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1 e5966052 Roman Shaposhnik
/*
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 * G.726 ADPCM audio codec
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 * Copyright (c) 2004 Roman Shaposhnik.
4
 *
5
 * This is a very straightforward rendition of the G.726
6 115329f1 Diego Biurrun
 * Section 4 "Computational Details".
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 *
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 * This file is part of FFmpeg.
9
 *
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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
12
 * 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
18
 * 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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 */
24
#include <limits.h>
25
#include "avcodec.h"
26
#include "common.h"
27 caa336b4 Michael Niedermayer
#include "bitstream.h"
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29 ef9c5d84 Michael Niedermayer
/**
30
 * G.726 11bit float.
31 115329f1 Diego Biurrun
 * G.726 Standard uses rather odd 11bit floating point arithmentic for
32 e5966052 Roman Shaposhnik
 * 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 e344c1ea Steve L'Homme
    int sign;   /**< 1bit sign */
37
    int exp;    /**< 4bit exponent */
38
    int mant;   /**< 6bit mantissa */
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} Float11;
40
41
static inline Float11* i2f(int16_t i, Float11* f)
42
{
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    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;
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}
50
51
static inline int16_t mult(Float11* f1, Float11* f2)
52
{
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        int res, exp;
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        exp = f1->exp + f2->exp;
56
        res = (((f1->mant * f2->mant) + 0x30) >> 4) << 7;
57
        res = exp > 26 ? res << (exp - 26) : res >> (26 - exp);
58
        return (f1->sign ^ f2->sign) ? -res : res;
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}
60
61
static inline int sgn(int value)
62
{
63 e344c1ea Steve L'Homme
    return (value < 0) ? -1 : 1;
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}
65
66
typedef struct G726Tables {
67 e344c1ea Steve L'Homme
    int  bits;          /**< bits per sample */
68
    int* quant;         /**< quantization table */
69
    int* iquant;        /**< inverse quantization table */
70
    int* W;             /**< special table #1 ;-) */
71
    int* F;             /**< special table #2 */
72 e5966052 Roman Shaposhnik
} G726Tables;
73
74
typedef struct G726Context {
75 e344c1ea Steve L'Homme
    G726Tables* tbls;   /**< static tables needed for computation */
76
77
    Float11 sr[2];      /**< prev. reconstructed samples */
78
    Float11 dq[6];      /**< prev. difference */
79
    int a[2];           /**< second order predictor coeffs */
80
    int b[6];           /**< sixth order predictor coeffs */
81
    int pk[2];          /**< signs of prev. 2 sez + dq */
82
83
    int ap;             /**< scale factor control */
84
    int yu;             /**< fast scale factor */
85
    int yl;             /**< slow scale factor */
86
    int dms;            /**< short average magnitude of F[i] */
87
    int dml;            /**< long average magnitude of F[i] */
88
    int td;             /**< tone detect */
89
90
    int se;             /**< estimated signal for the next iteration */
91
    int sez;            /**< estimated second order prediction */
92
    int y;              /**< quantizer scaling factor for the next iteration */
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} G726Context;
94
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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[] =
98
           { 116, 365, 365, 116 };
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static int W_tbl16[] =
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           { -22, 439, 439, -22 };
101
static int F_tbl16[] =
102
           { 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 };
106
static int iquant_tbl24[] =
107
           { INT_MIN, 135, 273, 373, 373, 273, 135, INT_MIN };
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static int W_tbl24[] =
109
           { -4,  30, 137, 582, 582, 137,  30, -4 };
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static int F_tbl24[] =
111
           { 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 };
115
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 },
144
            { 4, quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
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            { 5, quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
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148 ef9c5d84 Michael Niedermayer
/**
149 115329f1 Diego Biurrun
 * Para 4.2.2 page 18: Adaptive quantizer.
