cabac_functions.h 4.88 KB
Newer Older
1 2 3 4
/*
 * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
 *
5
 * This file is part of FFmpeg.
6
 *
7
 * FFmpeg is free software; you can redistribute it and/or
8 9 10 11
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * 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 14 15 16 17
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * 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 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * Context Adaptive Binary Arithmetic Coder inline functions
 */

#ifndef AVCODEC_CABAC_FUNCTIONS_H
#define AVCODEC_CABAC_FUNCTIONS_H

#include <stdint.h>

#include "cabac.h"
#include "config.h"

#if ARCH_X86
#   include "x86/cabac.h"
#endif

39 40 41 42 43
extern uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63];
static uint8_t * const ff_h264_norm_shift = ff_h264_cabac_tables + H264_NORM_SHIFT_OFFSET;
static uint8_t * const ff_h264_lps_range = ff_h264_cabac_tables + H264_LPS_RANGE_OFFSET;
static uint8_t * const ff_h264_mlps_state = ff_h264_cabac_tables + H264_MLPS_STATE_OFFSET;
static uint8_t * const ff_h264_last_coeff_flag_offset_8x8 = ff_h264_cabac_tables + H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET;
44 45 46 47 48 49 50 51

static void refill(CABACContext *c){
#if CABAC_BITS == 16
        c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
#else
        c->low+= c->bytestream[0]<<1;
#endif
    c->low -= CABAC_MASK;
52 53 54 55
#if !UNCHECKED_BITSTREAM_READER
    if (c->bytestream < c->bytestream_end)
#endif
        c->bytestream += CABAC_BITS / 8;
56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81
}

static inline void renorm_cabac_decoder_once(CABACContext *c){
    int shift= (uint32_t)(c->range - 0x100)>>31;
    c->range<<= shift;
    c->low  <<= shift;
    if(!(c->low & CABAC_MASK))
        refill(c);
}

#ifndef get_cabac_inline
static void refill2(CABACContext *c){
    int i, x;

    x= c->low ^ (c->low-1);
    i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];

    x= -CABAC_MASK;

#if CABAC_BITS == 16
        x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
#else
        x+= c->bytestream[0]<<1;
#endif

    c->low += x<<i;
82 83 84 85
#if !UNCHECKED_BITSTREAM_READER
    if (c->bytestream < c->bytestream_end)
#endif
        c->bytestream += CABAC_BITS/8;
86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119
}

static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
    int s = *state;
    int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
    int bit, lps_mask;

    c->range -= RangeLPS;
    lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;

    c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
    c->range += (RangeLPS - c->range) & lps_mask;

    s^=lps_mask;
    *state= (ff_h264_mlps_state+128)[s];
    bit= s&1;

    lps_mask= ff_h264_norm_shift[c->range];
    c->range<<= lps_mask;
    c->low  <<= lps_mask;
    if(!(c->low & CABAC_MASK))
        refill2(c);
    return bit;
}
#endif

static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
    return get_cabac_inline(c,state);
}

static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
    return get_cabac_inline(c,state);
}

120
#ifndef get_cabac_bypass
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135
static int av_unused get_cabac_bypass(CABACContext *c){
    int range;
    c->low += c->low;

    if(!(c->low & CABAC_MASK))
        refill(c);

    range= c->range<<(CABAC_BITS+1);
    if(c->low < range){
        return 0;
    }else{
        c->low -= range;
        return 1;
    }
}
136
#endif
137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168

#ifndef get_cabac_bypass_sign
static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
    int range, mask;
    c->low += c->low;

    if(!(c->low & CABAC_MASK))
        refill(c);

    range= c->range<<(CABAC_BITS+1);
    c->low -= range;
    mask= c->low >> 31;
    range &= mask;
    c->low += range;
    return (val^mask)-mask;
}
#endif

/**
 *
 * @return the number of bytes read or 0 if no end
 */
static int av_unused get_cabac_terminate(CABACContext *c){
    c->range -= 2;
    if(c->low < c->range<<(CABAC_BITS+1)){
        renorm_cabac_decoder_once(c);
        return 0;
    }else{
        return c->bytestream - c->bytestream_start;
    }
}

169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188
/**
 * Skip @p n bytes and reset the decoder.
 * @return the address of the first skipped byte or NULL if there's less than @p n bytes left
 */
static av_unused const uint8_t* skip_bytes(CABACContext *c, int n) {
    const uint8_t *ptr = c->bytestream;

    if (c->low & 0x1)
        ptr--;
#if CABAC_BITS == 16
    if (c->low & 0x1FF)
        ptr--;
#endif
    if ((int) (c->bytestream_end - ptr) < n)
        return NULL;
    ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n);

    return ptr;
}

189
#endif /* AVCODEC_CABAC_FUNCTIONS_H */