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);
61 * Check if at the current position there is a valid looking termination
62 * @param version version 0 requires the decoder to know the data size in bytes
63 * version 1 needs about 1 bit more space but does not need to
64 * carry the size from encoder to decoder
65 * @returns negative AVERROR code on error or non negative.
67 int ff_rac_check_termination(RangeCoder *c, int version);
69 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
71 static inline void renorm_encoder(RangeCoder *c)
74 while (c->range < 0x100) {
75 if (c->outstanding_byte < 0) {
76 c->outstanding_byte = c->low >> 8;
77 } else if (c->low <= 0xFF00) {
78 *c->bytestream++ = c->outstanding_byte;
79 for (; c->outstanding_count; c->outstanding_count--)
80 *c->bytestream++ = 0xFF;
81 c->outstanding_byte = c->low >> 8;
82 } else if (c->low >= 0x10000) {
83 *c->bytestream++ = c->outstanding_byte + 1;
84 for (; c->outstanding_count; c->outstanding_count--)
85 *c->bytestream++ = 0x00;
86 c->outstanding_byte = (c->low >> 8) & 0xFF;
88 c->outstanding_count++;
91 c->low = (c->low & 0xFF) << 8;
96 static inline int get_rac_count(RangeCoder *c)
98 int x = c->bytestream - c->bytestream_start + c->outstanding_count;
99 if (c->outstanding_byte >= 0)
101 return 8 * x - av_log2(c->range);
104 static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit)
106 int range1 = (c->range * (*state)) >> 8;
109 av_assert2(range1 < c->range);
110 av_assert2(range1 > 0);
113 *state = c->zero_state[*state];
115 c->low += c->range - range1;
117 *state = c->one_state[*state];
123 static inline void refill(RangeCoder *c)
125 if (c->range < 0x100) {
128 if (c->bytestream < c->bytestream_end) {
129 c->low += c->bytestream[0];
136 static inline int get_rac(RangeCoder *c, uint8_t *const state)
138 int range1 = (c->range * (*state)) >> 8;
141 if (c->low < c->range) {
142 *state = c->zero_state[*state];
147 *state = c->one_state[*state];
154 #endif /* AVCODEC_RANGECODER_H */