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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 <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 #if ARCH_MIPS
49 # include "mips/cabac.h"
50 #endif
51 
56 
57 #if !defined(get_cabac_bypass) || !defined(get_cabac_terminate)
58 static void refill(CABACContext *c){
59 #if CABAC_BITS == 16
60  c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
61 #else
62  c->low+= c->bytestream[0]<<1;
63 #endif
64  c->low -= CABAC_MASK;
65 #if !UNCHECKED_BITSTREAM_READER
66  if (c->bytestream < c->bytestream_end)
67 #endif
68  c->bytestream += CABAC_BITS / 8;
69 }
70 #endif
71 
72 #ifndef get_cabac_terminate
74  int shift= (uint32_t)(c->range - 0x100)>>31;
75  c->range<<= shift;
76  c->low <<= shift;
77  if(!(c->low & CABAC_MASK))
78  refill(c);
79 }
80 #endif
81 
82 #ifndef get_cabac_inline
83 static void refill2(CABACContext *c){
84  int i;
85  unsigned x;
86 #if !HAVE_FAST_CLZ
87  x= c->low ^ (c->low-1);
88  i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
89 #else
90  i = ff_ctz(c->low) - CABAC_BITS;
91 #endif
92 
93  x= -CABAC_MASK;
94 
95 #if CABAC_BITS == 16
96  x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
97 #else
98  x+= c->bytestream[0]<<1;
99 #endif
100 
101  c->low += x<<i;
102 #if !UNCHECKED_BITSTREAM_READER
103  if (c->bytestream < c->bytestream_end)
104 #endif
105  c->bytestream += CABAC_BITS/8;
106 }
107 #endif
108 
109 #ifndef get_cabac_inline
111  int s = *state;
112  int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
113  int bit, lps_mask;
114 
115  c->range -= RangeLPS;
116  lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
117 
118  c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
119  c->range += (RangeLPS - c->range) & lps_mask;
120 
121  s^=lps_mask;
122  *state= (ff_h264_mlps_state+128)[s];
123  bit= s&1;
124 
125  lps_mask= ff_h264_norm_shift[c->range];
126  c->range<<= lps_mask;
127  c->low <<= lps_mask;
128  if(!(c->low & CABAC_MASK))
129  refill2(c);
130  return bit;
131 }
132 #endif
133 
135  return get_cabac_inline(c,state);
136 }
137 
139  return get_cabac_inline(c,state);
140 }
141 
142 #ifndef get_cabac_bypass
144  int range;
145  c->low += c->low;
146 
147  if(!(c->low & CABAC_MASK))
148  refill(c);
149 
150  range= c->range<<(CABAC_BITS+1);
151  if(c->low < range){
152  return 0;
153  }else{
154  c->low -= range;
155  return 1;
156  }
157 }
158 #endif
159 
160 #ifndef get_cabac_bypass_sign
162  int range, mask;
163  c->low += c->low;
164 
165  if(!(c->low & CABAC_MASK))
166  refill(c);
167 
168  range= c->range<<(CABAC_BITS+1);
169  c->low -= range;
170  mask= c->low >> 31;
171  range &= mask;
172  c->low += range;
173  return (val^mask)-mask;
174 }
175 #endif
176 
177 /**
178  * @return the number of bytes read or 0 if no end
179  */
180 #ifndef get_cabac_terminate
182  c->range -= 2;
183  if(c->low < c->range<<(CABAC_BITS+1)){
185  return 0;
186  }else{
187  return c->bytestream - c->bytestream_start;
188  }
189 }
190 #endif
191 
192 /**
193  * Skip @p n bytes and reset the decoder.
194  * @return the address of the first skipped byte or NULL if there's less than @p n bytes left
195  */
196 #ifndef skip_bytes
197 static av_unused const uint8_t* skip_bytes(CABACContext *c, int n) {
198  const uint8_t *ptr = c->bytestream;
199 
200  if (c->low & 0x1)
201  ptr--;
202 #if CABAC_BITS == 16
203  if (c->low & 0x1FF)
204  ptr--;
205 #endif
206  if ((int) (c->bytestream_end - ptr) < n)
207  return NULL;
208  if (ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n) < 0)
209  return NULL;
210 
211  return ptr;
212 }
213 #endif
214 
215 #endif /* AVCODEC_CABAC_FUNCTIONS_H */
#define NULL
Definition: coverity.c:32
const char const char void * val
Definition: avisynth_c.h:771
#define ff_ctz
Definition: intmath.h:106
static int shift(int a, int b)
Definition: sonic.c:82
const uint8_t * bytestream_end
Definition: cabac.h:49
#define CABAC_BITS
Definition: cabac.h:40
static void renorm_cabac_decoder_once(CABACContext *c)
static int av_unused get_cabac(CABACContext *c, uint8_t *const state)
static const uint8_t *const ff_h264_last_coeff_flag_offset_8x8
static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t *const state)
const uint8_t * bytestream
Definition: cabac.h:48
uint8_t
static av_unused const uint8_t * skip_bytes(CABACContext *c, int n)
Skip n bytes and reset the decoder.
static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t *const state)
static const uint16_t mask[17]
Definition: lzw.c:38
const uint8_t * bytestream_start
Definition: cabac.h:47
#define H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET
Definition: cabac.h:38
int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size)
Definition: cabac.c:177
#define s(width, name)
Definition: cbs_vp9.c:257
int n
Definition: avisynth_c.h:684
static int av_unused get_cabac_terminate(CABACContext *c)
static void refill(CABACContext *c)
int range
Definition: cabac.h:45
#define H264_MLPS_STATE_OFFSET
Definition: cabac.h:37
static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val)
static int av_unused get_cabac_bypass(CABACContext *c)
#define H264_NORM_SHIFT_OFFSET
Definition: cabac.h:35
int low
Definition: cabac.h:44
const uint8_t ff_h264_cabac_tables[512+4 *2 *64+4 *64+63]
static double c[64]
static void refill2(CABACContext *c)
static struct @290 state
static const uint8_t *const ff_h264_lps_range
#define av_noinline
Definition: attributes.h:62
#define av_always_inline
Definition: attributes.h:39
static const uint8_t *const ff_h264_mlps_state
#define CABAC_MASK
Definition: cabac.h:41
#define av_unused
Definition: attributes.h:125
Context Adaptive Binary Arithmetic Coder.
static const uint8_t *const ff_h264_norm_shift
#define H264_LPS_RANGE_OFFSET
Definition: cabac.h:36