gethdr.cpp

mpeg2编码解码源程序代码

    ((frame_rate_extension_n+1)/(frame_rate_extension_d+1));

  /* special case for 422 profile & level must be made */
  if((profile_and_level_indication>>7) & 1)
  {  /* escape bit of profile_and_level_indication set */
  
    /* 4:2:2 Profile @ Main Level */
    if((profile_and_level_indication&15)==5)
    {
      profile = PROFILE_422;
      level   = MAIN_LEVEL;  
    }
  }
  else
  {
    profile = profile_and_level_indication >> 4;  /* Profile is upper nibble */
    level   = profile_and_level_indication & 0xF;  /* Level is lower nibble */
  }
  
 
  horizontal_size = (horizontal_size_extension<<12) | (horizontal_size&0x0fff);
  vertical_size = (vertical_size_extension<<12) | (vertical_size&0x0fff);


  /* ISO/IEC 13818-2 does not define bit_rate_value to be composed of
   * both the original bit_rate_value parsed in sequence_header() and
   * the optional bit_rate_extension in sequence_extension_header(). 
   * However, we use it for bitstream verification purposes. 
   */

  bit_rate_value += (bit_rate_extension << 18);
  bit_rate = ((double) bit_rate_value) * 400.0;
  vbv_buffer_size += (vbv_buffer_size_extension << 10);



#ifdef VERIFY
  verify_sequence_extension++;
#endif /* VERIFY */


}


/* decode sequence display extension */

static void sequence_display_extension()
{
  int pos;
  pos = ld->Bitcnt;
  video_format      = Get_Bits(3);
  color_description = Get_Bits(1);
 
  if (color_description)
  {
    color_primaries          = Get_Bits(8);
    transfer_characteristics = Get_Bits(8);
    matrix_coefficients      = Get_Bits(8);
  }

  display_horizontal_size = Get_Bits(14);
  marker_bit("sequence_display_extension");
  display_vertical_size   = Get_Bits(14);


#ifdef VERIFY
  verify_sequence_display_extension++;
#endif /* VERIFY */

}


/* decode quant matrix entension */
/* ISO/IEC 13818-2 section 6.2.3.2 */
static void quant_matrix_extension()
{
  int i;
  int pos;

  pos = ld->Bitcnt;

  if((ld->load_intra_quantizer_matrix = Get_Bits(1)))
  {
    for (i=0; i<64; i++)
    {
      ld->chroma_intra_quantizer_matrix[scan[ZIG_ZAG][i]]
      = ld->intra_quantizer_matrix[scan[ZIG_ZAG][i]]
      = Get_Bits(8);
    }
  }

  if((ld->load_non_intra_quantizer_matrix = Get_Bits(1)))
  {
    for (i=0; i<64; i++)
    {
      ld->chroma_non_intra_quantizer_matrix[scan[ZIG_ZAG][i]]
      = ld->non_intra_quantizer_matrix[scan[ZIG_ZAG][i]]
      = Get_Bits(8);
    }
  }

  if((ld->load_chroma_intra_quantizer_matrix = Get_Bits(1)))
  {
    for (i=0; i<64; i++)
      ld->chroma_intra_quantizer_matrix[scan[ZIG_ZAG][i]] = Get_Bits(8);
  }

  if((ld->load_chroma_non_intra_quantizer_matrix = Get_Bits(1)))
  {
    for (i=0; i<64; i++)
      ld->chroma_non_intra_quantizer_matrix[scan[ZIG_ZAG][i]] = Get_Bits(8);
  }



#ifdef VERIFY
  verify_quant_matrix_extension++;
#endif /* VERIFY */

}


/* decode sequence scalable extension */
/* ISO/IEC 13818-2   section 6.2.2.5 */
static void sequence_scalable_extension()
{
  int pos;

  pos = ld->Bitcnt;

