Vorbisfile documentation

vorbisfile version 1.3.2 - 20101101

Example Code: seeking

The following is a run-through of the seeking example program supplied with vorbisfile - seeking_test.c. This program tests the vorbisfile ov_time_seek function by seeking to random points within the file.

First, relevant headers, including vorbis-specific "codec.h" and "vorbisfile.h" have to be included.

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

Inside main(), we declare our primary OggVorbis_File structure. We also declare other helpful variables to track our progress within the file.

int main(){
  OggVorbis_File ov;
  int i;

This example takes its input on stdin which is in 'text' mode by default under Windows; this will corrupt the input data unless set to binary mode. This applies only to Windows.

#ifdef _WIN32 /* We need to set stdin to binary mode under Windows */
  _setmode( _fileno( stdin ), _O_BINARY );

ov_open() must be called to initialize the OggVorbis_File structure with default values. ov_open_callbacks() also checks to ensure that we're reading Vorbis format and not something else.

  if(ov_open_callbacks(stdin,&ov,NULL,-1, OV_CALLBACKS_NOCLOSE)<0){
    printf("Could not open input as an OggVorbis file.\n\n");

First we check to make sure the stream is seekable using ov_seekable.

Then we seek to 100 random spots in the bitstream using ov_time_seek with randomly generated values.

  /* print details about each logical bitstream in the input */
    double length=ov_time_total(&ov,-1);
    printf("testing seeking to random places in %g seconds....\n",length);
      double val=(double)rand()/RAND_MAX*length;
      printf("\r\t%d [%gs]...     ",i,val);
    printf("\r                                   \nOK.\n\n");
    printf("Standard input was not seekable.\n");

When we're done seeking, we need to call ov_clear() to release the bitstream.

  return 0;

The full source for seeking_test.c can be found with the vorbis distribution in seeking_test.c.

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Ogg Vorbis

Vorbisfile documentation

vorbisfile version 1.3.2 - 20101101