ffmpeg / libavcodec / g726.c @ 2912e87a
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/*


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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 Libav.

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*

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* Libav 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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* Libav 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 Libav; if not, write to the Free Software

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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 021101301 USA

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*/

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#include <limits.h> 
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#include "avcodec.h" 
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#include "get_bits.h" 
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#include "put_bits.h" 
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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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uint8_t sign; /**< 1bit sign */

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uint8_t exp; /**< 4bit exponent */

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uint8_t mant; /**< 6bit mantissa */

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} Float11; 
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static inline Float11* i2f(int 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); 
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res = exp > 19 ? res << (exp  19) : res >> (19  exp); 
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return (f1>sign ^ f2>sign) ? res : res;

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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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const int* quant; /**< quantization table */ 
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const int16_t* iquant; /**< inverse quantization table */ 
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const int16_t* W; /**< special table #1 ;) */ 
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const uint8_t* 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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int code_size;

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} G726Context; 
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static const int quant_tbl16[] = /**< 16kbit/s 2bits per sample */ 
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{ 260, INT_MAX };

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static const int16_t iquant_tbl16[] = 
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{ 116, 365, 365, 116 }; 
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static const int16_t W_tbl16[] = 
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{ 22, 439, 439, 22 }; 
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static const uint8_t F_tbl16[] = 
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{ 0, 7, 7, 0 }; 
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static const int quant_tbl24[] = /**< 24kbit/s 3bits per sample */ 
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{ 7, 217, 330, INT_MAX }; 
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static const int16_t iquant_tbl24[] = 
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{ INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN }; 
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static const int16_t W_tbl24[] = 
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{ 4, 30, 137, 582, 582, 137, 30, 4 }; 
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static const uint8_t F_tbl24[] = 
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{ 0, 1, 2, 7, 7, 2, 1, 0 }; 
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static const 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 const int16_t iquant_tbl32[] = 
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{ INT16_MIN, 4, 135, 213, 273, 323, 373, 425, 
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425, 373, 323, 273, 213, 135, 4, INT16_MIN }; 
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static const int16_t 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 const uint8_t 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 const 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 const int16_t iquant_tbl40[] = 
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{ INT16_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, INT16_MIN }; 
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static const int16_t 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 const uint8_t 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 const G726Tables G726Tables_pool[] = 
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{{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 }, 
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{ quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 }, 
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{ quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 }, 
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{ quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }}; 
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/**

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* 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) 
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{ 
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int sign, exp, i, dln;

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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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if (sign)

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i = ~i; 
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if (c>code_size != 2 && i == 0) /* I'm not sure this is a good idea */ 
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i = 0xff;

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return i;

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} 
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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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{ 
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int dql, dex, dqt;

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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<<dex) >> 7); 
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} 
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static int16_t g726_decode(G726Context* c, int I) 
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{ 
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int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;

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Float11 f; 
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int I_sig= I >> (c>code_size  1); 
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dq = inverse_quant(c, I); 
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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; 
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tr= (c>td == 1 && dq > ((3*thr2)>>2)); 
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if (I_sig) /* get the sign */ 
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dq = dq; 
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re_signal = c>se + dq; 
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/* Update second order predictor coefficient A2 and A1 */

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pk0 = (c>sez + dq) ? sgn(c>sez + dq) : 0;

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dq0 = dq ? sgn(dq) : 0;

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if (tr) {

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c>a[0] = 0; 
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c>a[1] = 0; 
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for (i=0; i<6; i++) 
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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 */

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fa1 = av_clip((c>a[0]*c>pk[0]*pk0)>>5, 256, 255); 
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c>a[1] += 128*pk0*c>pk[1] + fa1  (c>a[1]>>7); 
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c>a[1] = av_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] = av_clip(c>a[0], (15360  c>a[1]), 15360  c>a[1]); 
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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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} 
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/* Update Dq and Sr and Pk */

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c>pk[1] = c>pk[0]; 
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c>pk[0] = pk0 ? pk0 : 1; 
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c>sr[1] = c>sr[0]; 
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i2f(re_signal, &c>sr[0]);

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for (i=5; i>0; i) 
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c>dq[i] = c>dq[i1];

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i2f(dq, &c>dq[0]);

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c>dq[0].sign = I_sig; /* Isn't it crazy ?!?! */ 
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c>td = c>a[1] < 11776; 
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/* Update Ap */

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c>dms += (c>tbls.F[I]<<4) + (( c>dms) >> 5); 
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c>dml += (c>tbls.F[I]<<4) + (( c>dml) >> 7); 
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if (tr)

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c>ap = 256;

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else {

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c>ap += (c>ap) >> 4;

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if (c>y <= 1535  c>td  abs((c>dms << 2)  c>dml) >= (c>dml >> 3)) 
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c>ap += 0x20;

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} 
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/* Update Yu and Yl */

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c>yu = av_clip(c>y + c>tbls.W[I] + ((c>y)>>5), 544, 5120); 
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c>yl += c>yu + ((c>yl)>>6);

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/* Next iteration for Y */

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al = (c>ap >= 256) ? 1<<6 : c>ap >> 2; 
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c>y = (c>yl + (c>yu  (c>yl>>6))*al) >> 6; 
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/* Next iteration for SE and SEZ */

