1/*
2 * MJPEG encoder
3 * Copyright (c) 2016 William Ma, Ted Ying, Jerry Jiang
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file
24 * Huffman table generation for MJPEG encoder.
25 */
26
27#ifndef AVCODEC_MJPEGENC_HUFFMAN_H
28#define AVCODEC_MJPEGENC_HUFFMAN_H
29
30#include <stdint.h>
31
32typedef struct MJpegEncHuffmanContext {
33    int val_count[256];
34} MJpegEncHuffmanContext;
35
36// Uses the package merge algorithm to compute the Huffman table.
37void ff_mjpeg_encode_huffman_init(MJpegEncHuffmanContext *s);
38static inline void ff_mjpeg_encode_huffman_increment(MJpegEncHuffmanContext *s,
39                                                     uint8_t val)
40{
41    s->val_count[val]++;
42}
43void ff_mjpeg_encode_huffman_close(MJpegEncHuffmanContext *s,
44                                   uint8_t bits[17], uint8_t val[],
45                                   int max_nval);
46
47
48/**
49 * Used to assign a occurrence count or "probability" to an input value
50 */
51typedef struct PTable {
52    int value;  ///< input value
53    int prob;   ///< number of occurences of this value in input
54} PTable;
55
56/**
57 * Used to store intermediate lists in the package merge algorithm
58 */
59typedef struct PackageMergerList {
60    int nitems;             ///< number of items in the list and probability      ex. 4
61    int item_idx[515];      ///< index range for each item in items                   0, 2, 5, 9, 13
62    int probability[514];   ///< probability of each item                             3, 8, 18, 46
63    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
64} PackageMergerList;
65
66/**
67 * Used to store optimal huffman encoding results
68 */
69typedef struct HuffTable {
70    int code;       ///< code is the input value
71    int length;     ///< length of the encoding
72} HuffTable;
73
74void ff_mjpegenc_huffman_compute_bits(PTable *prob_table, HuffTable *distincts,
75                                      int size, int max_length);
76#endif /* AVCODEC_MJPEGENC_HUFFMAN_H */
77