oggdsf/src/lib/codecs/vorbis/libs/libvorbis/doc/vorbisfile/seekexample.html

   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>
  19 The following is a run-through of the seeking example program supplied
  20 with vorbisfile - <a href="seeking_test_c.html">seeking_test.c</a>.
  21 This 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>
  24 First, 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>
  46 int 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
  69 called 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>
  88 First 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>
 119 When 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>
 135 The full source for seeking_test.c can be found with the vorbis
 136 distribution 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>