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source: downloads/libvorbis-1.2.0/doc/vorbisfile/seekexample.html @ 62

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1<html>
2
3<head>
4<title>vorbisfile - Example Code</title>
5<link rel=stylesheet href="style.css" type="text/css">
6</head>
7
8<body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
9<table border=0 width=100%>
10<tr>
11<td><p class=tiny>Vorbisfile documentation</p></td>
12<td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td>
13</tr>
14</table>
15
16<h1>Example Code: seeking</h1>
17
18<p>
19The following is a run-through of the seeking example program supplied
20with vorbisfile - <a href="seeking_test_c.html">seeking_test.c</a>. 
21This program tests the vorbisfile <a href="ov_time_seek.html">ov_time_seek</a> function by seeking to random points within the file.
22
23<p>
24First, relevant headers, including vorbis-specific "codec.h" and "vorbisfile.h" have to be included.
25
26<br><br>
27<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
28<tr bgcolor=#cccccc>
29        <td>
30<pre><b>
31#include &lt;stdlib.h>
32#include &lt;stdio.h>
33#include "vorbis/codec.h"
34#include "vorbis/vorbisfile.h"
35</b></pre>
36        </td>
37</tr>
38</table>
39
40<p>Inside main(), we declare our primary OggVorbis_File structure.  We also declare other helpful variables to track our progress within the file.
41<br><br>
42<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
43<tr bgcolor=#cccccc>
44        <td>
45<pre><b>
46int main(){
47  OggVorbis_File ov;
48  int i;
49</b></pre>
50        </td>
51</tr>
52</table>
53
54<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.
55<br><br>
56<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
57<tr bgcolor=#cccccc>
58        <td>
59<pre><b>
60#ifdef _WIN32 /* We need to set stdin to binary mode under Windows */
61  _setmode( _fileno( stdin ), _O_BINARY );
62#endif
63</b></pre>
64        </td>
65</tr>
66</table>
67
68<p><a href="ov_open_callbacks.html">ov_open()</a> must be
69called to initialize the <a href="OggVorbis_File.html">OggVorbis_File</a> structure with default values. 
70<a href="ov_open_callbacks.html">ov_open_callbacks()</a> also checks to ensure that we're reading Vorbis format and not something else.
71
72<br><br>
73<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
74<tr bgcolor=#cccccc>
75        <td>
76<pre><b>
77  if(ov_open_callbacks(stdin,&ov,NULL,-1, OV_CALLBACKS_NOCLOSE)<0){
78    printf("Could not open input as an OggVorbis file.\n\n");
79    exit(1);
80  }
81
82</b></pre>
83        </td>
84</tr>
85</table>
86
87<p>
88First we check to make sure the stream is seekable using <a href="ov_seekable.html">ov_seekable</a>.
89
90<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.
91
92<br><br>
93<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
94<tr bgcolor=#cccccc>
95        <td>
96<pre><b>
97 
98  /* print details about each logical bitstream in the input */
99  if(ov_seekable(&ov)){
100    double length=ov_time_total(&ov,-1);
101    printf("testing seeking to random places in %g seconds....\n",length);
102    for(i=0;i<100;i++){
103      double val=(double)rand()/RAND_MAX*length;
104      ov_time_seek(&ov,val);
105      printf("\r\t%d [%gs]...     ",i,val);
106      fflush(stdout);
107    }
108   
109    printf("\r                                   \nOK.\n\n");
110  }else{
111    printf("Standard input was not seekable.\n");
112  }
113 
114</b></pre>
115        </td>
116</tr>
117</table>
118<p>
119When we're done seeking, we need to call <a href="ov_clear.html">ov_clear()</a> to release the bitstream.
120
121<br><br>
122<table border=0 width=100% color=black cellspacing=0 cellpadding=7>
123<tr bgcolor=#cccccc>
124        <td>
125<pre><b>
126  ov_clear(&ov);
127  return 0;
128}
129</b></pre>
130        </td>
131</tr>
132</table>
133
134<p>
135The full source for seeking_test.c can be found with the vorbis
136distribution in <a href="seeking_test_c.html">seeking_test.c</a>.
137
138<br><br>
139<hr noshade>
140<table border=0 width=100%>
141<tr valign=top>
142<td><p class=tiny>copyright &copy; 2007 Xiph.org</p></td>
143<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a><br><a href="mailto:team@vorbis.org">team@vorbis.org</a></p></td>
144</tr><tr>
145<td><p class=tiny>Vorbisfile documentation</p></td>
146<td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td>
147</tr>
148</table>
149
150</body>
151
152</html>
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