  /* values (without the +1 offset) of scalable_mode are defined in 
     Table 6-10 of ISO/IEC 13818-2 */
  ld->scalable_mode = Get_Bits(2) + 1; /* add 1 to make SC_DP != SC_NONE */

  layer_id = Get_Bits(4);

  if (ld->scalable_mode==SC_SPAT)
  {
    lower_layer_prediction_horizontal_size = Get_Bits(14);
    marker_bit("sequence_scalable_extension()");
    lower_layer_prediction_vertical_size   = Get_Bits(14); 
    horizontal_subsampling_factor_m        = Get_Bits(5);
    horizontal_subsampling_factor_n        = Get_Bits(5);
    vertical_subsampling_factor_m          = Get_Bits(5);
    vertical_subsampling_factor_n          = Get_Bits(5);
  }

  if (ld->scalable_mode==SC_TEMP)
    Error("temporal scalability not implemented\n");



#ifdef VERIFY
  verify_sequence_scalable_extension++;
#endif /* VERIFY */

}


/* decode picture display extension */
/* ISO/IEC 13818-2 section 6.2.3.3. */
static void picture_display_extension()
{
  int i;
  int number_of_frame_center_offsets;
  int pos;

  pos = ld->Bitcnt;
  /* based on ISO/IEC 13818-2 section 6.3.12 
    (November 1994) Picture display extensions */

  /* derive number_of_frame_center_offsets */
  if(progressive_sequence)
  {
    if(repeat_first_field)
    {
      if(top_field_first)
        number_of_frame_center_offsets = 3;
      else
        number_of_frame_center_offsets = 2;
    }
    else
    {
      number_of_frame_center_offsets = 1;
    }
  }
  else
  {
    if(picture_structure!=FRAME_PICTURE)
    {
      number_of_frame_center_offsets = 1;
    }
    else
    {
      if(repeat_first_field)
        number_of_frame_center_offsets = 3;
      else
        number_of_frame_center_offsets = 2;
    }
  }


  /* now parse */
  for (i=0; i<number_of_frame_center_offsets; i++)
  {
    frame_center_horizontal_offset[i] = Get_Bits(16);
    marker_bit("picture_display_extension, first marker bit");
    
    frame_center_vertical_offset[i]   = Get_Bits(16);
    marker_bit("picture_display_extension, second marker bit");
  }



#ifdef VERIFY
  verify_picture_display_extension++;
#endif /* VERIFY */

}


/* decode picture coding extension */
static void picture_coding_extension()
{
  int pos;

  pos = ld->Bitcnt;

  f_code[0][0] = Get_Bits(4);
  f_code[0][1] = Get_Bits(4);
  f_code[1][0] = Get_Bits(4);
  f_code[1][1] = Get_Bits(4);

  intra_dc_precision         = Get_Bits(2);
  picture_structure          = Get_Bits(2);
  top_field_first            = Get_Bits(1);
  frame_pred_frame_dct       = Get_Bits(1);
  concealment_motion_vectors = Get_Bits(1);
  ld->q_scale_type           = Get_Bits(1);
  intra_vlc_format           = Get_Bits(1);
  ld->alternate_scan         = Get_Bits(1);
  repeat_first_field         = Get_Bits(1);
  chroma_420_type            = Get_Bits(1);
  progressive_frame          = Get_Bits(1);
  composite_display_flag     = Get_Bits(1);

  if (composite_display_flag)
  {
    v_axis            = Get_Bits(1);
    field_sequence    = Get_Bits(3);
    sub_carrier       = Get_Bits(1);
    burst_amplitude   = Get_Bits(7);
    sub_carrier_phase = Get_Bits(8);
  }



#ifdef VERIFY
  verify_picture_coding_extension++;
#endif /* VERIFY */
}


/* decode picture spatial scalable extension */
/* ISO/IEC 13818-2 section 6.2.3.5. */
static void picture_spatial_scalable_extension()
{
  int pos;

  pos = ld->Bitcnt;

  ld->pict_scal = 1; /* use spatial scalability in this picture */

  lower_layer_temporal_reference = Get_Bits(10);
  marker_bit("picture_spatial_scalable_extension(), first marker bit");
  lower_layer_horizontal_offset = Get_Bits(15);
  if (lower_layer_horizontal_offset>=16384)
    lower_layer_horizontal_offset-= 32768;
  marker_bit("picture_spatial_scalable_extension(), second marker bit");
  lower_layer_vertical_offset = Get_Bits(15);
  if (lower_layer_vertical_offset>=16384)
    lower_layer_vertical_offset-= 32768;
  spatial_temporal_weight_code_table_index = Get_Bits(2);
  lower_layer_progressive_frame = Get_Bits(1);
  lower_layer_deinterlaced_field_select = Get_Bits(1);



