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| <title>Tremor - function - ov_open_callbacks</title> |
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| <td><p class=tiny>Tremor documentation</p></td> |
| <td align=right><p class=tiny>Tremor version 1.0 - 20020403</p></td> |
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| |
| <h1>ov_open_callbacks</h1> |
| |
| <p><i>declared in "ivorbisfile.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. It allows you to specify custom file manipulation routines and sets up all the related decoding structure. |
| <p>Once this has been called, the same <tt>OggVorbis_File</tt> |
| struct should be passed to all the libvorbisidec functions. |
| <p> |
| It is often useful to call <tt>ov_open_callbacks()</tt> |
| simply to determine whether a given file is a vorbis bitstream. If the |
| <tt>ov_open_callbacks()</tt> |
| call fails, then the file is not recognizable as such. When you use <tt>ov_open_callbacks() |
| </tt>for |
| this, you should <tt>fclose()</tt> the file pointer if, and only if, the |
| <tt>ov_open_callbacks()</tt> |
| call fails. If it succeeds, you must call <a href=ov_clear.html>ov_clear()</a> to clear |
| the decoder's buffers and close the file for you.<p> |
| |
| See also <a href="callbacks.html">Callbacks and Non-stdio I/O</a> for information on designing and specifying the required callback functions.<p> |
| |
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| <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> |
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| <h3>Parameters</h3> |
| <dl> |
| <dt><i>f</i></dt> |
| <dd>File pointer to an already opened file |
| or pipe (it need not be seekable--though this obviously restricts what |
| can be done with the bitstream).</dd> |
| <dt><i>vf</i></dt> |
| <dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisidec |
| functions. Once this has been called, the same <tt>OggVorbis_File</tt> |
| struct should be passed to all the libvorbisidec 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 file 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 file 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>Pointer to a completed <a href="ov_callbacks.html">ov_callbacks</a> struct which indicates desired custom file manipulation routines.</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 is not 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> |
| <p>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 libvorbisidec with threads. |
| |
| <br><br> |
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| <td><p class=tiny>copyright © 2002 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>Tremor documentation</p></td> |
| <td align=right><p class=tiny>Tremor version 1.0 - 20020403</p></td> |
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| </table> |
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