doc/vorbisfile/ov_open_callbacks.html - platform/external/libvorbis - Git at Google

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 <title>Vorbisfile - function - ov_open_callbacks</title>
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 <td><p class=tiny>Vorbisfile documentation</p></td>
 <td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td>
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 <h1>ov_open_callbacks</h1>

 <p><i>declared in "vorbis/vorbisfile.h";</i></p>

 <p>This is an alternative function used to open and initialize an
 OggVorbis_File structure when using a data source other than a file,
 when its necessary to modify default file access behavior, or to
 initialize a Vorbis decode from a <tt>FILE *</tt> pointer under
 Windows where <a href="ov_open.html">ov_open()</a> cannot be used.  It
 allows the application to specify custom file manipulation routines
 and sets up all the related decoding structures.

 <p>Once ov_open_callbacks() has been called, the same
 <tt>OggVorbis_File</tt> struct should be passed to all the
 libvorbisfile functions.  Unlike <a
 href="ov_fopen.html">ov_fopen()</a> and <a
 href="ov_open.html">ov_open()</a>, ov_open_callbacks() may be used to
 instruct vorbisfile to either automatically close or not to close the
 file/data access handle in <a href="ov_clear.html">ov_clear()</a>.
 Automatic closure is disabled by passing NULL as the close callback,
 or using one of the predefined callback sets that specify a NULL close
 callback.  The application is responsible for closing a file when a
 call to ov_open_callbacks() is unsuccessful.<p>

 See also <a href="callbacks.html">Callbacks and Non-stdio I/O</a> for
 information on designing and specifying custom callback functions.<p>

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

 <h3>Parameters</h3>
 <dl>
 <dt><i>datasource</i></dt>
 <dd>Pointer to a data structure allocated by the calling application, containing any state needed by the callbacks provided.</dd>
 <dt><i>vf</i></dt>
 <dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisfile
 functions. Once this has been called, the same <tt>OggVorbis_File</tt>
 struct should be passed to all the libvorbisfile functions.</dd>
 <dt><i>initial</i></dt>
 <dd>Typically set to NULL.  This parameter is useful if some data has already been
 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>
 should be a pointer to a buffer containing the data read.</dd>
 <dt><i>ibytes</i></dt>
 <dd>Typically set to 0.  This parameter is useful if some data has already been
 read from the stream and the stream is not seekable. In this case, <tt>ibytes</tt>
 should contain the length (in bytes) of the buffer.  Used together with <tt>initial</tt>.</dd>
 <dt><i>callbacks</i></dt>
 <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>
 </dl>


 <h3>Return Values</h3>
 <blockquote>
 <li>0 for success</li>
 <li>less than zero for failure:</li>
 <ul>
 <li>OV_EREAD - A read from media returned an error.</li>
 <li>OV_ENOTVORBIS - Bitstream does not contain any Vorbis data.</li>
 <li>OV_EVERSION - Vorbis version mismatch.</li>
 <li>OV_EBADHEADER - Invalid Vorbis bitstream header.</li>
 <li>OV_EFAULT - Internal logic fault; indicates a bug or heap/stack corruption.</li>
 </ul>
 </blockquote>
 <p>

 <h3>Notes</h3>
 <dl>

 <dt><b>[a] Windows and use as an ov_open() substitute</b><p> Windows
 applications should not use <a href="ov_open.html">ov_open()</a> due
 to the likelihood of <a href="ov_open.html#winfoot">CRT linking
 mismatches and runtime protection faults
 [ov_open:a]</a>. ov_open_callbacks() is a safe substitute; specifically:

 <pre><tt>ov_open_callbacks(f, vf, initial, ibytes, OV_CALLBACKS_DEFAULT);</tt>
 </pre>

 ... provides exactly the same functionality as <a
 href="ov_open.html">ov_open()</a> but will always work correctly under
 Windows, regardless of linking setup details.<p>

 <dt><b>[b] Threaded decode</b><p>
 <dd>If your decoder is threaded, it is recommended that you NOT call
 <tt>ov_open_callbacks()</tt>
 in the main control thread--instead, call <tt>ov_open_callbacks()</tt> in your decode/playback
 thread. This is important because <tt>ov_open_callbacks()</tt> may be a fairly time-consuming
 call, given that the full structure of the file is determined at this point,
 which may require reading large parts of the file under certain circumstances
 (determining all the logical bitstreams in one physical bitstream, for
 example).  See <a href="threads.html">Thread Safety</a> for other information on using libvorbisfile with threads.
 <p>

 <dt><b>[c] Mixed media streams</b><p>
 <dd>
 As of Vorbisfile release 1.2.0, Vorbisfile is able to access the
 Vorbis content in mixed-media Ogg streams, not just Vorbis-only
 streams.  For example, Vorbisfile may be used to open and access the
 audio from an Ogg stream consisting of Theora video and Vorbis audio.
 Vorbisfile 1.2.0 decodes the first logical audio stream of each
 physical stream section.<p>

 <dt><b>[d] Faster testing for Vorbis files</b><p>
 <dd><a href="ov_test.html">ov_test()</a> and <a
 href="ov_test_callbacks.html">ov_test_callbacks()</a> provide less
 computationally expensive ways to test a file for Vorbisness, but
 require more setup code.<p>

 </dl>

 <br><br>
 <hr noshade>
 <table border=0 width=100%>
 <tr valign=top>
 <td><p class=tiny>copyright &copy; 2007 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 1.2.0 - 20070723</p></td>
 </tr>
 </table>

 </body>

 </html>
	<html>

	<head>
	<title>Vorbisfile - function - ov_open_callbacks</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 1.2.0 - 20070723</p></td>
	</tr>
	</table>

	<h1>ov_open_callbacks</h1>

	<p><i>declared in "vorbis/vorbisfile.h";</i></p>

	<p>This is an alternative function used to open and initialize an
	OggVorbis_File structure when using a data source other than a file,
	when its necessary to modify default file access behavior, or to
	initialize a Vorbis decode from a <tt>FILE *</tt> pointer under
	Windows where <a href="ov_open.html">ov_open()</a> cannot be used. It
	allows the application to specify custom file manipulation routines
	and sets up all the related decoding structures.

