Re: ov_open_callbacks takes so much time to open 210 MB OGG file

/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2007             *
 * by the Xiph.Org Foundation http://www.xiph.org/                  *
 *                                                                  *
 ********************************************************************

 function: simple example decoder using vorbisfile
 last mod: $Id: vorbisfile_example.c 16328 2009-07-24 01:51:10Z xiphmont $

 ********************************************************************/

/* Takes a vorbis bitstream from stdin and writes raw stereo PCM to
   stdout using vorbisfile. Using vorbisfile is much simpler than
   dealing with libvorbis. */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <vorbis/codec.h>
#include <vorbis/vorbisfile.h>
#include <ctime>

#ifdef _WIN32 /* We need the following two to set stdin/stdout to binary */
#include <io.h>
#include <fcntl.h>
#endif

char pcmout[4096]; /* take 4k out of the data segment, not the stack */

int main(){
  OggVorbis_File vf;
  int eof=0;
  int current_section;

#ifdef _WIN32 /* We need to set stdin/stdout to binary mode. Damn windows. */
  /* Beware the evil ifdef. We avoid these where we can, but this one we 
     cannot. Don't add any more, you'll probably go to hell if you do. */
  _setmode( _fileno( stdin ), _O_BINARY );
  _setmode( _fileno( stdout ), _O_BINARY );
#endif

  fprintf(stderr,"Starting to measure time of ov_open_callbacks.");
  clock_t start,end;
  start=clock();
  fprintf(stderr,"\nclock start:=%d\n",start);

  if(ov_open_callbacks(stdin, &vf, NULL, 0, OV_CALLBACKS_NOCLOSE) < 0) {
      fprintf(stderr,"Input does not appear to be an Ogg bitstream.\n");
      exit(1);
  }

  end=clock();
  fprintf(stderr,"clock end:=%d\n",end);
  fprintf(stderr,"time=%f\n",((double)(end-start))/CLK_TCK);

  /* Throw the comments plus a few lines about the bitstream we're
     decoding */
  {
    char **ptr=ov_comment(&vf,-1)->user_comments;
    vorbis_info *vi=ov_info(&vf,-1);
    while(*ptr){
      fprintf(stderr,"%s\n",*ptr);
      ++ptr;
    }
    fprintf(stderr,"\nBitstream is %d channel, %ldHz\n",vi->channels,vi->rate);
    fprintf(stderr,"\nDecoded length: %ld samples\n",
            (long)ov_pcm_total(&vf,-1));
    fprintf(stderr,"Encoded by: %s\n\n",ov_comment(&vf,-1)->vendor);
  }
  
  fprintf(stderr,"Decompressing...");
  while(!eof){
    long ret=ov_read(&vf,pcmout,sizeof(pcmout),0,2,1,&current_section);
    if (ret == 0) {
      /* EOF */
      eof=1;
    } else if (ret < 0) {
      if(ret==OV_EBADLINK){
        fprintf(stderr,"Corrupt bitstream section! Exiting.\n");
        exit(1);
      }

      /* some other error in the stream.  Not a problem, just reporting it in
         case we (the app) cares.  In this case, we don't. */
    } else {
      /* we don't bother dealing with sample rate changes, etc, but
         you'll have to*/
      fwrite(pcmout,1,ret,stdout);
    }
  }
  fprintf(stderr,"Decompressing finished.");

  /* cleanup */
  ov_clear(&vf);
    
  fprintf(stderr,"Done.\n");
  return(0);
}