src/gallium/auxiliary/vl/vl_rbsp.h

   1 /**************************************************************************
   2  *
   3  * Copyright 2013 Advanced Micro Devices, Inc.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR
  22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27
  28 /*
  29  * Authors:
  30  *      Christian König <christian.koenig@amd.com>
  31  *
  32  */
  33
  34 /*
  35  * Functions for reading the raw byte sequence payload of H.264
  36  */
  37
  38 #ifndef vl_rbsp_h
  39 #define vl_rbsp_h
  40
  41 #include "vl/vl_vlc.h"
  42
  43 struct vl_rbsp {
  44    struct vl_vlc nal;
  45    unsigned escaped;
  46 };
  47
  48 /**
  49  * Initialize the RBSP object
  50  */
  51 static inline void vl_rbsp_init(struct vl_rbsp *rbsp, struct vl_vlc *nal, unsigned num_bits)
  52 {
  53    unsigned valid, bits_left = vl_vlc_bits_left(nal);
  54    int i;
  55
  56    /* copy the position */
  57    rbsp->nal = *nal;
  58
  59    rbsp->escaped = 16;
  60
  61    /* search for the end of the NAL unit */
  62    while (vl_vlc_search_byte(nal, num_bits, 0x00)) {
  63       if (vl_vlc_peekbits(nal, 24) == 0x000001 ||
  64           vl_vlc_peekbits(nal, 32) == 0x00000001) {
  65          vl_vlc_limit(&rbsp->nal, bits_left - vl_vlc_bits_left(nal));
  66          break;
  67       }
  68       vl_vlc_eatbits(nal, 8);
  69    }
  70
  71    valid = vl_vlc_valid_bits(&rbsp->nal);
  72    /* search for the emulation prevention three byte */
  73    for (i = 24; i <= valid; i += 8) {
  74       if ((vl_vlc_peekbits(&rbsp->nal, i) & 0xffffff) == 0x3) {
  75          vl_vlc_removebits(&rbsp->nal, i - 8, 8);
  76          i += 8;
  77       }
  78    }
  79 }
  80
  81 /**
  82  * Make at least 16 more bits available
  83  */
  84 static inline void vl_rbsp_fillbits(struct vl_rbsp *rbsp)
  85 {
  86    unsigned valid = vl_vlc_valid_bits(&rbsp->nal);
  87    unsigned i, bits;
  88
  89    /* abort if we still have enough bits */
  90    if (valid >= 32)
  91       return;
  92
  93    vl_vlc_fillbits(&rbsp->nal);
  94
  95    /* abort if we have less than 24 bits left in this nal */
  96    if (vl_vlc_bits_left(&rbsp->nal) < 24)
  97       return;
  98
  99    /* check that we have enough bits left from the last fillbits */
 100    assert(valid >= rbsp->escaped);
 101
 102    /* handle the already escaped bits */
 103    valid -= rbsp->escaped;
 104
 105    /* search for the emulation prevention three byte */
 106    rbsp->escaped = 16;
 107    bits = vl_vlc_valid_bits(&rbsp->nal);
 108    for (i = valid + 24; i <= bits; i += 8) {
 109       if ((vl_vlc_peekbits(&rbsp->nal, i) & 0xffffff) == 0x3) {
 110          vl_vlc_removebits(&rbsp->nal, i - 8, 8);
 111          rbsp->escaped = bits - i;
 112          bits -= 8;
 113          i += 8;
 114       }
 115    }
 116 }
 117
 118 /**
 119  * Return an unsigned integer from the first n bits
 120  */
 121 static inline unsigned vl_rbsp_u(struct vl_rbsp *rbsp, unsigned n)
 122 {
 123    if (n == 0)
 124       return 0;
 125
 126    vl_rbsp_fillbits(rbsp);
 127    return vl_vlc_get_uimsbf(&rbsp->nal, n);
 128 }
 129
 130 /**
 131  * Return an unsigned exponential Golomb encoded integer
 132  */
 133 static inline unsigned vl_rbsp_ue(struct vl_rbsp *rbsp)
 134 {
 135    unsigned bits = 0;
 136
 137    vl_rbsp_fillbits(rbsp);
 138    while (!vl_vlc_get_uimsbf(&rbsp->nal, 1))
 139       ++bits;
 140
 141    return (1 << bits) - 1 + vl_rbsp_u(rbsp, bits);
 142 }
 143
 144 /**
 145  * Return an signed exponential Golomb encoded integer
 146  */
 147 static inline signed vl_rbsp_se(struct vl_rbsp *rbsp)
 148 {
 149    signed codeNum = vl_rbsp_ue(rbsp);
 150    if (codeNum & 1)
 151       return (codeNum + 1) >> 1;
 152    else
 153       return -(codeNum >> 1);
 154 }
 155
 156 /**
 157  * Are more data available in the RBSP ?
 158  */
 159 static inline bool vl_rbsp_more_data(struct vl_rbsp *rbsp)
 160 {
 161    unsigned bits, value;
 162
 163    if (vl_vlc_bits_left(&rbsp->nal) > 8)
 164       return TRUE;
 165
 166    bits = vl_vlc_valid_bits(&rbsp->nal);
 167    value = vl_vlc_peekbits(&rbsp->nal, bits);
 168    if (value == 0 || value == (1 << (bits - 1)))
 169       return FALSE;
 170
 171    return TRUE;
 172 }
 173
 174 #endif /* vl_rbsp_h */