[Tremor] ov_open always returns -132 err

[Sam Man]

hi, 
 i have got the tremor code, 
after compiling it nder VC++ , i always get that the file is not a
valid ogg file in the
ov_open ().
someone please guide me .. i am putting the code i have modified in the 
ivorbisfile_example.c file

//******************
  if( (ogg_file=fopen("song.ogg","rb"))== NULL )
      printf( "The file  song.ogg was not opened\n" );
   else
      printf( "The file song.ogg was opened\n" );

if(ov_open(stdin, &vf, NULL, 0) < 0) {
fcolse(ogg_file);
 fprintf(stderr,"Input does not appear to be an Ogg bitstream.\n");
      exit(1);
  }
//******************
The code always exits..
i've seen some problems reported here but no explanation. Can someone
help please......
PS: i am new to vorbis, please bear with me ans help me.
thanks and regards
Sam