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 */
151
static inline uint8_t quant(G726Context* c, int d)
152
{
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    int sign, exp, i, dln;
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    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);
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    while (c->tbls->quant[i] < INT_MAX && c->tbls->quant[i] < dln)
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        ++i;
165 115329f1 Diego Biurrun
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    if (sign)
167
        i = ~i;
168
    if (c->tbls->bits != 2 && i == 0) /* I'm not sure this is a good idea */
169
        i = 0xff;
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    return i;
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}
173
174 ef9c5d84 Michael Niedermayer
/**
175 e5966052 Roman Shaposhnik
 * 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;
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    dql = c->tbls->iquant[i] + (c->y >> 2);
182
    dex = (dql>>7) & 0xf;        /* 4bit exponent */
183
    dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
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    return (dql < 0) ? 0 : ((dqt<<7) >> (14-dex));
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}
186
187
static inline int16_t g726_iterate(G726Context* c, int16_t I)
188
{
189
    int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
190
    Float11 f;
191 115329f1 Diego Biurrun
192 e5966052 Roman Shaposhnik
    dq = inverse_quant(c, I);
193
    if (I >> (c->tbls->bits - 1))  /* get the sign */
194
        dq = -dq;
195
    re_signal = c->se + dq;
196
197
    /* Transition detect */
198
    ylint = (c->yl >> 15);
199
    ylfrac = (c->yl >> 10) & 0x1f;
200
    thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
201
    if (c->td == 1 && abs(dq) > ((thr2+(thr2>>1))>>1))
202
        tr = 1;
203
    else
204
        tr = 0;
205 115329f1 Diego Biurrun
206 e5966052 Roman Shaposhnik
    /* Update second order predictor coefficient A2 and A1 */
207
    pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
208
    dq0 = dq ? sgn(dq) : 0;
209
    if (tr) {
210
        c->a[0] = 0;
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        c->a[1] = 0;
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        for (i=0; i<6; i++)
213 e344c1ea Steve L'Homme
            c->b[i] = 0;
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    } else {
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        /* This is a bit crazy, but it really is +255 not +256 */
216
        fa1 = clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
217 115329f1 Diego Biurrun
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        c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
219
        c->a[1] = clip(c->a[1], -12288, 12288);
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        c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
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        c->a[0] = clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
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223
        for (i=0; i<6; i++)
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            c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
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    }
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--)
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        c->dq[i] = c->dq[i-1];
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    i2f(dq, &c->dq[0]);
235
    c->dq[0].sign = I >> (c->tbls->bits - 1); /* Isn't it crazy ?!?! */
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    /* Update tone detect [I'm not sure 'tr == 0' is really needed] */
238 115329f1 Diego Biurrun
    c->td = (tr == 0 && c->a[1] < -11776);
239
240 e5966052 Roman Shaposhnik
    /* 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 115329f1 Diego Biurrun
    if (tr)
244 e344c1ea Steve L'Homme
        c->ap = 256;
245 e5966052 Roman Shaposhnik
    else if (c->y > 1535 && !c->td && (abs((c->dms << 2) - c->dml) < (c->dml >> 3)))
246 e344c1ea Steve L'Homme
        c->ap += (-c->ap) >> 4;
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    else
248 e344c1ea Steve L'Homme
        c->ap += (0x200 - c->ap) >> 4;
249 e5966052 Roman Shaposhnik
250
    /* Update Yu and Yl */
251 eb5b0422 Michael Niedermayer
    c->yu = clip(c->y + (((c->tbls->W[I] << 5) - c->y) >> 5), 544, 5120);
252 e5966052 Roman Shaposhnik
