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38 lines
1.1 KiB
C
38 lines
1.1 KiB
C
/*
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* dither.h
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*
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* Copyright (C) Aaron Holtzman - May 1999
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*
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* This file is part of ac3dec, a free Dolby AC-3 stream decoder.
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*
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* ac3dec is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* ac3dec 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
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Make; see the file COPYING. If not, write to
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* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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extern uint16_t lfsr_state;
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extern const uint16_t dither_lut[256];
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static inline uint16_t dither_gen(void)
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{
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int16_t state;
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state = dither_lut[lfsr_state >> 8] ^ (lfsr_state << 8);
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lfsr_state = (uint16_t) state;
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return ((state * (int32_t) (0.707106 * 256.0))>>8);
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}
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