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comparison src/libvorbis-1.3.3/doc/vorbisfile/ov_open_callbacks.html @ 1:05aa0afa9217
Bring in flac, ogg, vorbis
| author | Chris Cannam |
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| date | Tue, 19 Mar 2013 17:37:49 +0000 |
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| 0:c7265573341e | 1:05aa0afa9217 |
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| 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 1.3.2 - 20101101</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 © 2000-2010 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 1.3.2 - 20101101</p></td> | |
| 142 </tr> | |
| 143 </table> | |
| 144 | |
| 145 </body> | |
| 146 | |
| 147 </html> |