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);
53 * Terminates the range coder
54 * @param version version 0 requires the decoder to know the data size in bytes
55 * version 1 needs about 1 bit more space but does not need to
56 * carry the size from encoder to decoder
58 int ff_rac_terminate(RangeCoder *c, int version);
60 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
62 static inline void renorm_encoder(RangeCoder *c)
65 while (c->range < 0x100) {
66 if (c->outstanding_byte < 0) {
67 c->outstanding_byte = c->low >> 8;
68 } else if (c->low <= 0xFF00) {
69 *c->bytestream++ = c->outstanding_byte;
70 for (; c->outstanding_count; c->outstanding_count--)
71 *c->bytestream++ = 0xFF;
72 c->outstanding_byte = c->low >> 8;
73 } else if (c->low >= 0x10000) {
74 *c->bytestream++ = c->outstanding_byte + 1;
75 for (; c->outstanding_count; c->outstanding_count--)
76 *c->bytestream++ = 0x00;
77 c->outstanding_byte = (c->low >> 8) & 0xFF;
79 c->outstanding_count++;
82 c->low = (c->low & 0xFF) << 8;
87 static inline int get_rac_count(RangeCoder *c)
89 int x = c->bytestream - c->bytestream_start + c->outstanding_count;
90 if (c->outstanding_byte >= 0)
92 return 8 * x - av_log2(c->range);
95 static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit)
97 int range1 = (c->range * (*state)) >> 8;
100 av_assert2(range1 < c->range);
101 av_assert2(range1 > 0);
104 *state = c->zero_state[*state];
106 c->low += c->range - range1;
108 *state = c->one_state[*state];
114 static inline void refill(RangeCoder *c)
116 if (c->range < 0x100) {
119 if (c->bytestream < c->bytestream_end) {
120 c->low += c->bytestream[0];
127 static inline int get_rac(RangeCoder *c, uint8_t *const state)
129 int range1 = (c->range * (*state)) >> 8;
132 if (c->low < c->range) {
133 *state = c->zero_state[*state];
138 *state = c->one_state[*state];
145 #endif /* AVCODEC_RANGECODER_H */