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99 lines
2.4 KiB
99 lines
2.4 KiB
/* |
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* bitstream.c |
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* Copyright (C) 2000-2002 Michel Lespinasse <walken@zoy.org> |
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* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca> |
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* |
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* This file is part of a52dec, a free ATSC A-52 stream decoder. |
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* See http://liba52.sourceforge.net/ for updates. |
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* |
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* a52dec 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 of the License, or |
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* (at your option) any later version. |
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* |
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* a52dec 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 this program; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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*/ |
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#include "a52.h" |
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#include "a52_internal.h" |
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#include "bitstream.h" |
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#define BUFFER_SIZE 4096 |
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static uint32_t * buffer_start; |
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uint32_t a52_bits_left; |
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uint32_t a52_current_word; |
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void a52_bitstream_set_ptr (uint8_t * buf) |
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{ |
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int align; |
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align = (long)buf & 3; |
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buffer_start = (uint32_t *) (buf - align); |
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a52_bits_left = 0; |
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bitstream_get (align * 8); |
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} |
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static inline void |
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bitstream_fill_current() |
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{ |
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uint32_t tmp; |
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tmp = *(buffer_start++); |
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a52_current_word = swab32 (tmp); |
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} |
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/* |
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* The fast paths for _get is in the |
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* bitstream.h header file so it can be inlined. |
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* |
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* The "bottom half" of this routine is suffixed _bh |
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* |
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* -ah |
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*/ |
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uint32_t |
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a52_bitstream_get_bh(uint32_t num_bits) |
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{ |
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uint32_t result; |
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num_bits -= a52_bits_left; |
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result = ((a52_current_word << (32 - a52_bits_left)) >> |
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(32 - a52_bits_left)); |
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bitstream_fill_current(); |
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if(num_bits != 0) |
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result = (result << num_bits) | (a52_current_word >> (32 - num_bits)); |
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a52_bits_left = 32 - num_bits; |
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return result; |
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} |
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int32_t |
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a52_bitstream_get_bh_2(uint32_t num_bits) |
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{ |
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int32_t result; |
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num_bits -= a52_bits_left; |
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result = ((((int32_t)a52_current_word) << (32 - a52_bits_left)) >> |
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(32 - a52_bits_left)); |
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bitstream_fill_current(); |
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if(num_bits != 0) |
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result = (result << num_bits) | (a52_current_word >> (32 - num_bits)); |
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a52_bits_left = 32 - num_bits; |
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return result; |
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}
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