H.264/AVC Reference Software Encoder: nal.c Source File

00001 
00002 /*!
00003  **************************************************************************************
00004  * \file
00005  *    nal.c
00006  * \brief
00007  *    Handles the operations on converting String of Data Bits (SODB)
00008  *    to Raw Byte Sequence Payload (RBSP), and then
00009  *    onto Encapsulate Byte Sequence Payload (EBSP).
00010  *  \date 14 June 2002
00011  * \author
00012  *    Main contributors (see contributors.h for copyright, address and affiliation details)
00013  *      - Shankar Regunathan                  <shanre@microsoft.de>
00014  *      - Stephan Wenger                      <stewe@cs.tu-berlin.de>
00015  ***************************************************************************************
00016  */
00017 
00018 #include "contributors.h"
00019 #include "global.h"
00020 #include "enc_statistics.h"
00021 #include "biariencode.h"
00022 
00023 static const int MbWidthC  [4]= { 0, 8, 8,  16};
00024 static const int MbHeightC [4]= { 0, 8, 16, 16};
00025 
00026  /*!
00027  ************************************************************************
00028  * \brief
00029  *    Converts String Of Data Bits (SODB) to Raw Byte Sequence
00030  *    Packet (RBSP)
00031  * \param currStream
00032  *        Bitstream which contains data bits.
00033  * \return None
00034  * \note currStream is byte-aligned at the end of this function
00035  *
00036  ************************************************************************
00037 */
00038 
00039 void SODBtoRBSP(Bitstream *currStream)
00040 {
00041   currStream->byte_buf <<= 1;
00042   currStream->byte_buf |= 1;
00043   currStream->bits_to_go--;
00044   currStream->byte_buf <<= currStream->bits_to_go;
00045   currStream->streamBuffer[currStream->byte_pos++] = currStream->byte_buf;
00046   currStream->bits_to_go = 8;
00047   currStream->byte_buf = 0;
00048 }
00049 
00050 
00051 /*!
00052 ************************************************************************
00053 *  \brief
00054 *     This function add emulation_prevention_three_byte for all occurrences
00055 *     of the following byte sequences in the stream
00056 *       0x000000  -> 0x00000300
00057 *       0x000001  -> 0x00000301
00058 *       0x000002  -> 0x00000302
00059 *       0x000003  -> 0x00000303
00060 *
00061 *  \param NaluBuffer
00062 *            pointer to target buffer
00063 *  \param rbsp
00064 *            pointer to source buffer
00065 *  \param rbsp_size
00066 *           Size of source
00067 *  \return
00068 *           Size target buffer after emulation prevention.
00069 *
00070 ************************************************************************
00071 */
00072 
00073 int RBSPtoEBSP(byte *NaluBuffer, unsigned char *rbsp, int rbsp_size)
00074 {
00075   int j     = 0;
00076   int count = 0;
00077   int i;
00078 
00079   for(i = 0; i < rbsp_size; i++)
00080   {
00081     if(count == ZEROBYTES_SHORTSTARTCODE && !(rbsp[i] & 0xFC))
00082     {
00083       NaluBuffer[j] = 0x03;
00084       j++;
00085       count = 0;
00086     }
00087     NaluBuffer[j] = rbsp[i];
00088     if(rbsp[i] == 0x00)
00089       count++;
00090     else
00091       count = 0;
00092     j++;
00093   }
00094   return j;
00095 }
00096 
00097 /*!
00098 ************************************************************************
00099 *  \brief
00100 *     This function adds cabac_zero_word syntax elements at the end of the
00101 *     NAL unit to
00102 *
00103 *  \param p_Img
00104 *            ImageParameters structure
00105 *  \param nalu
00106 *            target NAL unit
00107 *  \param cur_stats
00108 *            currently used statistics parameters
00109 *  \return
00110 *           number of added bytes
00111 *
00112 ************************************************************************
00113 */
00114 int addCabacZeroWords(ImageParameters *p_Img, NALU_t *nalu, StatParameters *cur_stats)
00115 {
00116   seq_parameter_set_rbsp_t *active_sps = p_Img->active_sps;
00117 
00118   int stuffing_bytes = 0;
00119   int i = 0;
00120 
00121   byte *buf = &nalu->buf[nalu->len];
00122 
00123   int RawMbBits = 256 * p_Img->bitdepth_luma + 2 * MbWidthC[active_sps->chroma_format_idc] * MbHeightC[active_sps->chroma_format_idc] * p_Img->bitdepth_chroma;
00124   int min_num_bytes = ((96 * get_pic_bin_count(p_Img)) - (RawMbBits * (int)p_Img->PicSizeInMbs *3) + 1023) / 1024;
00125 
00126   if (min_num_bytes > p_Img->bytes_in_picture)
00127   {
00128     stuffing_bytes = min_num_bytes - p_Img->bytes_in_picture;
00129     printf ("Inserting %d/%d cabac_zero_word syntax elements/bytes (Clause 7.4.2.10)\n", ((stuffing_bytes + 2)/3), stuffing_bytes);  
00130 
00131     for (i = 0; i < stuffing_bytes; i+=3 )
00132     {
00133       *buf++ = 0x00; // CABAC zero word
00134       *buf++ = 0x00;
00135       *buf++ = 0x03;
00136     }
00137     cur_stats->bit_use_stuffingBits[p_Img->type] += (i<<3);
00138     nalu->len += i;
00139   }  
00140 
00141   return i;
00142 }
00143