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 bits_left = vl_vlc_bits_left(nal);
  54
  55    /* copy the position */
  56    rbsp->nal = *nal;
  57
  58    rbsp->escaped = 0;
  59
  60    /* search for the end of the NAL unit */
  61    while (vl_vlc_search_byte(nal, num_bits, 0x00)) {
  62       if (vl_vlc_peekbits(nal, 24) == 0x000001 ||
  63           vl_vlc_peekbits(nal, 32) == 0x00000001) {
  64          vl_vlc_limit(&rbsp->nal, bits_left - vl_vlc_bits_left(nal));
  65          return;
  66       }
  67       vl_vlc_eatbits(nal, 8);
  68    }
  69 }
  70
  71 /**
  72  * Make at least 16 more bits available
  73  */
  74 static INLINE void vl_rbsp_fillbits(struct vl_rbsp *rbsp)
  75 {
  76    unsigned valid = vl_vlc_valid_bits(&rbsp->nal);
  77    unsigned i, bits;
  78
  79    /* abort if we still have enough bits */
  80    if (valid >= 32)
  81       return;
  82
  83    vl_vlc_fillbits(&rbsp->nal);
  84
  85    /* abort if we have less than 24 bits left in this nal */
  86    if (vl_vlc_bits_left(&rbsp->nal) < 24)
  87       return;
  88
  89    /* check that we have enough bits left from the last fillbits */
  90    assert(valid >= rbsp->escaped);
  91
  92    /* handle the already escaped bits */
  93    valid -= rbsp->escaped;
  94
  95    /* search for the emulation prevention three byte */
  96    rbsp->escaped = 16;
  97    bits = vl_vlc_valid_bits(&rbsp->nal);
  98    for (i = valid + 24; i <= bits; i += 8) {
  99       if ((vl_vlc_peekbits(&rbsp->nal, i) & 0xffffff) == 0x3) {
 100          vl_vlc_removebits(&rbsp->nal, i - 8, 8);
 101          rbsp->escaped = bits - i;
 102          bits -= 8;
 103          i += 8;
 104       }
 105    }
 106 }
 107
 108 /**
 109  * Return an unsigned integer from the first n bits
 110  */
 111 static INLINE unsigned vl_rbsp_u(struct vl_rbsp *rbsp, unsigned n)
 112 {
 113    if (n == 0)
 114       return 0;
 115
 116    vl_rbsp_fillbits(rbsp);
 117    return vl_vlc_get_uimsbf(&rbsp->nal, n);
 118 }
 119
 120 /**
 121  * Return an unsigned exponential Golomb encoded integer
 122  */
 123 static INLINE unsigned vl_rbsp_ue(struct vl_rbsp *rbsp)
 124 {
 125    unsigned bits = 0;
 126
 127    vl_rbsp_fillbits(rbsp);
 128    while (!vl_vlc_get_uimsbf(&rbsp->nal, 1))
 129       ++bits;
 130
 131    return (1 << bits) - 1 + vl_rbsp_u(rbsp, bits);
 132 }
 133
 134 /**
 135  * Return an signed exponential Golomb encoded integer
 136  */
 137 static INLINE signed vl_rbsp_se(struct vl_rbsp *rbsp)
 138 {
 139    signed codeNum = vl_rbsp_ue(rbsp);
 140    if (codeNum & 1)
 141       return (codeNum + 1) >> 1;
 142    else
 143       return -(codeNum >> 1);
 144 }
 145
 146 /**
 147  * Are more data available in the RBSP ?
 148  */
 149 static INLINE bool vl_rbsp_more_data(struct vl_rbsp *rbsp)
 150 {
 151    unsigned bits, value;
 152
 153    if (vl_vlc_bits_left(&rbsp->nal) > 8)
 154       return TRUE;
 155
 156    bits = vl_vlc_valid_bits(&rbsp->nal);
 157    value = vl_vlc_peekbits(&rbsp->nal, bits);
 158    if (value == 0 || value == (1 << (bits - 1)))
 159       return FALSE;
 160
 161    return TRUE;
 162 }
 163
 164 #endif /* vl_rbsp_h */