public String version_string()
	{
	  switch (h_version)
	  {
	    case MPEG1:
	      return "MPEG-1";
	    case MPEG2_LSF:
	      return "MPEG-2 LSF";
	    case MPEG25_LSF:	// SZD
	      return "MPEG-2.5 LSF";
	  }
	  return(null);
	}