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      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 Knig <christian.koenig (at) 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    /* search for the end of the NAL unit */
     60    while (vl_vlc_search_byte(nal, num_bits, 0x00)) {
     61       if (vl_vlc_peekbits(nal, 24) == 0x000001 ||
     62           vl_vlc_peekbits(nal, 32) == 0x00000001) {
     63          vl_vlc_limit(&rbsp->nal, bits_left - vl_vlc_bits_left(nal));
     64          break;
     65       }
     66       vl_vlc_eatbits(nal, 8);
     67    }
     68 
     69    valid = vl_vlc_valid_bits(&rbsp->nal);
     70    /* search for the emulation prevention three byte */
     71    for (i = 24; i <= valid; i += 8) {
     72       if ((vl_vlc_peekbits(&rbsp->nal, i) & 0xffffff) == 0x3) {
     73          vl_vlc_removebits(&rbsp->nal, i - 8, 8);
     74          i += 8;
     75       }
     76    }
     77 
     78    valid = vl_vlc_valid_bits(&rbsp->nal);
     79 
     80    rbsp->escaped = (valid >= 16) ? 16 : ((valid >= 8) ? 8 : 0);
     81 }
     82 
     83 /**
     84  * Make at least 16 more bits available
     85  */
     86 static inline void vl_rbsp_fillbits(struct vl_rbsp *rbsp)
     87 {
     88    unsigned valid = vl_vlc_valid_bits(&rbsp->nal);
     89    unsigned i, bits;
     90 
     91    /* abort if we still have enough bits */
     92    if (valid >= 32)
     93       return;
     94 
     95    vl_vlc_fillbits(&rbsp->nal);
     96 
     97    /* abort if we have less than 24 bits left in this nal */
     98    if (vl_vlc_bits_left(&rbsp->nal) < 24)
     99       return;
    100 
    101    /* check that we have enough bits left from the last fillbits */
    102    assert(valid >= rbsp->escaped);
    103 
    104    /* handle the already escaped bits */
    105    valid -= rbsp->escaped;
    106 
    107    /* search for the emulation prevention three byte */
    108    rbsp->escaped = 16;
    109    bits = vl_vlc_valid_bits(&rbsp->nal);
    110    for (i = valid + 24; i <= bits; i += 8) {
    111       if ((vl_vlc_peekbits(&rbsp->nal, i) & 0xffffff) == 0x3) {
    112          vl_vlc_removebits(&rbsp->nal, i - 8, 8);
    113          rbsp->escaped = bits - i;
    114          bits -= 8;
    115          i += 8;
    116       }
    117    }
    118 }
    119 
    120 /**
    121  * Return an unsigned integer from the first n bits
    122  */
    123 static inline unsigned vl_rbsp_u(struct vl_rbsp *rbsp, unsigned n)
    124 {
    125    if (n == 0)
    126       return 0;
    127 
    128    vl_rbsp_fillbits(rbsp);
    129    return vl_vlc_get_uimsbf(&rbsp->nal, n);
    130 }
    131 
    132 /**
    133  * Return an unsigned exponential Golomb encoded integer
    134  */
    135 static inline unsigned vl_rbsp_ue(struct vl_rbsp *rbsp)
    136 {
    137    unsigned bits = 0;
    138 
    139    vl_rbsp_fillbits(rbsp);
    140    while (!vl_vlc_get_uimsbf(&rbsp->nal, 1))
    141       ++bits;
    142 
    143    return (1 << bits) - 1 + vl_rbsp_u(rbsp, bits);
    144 }
    145 
    146 /**
    147  * Return an signed exponential Golomb encoded integer
    148  */
    149 static inline signed vl_rbsp_se(struct vl_rbsp *rbsp)
    150 {
    151    signed codeNum = vl_rbsp_ue(rbsp);
    152    if (codeNum & 1)
    153       return (codeNum + 1) >> 1;
    154    else
    155       return -(codeNum >> 1);
    156 }
    157 
    158 /**
    159  * Are more data available in the RBSP ?
    160  */
    161 static inline bool vl_rbsp_more_data(struct vl_rbsp *rbsp)
    162 {
    163    unsigned bits, value;
    164 
    165    if (vl_vlc_bits_left(&rbsp->nal) > 8)
    166       return TRUE;
    167 
    168    bits = vl_vlc_valid_bits(&rbsp->nal);
    169    value = vl_vlc_peekbits(&rbsp->nal, bits);
    170    if (value == 0 || value == (1 << (bits - 1)))
    171       return FALSE;
    172 
    173    return TRUE;
    174 }
    175 
    176 #endif /* vl_rbsp_h */
    177