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
52 static const uint8_t * const ff_h264_norm_shift = ff_h264_cabac_tables + H264_NORM_SHIFT_OFFSET;
53 static const uint8_t * const ff_h264_lps_range = ff_h264_cabac_tables + H264_LPS_RANGE_OFFSET;
54 static const uint8_t * const ff_h264_mlps_state = ff_h264_cabac_tables + H264_MLPS_STATE_OFFSET;
55 static const uint8_t * const ff_h264_last_coeff_flag_offset_8x8 = ff_h264_cabac_tables + H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET;
56
57 #if !defined(get_cabac_bypass) || !defined(get_cabac_terminate)
refill(CABACContext * c)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
renorm_cabac_decoder_once(CABACContext * c)73 static inline void renorm_cabac_decoder_once(CABACContext *c){
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
refill2(CABACContext * c)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
get_cabac_inline(CABACContext * c,uint8_t * const state)110 static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
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
get_cabac_noinline(CABACContext * c,uint8_t * const state)134 static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
135 return get_cabac_inline(c,state);
136 }
137
get_cabac(CABACContext * c,uint8_t * const state)138 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
139 return get_cabac_inline(c,state);
140 }
141
142 #ifndef get_cabac_bypass
get_cabac_bypass(CABACContext * c)143 static int av_unused get_cabac_bypass(CABACContext *c){
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
get_cabac_bypass_sign(CABACContext * c,int val)161 static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
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
get_cabac_terminate(CABACContext * c)181 static int av_unused get_cabac_terminate(CABACContext *c){
182 c->range -= 2;
183 if(c->low < c->range<<(CABAC_BITS+1)){
184 renorm_cabac_decoder_once(c);
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
skip_bytes(CABACContext * c,int n)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 */
216