    c->yl += c->yu + ((-c->yl)>>6);
253 115329f1 Diego Biurrun
254 e5966052 Roman Shaposhnik
    /* 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 115329f1 Diego Biurrun
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    /* Next iteration for SE and SEZ */
259
    c->se = 0;
260
    for (i=0; i<6; i++)
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        c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
262 e5966052 Roman Shaposhnik
    c->sez = c->se >> 1;
263
    for (i=0; i<2; i++)
264 e344c1ea Steve L'Homme
        c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
265 e5966052 Roman Shaposhnik
    c->se >>= 1;
266
267 eb5b0422 Michael Niedermayer
    return clip(re_signal << 2, -0xffff, 0xffff);
268 e5966052 Roman Shaposhnik
}
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 e344c1ea Steve L'Homme
        i2f(0, &c->sr[i]);
277
        c->a[i] = 0;
278
        c->pk[i] = 1;
279 e5966052 Roman Shaposhnik
    }
280
    for (i=0; i<6; i++) {
281 e344c1ea Steve L'Homme
        i2f(0, &c->dq[i]);
282
        c->b[i] = 0;
283 e5966052 Roman Shaposhnik
    }
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 62bb489b Måns Rullgård
#ifdef CONFIG_ENCODERS
304 e5966052 Roman Shaposhnik
static int16_t g726_encode(G726Context* c, int16_t sig)
305
{
306 e344c1ea Steve L'Homme
    uint8_t i;
307 115329f1 Diego Biurrun
308 e344c1ea Steve L'Homme
    i = quant(c, sig/4 - c->se) & ((1<<c->tbls->bits) - 1);
309
    g726_iterate(c, i);
310
    return i;
311 e5966052 Roman Shaposhnik
}
312 62bb489b Måns Rullgård
#endif
313 e5966052 Roman Shaposhnik
314
/* Interfacing to the libavcodec */
315
316
typedef struct AVG726Context {
317 e344c1ea Steve L'Homme
    G726Context c;
318
    int bits_left;
319
    int bit_buffer;
320
    int code_size;
321 e5966052 Roman Shaposhnik
} AVG726Context;
322
323
static int g726_init(AVCodecContext * avctx)
324
{
325
    AVG726Context* c = (AVG726Context*)avctx->priv_data;
326 115329f1 Diego Biurrun
327 eb5b0422 Michael Niedermayer
    if (avctx->channels != 1 ||
328 e5966052 Roman Shaposhnik
        (avctx->bit_rate != 16000 && avctx->bit_rate != 24000 &&
329 bb270c08 Diego Biurrun
         avctx->bit_rate != 32000 && avctx->bit_rate != 40000)) {
330 e5966052 Roman Shaposhnik
        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
331 bb270c08 Diego Biurrun
        return -1;
332 e5966052 Roman Shaposhnik
    }
333 9cd81798 Michael Niedermayer
    if (avctx->sample_rate != 8000 && avctx->strict_std_compliance>FF_COMPLIANCE_INOFFICIAL) {
334 eb5b0422 Michael Niedermayer
        av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
335 bb270c08 Diego Biurrun
        return -1;
336 eb5b0422 Michael Niedermayer
    }
337 e5966052 Roman Shaposhnik
    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 826ca104 Roman Shaposhnik
    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 e5966052 Roman Shaposhnik
    return 0;
354
}
355
356 62bb489b Måns Rullgård
#ifdef CONFIG_ENCODERS
357 e5966052 Roman Shaposhnik
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 e344c1ea Steve L'Homme
        put_bits(&pb, c->code_size, g726_encode(&c->c, *samples++));
368 e5966052 Roman Shaposhnik
369
    flush_put_bits(&pb);
370
371 115329f1 Diego Biurrun
    return put_bits_count(&pb)>>3;
372
}
373 62bb489b Måns Rullgård
#endif
374 e5966052 Roman Shaposhnik
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 115329f1 Diego Biurrun
    GetBitContext gb;
384
385 e5966052 Roman Shaposhnik
    if (!buf_size)
386
        goto out;
387 115329f1 Diego Biurrun
388 e5966052 Roman Shaposhnik
    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 bb270c08 Diego Biurrun
        code = (c->bit_buffer << s) | get_bits(&gb, s);
393
        *samples++ = g726_decode(&c->c, code & mask);
394 e5966052 Roman Shaposhnik
    }
395 115329f1 Diego Biurrun
396 e5966052 Roman Shaposhnik
    while (get_bits_count(&gb) + c->code_size <= buf_size*8)
397 bb270c08 Diego Biurrun
        *samples++ = g726_decode(&c->c, get_bits(&gb, c->code_size) & mask);
398 115329f1 Diego Biurrun
399 e5966052 Roman Shaposhnik
    c->bits_left = buf_size*8 - get_bits_count(&gb);
400
    c->bit_buffer = get_bits(&gb, c->bits_left);
401 115329f1 Diego Biurrun
402 e5966052 Roman Shaposhnik
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 826ca104 Roman Shaposhnik
    g726_close,
416 e5966052 Roman Shaposhnik
    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 826ca104 Roman Shaposhnik
    g726_close,
428 e5966052 Roman Shaposhnik
    g726_decode_frame,
429
};