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1/*
2 * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
3 * Copyright (c) 2003 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 * Context Adaptive Binary Arithmetic Coder inline functions
25 */
26
27#ifndef AVCODEC_CABAC_FUNCTIONS_H
28#define AVCODEC_CABAC_FUNCTIONS_H
29
30#include <stdint.h>
31
32#include "cabac.h"
33#include "config.h"
34
35#ifndef UNCHECKED_BITSTREAM_READER
36#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
37#endif
38
39#if ARCH_AARCH64
40# include "aarch64/cabac.h"
41#endif
42#if ARCH_ARM
43# include "arm/cabac.h"
44#endif
45#if ARCH_X86
46# include "x86/cabac.h"
47#endif
48
49static const uint8_t * const ff_h264_norm_shift = ff_h264_cabac_tables + H264_NORM_SHIFT_OFFSET;
50static const uint8_t * const ff_h264_lps_range = ff_h264_cabac_tables + H264_LPS_RANGE_OFFSET;
51static const uint8_t * const ff_h264_mlps_state = ff_h264_cabac_tables + H264_MLPS_STATE_OFFSET;
52static const uint8_t * const ff_h264_last_coeff_flag_offset_8x8 = ff_h264_cabac_tables + H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET;
53
54#if !defined(get_cabac_bypass) || !defined(get_cabac_terminate)
55static void refill(CABACContext *c){
56#if CABAC_BITS == 16
57 c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
58#else
59 c->low+= c->bytestream[0]<<1;
60#endif
61 c->low -= CABAC_MASK;
62#if !UNCHECKED_BITSTREAM_READER
63 if (c->bytestream < c->bytestream_end)
64#endif
65 c->bytestream += CABAC_BITS / 8;
66}
67#endif
68
69#ifndef get_cabac_terminate
70static inline void renorm_cabac_decoder_once(CABACContext *c){
71 int shift= (uint32_t)(c->range - 0x100)>>31;
72 c->range<<= shift;
73 c->low <<= shift;
74 if(!(c->low & CABAC_MASK))
75 refill(c);
76}
77#endif
78
79#ifndef get_cabac_inline
80static void refill2(CABACContext *c){
81 int i;
82 unsigned x;
83#if !HAVE_FAST_CLZ
84 x= c->low ^ (c->low-1);
85 i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
86#else
87 i = ff_ctz(c->low) - CABAC_BITS;
88#endif
89
90 x= -CABAC_MASK;
91
92#if CABAC_BITS == 16
93 x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
94#else
95 x+= c->bytestream[0]<<1;
96#endif
97
98 c->low += x<<i;
99#if !UNCHECKED_BITSTREAM_READER
100 if (c->bytestream < c->bytestream_end)
101#endif
102 c->bytestream += CABAC_BITS/8;
103}
104#endif
105
106#ifndef get_cabac_inline
107static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
108 int s = *state;
109 int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
110 int bit, lps_mask;
111
112 c->range -= RangeLPS;
113 lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
114
115 c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
116 c->range += (RangeLPS - c->range) & lps_mask;
117
118 s^=lps_mask;
119 *state= (ff_h264_mlps_state+128)[s];
120 bit= s&1;
121
122 lps_mask= ff_h264_norm_shift[c->range];
123 c->range<<= lps_mask;
124 c->low <<= lps_mask;
125 if(!(c->low & CABAC_MASK))
126 refill2(c);
127 return bit;
128}
129#endif
130
131static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
132 return get_cabac_inline(c,state);
133}
134
135static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
136 return get_cabac_inline(c,state);
137}
138
139#ifndef get_cabac_bypass
140static int av_unused get_cabac_bypass(CABACContext *c){
141 int range;
142 c->low += c->low;
143
144 if(!(c->low & CABAC_MASK))
145 refill(c);
146
147 range= c->range<<(CABAC_BITS+1);
148 if(c->low < range){
149 return 0;
150 }else{
151 c->low -= range;
152 return 1;
153 }
154}
155#endif
156
157#ifndef get_cabac_bypass_sign
158static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
159 int range, mask;
160 c->low += c->low;
161
162 if(!(c->low & CABAC_MASK))
163 refill(c);
164
165 range= c->range<<(CABAC_BITS+1);
166 c->low -= range;
167 mask= c->low >> 31;
168 range &= mask;
169 c->low += range;
170 return (val^mask)-mask;
171}
172#endif
173
174/**
175 * @return the number of bytes read or 0 if no end
176 */
177#ifndef get_cabac_terminate
178static int av_unused get_cabac_terminate(CABACContext *c){
179 c->range -= 2;
180 if(c->low < c->range<<(CABAC_BITS+1)){
181 renorm_cabac_decoder_once(c);
182 return 0;
183 }else{
184 return c->bytestream - c->bytestream_start;
185 }
186}
187#endif
188
189/**
190 * Skip @p n bytes and reset the decoder.
191 * @return the address of the first skipped byte or NULL if there's less than @p n bytes left
192 */
193#ifndef skip_bytes
194static av_unused const uint8_t* skip_bytes(CABACContext *c, int n) {
195 const uint8_t *ptr = c->bytestream;
196
197 if (c->low & 0x1)
198 ptr--;
199#if CABAC_BITS == 16
200 if (c->low & 0x1FF)
201 ptr--;
202#endif
203 if ((int) (c->bytestream_end - ptr) < n)
204 return NULL;
205 if (ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n) < 0)
206 return NULL;
207
208 return ptr;
209}
210#endif
211
212#endif /* AVCODEC_CABAC_FUNCTIONS_H */
213
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