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| 3 | <head>
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| 4 | <title>Vorbisfile - function - ov_open_callbacks</title>
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| 5 | <link rel=stylesheet href="style.css" type="text/css">
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| 6 | </head>
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| 7 |
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| 8 | <body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
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| 9 | <table border=0 width=100%>
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| 10 | <tr>
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| 11 | <td><p class=tiny>Vorbisfile documentation</p></td>
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| 12 | <td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
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| 13 | </tr>
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| 14 | </table>
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| 15 |
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| 16 | <h1>ov_open_callbacks</h1>
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| 17 |
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| 18 | <p><i>declared in "vorbis/vorbisfile.h";</i></p>
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| 19 |
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| 20 | <p>This is an alternative function used to open and initialize an
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| 21 | OggVorbis_File structure when using a data source other than a file,
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| 22 | when its necessary to modify default file access behavior, or to
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| 23 | initialize a Vorbis decode from a <tt>FILE *</tt> pointer under
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| 24 | Windows where <a href="ov_open.html">ov_open()</a> cannot be used. It
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| 25 | allows the application to specify custom file manipulation routines
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| 26 | and sets up all the related decoding structures.
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| 27 |
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| 28 | <p>Once ov_open_callbacks() has been called, the same
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| 29 | <tt>OggVorbis_File</tt> struct should be passed to all the
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| 30 | libvorbisfile functions. Unlike <a
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| 31 | href="ov_fopen.html">ov_fopen()</a> and <a
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| 32 | href="ov_open.html">ov_open()</a>, ov_open_callbacks() may be used to
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| 33 | instruct vorbisfile to either automatically close or not to close the
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| 34 | file/data access handle in <a href="ov_clear.html">ov_clear()</a>.
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| 35 | Automatic closure is disabled by passing NULL as the close callback,
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| 36 | or using one of the predefined callback sets that specify a NULL close
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| 37 | callback. The application is responsible for closing a file when a
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| 38 | call to ov_open_callbacks() is unsuccessful.<p>
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| 39 |
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| 40 | See also <a href="callbacks.html">Callbacks and Non-stdio I/O</a> for
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| 41 | information on designing and specifying custom callback functions.<p>
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| 42 |
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| 43 | <br><br>
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| 44 | <table border=0 color=black cellspacing=0 cellpadding=7>
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| 45 | <tr bgcolor=#cccccc>
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| 46 | <td>
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| 47 | <pre><b>
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| 48 | int ov_open_callbacks(void *datasource, <a href="OggVorbis_File.html">OggVorbis_File</a> *vf, char *initial, long ibytes, <a href="ov_callbacks.html">ov_callbacks</a> callbacks);
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| 49 | </b></pre>
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| 50 | </td>
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| 51 | </tr>
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| 52 | </table>
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| 53 |
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| 54 | <h3>Parameters</h3>
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| 55 | <dl>
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| 56 | <dt><i>datasource</i></dt>
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| 57 | <dd>Pointer to a data structure allocated by the calling application, containing any state needed by the callbacks provided.</dd>
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| 58 | <dt><i>vf</i></dt>
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| 59 | <dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisfile
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| 60 | functions. Once this has been called, the same <tt>OggVorbis_File</tt>
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| 61 | struct should be passed to all the libvorbisfile functions.</dd>
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| 62 | <dt><i>initial</i></dt>
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| 63 | <dd>Typically set to NULL. This parameter is useful if some data has already been
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| 64 | read from the stream and the stream is not seekable. It is used in conjunction with <tt>ibytes</tt>. In this case, <tt>initial</tt>
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| 65 | should be a pointer to a buffer containing the data read.</dd>
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| 66 | <dt><i>ibytes</i></dt>
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| 67 | <dd>Typically set to 0. This parameter is useful if some data has already been
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| 68 | read from the stream and the stream is not seekable. In this case, <tt>ibytes</tt>
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| 69 | should contain the length (in bytes) of the buffer. Used together with <tt>initial</tt>.</dd>
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| 70 | <dt><i>callbacks</i></dt>
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| 71 | <dd>A completed <a href="ov_callbacks.html">ov_callbacks</a> struct which indicates desired custom file manipulation routines. vorbisfile.h defines several preprovided callback sets; see <a href="ov_callbacks.html">ov_callbacks</a> for details.</dd>