	<p>Once ov_open_callbacks() has been called, the same
	<tt>OggVorbis_File</tt> struct should be passed to all the
	libvorbisfile functions. Unlike <a
	href="ov_fopen.html">ov_fopen()</a> and <a
	href="ov_open.html">ov_open()</a>, ov_open_callbacks() may be used to
	instruct vorbisfile to either automatically close or not to close the
	file/data access handle in <a href="ov_clear.html">ov_clear()</a>.
	Automatic closure is disabled by passing NULL as the close callback,
	or using one of the predefined callback sets that specify a NULL close
	callback. The application is responsible for closing a file when a
	call to ov_open_callbacks() is unsuccessful.<p>

	See also <a href="callbacks.html">Callbacks and Non-stdio I/O</a> for
	information on designing and specifying custom callback functions.<p>

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

	<h3>Parameters</h3>
	<dl>
	<dt><i>datasource</i></dt>
	<dd>Pointer to a data structure allocated by the calling application, containing any state needed by the callbacks provided.</dd>
	<dt><i>vf</i></dt>
	<dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisfile
	functions. Once this has been called, the same <tt>OggVorbis_File</tt>
	struct should be passed to all the libvorbisfile functions.</dd>
	<dt><i>initial</i></dt>
	<dd>Typically set to NULL. This parameter is useful if some data has already been
	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>
	should be a pointer to a buffer containing the data read.</dd>
	<dt><i>ibytes</i></dt>
	<dd>Typically set to 0. This parameter is useful if some data has already been
	read from the stream and the stream is not seekable. In this case, <tt>ibytes</tt>
	should contain the length (in bytes) of the buffer. Used together with <tt>initial</tt>.</dd>
	<dt><i>callbacks</i></dt>
	<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>
	</dl>


	<h3>Return Values</h3>
	<blockquote>
	<li>0 for success</li>
	<li>less than zero for failure:</li>
	<ul>
	<li>OV_EREAD - A read from media returned an error.</li>
	<li>OV_ENOTVORBIS - Bitstream does not contain any Vorbis data.</li>
	<li>OV_EVERSION - Vorbis version mismatch.</li>
	<li>OV_EBADHEADER - Invalid Vorbis bitstream header.</li>
	<li>OV_EFAULT - Internal logic fault; indicates a bug or heap/stack corruption.</li>
	</ul>
	</blockquote>
	<p>

	<h3>Notes</h3>
	<dl>

	<dt><b>[a] Windows and use as an ov_open() substitute</b><p> Windows
	applications should not use <a href="ov_open.html">ov_open()</a> due
	to the likelihood of <a href="ov_open.html#winfoot">CRT linking
	mismatches and runtime protection faults
	[ov_open:a]</a>. ov_open_callbacks() is a safe substitute; specifically:

	<pre><tt>ov_open_callbacks(f, vf, initial, ibytes, OV_CALLBACKS_DEFAULT);</tt>
	</pre>

	... provides exactly the same functionality as <a
	href="ov_open.html">ov_open()</a> but will always work correctly under
	Windows, regardless of linking setup details.<p>

	<dt><b>[b] Threaded decode</b><p>
	<dd>If your decoder is threaded, it is recommended that you NOT call
	<tt>ov_open_callbacks()</tt>
	in the main control thread--instead, call <tt>ov_open_callbacks()</tt> in your decode/playback
	thread. This is important because <tt>ov_open_callbacks()</tt> may be a fairly time-consuming
	call, given that the full structure of the file is determined at this point,
	which may require reading large parts of the file under certain circumstances
	(determining all the logical bitstreams in one physical bitstream, for
	example). See <a href="threads.html">Thread Safety</a> for other information on using libvorbisfile with threads.
	<p>

	<dt><b>[c] Mixed media streams</b><p>
	<dd>
	As of Vorbisfile release 1.2.0, Vorbisfile is able to access the
	Vorbis content in mixed-media Ogg streams, not just Vorbis-only
	streams. For example, Vorbisfile may be used to open and access the
	audio from an Ogg stream consisting of Theora video and Vorbis audio.
	Vorbisfile 1.2.0 decodes the first logical audio stream of each
	physical stream section.<p>

	<dt><b>[d] Faster testing for Vorbis files</b><p>
	<dd><a href="ov_test.html">ov_test()</a> and <a
	href="ov_test_callbacks.html">ov_test_callbacks()</a> provide less
	computationally expensive ways to test a file for Vorbisness, but
	require more setup code.<p>

	</dl>

	<br><br>
	<hr noshade>
	<table border=0 width=100%>
	<tr valign=top>
	<td><p class=tiny>copyright © 2007 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 1.2.0 - 20070723</p></td>
	</tr>
	</table>

	</body>

	</html>