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Channel coupling is an optional AC-3 feature that increases quality by combining high frequency information from multiple channels into a single channel. The per-channel high frequency information is sent with less accuracy in both the frequency and time domains. This allows more bits to be used for lower frequencies while preserving enough information to reconstruct the high frequencies.
61 lines
2.1 KiB
C
61 lines
2.1 KiB
C
/*
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* AC-3 and E-AC-3 decoder tables
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* Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
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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 02110-1301 USA
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*/
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/**
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* @file
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* Tables taken directly from the AC-3 spec.
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*/
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#include "ac3dec_data.h"
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#include "ac3.h"
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/**
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* Table used to ungroup 3 values stored in 5 bits.
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* Used by bap=1 mantissas and GAQ.
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* ff_ac3_ungroup_3_in_5_bits_tab[i] = { i/9, (i%9)/3, (i%9)%3 }
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*/
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const uint8_t ff_ac3_ungroup_3_in_5_bits_tab[32][3] = {
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{ 0, 0, 0 }, { 0, 0, 1 }, { 0, 0, 2 }, { 0, 1, 0 },
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{ 0, 1, 1 }, { 0, 1, 2 }, { 0, 2, 0 }, { 0, 2, 1 },
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{ 0, 2, 2 }, { 1, 0, 0 }, { 1, 0, 1 }, { 1, 0, 2 },
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{ 1, 1, 0 }, { 1, 1, 1 }, { 1, 1, 2 }, { 1, 2, 0 },
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{ 1, 2, 1 }, { 1, 2, 2 }, { 2, 0, 0 }, { 2, 0, 1 },
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{ 2, 0, 2 }, { 2, 1, 0 }, { 2, 1, 1 }, { 2, 1, 2 },
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{ 2, 2, 0 }, { 2, 2, 1 }, { 2, 2, 2 }, { 3, 0, 0 },
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{ 3, 0, 1 }, { 3, 0, 2 }, { 3, 1, 0 }, { 3, 1, 1 }
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};
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const uint8_t ff_eac3_hebap_tab[64] = {
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0, 1, 2, 3, 4, 5, 6, 7, 8, 8,
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8, 8, 9, 9, 9, 10, 10, 10, 10, 11,
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11, 11, 11, 12, 12, 12, 12, 13, 13, 13,
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13, 14, 14, 14, 14, 15, 15, 15, 15, 16,
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16, 16, 16, 17, 17, 17, 17, 18, 18, 18,
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18, 18, 18, 18, 18, 19, 19, 19, 19, 19,
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19, 19, 19, 19,
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};
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/**
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* Table E2.15 Default Spectral Extension Banding Structure
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*/
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const uint8_t ff_eac3_default_spx_band_struct[17] =
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{ 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1 };
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