blob: 5fe65504e42079f32d7dab41b27fb8cd8dffc913
| 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 | |
| 32 | typedef struct MJpegEncHuffmanContext { |
| 33 | int val_count[256]; |
| 34 | } MJpegEncHuffmanContext; |
| 35 | |
| 36 | // Uses the package merge algorithm to compute the Huffman table. |
| 37 | void ff_mjpeg_encode_huffman_init(MJpegEncHuffmanContext *s); |
| 38 | static inline void ff_mjpeg_encode_huffman_increment(MJpegEncHuffmanContext *s, |
| 39 | uint8_t val) |
| 40 | { |
| 41 | s->val_count[val]++; |
| 42 | } |
| 43 | void 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 | */ |
| 51 | typedef 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 | */ |
| 59 | typedef 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 | */ |
| 69 | typedef struct HuffTable { |
| 70 | int code; ///< code is the input value |
| 71 | int length; ///< length of the encoding |
| 72 | } HuffTable; |
| 73 | |
| 74 | void ff_mjpegenc_huffman_compute_bits(PTable *prob_table, HuffTable *distincts, |
| 75 | int size, int max_length); |
| 76 | #endif /* AVCODEC_MJPEGENC_HUFFMAN_H */ |
| 77 |