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81 lines
2.2 KiB
C
81 lines
2.2 KiB
C
/*
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* E-AC-3 decoder
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* Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
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* Copyright (c) 2008 Justin Ruggles
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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 "avcodec.h"
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#include "ac3.h"
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#include "ac3_parser.h"
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#include "ac3dec.h"
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#include "ac3dec_data.h"
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/** gain adaptive quantization mode */
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typedef enum {
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EAC3_GAQ_NO =0,
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EAC3_GAQ_12,
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EAC3_GAQ_14,
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EAC3_GAQ_124
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} EAC3GaqMode;
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#define EAC3_SR_CODE_REDUCED 3
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/** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */
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#define COEFF_0 10273905LL
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/** lrint(M_SQRT2*cos(0*M_PI/12)*(1<<23)) = lrint(M_SQRT2*(1<<23)) */
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#define COEFF_1 11863283LL
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/** lrint(M_SQRT2*cos(5*M_PI/12)*(1<<23)) */
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#define COEFF_2 3070444LL
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/**
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* Calculate 6-point IDCT of the pre-mantissas.
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* All calculations are 24-bit fixed-point.
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*/
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static void idct6(int pre_mant[6])
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{
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int tmp;
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int even0, even1, even2, odd0, odd1, odd2;
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odd1 = pre_mant[1] - pre_mant[3] - pre_mant[5];
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even2 = ( pre_mant[2] * COEFF_0) >> 23;
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tmp = ( pre_mant[4] * COEFF_1) >> 23;
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odd0 = ((pre_mant[1] + pre_mant[5]) * COEFF_2) >> 23;
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even0 = pre_mant[0] + (tmp >> 1);
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even1 = pre_mant[0] - tmp;
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tmp = even0;
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even0 = tmp + even2;
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even2 = tmp - even2;
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tmp = odd0;
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odd0 = tmp + pre_mant[1] + pre_mant[3];
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odd2 = tmp + pre_mant[5] - pre_mant[3];
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pre_mant[0] = even0 + odd0;
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pre_mant[1] = even1 + odd1;
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pre_mant[2] = even2 + odd2;
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pre_mant[3] = even2 - odd2;
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pre_mant[4] = even1 - odd1;
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pre_mant[5] = even0 - odd0;
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}
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