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77 lines
2.6 KiB
C
77 lines
2.6 KiB
C
/*
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* MJPEG encoder
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* Copyright (c) 2016 William Ma, Ted Ying, Jerry Jiang
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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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* Huffman table generation for MJPEG encoder.
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*/
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#ifndef AVCODEC_MJPEGENC_HUFFMAN_H
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#define AVCODEC_MJPEGENC_HUFFMAN_H
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#include <stdint.h>
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typedef struct MJpegEncHuffmanContext {
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int val_count[256];
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} MJpegEncHuffmanContext;
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// Uses the package merge algorithm to compute the Huffman table.
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void ff_mjpeg_encode_huffman_init(MJpegEncHuffmanContext *s);
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static inline void ff_mjpeg_encode_huffman_increment(MJpegEncHuffmanContext *s,
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uint8_t val)
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{
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s->val_count[val]++;
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}
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void ff_mjpeg_encode_huffman_close(MJpegEncHuffmanContext *s,
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uint8_t bits[17], uint8_t val[],
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int max_nval);
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/**
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* Used to assign a occurrence count or "probability" to an input value
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*/
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typedef struct PTable {
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int value; ///< input value
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int prob; ///< number of occurences of this value in input
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} PTable;
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/**
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* Used to store intermediate lists in the package merge algorithm
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*/
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typedef struct PackageMergerList {
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int nitems; ///< number of items in the list and probability ex. 4
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int item_idx[515]; ///< index range for each item in items 0, 2, 5, 9, 13
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int probability[514]; ///< probability of each item 3, 8, 18, 46
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int items[257 * 16]; ///< chain of all individual values that make up items A, B, A, B, C, A, B, C, D, C, D, D, E
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} PackageMergerList;
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/**
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* Used to store optimal huffman encoding results
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*/
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typedef struct HuffTable {
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int code; ///< code is the input value
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int length; ///< length of the encoding
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} HuffTable;
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void ff_mjpegenc_huffman_compute_bits(PTable *prob_table, HuffTable *distincts,
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int size, int max_length);
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#endif /* AVCODEC_MJPEGENC_HUFFMAN_H */
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