libavcodec/cabac_functions.h

   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 Libav.
   6  *
   7  * Libav 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  * Libav 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 Libav; 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 #if ARCH_X86
  36 #   include "x86/cabac.h"
  37 #endif
  38
  39 extern uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63];
  40 static uint8_t * const ff_h264_norm_shift = ff_h264_cabac_tables + H264_NORM_SHIFT_OFFSET;
  41 static uint8_t * const ff_h264_lps_range = ff_h264_cabac_tables + H264_LPS_RANGE_OFFSET;
  42 static uint8_t * const ff_h264_mlps_state = ff_h264_cabac_tables + H264_MLPS_STATE_OFFSET;
  43 static uint8_t * const ff_h264_last_coeff_flag_offset_8x8 = ff_h264_cabac_tables + H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET;
  44
  45 static void refill(CABACContext *c){
  46 #if CABAC_BITS == 16
  47         c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
  48 #else
  49         c->low+= c->bytestream[0]<<1;
  50 #endif
  51     c->low -= CABAC_MASK;
  52     if (c->bytestream < c->bytestream_end)
  53         c->bytestream += CABAC_BITS / 8;
  54 }
  55
  56 static inline void renorm_cabac_decoder_once(CABACContext *c){
  57     int shift= (uint32_t)(c->range - 0x100)>>31;
  58     c->range<<= shift;
  59     c->low  <<= shift;
  60     if(!(c->low & CABAC_MASK))
  61         refill(c);
  62 }
  63
  64 #ifndef get_cabac_inline
  65 static void refill2(CABACContext *c){
  66     int i, x;
  67
  68     x= c->low ^ (c->low-1);
  69     i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
  70
  71     x= -CABAC_MASK;
  72
  73 #if CABAC_BITS == 16
  74         x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
  75 #else
  76         x+= c->bytestream[0]<<1;
  77 #endif
  78
  79     c->low += x<<i;
  80     if (c->bytestream < c->bytestream_end)
  81         c->bytestream += CABAC_BITS/8;
  82 }
  83
  84 static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
  85     int s = *state;
  86     int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
  87     int bit, lps_mask;
  88
  89     c->range -= RangeLPS;
  90     lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
  91
  92     c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
  93     c->range += (RangeLPS - c->range) & lps_mask;
  94
  95     s^=lps_mask;
  96     *state= (ff_h264_mlps_state+128)[s];
  97     bit= s&1;
  98
  99     lps_mask= ff_h264_norm_shift[c->range];
 100     c->range<<= lps_mask;
 101     c->low  <<= lps_mask;
 102     if(!(c->low & CABAC_MASK))
 103         refill2(c);
 104     return bit;
 105 }
 106 #endif
 107
 108 static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
 109     return get_cabac_inline(c,state);
 110 }
 111
 112 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
 113     return get_cabac_inline(c,state);
 114 }
 115
 116 static int av_unused get_cabac_bypass(CABACContext *c){
 117     int range;
 118     c->low += c->low;
 119
 120     if(!(c->low & CABAC_MASK))
 121         refill(c);
 122
 123     range= c->range<<(CABAC_BITS+1);
 124     if(c->low < range){
 125         return 0;
 126     }else{
 127         c->low -= range;
 128         return 1;
 129     }
 130 }
 131
 132
 133 #ifndef get_cabac_bypass_sign
 134 static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
 135     int range, mask;
 136     c->low += c->low;
 137
 138     if(!(c->low & CABAC_MASK))
 139         refill(c);
 140
 141     range= c->range<<(CABAC_BITS+1);
 142     c->low -= range;
 143     mask= c->low >> 31;
 144     range &= mask;
 145     c->low += range;
 146     return (val^mask)-mask;
 147 }
 148 #endif
 149
 150 /**
 151  *
 152  * @return the number of bytes read or 0 if no end
 153  */
 154 static int av_unused get_cabac_terminate(CABACContext *c){
 155     c->range -= 2;
 156     if(c->low < c->range<<(CABAC_BITS+1)){
 157         renorm_cabac_decoder_once(c);
 158         return 0;
 159     }else{
 160         return c->bytestream - c->bytestream_start;
 161     }
 162 }
 163
 164 #endif /* AVCODEC_CABAC_FUNCTIONS_H */