modules/packetizer/hxxx_nal.h

   1 /*****************************************************************************
   2  * hxxx_nal.h: Common helpers for AVC/HEVC NALU
   3  *****************************************************************************
   4  * Copyright (C) 2014-2015 VLC authors and VideoLAN
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20 #ifndef HXXX_NAL_H
  21 #define HXXX_NAL_H
  22
  23 #include <vlc_common.h>
  24 #include <vlc_es.h>
  25 #include "startcode_helper.h"
  26
  27 static const uint8_t  annexb_startcode4[] = { 0x00, 0x00, 0x00, 0x01 };
  28 #define annexb_startcode3 (&annexb_startcode4[1])
  29
  30 /* strips any AnnexB startcode [0] 0 0 1 */
  31 static inline bool hxxx_strip_AnnexB_startcode( const uint8_t **pp_data, size_t *pi_data )
  32 {
  33     unsigned bitflow = 0;
  34     const uint8_t *p_data = *pp_data;
  35     size_t i_data = *pi_data;
  36
  37     while( i_data && p_data[0] <= 1 )
  38     {
  39         bitflow = (bitflow << 1) | (!p_data[0]);
  40         p_data++;
  41         i_data--;
  42         if( !(bitflow & 0x01) )
  43         {
  44             if( (bitflow & 0x06) == 0x06 ) /* there was at least 2 leading zeros */
  45             {
  46                 *pi_data = i_data;
  47                 *pp_data = p_data;
  48                 return true;
  49             }
  50             return false;
  51         }
  52     }
  53     return false;
  54 }
  55
  56 /* Declarations */
  57
  58 typedef struct
  59 {
  60     const uint8_t *p_head;
  61     const uint8_t *p_tail;
  62     uint8_t i_nal_length_size;
  63 } hxxx_iterator_ctx_t;
  64
  65 static inline void hxxx_iterator_init( hxxx_iterator_ctx_t *p_ctx, const uint8_t *p_data, size_t i_data,
  66                                        uint8_t i_nal_length_size )
  67 {
  68     p_ctx->p_head = p_data;
  69     p_ctx->p_tail = p_data + i_data;
  70     if( vlc_popcount(i_nal_length_size) == 1 && i_nal_length_size <= 4 )
  71         p_ctx->i_nal_length_size = i_nal_length_size;
  72     else
  73         p_ctx->i_nal_length_size = 0;
  74 }
  75
  76 static inline bool hxxx_iterate_next( hxxx_iterator_ctx_t *p_ctx, const uint8_t **pp_start, size_t *pi_size )
  77 {
  78     if( p_ctx->i_nal_length_size == 0 )
  79         return false;
  80
  81     if( p_ctx->p_tail - p_ctx->p_head < p_ctx->i_nal_length_size )
  82         return false;
  83
  84     uint32_t i_nal_size = 0;
  85     for( uint8_t i=0; i < p_ctx->i_nal_length_size ; i++ )
  86         i_nal_size = (i_nal_size << 8) | *p_ctx->p_head++;
  87
  88     if( i_nal_size > p_ctx->p_tail - p_ctx->p_head )
  89         return false;
  90
  91     *pp_start = p_ctx->p_head;
  92     *pi_size = i_nal_size;
  93     p_ctx->p_head += i_nal_size;
  94
  95     return true;
  96 }
  97
  98 static inline bool hxxx_annexb_iterate_next( hxxx_iterator_ctx_t *p_ctx, const uint8_t **pp_start, size_t *pi_size )
  99 {
 100     if( !p_ctx->p_head )
 101         return false;
 102
 103     p_ctx->p_head = startcode_FindAnnexB( p_ctx->p_head, p_ctx->p_tail );
 104     if( !p_ctx->p_head )
 105         return false;
 106
 107     const uint8_t *p_end = startcode_FindAnnexB( p_ctx->p_head + 3, p_ctx->p_tail );
 108     if( !p_end )
 109         p_end = p_ctx->p_tail;
 110
 111     /* fix 3 to 4 startcode offset and strip any trailing zeros */
 112     while( p_end > p_ctx->p_head && p_end[-1] == 0 )
 113         p_end--;
 114
 115     *pp_start = p_ctx->p_head;
 116     *pi_size = p_end - p_ctx->p_head;
 117     p_ctx->p_head = p_end;
 118
 119     return hxxx_strip_AnnexB_startcode( pp_start, pi_size );
 120 }
 121
 122 /* Takes any AnnexB NAL buffer and converts it to prefixed size (AVC/HEVC) */
 123 block_t *hxxx_AnnexB_to_xVC( block_t *p_block, uint8_t i_nal_length_size );
 124
 125 #endif // HXXX_NAL_H