Mercurial > hg > sv-dependency-builds

<html>

<head>
<title>vorbisfile - Example Code</title>
<link rel=stylesheet href="style.css" type="text/css">
</head>

<body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
<table border=0 width=100%>
<tr>
<td><p class=tiny>Vorbisfile documentation</p></td>
<td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
</tr>
</table>

<h1>Example Code: seeking</h1>

<p>
The following is a run-through of the seeking example program supplied
with vorbisfile - <a href="seeking_test_c.html">seeking_test.c</a>.
This program tests the vorbisfile <a href="ov_time_seek.html">ov_time_seek</a> function by seeking to random points within the file.

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

<br><br>
<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
<tr bgcolor=#cccccc>
	<td>
<pre><b>
#include &lt;stdlib.h>
#include &lt;stdio.h>
#include "vorbis/codec.h"
#include "vorbis/vorbisfile.h"
</b></pre>
	</td>
</tr>
</table>

<p>Inside main(), we declare our primary OggVorbis_File structure.  We also declare other helpful variables to track our progress within the file.
<br><br>
<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
<tr bgcolor=#cccccc>
        <td>
<pre><b>
int main(){
  OggVorbis_File ov;
  int i;
</b></pre>
        </td>
</tr>
</table>

<p>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.
<br><br>
<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
<tr bgcolor=#cccccc>
        <td>
<pre><b>
#ifdef _WIN32 /* We need to set stdin to binary mode under Windows */
  _setmode( _fileno( stdin ), _O_BINARY );
#endif
</b></pre>
        </td>
</tr>
</table>

<p><a href="ov_open_callbacks.html">ov_open()</a> must be
called to initialize the <a href="OggVorbis_File.html">OggVorbis_File</a> structure with default values.
<a href="ov_open_callbacks.html">ov_open_callbacks()</a> also checks to ensure that we're reading Vorbis format and not something else.

<br><br>
<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
<tr bgcolor=#cccccc>
        <td>
<pre><b>
  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);
  }

</b></pre>
        </td>
</tr>
</table>

<p>
First we check to make sure the stream is seekable using <a href="ov_seekable.html">ov_seekable</a>.

<p>Then we seek to 100 random spots in the bitstream using <a href="ov_time_seek.html">ov_time_seek</a> with randomly generated values.

<br><br>
<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
<tr bgcolor=#cccccc>
        <td>
<pre><b>

  /* 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");
  }

</b></pre>
        </td>
</tr>
</table>
<p>
When we're done seeking, we need to call <a href="ov_clear.html">ov_clear()</a> to release the bitstream.

<br><br>
<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
<tr bgcolor=#cccccc>
        <td>
<pre><b>
  ov_clear(&ov);
  return 0;
}
</b></pre>
        </td>
</tr>
</table>

<p>
The full source for seeking_test.c can be found with the vorbis
distribution in <a href="seeking_test_c.html">seeking_test.c</a>.

<br><br>
<hr noshade>
<table border=0 width=100%>
<tr valign=top>
<td><p class=tiny>copyright &copy; 2000-2010 Xiph.Org</p></td>
<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td>
</tr><tr>
<td><p class=tiny>Vorbisfile documentation</p></td>
<td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
</tr>
</table>

</body>

</html>
author	Chris Cannam
date	Fri, 07 Feb 2020 11:51:13 +0000
parents	05aa0afa9217
children