#ifdef VERIFY
  verify_picture_spatial_scalable_extension++;
#endif /* VERIFY */

}


/* decode picture temporal scalable extension
 *
 * not implemented
 */
/* ISO/IEC 13818-2 section 6.2.3.4. */
static void picture_temporal_scalable_extension()
{
  Error("temporal scalability not supported\n");

#ifdef VERIFY
  verify_picture_temporal_scalable_extension++;
#endif /* VERIFY */
}


/* decode extra bit information */
/* ISO/IEC 13818-2 section 6.2.3.4. */
static int extra_bit_information()
{
  int Byte_Count = 0;

  while (Get_Bits1())
  {
    FLUSH_BUFFER(8);
    Byte_Count++;
  }

  return(Byte_Count);
}



/* ISO/IEC 13818-2 section 5.3 */
/* Purpose: this function is mainly designed to aid in bitstream conformance
   testing.  A simple Flush_Buffer(1) would do */
void marker_bit(
char *text)
{
  int marker;

  marker = Get_Bits(1);

#ifdef VERIFY  
 
#endif
}


/* ISO/IEC 13818-2  sections 6.3.4.1 and 6.2.2.2.2 */
static void user_data()
{
  /* skip ahead to the next start code */
  next_start_code();
}



/* Copyright extension */
/* ISO/IEC 13818-2 section 6.2.3.6. */
/* (header added in November, 1994 to the IS document) */


static void copyright_extension()
{
  int pos;
  int reserved_data;

  pos = ld->Bitcnt;
  

  copyright_flag =       Get_Bits(1); 
  copyright_identifier = Get_Bits(8);
  original_or_copy =     Get_Bits(1);
  
  /* reserved */
  reserved_data = Get_Bits(7);

  marker_bit("copyright_extension(), first marker bit");
  copyright_number_1 =   Get_Bits(20);
  marker_bit("copyright_extension(), second marker bit");
  copyright_number_2 =   Get_Bits(22);
  marker_bit("copyright_extension(), third marker bit");
  copyright_number_3 =   Get_Bits(22);

 

#ifdef VERIFY
  verify_copyright_extension++;
#endif /* VERIFY */
}



/* introduced in September 1995 to assist Spatial Scalability */
static void Update_Temporal_Reference_Tacking_Data()
{
  static int temporal_reference_wrap  = 0;
  static int temporal_reference_old   = 0;

  if (ld == &base)			/* *CH* */
  {
    if (picture_coding_type!=B_TYPE && temporal_reference!=temporal_reference_old) 	
    /* check first field of */
    {							
       /* non-B-frame */
      if (temporal_reference_wrap) 		
      {/* wrap occured at previous I- or P-frame */	
       /* now all intervening B-frames which could 
          still have high temporal_reference values are done  */
        Temporal_Reference_Base += 1024;
	    temporal_reference_wrap = 0;
      }
      
      /* distinguish from a reset */
      if (temporal_reference<temporal_reference_old && !Temporal_Reference_GOP_Reset)	
	    temporal_reference_wrap = 1;  /* we must have just passed a GOP-Header! */
      
      temporal_reference_old = temporal_reference;
      Temporal_Reference_GOP_Reset = 0;
    }

    True_Framenum = Temporal_Reference_Base + temporal_reference;
    
    /* temporary wrap of TR at 1024 for M frames */
    if (temporal_reference_wrap && temporal_reference <= temporal_reference_old)	
      True_Framenum += 1024;				

    True_Framenum_max = (True_Framenum > True_Framenum_max) ?
                        True_Framenum : True_Framenum_max;
  }
}