nalu.c

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#include "global.h"
#include "annexb.h"
#include "nalu.h"
#include "memalloc.h"
#include "rtp.h"

void initBitsFile (ImageParameters *p_Img, int filemode)
{

  switch (filemode)
  {
  case PAR_OF_ANNEXB:
    if ((p_Img->bitsfile  =  (BitsFile *) calloc(1, sizeof(BitsFile)))==NULL) 
      no_mem_exit("initBitsFile : p_Img->bitsfile");

    p_Img->bitsfile->OpenBitsFile     = OpenAnnexBFile;
    p_Img->bitsfile->CloseBitsFile    = CloseAnnexBFile;
    p_Img->bitsfile->GetNALU          = GetAnnexbNALU;
    malloc_annex_b(p_Img);
    break;
  case PAR_OF_RTP:
    if ((p_Img->bitsfile  =  (BitsFile *) calloc(1, sizeof(BitsFile)))==NULL) 
      no_mem_exit("initBitsFile : p_Img->bitsfile");

    p_Img->bitsfile->OpenBitsFile     = OpenRTPFile;
    p_Img->bitsfile->CloseBitsFile    = CloseRTPFile;
    p_Img->bitsfile->GetNALU          = GetRTPNALU;
    break;
  default:
    error ("initBitsFile: Unknown bitstream file mode", 255);
    break;
  }    
}

static int NALUtoRBSP (NALU_t *nalu)
{
  assert (nalu != NULL);

  nalu->len = EBSPtoRBSP (nalu->buf, nalu->len, 1) ;

  return nalu->len ;
}

int read_next_nalu(ImageParameters *p_Img, NALU_t *nalu)
{
  InputParameters *p_Inp = p_Img->p_Inp;
  int ret;

  ret = p_Img->bitsfile->GetNALU(p_Img, nalu);

  if (ret < 0)
  {
    snprintf (errortext, ET_SIZE, "Error while getting the NALU in file format %s, exit\n", p_Inp->FileFormat==PAR_OF_ANNEXB?"Annex B":"RTP");
    error (errortext, 601);
  }
  if (ret == 0)
  {
    FreeNALU(nalu);
    return 0;
  }

  //In some cases, zero_byte shall be present. If current NALU is a VCL NALU, we can't tell
  //whether it is the first VCL NALU at this point, so only non-VCL NAL unit is checked here.
  CheckZeroByteNonVCL(p_Img, nalu);

  ret = NALUtoRBSP(nalu);

  if (ret < 0)
    error ("Invalid startcode emulation prevention found.", 602);


  // Got a NALU
  if (nalu->forbidden_bit)
  {
    error ("Found NALU with forbidden_bit set, bit error?", 603);
  }

  return nalu->len;
}

void CheckZeroByteNonVCL(ImageParameters *p_Img, NALU_t *nalu)
{
  int CheckZeroByte=0;

  //This function deals only with non-VCL NAL units
  if(nalu->nal_unit_type>=1&&nalu->nal_unit_type<=5)
    return;

  //for SPS and PPS, zero_byte shall exist
  if(nalu->nal_unit_type==NALU_TYPE_SPS || nalu->nal_unit_type==NALU_TYPE_PPS)
    CheckZeroByte=1;
  //check the possibility of the current NALU to be the start of a new access unit, according to 7.4.1.2.3
  if(nalu->nal_unit_type==NALU_TYPE_AUD  || nalu->nal_unit_type==NALU_TYPE_SPS ||
    nalu->nal_unit_type==NALU_TYPE_PPS || nalu->nal_unit_type==NALU_TYPE_SEI ||
    (nalu->nal_unit_type>=13 && nalu->nal_unit_type<=18))
  {
    if(p_Img->LastAccessUnitExists)
    {
      p_Img->LastAccessUnitExists=0;    //deliver the last access unit to decoder
      p_Img->NALUCount=0;
    }
  }
  p_Img->NALUCount++;
  //for the first NAL unit in an access unit, zero_byte shall exists
  if(p_Img->NALUCount==1)
    CheckZeroByte=1;
  if(CheckZeroByte && nalu->startcodeprefix_len==3)
  {
    printf("Warning: zero_byte shall exist\n");
    //because it is not a very serious problem, we do not exit here
  }
}

void CheckZeroByteVCL(ImageParameters *p_Img, NALU_t *nalu)
{
  int CheckZeroByte=0;

  //This function deals only with VCL NAL units
  if(!(nalu->nal_unit_type>=1&&nalu->nal_unit_type<=5))
    return;

  if(p_Img->LastAccessUnitExists)
  {
    p_Img->NALUCount=0;
  }
  p_Img->NALUCount++;
  //the first VCL NAL unit that is the first NAL unit after last VCL NAL unit indicates
  //the start of a new access unit and hence the first NAL unit of the new access unit.           (sounds like a tongue twister :-)
  if(p_Img->NALUCount == 1)
    CheckZeroByte = 1;
  p_Img->LastAccessUnitExists = 1;
  if(CheckZeroByte && nalu->startcodeprefix_len==3)
  {
    printf("warning: zero_byte shall exist\n");
    //because it is not a very serious problem, we do not exit here
  }
}

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