A recent comment change for gst_rtp_buffer_compare_seqnum says that it will return the difference in sequence numbers. In its current implementation, it does not. e.g. gst_rtp_buffer_compare_seqnum(0xFFFF, 0) returns 65535, not -1 as desired.

A much easier approach is to cast the difference into a signed gint16, then into an gint (the function's return type), then the compiler and OS takes care of the wraparound and sign extension for you. e.g.

gint
gst_rtp_buffer_compare_seqnum (guint16 seqnum1, guint16 seqnum2)
{
  return (gint16)(seqnum2-seqnum1);
}

This survives this simple test below (apologies for not making it an attachment), where as the original function (revision 1.22 of gstrtpbuffer.c) does not.

void test()
{
  int i, diff;
  uint16 a, b;
  for (diff = -100; diff < 100; diff++) {
    a = 0;
    for (i = 0; i < 0x20000; i++) {
      b = a + diff;
      assert(gst_rtp_buffer_compare_seqnum(a, b) == diff);
      a++;
    }
  }
}