t i)
299
{
300
    return g726_iterate(c, i);
301
}
302

    
303
#ifdef CONFIG_ENCODERS
304
static int16_t g726_encode(G726Context* c, int16_t sig)
305
{
306
    uint8_t i;
307

    
308
    i = quant(c, sig/4 - c->se) & ((1<<c->tbls->bits) - 1);
309
    g726_iterate(c, i);
310
    return i;
311
}
312
#endif
313

    
314
/* Interfacing to the libavcodec */
315

    
316
typedef struct AVG726Context {
317
    G726Context c;
318
    int bits_left;
319
    int bit_buffer;
320
    int code_size;
321
} AVG726Context;
322

    
323
static int g726_init(AVCodecContext * avctx)
324
{
325
    AVG726Context* c = (AVG726Context*)avctx->priv_data;
326

    
327
    if (avctx->channels != 1 ||
328
        (avctx->bit_rate != 16000 && avctx->bit_rate != 24000 &&
329
         avctx->bit_rate != 32000 && avctx->bit_rate != 40000)) {
330
        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
331
        return -1;
332
    }
333
    if (avctx->sample_rate != 8000 && avctx->strict_std_compliance>FF_COMPLIANCE_INOFFICIAL) {
334
        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
335
        return -1;
336
    }
337
    g726_reset(&c->c, avctx->bit_rate);
338
    c->code_size = c->c.tbls->bits;
339
    c->bit_buffer = 0;
340
    c->bits_left = 0;
341

    
342
    avctx->coded_frame = avcodec_alloc_frame();
343
    if (!avctx->coded_frame)
344
        return -ENOMEM;
345
    avctx->coded_frame->key_frame = 1;
346

    
347
    return 0;
348
}
349

    
350
static int g726_close(AVCodecContext *avctx)
351
{
352
    av_freep(&avctx->coded_frame);
353
    return 0;
354
}
355

    
356
#ifdef CONFIG_ENCODERS
357
static int g726_encode_frame(AVCodecContext *avctx,
358
                            uint8_t *dst, int buf_size, void *data)
359
{
360
    AVG726Context *c = avctx->priv_data;
361
    short *samples = data;
362
    PutBitContext pb;
363

    
364
    init_put_bits(&pb, dst, 1024*1024);
365

    
366
    for (; buf_size; buf_size--)
367
        put_bits(&pb, c->code_size, g726_encode(&c->c, *samples++));
368

    
369
    flush_put_bits(&pb);
370

    
371
    return put_bits_count(&pb)>>3;
372
}
373
#endif
374

    
375
static int g726_decode_frame(AVCodecContext *avctx,
376
                             void *data, int *data_size,
377
                             uint8_t *buf, int buf_size)
378
{
379
    AVG726Context *c = avctx->priv_data;
380
    short *samples = data;
381
    uint8_t code;
382
    uint8_t mask;
383
    GetBitContext gb;
384

    
385
    if (!buf_size)
386
        goto out;
387

    
388
    mask = (1<<c->code_size) - 1;
389
    init_get_bits(&gb, buf, buf_size * 8);
390
    if (c->bits_left) {
391
        int s = c->code_size - c->bits_left;;
392
        code = (c->bit_buffer << s) | get_bits(&gb, s);
393
        *samples++ = g726_decode(&c->c, code & mask);
394
    }
395

    
396
    while (get_bits_count(&gb) + c->code_size <= buf_size*8)
397
        *samples++ = g726_decode(&c->c, get_bits(&gb, c->code_size) & mask);
398

    
399
    c->bits_left = buf_size*8 - get_bits_count(&gb);
400
    c->bit_buffer = get_bits(&gb, c->bits_left);
401

    
402
out:
403
    *data_size = (uint8_t*)samples - (uint8_t*)data;
404
    return buf_size;
405
}
406

    
407
#ifdef CONFIG_ENCODERS
408
AVCodec adpcm_g726_encoder = {
409
    "g726",
410
    CODEC_TYPE_AUDIO,
411
    CODEC_ID_ADPCM_G726,
412
    sizeof(AVG726Context),
413
    g726_init,
414
    g726_encode_frame,
415
    g726_close,
416
    NULL,
417
};
418
#endif //CONFIG_ENCODERS
419

    
420
AVCodec adpcm_g726_decoder = {
421
    "g726",
422
    CODEC_TYPE_AUDIO,
423
    CODEC_ID_ADPCM_G726,
424
    sizeof(AVG726Context),
425
    g726_init,
426
    NULL,
427
    g726_close,
428
    g726_decode_frame,
429
};