09c2d08c
 Hu Chunming
arm交付版
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/*
* MJPEG decoder VLC code
* Copyright (c) 2000, 2001 Fabrice Bellard
* Copyright (c) 2003 Alex Beregszaszi
* Copyright (c) 2003-2004 Michael Niedermayer
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <stdint.h>
#include "libavutil/avassert.h"
#include "mjpegdec.h"
#include "vlc.h"
static int build_huffman_codes(uint8_t *huff_size, const uint8_t *bits_table)
{
int nb_codes = 0;
for (int i = 1, j = 0; i <= 16; i++) {
nb_codes += bits_table[i];
av_assert1(nb_codes <= 256);
for (; j < nb_codes; j++)
huff_size[j] = i;
}
return nb_codes;
}
int ff_mjpeg_build_vlc(VLC *vlc, const uint8_t *bits_table,
const uint8_t *val_table, int is_ac, void *logctx)
{
uint8_t huff_size[256];
uint16_t huff_sym[256];
int nb_codes = build_huffman_codes(huff_size, bits_table);
for (int i = 0; i < nb_codes; i++) {
huff_sym[i] = val_table[i] + 16 * is_ac;
if (is_ac && !val_table[i])
huff_sym[i] = 16 * 256;
}
return ff_init_vlc_from_lengths(vlc, 9, nb_codes, huff_size, 1,
huff_sym, 2, 2, 0, 0, logctx);
}
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