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/* |
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* Lagarith range decoder |
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* Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com> |
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* Copyright (c) 2009 David Conrad |
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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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/** |
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* @file |
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* Lagarith range decoder |
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* @author Nathan Caldwell |
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* @author David Conrad |
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*/ |
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#include "get_bits.h" |
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#include "lagarithrac.h" |
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void ff_lag_rac_init(lag_rac *l, GetBitContext *gb, int length) |
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{ |
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int i, j, left; |
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/* According to reference decoder "1st byte is garbage", |
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* however, it gets skipped by the call to align_get_bits() |
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*/ |
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align_get_bits(gb); |
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left = get_bits_left(gb) >> 3; |
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l->bytestream_start = |
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l->bytestream = gb->buffer + get_bits_count(gb) / 8; |
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l->bytestream_end = l->bytestream_start + left; |
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l->range = 0x80; |
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l->low = *l->bytestream >> 1; |
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l->hash_shift = FFMAX(l->scale, 10) - 10; |
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l->overread = 0; |
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✓✓ |
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for (i = j = 0; i < 1024; i++) { |
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unsigned r = i << l->hash_shift; |
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✓✓ |
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while (l->prob[j + 1] <= r) |
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j++; |
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l->range_hash[i] = j; |
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} |
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} |