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<title>Vorbisfile - function - ov_fopen</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_fopen</h1>

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

<p>This is the simplest function used to open and initialize an OggVorbis_File
structure. It sets up all the related decoding structure.
<p>The first argument is a file path suitable
for passing to fopen(). <tt>vf</tt> should be a pointer to an empty
OggVorbis_File structure -- this is used for ALL the externally visible
libvorbisfile functions. Once this has been called, the same <a
href="OggVorbis_File.html">OggVorbis_File</a> struct should be passed
to all the libvorbisfile functions.
<p>The <tt>vf</tt> structure initialized using ov_fopen() must
eventually be cleaned using <a href="ov_clear.html">ov_clear()</a>.

<p>
It is often useful to call <tt>ov_fopen()</tt> simply to determine
whether a given file is a Vorbis bitstream. If the <tt>ov_fopen()</tt>
call fails, then the file is either inaccessable (errno is set) or not
recognizable as Vorbis (errno unchanged).  If the call succeeds but
the initialized <tt>vf</tt> structure will not be used, the
application is responsible for calling <a
href="ov_clear.html">ov_clear()</a> to clear the decoder's buffers and
close the file.<p>

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<pre><b>
int ov_fopen(char *path,<a href="OggVorbis_File.html">OggVorbis_File</a> *vf);
</b></pre>
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<h3>Parameters</h3>
<dl>
<dt><i>path</i></dt>
<dd>Null terminated string containing a file path suitable for passing to <tt>fopen()</tt>.
</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>
</dl>


<h3>Return Values</h3>
<blockquote>
<li>0 indicates 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] 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>[b] 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>[c] 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>

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<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>

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