3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
5 * This file is part of FFmpeg.
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.
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.
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
27 #ifndef AVCODEC_RANGECODER_H
28 #define AVCODEC_RANGECODER_H
32 #include "libavutil/common.h"
33 #include "libavutil/avassert.h"
35 typedef struct RangeCoder {
38 int outstanding_count;
40 uint8_t zero_state[256];
41 uint8_t one_state[256];
42 uint8_t *bytestream_start;
44 uint8_t *bytestream_end;
46 #define MAX_OVERREAD 2
49 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
50 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
51 int ff_rac_terminate(RangeCoder *c);
52 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
54 static inline void renorm_encoder(RangeCoder *c)
57 while (c->range < 0x100) {
58 if (c->outstanding_byte < 0) {
59 c->outstanding_byte = c->low >> 8;
60 } else if (c->low <= 0xFF00) {
61 *c->bytestream++ = c->outstanding_byte;
62 for (; c->outstanding_count; c->outstanding_count--)
63 *c->bytestream++ = 0xFF;
64 c->outstanding_byte = c->low >> 8;
65 } else if (c->low >= 0x10000) {
66 *c->bytestream++ = c->outstanding_byte + 1;
67 for (; c->outstanding_count; c->outstanding_count--)
68 *c->bytestream++ = 0x00;
69 c->outstanding_byte = (c->low >> 8) & 0xFF;
71 c->outstanding_count++;
74 c->low = (c->low & 0xFF) << 8;
79 static inline int get_rac_count(RangeCoder *c)
81 int x = c->bytestream - c->bytestream_start + c->outstanding_count;
82 if (c->outstanding_byte >= 0)
84 return 8 * x - av_log2(c->range);
87 static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit)
89 int range1 = (c->range * (*state)) >> 8;
92 av_assert2(range1 < c->range);
93 av_assert2(range1 > 0);
96 *state = c->zero_state[*state];
98 c->low += c->range - range1;
100 *state = c->one_state[*state];
106 static inline void refill(RangeCoder *c)
108 if (c->range < 0x100) {
111 if (c->bytestream < c->bytestream_end) {
112 c->low += c->bytestream[0];
119 static inline int get_rac(RangeCoder *c, uint8_t *const state)
121 int range1 = (c->range * (*state)) >> 8;
124 if (c->low < c->range) {
125 *state = c->zero_state[*state];
130 *state = c->one_state[*state];
137 #endif /* AVCODEC_RANGECODER_H */