| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /* | ||
| 2 | * Range coder | ||
| 3 | * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at> | ||
| 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 | * Range coder. | ||
| 25 | * based upon | ||
| 26 | * "Range encoding: an algorithm for removing redundancy from a digitised | ||
| 27 | * message. | ||
| 28 | * G. N. N. Martin Presented in March 1979 to the Video & | ||
| 29 | * Data Recording Conference, | ||
| 30 | * IBM UK Scientific Center held in Southampton July 24-27 1979." | ||
| 31 | */ | ||
| 32 | |||
| 33 | #include <string.h> | ||
| 34 | |||
| 35 | #include "libavutil/attributes.h" | ||
| 36 | #include "libavutil/avassert.h" | ||
| 37 | #include "libavutil/bswap.h" | ||
| 38 | #include "libavutil/intreadwrite.h" | ||
| 39 | |||
| 40 | #include "rangecoder.h" | ||
| 41 | |||
| 42 | 24238 | av_cold void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size) | |
| 43 | { | ||
| 44 | 24238 | c->bytestream_start = | |
| 45 | 24238 | c->bytestream = buf; | |
| 46 | 24238 | c->bytestream_end = buf + buf_size; | |
| 47 | 24238 | c->low = 0; | |
| 48 | 24238 | c->range = 0xFF00; | |
| 49 | 24238 | c->outstanding_count = 0; | |
| 50 | 24238 | c->outstanding_byte = -1; | |
| 51 | 24238 | } | |
| 52 | |||
| 53 | 12464 | av_cold void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, | |
| 54 | int buf_size) | ||
| 55 | { | ||
| 56 | /* cast to avoid compiler warning */ | ||
| 57 | 12464 | ff_init_range_encoder(c, (uint8_t *)buf, buf_size); | |
| 58 | |||
| 59 | 12464 | c->low = AV_RB16(c->bytestream); | |
| 60 | 12464 | c->bytestream += 2; | |
| 61 | 12464 | c->overread = 0; | |
| 62 |
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12464 | if (c->low >= 0xFF00) { |
| 63 | ✗ | c->low = 0xFF00; | |
| 64 | ✗ | c->bytestream_end = c->bytestream; | |
| 65 | } | ||
| 66 | 12464 | } | |
| 67 | |||
| 68 | 15836 | void ff_build_rac_states(RangeCoder *c, int factor, int max_p) | |
| 69 | { | ||
| 70 | 15836 | const int64_t one = 1LL << 32; | |
| 71 | int64_t p; | ||
| 72 | int last_p8, p8, i; | ||
| 73 | |||
| 74 | 15836 | memset(c->zero_state, 0, sizeof(c->zero_state)); | |
| 75 | 15836 | memset(c->one_state, 0, sizeof(c->one_state)); | |
| 76 | |||
| 77 | 15836 | last_p8 = 0; | |
| 78 | 15836 | p = one / 2; | |
| 79 |
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2042844 | for (i = 0; i < 128; i++) { |
| 80 | 2027008 | p8 = (256 * p + one / 2) >> 32; // FIXME: try without the one | |
| 81 |
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2027008 | if (p8 <= last_p8) |
| 82 | 1377732 | p8 = last_p8 + 1; | |
| 83 |
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2027008 | if (last_p8 && last_p8 < 256 && p8 <= max_p) |
| 84 | 743744 | c->one_state[last_p8] = p8; | |
| 85 | |||
| 86 | 2027008 | p += ((one - p) * factor + one / 2) >> 32; | |
| 87 | 2027008 | last_p8 = p8; | |
| 88 | } | ||
| 89 | |||
| 90 |
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3799544 | for (i = 256 - max_p; i <= max_p; i++) { |
| 91 |
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3783708 | if (c->one_state[i]) |
| 92 | 743744 | continue; | |
| 93 | |||
| 94 | 3039964 | p = (i * one + 128) >> 8; | |
| 95 | 3039964 | p += ((one - p) * factor + one / 2) >> 32; | |
| 96 | 3039964 | p8 = (256 * p + one / 2) >> 32; // FIXME: try without the one | |
| 97 |
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3039964 | if (p8 <= i) |
| 98 | 13788 | p8 = i + 1; | |
| 99 |
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3039964 | if (p8 > max_p) |
| 100 | 15836 | p8 = max_p; | |
| 101 | 3039964 | c->one_state[i] = p8; | |
| 102 | } | ||
| 103 | |||
| 104 |
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4038180 | for (i = 1; i < 255; i++) |
| 105 | 4022344 | c->zero_state[i] = 256 - c->one_state[256 - i]; | |
| 106 | 15836 | } | |
| 107 | |||
| 108 | /* Return the number of bytes written. */ | ||
| 109 | 11174 | int ff_rac_terminate(RangeCoder *c, int version) | |
| 110 | { | ||
| 111 |
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11174 | if (version == 1) |
| 112 | 9144 | put_rac(c, (uint8_t[]) { 129 }, 0); | |
| 113 | 11174 | c->range = 0xFF; | |
| 114 | 11174 | c->low += 0xFF; | |
| 115 | 11174 | renorm_encoder(c); | |
| 116 | 11174 | c->range = 0xFF; | |
| 117 | 11174 | renorm_encoder(c); | |
| 118 | |||
| 119 | av_assert1(c->low == 0); | ||
| 120 | av_assert1(c->range >= 0x100); | ||
| 121 | |||
| 122 | 11174 | return c->bytestream - c->bytestream_start; | |
| 123 | } | ||
| 124 |