rtp.c

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#ifdef WIN32
#include <Winsock2.h>
#else
#include <netinet/in.h>
#endif

#include "contributors.h"
#include "global.h"
#include "errorconcealment.h"
#include "rtp.h"
#include "fmo.h"
#include "sei.h"
#include "memalloc.h"

static int BitStreamFile;

int RTPReadPacket (RTPpacket_t *p, int bitstream);

void OpenRTPFile (char *fn)
{
  if ((BitStreamFile = open(fn, OPENFLAGS_READ)) == -1)
  {
    snprintf (errortext, ET_SIZE, "Cannot open RTP file '%s'", fn);
    error(errortext,500);
  }
}


void CloseRTPFile(void)
{
  if (BitStreamFile != -1)
  {
    close(BitStreamFile);
    BitStreamFile = - 1;
  }
}


int GetRTPNALU (NALU_t *nalu)
{
  static unsigned short first_call = 1;  
  static unsigned short old_seq = 0;     

  RTPpacket_t *p;
  int ret;

  if ((p=malloc (sizeof (RTPpacket_t)))== NULL)
    no_mem_exit ("GetRTPNALU-1");
  if ((p->packet=malloc (MAXRTPPACKETSIZE))== NULL)
    no_mem_exit ("GetRTPNALU-2");
  if ((p->payload=malloc (MAXRTPPACKETSIZE))== NULL)
    no_mem_exit ("GetRTPNALU-3");

  ret = RTPReadPacket (p, BitStreamFile);
  nalu->forbidden_bit = 1;
  nalu->len = 0;

  if (ret > 0) // we got a packet ( -1=error, 0=end of file )
  {
    if (first_call)
    {
      first_call = 0;
      old_seq = (unsigned short) (p->seq - 1);
    }

    nalu->lost_packets = (unsigned short) ( p->seq - (old_seq + 1) );
    old_seq = p->seq;

    assert (p->paylen < nalu->max_size);

    nalu->len = p->paylen;
    memcpy (nalu->buf, p->payload, p->paylen);
    nalu->forbidden_bit = (nalu->buf[0]>>7) & 1;
    nalu->nal_reference_idc = (nalu->buf[0]>>5) & 3;
    nalu->nal_unit_type = (nalu->buf[0]) & 0x1f;
    if (nalu->lost_packets)
    {
      printf ("Warning: RTP sequence number discontinuity detected\n");
    }
  }

  // free memory
  free (p->payload);
  free (p->packet);
  free (p);

//  printf ("Got an RTP NALU, len %d, first byte %x\n", nalu->len, nalu->buf[0]);
  
  if (ret>0)
    // length of packet
    return nalu->len;
  else 
    // error code
    return ret;
}



int DecomposeRTPpacket (RTPpacket_t *p)

{
  // consistency check
  assert (p->packlen < 65536 - 28);  // IP, UDP headers
  assert (p->packlen >= 12);         // at least a complete RTP header
  assert (p->payload != NULL);
  assert (p->packet != NULL);

  // Extract header information

  p->v  = (p->packet[0] >> 6) & 0x03;
  p->p  = (p->packet[0] >> 5) & 0x01;
  p->x  = (p->packet[0] >> 4) & 0x01;
  p->cc = (p->packet[0] >> 0) & 0x0F;

  p->m  = (p->packet[1] >> 7) & 0x01;
  p->pt = (p->packet[1] >> 0) & 0x7F;

  memcpy (&p->seq, &p->packet[2], 2);
  p->seq = ntohs((unsigned short)p->seq);

  memcpy (&p->timestamp, &p->packet[4], 4);// change to shifts for unified byte sex
  p->timestamp = ntohl(p->timestamp);
  memcpy (&p->ssrc, &p->packet[8], 4);// change to shifts for unified byte sex
  p->ssrc = ntohl(p->ssrc);

  // header consistency checks
  if (     (p->v != 2)
        || (p->p != 0)
        || (p->x != 0)
        || (p->cc != 0) )
  {
    printf ("DecomposeRTPpacket, RTP header consistency problem, header follows\n");
    DumpRTPHeader (p);
    return -1;
  }
  p->paylen = p->packlen-12;
  memcpy (p->payload, &p->packet[12], p->paylen);
  return 0;
}

void DumpRTPHeader (RTPpacket_t *p)

{
  int i;
  for (i=0; i< 30; i++)
    printf ("%02x ", p->packet[i]);
  printf ("Version (V): %d\n", (int) p->v);
  printf ("Padding (P): %d\n", (int) p->p);
  printf ("Extension (X): %d\n", (int) p->x);
  printf ("CSRC count (CC): %d\n", (int) p->cc);
  printf ("Marker bit (M): %d\n", (int) p->m);
  printf ("Payload Type (PT): %d\n", (int) p->pt);
  printf ("Sequence Number: %d\n", (int) p->seq);
  printf ("Timestamp: %d\n", (int) p->timestamp);
  printf ("SSRC: %d\n", (int) p->ssrc);
}


int RTPReadPacket (RTPpacket_t *p, int bitstream)
{
  int64 Filepos;
  int intime;

  assert (p != NULL);
  assert (p->packet != NULL);
  assert (p->payload != NULL);

  Filepos = tell (bitstream);
  if (4 != read (bitstream, &p->packlen, 4))
  {
    return 0;
  }
  if (4 != read (bitstream, &intime, 4))
  {
    lseek (bitstream, Filepos, SEEK_SET);
    printf ("RTPReadPacket: File corruption, could not read Timestamp, exit\n");
    exit (-1);
  }

  assert (p->packlen < MAXRTPPACKETSIZE);

  if (p->packlen != read (bitstream, p->packet, p->packlen))
  {
    printf ("RTPReadPacket: File corruption, could not read %d bytes\n", (int) p->packlen);
    exit (-1);    // EOF inidication
  }

  if (DecomposeRTPpacket (p) < 0)
  {
    // this should never happen, hence exit() is ok.  We probably do not want to attempt
    // to decode a packet that obviously wasn't generated by RTP
    printf ("Errors reported by DecomposePacket(), exit\n");
    exit (-700);
  }
  assert (p->pt == H264PAYLOADTYPE);
  assert (p->ssrc == H264SSRC);
  return p->packlen;
}

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