FFmpeg
cabac_functions.h
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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 <stddef.h>
31 #include <stdint.h>
32 
33 #include "cabac.h"
34 #include "config.h"
35 
36 #ifndef UNCHECKED_BITSTREAM_READER
37 #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
38 #endif
39 
40 #if ARCH_AARCH64
41 # include "aarch64/cabac.h"
42 #endif
43 #if ARCH_ARM
44 # include "arm/cabac.h"
45 #endif
46 #if ARCH_X86
47 # include "x86/cabac.h"
48 #endif
49 #if ARCH_MIPS
50 # include "mips/cabac.h"
51 #endif
52 
57 
58 #if !defined(get_cabac_bypass) || !defined(get_cabac_terminate)
59 static void refill(CABACContext *c){
60 #if CABAC_BITS == 16
61  c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
62 #else
63  c->low+= c->bytestream[0]<<1;
64 #endif
65  c->low -= CABAC_MASK;
66 #if !UNCHECKED_BITSTREAM_READER
67  if (c->bytestream < c->bytestream_end)
68 #endif
69  c->bytestream += CABAC_BITS / 8;
70 }
71 #endif
72 
73 #ifndef get_cabac_terminate
75  int shift= (uint32_t)(c->range - 0x100)>>31;
76  c->range<<= shift;
77  c->low <<= shift;
78  if(!(c->low & CABAC_MASK))
79  refill(c);
80 }
81 #endif
82 
83 #ifndef get_cabac_inline
84 static void refill2(CABACContext *c){
85  int i;
86  unsigned x;
87 #if !HAVE_FAST_CLZ
88  x= c->low ^ (c->low-1);
89  i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
90 #else
91  i = ff_ctz(c->low) - CABAC_BITS;
92 #endif
93 
94  x= -CABAC_MASK;
95 
96 #if CABAC_BITS == 16
97  x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
98 #else
99  x+= c->bytestream[0]<<1;
100 #endif
101 
102  c->low += x<<i;
103 #if !UNCHECKED_BITSTREAM_READER
104  if (c->bytestream < c->bytestream_end)
105 #endif
106  c->bytestream += CABAC_BITS/8;
107 }
108 #endif
109 
110 #ifndef get_cabac_inline
111 static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
112  int s = *state;
113  int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
114  int bit, lps_mask;
115 
116  c->range -= RangeLPS;
117  lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
118 
119  c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
120  c->range += (RangeLPS - c->range) & lps_mask;
121 
122  s^=lps_mask;
123  *state= (ff_h264_mlps_state+128)[s];
124  bit= s&1;
125 
126  lps_mask= ff_h264_norm_shift[c->range];
127  c->range<<= lps_mask;
128  c->low <<= lps_mask;
129  if(!(c->low & CABAC_MASK))
130  refill2(c);
131  return bit;
132 }
133 #endif
134 
136  return get_cabac_inline(c,state);
137 }
138 
139 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
140  return get_cabac_inline(c,state);
141 }
142 
143 #ifndef get_cabac_bypass
145  int range;
146  c->low += c->low;
147 
148  if(!(c->low & CABAC_MASK))
149  refill(c);
150 
151  range= c->range<<(CABAC_BITS+1);
152  if(c->low < range){
153  return 0;
154  }else{
155  c->low -= range;
156  return 1;
157  }
158 }
159 #endif
160 
161 #ifndef get_cabac_bypass_sign
163  int range, mask;
164  c->low += c->low;
165 
166  if(!(c->low & CABAC_MASK))
167  refill(c);
168 
169  range= c->range<<(CABAC_BITS+1);
170  c->low -= range;
171  mask= c->low >> 31;
172  range &= mask;
173  c->low += range;
174  return (val^mask)-mask;
175 }
176 #endif
177 
178 /**
179  * @return the number of bytes read or 0 if no end
180  */
181 #ifndef get_cabac_terminate
183  c->range -= 2;
184  if(c->low < c->range<<(CABAC_BITS+1)){
186  return 0;
187  }else{
188  return c->bytestream - c->bytestream_start;
189  }
190 }
191 #endif
192 
193 /**
194  * Skip @p n bytes and reset the decoder.
