• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • Examples
  • File List
  • Globals

libavcodec/cabac_functions.h

Go to the documentation of this file.
00001 /*
00002  * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
00003  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
00004  *
00005  * This file is part of Libav.
00006  *
00007  * Libav is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * Libav is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with Libav; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00027 #ifndef AVCODEC_CABAC_FUNCTIONS_H
00028 #define AVCODEC_CABAC_FUNCTIONS_H
00029 
00030 #include <stdint.h>
00031 
00032 #include "cabac.h"
00033 #include "config.h"
00034 
00035 #if ARCH_X86
00036 #   include "x86/cabac.h"
00037 #endif
00038 
00039 extern const uint8_t ff_h264_norm_shift[512];
00040 extern uint8_t ff_h264_mlps_state[4*64];
00041 extern uint8_t ff_h264_lps_range[4*2*64];  
00042 
00043 static void refill(CABACContext *c){
00044 #if CABAC_BITS == 16
00045         c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
00046 #else
00047         c->low+= c->bytestream[0]<<1;
00048 #endif
00049     c->low -= CABAC_MASK;
00050     c->bytestream+= CABAC_BITS/8;
00051 }
00052 
00053 static inline void renorm_cabac_decoder_once(CABACContext *c){
00054     int shift= (uint32_t)(c->range - 0x100)>>31;
00055     c->range<<= shift;
00056     c->low  <<= shift;
00057     if(!(c->low & CABAC_MASK))
00058         refill(c);
00059 }
00060 
00061 #ifndef get_cabac_inline
00062 static void refill2(CABACContext *c){
00063     int i, x;
00064 
00065     x= c->low ^ (c->low-1);
00066     i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
00067 
00068     x= -CABAC_MASK;
00069 
00070 #if CABAC_BITS == 16
00071         x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
00072 #else
00073         x+= c->bytestream[0]<<1;
00074 #endif
00075 
00076     c->low += x<<i;
00077     c->bytestream+= CABAC_BITS/8;
00078 }
00079 
00080 static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
00081     int s = *state;
00082     int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
00083     int bit, lps_mask;
00084 
00085     c->range -= RangeLPS;
00086     lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
00087 
00088     c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
00089     c->range += (RangeLPS - c->range) & lps_mask;
00090 
00091     s^=lps_mask;
00092     *state= (ff_h264_mlps_state+128)[s];
00093     bit= s&1;
00094 
00095     lps_mask= ff_h264_norm_shift[c->range];
00096     c->range<<= lps_mask;
00097     c->low  <<= lps_mask;
00098     if(!(c->low & CABAC_MASK))
00099         refill2(c);
00100     return bit;
00101 }
00102 #endif
00103 
00104 static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
00105     return get_cabac_inline(c,state);
00106 }
00107 
00108 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
00109     return get_cabac_inline(c,state);
00110 }
00111 
00112 static int av_unused get_cabac_bypass(CABACContext *c){
00113     int range;
00114     c->low += c->low;
00115 
00116     if(!(c->low & CABAC_MASK))
00117         refill(c);
00118 
00119     range= c->range<<(CABAC_BITS+1);
00120     if(c->low < range){
00121         return 0;
00122     }else{
00123         c->low -= range;
00124         return 1;
00125     }
00126 }
00127 
00128 
00129 #ifndef get_cabac_bypass_sign
00130 static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
00131     int range, mask;
00132     c->low += c->low;
00133 
00134     if(!(c->low & CABAC_MASK))
00135         refill(c);
00136 
00137     range= c->range<<(CABAC_BITS+1);
00138     c->low -= range;
00139     mask= c->low >> 31;
00140     range &= mask;
00141     c->low += range;
00142     return (val^mask)-mask;
00143 }
00144 #endif
00145 
00150 static int av_unused get_cabac_terminate(CABACContext *c){
00151     c->range -= 2;
00152     if(c->low < c->range<<(CABAC_BITS+1)){
00153         renorm_cabac_decoder_once(c);
00154         return 0;
00155     }else{
00156         return c->bytestream - c->bytestream_start;
00157     }
00158 }
00159 
00160 #endif /* AVCODEC_CABAC_FUNCTIONS_H */
Generated on Sun Apr 22 2012 21:53:59 for Libav by doxygen 1.7.1