mirror of https://git.ffmpeg.org/ffmpeg.git
58 lines
1.8 KiB
C
58 lines
1.8 KiB
C
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/*
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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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