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c>se = 0;

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for (i=0; i<6; i++) 
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c>se += mult(i2f(c>b[i] >> 2, &f), &c>dq[i]);

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c>sez = c>se >> 1;

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for (i=0; i<2; i++) 
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c>se += mult(i2f(c>a[i] >> 2, &f), &c>sr[i]);

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c>se >>= 1;

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return av_clip(re_signal << 2, 0xffff, 0xffff); 
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} 
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static av_cold int g726_reset(G726Context* c, int index) 
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{ 
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int i;

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c>tbls = G726Tables_pool[index]; 
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for (i=0; i<2; i++) { 
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c>sr[i].mant = 1<<5; 
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c>pk[i] = 1;

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} 
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for (i=0; i<6; i++) { 
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c>dq[i].mant = 1<<5; 
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} 
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c>yu = 544;

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c>yl = 34816;

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c>y = 544;

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return 0; 
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} 
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#if CONFIG_ADPCM_G726_ENCODER

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static int16_t g726_encode(G726Context* c, int16_t sig)

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{ 
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uint8_t i; 
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i = quant(c, sig/4  c>se) & ((1<<c>code_size)  1); 
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g726_decode(c, i); 
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return i;

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} 
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#endif

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/* Interfacing to the libavcodec */

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static av_cold int g726_init(AVCodecContext * avctx) 
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{ 
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G726Context* c = avctx>priv_data; 
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unsigned int index; 
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if (avctx>sample_rate <= 0) { 
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av_log(avctx, AV_LOG_ERROR, "Samplerate is invalid\n");

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return 1; 
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} 
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index = (avctx>bit_rate + avctx>sample_rate/2) / avctx>sample_rate  2; 
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if (avctx>bit_rate % avctx>sample_rate && avctx>codec>encode) {

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av_log(avctx, AV_LOG_ERROR, "Bitrate  Samplerate combination is invalid\n");

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return 1; 
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} 
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if(avctx>channels != 1){ 
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av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");

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return 1; 
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} 
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if(index>3){ 
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av_log(avctx, AV_LOG_ERROR, "Unsupported number of bits %d\n", index+2); 
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return 1; 
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} 
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g726_reset(c, index); 
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c>code_size = index+2;

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avctx>coded_frame = avcodec_alloc_frame(); 
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if (!avctx>coded_frame)

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return AVERROR(ENOMEM);

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avctx>coded_frame>key_frame = 1;

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if (avctx>codec>decode)

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avctx>sample_fmt = AV_SAMPLE_FMT_S16; 
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/* select a frame size that will end on a byte boundary and have a size of

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approximately 1024 bytes */

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if (avctx>codec>encode)

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avctx>frame_size = ((int[]){ 4096, 2736, 2048, 1640 })[index]; 
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return 0; 
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} 
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static av_cold int g726_close(AVCodecContext *avctx) 
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{ 
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av_freep(&avctx>coded_frame); 
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return 0; 
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} 
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#if CONFIG_ADPCM_G726_ENCODER

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static int g726_encode_frame(AVCodecContext *avctx, 
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uint8_t *dst, int buf_size, void *data) 
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{ 
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G726Context *c = avctx>priv_data; 
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const short *samples = data; 
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PutBitContext pb; 
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int i;

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init_put_bits(&pb, dst, 1024*1024); 
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for (i = 0; i < avctx>frame_size; i++) 
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put_bits(&pb, c>code_size, g726_encode(c, *samples++)); 
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flush_put_bits(&pb); 
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return put_bits_count(&pb)>>3; 
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} 
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#endif

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static int g726_decode_frame(AVCodecContext *avctx, 
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void *data, int *data_size, 
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AVPacket *avpkt) 
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{ 
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const uint8_t *buf = avpkt>data;

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int buf_size = avpkt>size;

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G726Context *c = avctx>priv_data; 
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short *samples = data;

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GetBitContext gb; 
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init_get_bits(&gb, buf, buf_size * 8);

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while (get_bits_count(&gb) + c>code_size <= buf_size*8) 
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*samples++ = g726_decode(c, get_bits(&gb, c>code_size)); 
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if(buf_size*8 != get_bits_count(&gb)) 
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av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");

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*data_size = (uint8_t*)samples  (uint8_t*)data; 
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return buf_size;

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} 
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#if CONFIG_ADPCM_G726_ENCODER

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AVCodec ff_adpcm_g726_encoder = { 
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"g726",

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AVMEDIA_TYPE_AUDIO, 
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CODEC_ID_ADPCM_G726, 
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sizeof(G726Context),

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g726_init, 
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g726_encode_frame, 
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g726_close, 
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NULL,

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.capabilities = CODEC_CAP_SMALL_LAST_FRAME, 
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.sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, 
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.long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),

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}; 
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#endif

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AVCodec ff_adpcm_g726_decoder = { 
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"g726",

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AVMEDIA_TYPE_AUDIO, 
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CODEC_ID_ADPCM_G726, 
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sizeof(G726Context),

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g726_init, 
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NULL,

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g726_close, 
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g726_decode_frame, 
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.long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),

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}; 