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 ); #endif

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"); exit(1); }

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 */ if(ov_seekable(&ov)){ double length=ov_time_total(&ov,-1); printf("testing seeking to random places in %g seconds....\n",length); for(i=0;i<100;i++){ double val=(double)rand()/RAND_MAX*length; ov_time_seek(&ov,val); printf("\r\t%d [%gs]... ",i,val); fflush(stdout); } printf("\r \nOK.\n\n"); }else{ printf("Standard input was not seekable.\n"); }

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

ov_clear(&ov); return 0; }

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