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57 lines
1.8 KiB
57 lines
1.8 KiB
/* |
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* MJPEG decoder VLC code |
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* Copyright (c) 2000, 2001 Fabrice Bellard |
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* Copyright (c) 2003 Alex Beregszaszi |
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* Copyright (c) 2003-2004 Michael Niedermayer |
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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 <stdint.h> |
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#include "libavutil/avassert.h" |
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#include "mjpegdec.h" |
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#include "vlc.h" |
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static int build_huffman_codes(uint8_t *huff_size, const uint8_t *bits_table) |
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{ |
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int nb_codes = 0; |
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for (int i = 1, j = 0; i <= 16; i++) { |
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nb_codes += bits_table[i]; |
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av_assert1(nb_codes <= 256); |
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for (; j < nb_codes; j++) |
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huff_size[j] = i; |
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} |
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return nb_codes; |
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} |
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int ff_mjpeg_build_vlc(VLC *vlc, const uint8_t *bits_table, |
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const uint8_t *val_table, int is_ac, void *logctx) |
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{ |
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uint8_t huff_size[256]; |
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uint16_t huff_sym[256]; |
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int nb_codes = build_huffman_codes(huff_size, bits_table); |
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for (int i = 0; i < nb_codes; i++) { |
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huff_sym[i] = val_table[i] + 16 * is_ac; |
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if (is_ac && !val_table[i]) |
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huff_sym[i] = 16 * 256; |
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} |
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return ff_init_vlc_from_lengths(vlc, 9, nb_codes, huff_size, 1, |
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huff_sym, 2, 2, 0, 0, logctx); |
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}
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