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| 72 | </dl>
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| 73 |
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| 74 |
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| 75 | <h3>Return Values</h3>
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| 76 | <blockquote>
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| 77 | <li>0 for success</li>
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| 78 | <li>less than zero for failure:</li>
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| 79 | <ul>
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| 80 | <li>OV_EREAD - A read from media returned an error.</li>
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| 81 | <li>OV_ENOTVORBIS - Bitstream does not contain any Vorbis data.</li>
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| 82 | <li>OV_EVERSION - Vorbis version mismatch.</li>
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| 83 | <li>OV_EBADHEADER - Invalid Vorbis bitstream header.</li>
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| 84 | <li>OV_EFAULT - Internal logic fault; indicates a bug or heap/stack corruption.</li>
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| 85 | </ul>
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| 86 | </blockquote>
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| 87 | <p>
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| 88 |
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| 89 | <h3>Notes</h3>
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| 90 | <dl>
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| 91 |
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| 92 | <dt><b>[a] Windows and use as an ov_open() substitute</b><p> Windows
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| 93 | applications should not use <a href="ov_open.html">ov_open()</a> due
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| 94 | to the likelihood of <a href="ov_open.html#winfoot">CRT linking
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| 95 | mismatches and runtime protection faults
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| 96 | [ov_open:a]</a>. ov_open_callbacks() is a safe substitute; specifically:
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| 97 |
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| 98 | <pre><tt>ov_open_callbacks(f, vf, initial, ibytes, OV_CALLBACKS_DEFAULT);</tt>
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| 99 | </pre>
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| 100 |
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| 101 | ... provides exactly the same functionality as <a
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| 102 | href="ov_open.html">ov_open()</a> but will always work correctly under
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| 103 | Windows, regardless of linking setup details.<p>
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| 104 |
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| 105 | <dt><b>[b] Threaded decode</b><p>
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| 106 | <dd>If your decoder is threaded, it is recommended that you NOT call
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| 107 | <tt>ov_open_callbacks()</tt>
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| 108 | in the main control thread--instead, call <tt>ov_open_callbacks()</tt> in your decode/playback
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| 109 | thread. This is important because <tt>ov_open_callbacks()</tt> may be a fairly time-consuming
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| 110 | call, given that the full structure of the file is determined at this point,
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| 111 | which may require reading large parts of the file under certain circumstances
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| 112 | (determining all the logical bitstreams in one physical bitstream, for
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| 113 | example). See <a href="threads.html">Thread Safety</a> for other information on using libvorbisfile with threads.
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| 114 | <p>
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| 115 |
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| 116 | <dt><b>[c] Mixed media streams</b><p>
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| 117 | <dd>
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| 118 | As of Vorbisfile release 1.2.0, Vorbisfile is able to access the
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| 119 | Vorbis content in mixed-media Ogg streams, not just Vorbis-only
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| 120 | streams. For example, Vorbisfile may be used to open and access the
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| 121 | audio from an Ogg stream consisting of Theora video and Vorbis audio.
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| 122 | Vorbisfile 1.2.0 decodes the first logical audio stream of each
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| 123 | physical stream section.<p>
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| 124 |
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| 125 | <dt><b>[d] Faster testing for Vorbis files</b><p>
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| 126 | <dd><a href="ov_test.html">ov_test()</a> and <a
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| 127 | href="ov_test_callbacks.html">ov_test_callbacks()</a> provide less
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| 128 | computationally expensive ways to test a file for Vorbisness, but
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| 129 | require more setup code.<p>
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| 130 |
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| 131 | </dl>
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| 132 |
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| 133 | <br><br>
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| 134 | <hr noshade>
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| 135 | <table border=0 width=100%>
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| 136 | <tr valign=top>
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| 137 | <td><p class=tiny>copyright © 2000-2010 Xiph.Org</p></td>
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| 138 | <td align=right><p class=tiny><a href="https://xiph.org/vorbis/">Ogg Vorbis</a></p></td>
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| 139 | </tr><tr>
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| 140 | <td><p class=tiny>Vorbisfile documentation</p></td>
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| 141 | <td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
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| 142 | </tr>
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| 143 | </table>
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| 144 |
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| 145 | </body>
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| 146 |
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| 147 | </html>
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