195  * @return the address of the first skipped byte or NULL if there's less than @p n bytes left
196  */
197 #ifndef skip_bytes
198 static av_unused const uint8_t* skip_bytes(CABACContext *c, int n) {
199  const uint8_t *ptr = c->bytestream;
200 
201  if (c->low & 0x1)
202  ptr--;
203 #if CABAC_BITS == 16
204  if (c->low & 0x1FF)
205  ptr--;
206 #endif
207  if ((int) (c->bytestream_end - ptr) < n)
208  return NULL;
209  if (ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n) < 0)
210  return NULL;
211 
212  return ptr;
213 }
214 #endif
215 
216 #endif /* AVCODEC_CABAC_FUNCTIONS_H */
cabac.h
ff_ctz
#define ff_ctz
Definition: intmath.h:106
renorm_cabac_decoder_once
static void renorm_cabac_decoder_once(CABACContext *c)
Definition: cabac_functions.h:74
av_unused
#define av_unused
Definition: attributes.h:131
cabac.h
get_cabac_inline
static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t *const state)
Definition: cabac_functions.h:111
bit
#define bit(string, value)
Definition: cbs_mpeg2.c:58
get_cabac
static int av_unused get_cabac(CABACContext *c, uint8_t *const state)
Definition: cabac_functions.h:139
ff_h264_last_coeff_flag_offset_8x8
static const uint8_t *const ff_h264_last_coeff_flag_offset_8x8
Definition: cabac_functions.h:56
val
static double val(void *priv, double ch)
Definition: aeval.c:75
ff_h264_cabac_tables
const uint8_t ff_h264_cabac_tables[512+4 *2 *64+4 *64+63]
av_noinline
#define av_noinline
Definition: attributes.h:72
CABAC_MASK
#define CABAC_MASK
Definition: cabac.h:39
ff_h264_norm_shift
static const uint8_t *const ff_h264_norm_shift
Definition: cabac_functions.h:53
mask
static const uint16_t mask[17]
Definition: lzw.c:38
s
#define s(width, name)
Definition: cbs_vp9.c:257
cabac.h
refill2
static void refill2(CABACContext *c)
Definition: cabac_functions.h:84
NULL
#define NULL
Definition: coverity.c:32
state
static struct @317 state
ff_h264_mlps_state
static const uint8_t *const ff_h264_mlps_state
Definition: cabac_functions.h:55
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
get_cabac_noinline
static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t *const state)
Definition: cabac_functions.h:135
H264_LPS_RANGE_OFFSET
#define H264_LPS_RANGE_OFFSET
Definition: cabac.h:34
get_cabac_bypass_sign
static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val)
Definition: cabac_functions.h:162
get_cabac_terminate
static int av_unused get_cabac_terminate(CABACContext *c)
Definition: cabac_functions.h:182
ff_h264_lps_range
static const uint8_t *const ff_h264_lps_range
Definition: cabac_functions.h:54
ff_init_cabac_decoder
int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size)
Definition: cabac.c:165
i
int i
Definition: input.c:406
get_cabac_bypass
static int av_unused get_cabac_bypass(CABACContext *c)
Definition: cabac_functions.h:144
av_always_inline
#define av_always_inline
Definition: attributes.h:49
cabac.h
H264_NORM_SHIFT_OFFSET
#define H264_NORM_SHIFT_OFFSET
Definition: cabac.h:33
cabac.h
H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET
#define H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET
Definition: cabac.h:36
refill
static void refill(CABACContext *c)
Definition: cabac_functions.h:59
shift
static int shift(int a, int b)
Definition: sonic.c:83
skip_bytes
static const av_unused uint8_t * skip_bytes(CABACContext *c, int n)
Skip n bytes and reset the decoder.
Definition: cabac_functions.h:198
CABAC_BITS
#define CABAC_BITS
Definition: cabac.h:38
H264_MLPS_STATE_OFFSET
#define H264_MLPS_STATE_OFFSET
Definition: cabac.h:35
CABACContext
Definition: cabac.h:41