1 <html> 2 3 <head> 4 <title>Vorbisfile - function - ov_open_callbacks</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>ov_open_callbacks</h1> 17 18 <p><i>declared in "vorbis/vorbisfile.h";</i></p> 19 20 <p>This is an alternative function used to open and initialize an 21 OggVorbis_File structure when using a data source other than a file, 22 when its necessary to modify default file access behavior, or to 23 initialize a Vorbis decode from a <tt>FILE *</tt> pointer under 24 Windows where <a href="ov_open.html">ov_open()</a> cannot be used. It 25 allows the application to specify custom file manipulation routines 26 and sets up all the related decoding structures. 27 28 <p>Once ov_open_callbacks() has been called, the same 29 <tt>OggVorbis_File</tt> struct should be passed to all the 30 libvorbisfile functions. Unlike <a 31 href="ov_fopen.html">ov_fopen()</a> and <a 32 href="ov_open.html">ov_open()</a>, ov_open_callbacks() may be used to 33 instruct vorbisfile to either automatically close or not to close the 34 file/data access handle in <a href="ov_clear.html">ov_clear()</a>. 35 Automatic closure is disabled by passing NULL as the close callback, 36 or using one of the predefined callback sets that specify a NULL close 37 callback. The application is responsible for closing a file when a 38 call to ov_open_callbacks() is unsuccessful.<p> 39 40 See also <a href="callbacks.html">Callbacks and Non-stdio I/O</a> for 41 information on designing and specifying custom callback functions.<p> 42 43 <br><br> 44 <table border=0 color=black cellspacing=0 cellpadding=7> 45 <tr bgcolor=#cccccc> 46 <td> 47 <pre><b> 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); 49 </b></pre> 50 </td> 51 </tr> 52 </table> 53 54 <h3>Parameters</h3> 55 <dl> 56 <dt><i>datasource</i></dt> 57 <dd>Pointer to a data structure allocated by the calling application, containing any state needed by the callbacks provided.</dd> 58 <dt><i>vf</i></dt> 59 <dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisfile 60 functions. Once this has been called, the same <tt>OggVorbis_File</tt> 61 struct should be passed to all the libvorbisfile functions.</dd> 62 <dt><i>initial</i></dt> 63 <dd>Typically set to NULL. This parameter is useful if some data has already been 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> 65 should be a pointer to a buffer containing the data read.</dd> 66 <dt><i>ibytes</i></dt> 67 <dd>Typically set to 0. This parameter is useful if some data has already been 68 read from the stream and the stream is not seekable. In this case, <tt>ibytes</tt> 69 should contain the length (in bytes) of the buffer. Used together with <tt>initial</tt>.</dd> 70 <dt><i>callbacks</i></dt> 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> 72 </dl> 73 74 75 <h3>Return Values</h3> 76 <blockquote> 77 <li>0 for success</li> 78 <li>less than zero for failure:</li> 79 <ul> 80 <li>OV_EREAD - A read from media returned an error.</li> 81 <li>OV_ENOTVORBIS - Bitstream does not contain any Vorbis data.</li> 82 <li>OV_EVERSION - Vorbis version mismatch.</li> 83 <li>OV_EBADHEADER - Invalid Vorbis bitstream header.</li> 84 <li>OV_EFAULT - Internal logic fault; indicates a bug or heap/stack corruption.</li> 85 </ul> 86 </blockquote> 87 <p> 88 89 <h3>Notes</h3> 90 <dl> 91 92 <dt><b>[a] Windows and use as an ov_open() substitute</b><p> Windows 93 applications should not use <a href="ov_open.html">ov_open()</a> due 94 to the likelihood of <a href="ov_open.html#winfoot">CRT linking 95 mismatches and runtime protection faults 96 [ov_open:a]</a>. ov_open_callbacks() is a safe substitute; specifically: 97 98 <pre><tt>ov_open_callbacks(f, vf, initial, ibytes, OV_CALLBACKS_DEFAULT);</tt> 99 </pre> 100 101 ... provides exactly the same functionality as <a 102 href="ov_open.html">ov_open()</a> but will always work correctly under 103 Windows, regardless of linking setup details.<p> 104 105 <dt><b>[b] Threaded decode</b><p> 106 <dd>If your decoder is threaded, it is recommended that you NOT call 107 <tt>ov_open_callbacks()</tt> 108 in the main control thread--instead, call <tt>ov_open_callbacks()</tt> in your decode/playback 109 thread. This is important because <tt>ov_open_callbacks()</tt> may be a fairly time-consuming 110 call, given that the full structure of the file is determined at this point, 111 which may require reading large parts of the file under certain circumstances 112 (determining all the logical bitstreams in one physical bitstream, for 113 example). See <a href="threads.html">Thread Safety</a> for other information on using libvorbisfile with threads. 114 <p> 115 116 <dt><b>[c] Mixed media streams</b><p> 117 <dd> 118 As of Vorbisfile release 1.2.0, Vorbisfile is able to access the 119 Vorbis content in mixed-media Ogg streams, not just Vorbis-only 120 streams. For example, Vorbisfile may be used to open and access the 121 audio from an Ogg stream consisting of Theora video and Vorbis audio. 122 Vorbisfile 1.2.0 decodes the first logical audio stream of each 123 physical stream section.<p> 124 125 <dt><b>[d] Faster testing for Vorbis files</b><p> 126 <dd><a href="ov_test.html">ov_test()</a> and <a 127 href="ov_test_callbacks.html">ov_test_callbacks()</a> provide less 128 computationally expensive ways to test a file for Vorbisness, but 129 require more setup code.<p> 130 131 </dl> 132 133 <br><br> 134 <hr noshade> 135 <table border=0 width=100%> 136 <tr valign=top> 137 <td><p class=tiny>copyright © 2007 Xiph.org</p></td> 138 <td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td> 139 </tr><tr> 140 <td><p class=tiny>Vorbisfile documentation</p></td> 141 <td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td> 142 </tr> 143 </table> 144 145 </body> 146 147 </html> 148
