| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /* | ||
| 2 | * Lagarith range decoder | ||
| 3 | * Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com> | ||
| 4 | * Copyright (c) 2009 David Conrad | ||
| 5 | * | ||
| 6 | * This file is part of FFmpeg. | ||
| 7 | * | ||
| 8 | * FFmpeg is free software; you can redistribute it and/or | ||
| 9 | * modify it under the terms of the GNU Lesser General Public | ||
| 10 | * License as published by the Free Software Foundation; either | ||
| 11 | * version 2.1 of the License, or (at your option) any later version. | ||
| 12 | * | ||
| 13 | * FFmpeg is distributed in the hope that it will be useful, | ||
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| 16 | * Lesser General Public License for more details. | ||
| 17 | * | ||
| 18 | * You should have received a copy of the GNU Lesser General Public | ||
| 19 | * License along with FFmpeg; if not, write to the Free Software | ||
| 20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| 21 | */ | ||
| 22 | |||
| 23 | /** | ||
| 24 | * @file | ||
| 25 | * Lagarith range decoder | ||
| 26 | * @author Nathan Caldwell | ||
| 27 | * @author David Conrad | ||
| 28 | */ | ||
| 29 | |||
| 30 | #ifndef AVCODEC_LAGARITHRAC_H | ||
| 31 | #define AVCODEC_LAGARITHRAC_H | ||
| 32 | |||
| 33 | #include <stdint.h> | ||
| 34 | #include "libavutil/intreadwrite.h" | ||
| 35 | #include "avcodec.h" | ||
| 36 | #include "get_bits.h" | ||
| 37 | |||
| 38 | typedef struct lag_rac { | ||
| 39 | AVCodecContext *avctx; | ||
| 40 | unsigned low; | ||
| 41 | unsigned range; | ||
| 42 | unsigned scale; /**< Number of bits of precision in range. */ | ||
| 43 | unsigned hash_shift; /**< Number of bits to shift to calculate hash for radix search. */ | ||
| 44 | |||
| 45 | const uint8_t *bytestream_start; /**< Start of input bytestream. */ | ||
| 46 | const uint8_t *bytestream; /**< Current position in input bytestream. */ | ||
| 47 | const uint8_t *bytestream_end; /**< End position of input bytestream. */ | ||
| 48 | |||
| 49 | int overread; | ||
| 50 | #define MAX_OVERREAD 4 | ||
| 51 | |||
| 52 | uint32_t prob[258]; /**< Table of cumulative probability for each symbol. */ | ||
| 53 | uint8_t range_hash[1024]; /**< Hash table mapping upper byte to approximate symbol. */ | ||
| 54 | } lag_rac; | ||
| 55 | |||
| 56 | void ff_lag_rac_init(lag_rac *l, GetBitContext *gb, int length); | ||
| 57 | |||
| 58 | /* TODO: Optimize */ | ||
| 59 | 4610091 | static inline void lag_rac_refill(lag_rac *l) | |
| 60 | { | ||
| 61 |
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6421816 | while (l->range <= 0x800000) { |
| 62 | 1811725 | l->low <<= 8; | |
| 63 | 1811725 | l->range <<= 8; | |
| 64 | 1811725 | l->low |= 0xff & (AV_RB16(l->bytestream) >> 1); | |
| 65 |
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1811725 | if (l->bytestream < l->bytestream_end) |
| 66 | 1811725 | l->bytestream++; | |
| 67 | else | ||
| 68 | ✗ | l->overread++; | |
| 69 | } | ||
| 70 | 4610091 | } | |
| 71 | |||
| 72 | /** | ||
| 73 | * Decode a single byte from the compressed plane described by *l. | ||
| 74 | * @param l pointer to lag_rac for the current plane | ||
| 75 | * @return next byte of decoded data | ||
| 76 | */ | ||
| 77 | 4610091 | static inline uint8_t lag_get_rac(lag_rac *l) | |
| 78 | { | ||
| 79 | unsigned range_scaled, low_scaled; | ||
| 80 | int val; | ||
| 81 | |||
| 82 | 4610091 | lag_rac_refill(l); | |
| 83 | |||
| 84 | 4610091 | range_scaled = l->range >> l->scale; | |
| 85 | |||
| 86 |
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4610091 | if (l->low < range_scaled * l->prob[255]) { |
| 87 | /* val = 0 is frequent enough to deserve a shortcut */ | ||
| 88 |
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3832002 | if (l->low < range_scaled * l->prob[1]) { |
| 89 | 1476885 | val = 0; | |
| 90 | } else { | ||
| 91 | 2355117 | low_scaled = l->low / (range_scaled<<(l->hash_shift)); | |
| 92 | |||
| 93 | 2355117 | val = l->range_hash[low_scaled]; | |
| 94 |
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2875612 | while (l->low >= range_scaled * l->prob[val + 1]) |
| 95 | 520495 | val++; | |
| 96 | } | ||
| 97 | |||
| 98 | 3832002 | l->range = range_scaled * (l->prob[val + 1] - l->prob[val]); | |
| 99 | } else { | ||
| 100 | 778089 | val = 255; | |
| 101 | 778089 | l->range -= range_scaled * l->prob[255]; | |
| 102 | } | ||
| 103 | |||
| 104 |
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4610091 | if (!l->range) |
| 105 | ✗ | l->range = 0x80; | |
| 106 | |||
| 107 | 4610091 | l->low -= range_scaled * l->prob[val]; | |
| 108 | |||
| 109 | 4610091 | return val; | |
| 110 | } | ||
| 111 | |||
| 112 | |||
| 113 | #endif /* AVCODEC_LAGARITHRAC_H */ | ||
| 114 |