2 * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
3 * Copyright (c) 2003 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
24 * Context Adaptive Binary Arithmetic Coder.
27 #ifndef AVCODEC_CABAC_H
28 #define AVCODEC_CABAC_H
38 #define CABAC_MASK ((1<<CABAC_BITS)-1)
40 typedef struct CABACContext{
43 int outstanding_count;
44 const uint8_t *bytestream_start;
45 const uint8_t *bytestream;
46 const uint8_t *bytestream_end;
50 extern uint8_t ff_h264_mlps_state[4*64];
51 extern uint8_t ff_h264_lps_range[4*2*64]; ///< rangeTabLPS
52 extern uint8_t ff_h264_mps_state[2*64]; ///< transIdxMPS
53 extern uint8_t ff_h264_lps_state[2*64]; ///< transIdxLPS
54 extern const uint8_t ff_h264_norm_shift[512];
57 # include "x86/cabac.h"
60 void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
61 void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);
62 void ff_init_cabac_states(CABACContext *c);
65 static inline void put_cabac_bit(CABACContext *c, int b){
66 put_bits(&c->pb, 1, b);
67 for(;c->outstanding_count; c->outstanding_count--){
68 put_bits(&c->pb, 1, 1-b);
72 static inline void renorm_cabac_encoder(CABACContext *c){
73 while(c->range < 0x100){
77 }else if(c->low<0x200){
78 c->outstanding_count++;
90 static void refill(CABACContext *c){
92 c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
94 c->low+= c->bytestream[0]<<1;
97 c->bytestream+= CABAC_BITS/8;
100 static inline void renorm_cabac_decoder_once(CABACContext *c){
101 int shift= (uint32_t)(c->range - 0x100)>>31;
104 if(!(c->low & CABAC_MASK))
108 #ifndef get_cabac_inline
109 static void refill2(CABACContext *c){
112 x= c->low ^ (c->low-1);
113 i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
118 x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
120 x+= c->bytestream[0]<<1;
124 c->bytestream+= CABAC_BITS/8;
127 static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
129 int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
132 c->range -= RangeLPS;
133 lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
135 c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
136 c->range += (RangeLPS - c->range) & lps_mask;
139 *state= (ff_h264_mlps_state+128)[s];
142 lps_mask= ff_h264_norm_shift[c->range];
143 c->range<<= lps_mask;
145 if(!(c->low & CABAC_MASK))
151 static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
152 return get_cabac_inline(c,state);
155 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
156 return get_cabac_inline(c,state);
159 static int av_unused get_cabac_bypass(CABACContext *c){
163 if(!(c->low & CABAC_MASK))
166 range= c->range<<(CABAC_BITS+1);
176 #ifndef get_cabac_bypass_sign
177 static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
181 if(!(c->low & CABAC_MASK))
184 range= c->range<<(CABAC_BITS+1);
189 return (val^mask)-mask;
195 * @return the number of bytes read or 0 if no end
197 static int av_unused get_cabac_terminate(CABACContext *c){
199 if(c->low < c->range<<(CABAC_BITS+1)){
200 renorm_cabac_decoder_once(c);
203 return c->bytestream - c->bytestream_start;
207 #endif /* AVCODEC_CABAC_H */