93 lines
3.3 KiB
HTML
93 lines
3.3 KiB
HTML
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<html>
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<head>
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<title>Vorbisfile - Decoding</title>
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<link rel=stylesheet href="style.css" type="text/css">
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</head>
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<body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
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<table border=0 width=100%>
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<tr>
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<td><p class=tiny>Vorbisfile documentation</p></td>
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<td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
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</tr>
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</table>
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<h1>Decoding</h1>
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<p>
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All libvorbisfile decoding routines are declared in "vorbis/vorbisfile.h".
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<p>
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After <a href="initialization.html">initialization</a>, decoding audio
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is as simple as calling <a href="ov_read.html">ov_read()</a> (or the
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similar functions <a href="ov_read_float.html">ov_read_float()</a> and
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<a href="ov_read_filter.html">ov_read_filter</a>). This function works
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similarly to reading from a normal file using <tt>read()</tt>.<p>
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However, a few differences are worth noting:
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<h2>multiple stream links</h2>
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A Vorbis stream may consist of multiple sections (called links) that
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encode differing numbers of channels or sample rates. It is vitally
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important to pay attention to the link numbers returned by <a
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href="ov_read.html">ov_read</a> and handle audio changes that may
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occur at link boundaries. Such multi-section files do exist in the
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wild and are not merely a specification curiosity.
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<h2>returned data amount</h2>
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<a href="ov_read.html">ov_read</a> does not attempt to completely fill
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a large, passed in data buffer; it merely guarantees that the passed
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back data does not overflow the passed in buffer size. Large buffers
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may be filled by iteratively looping over calls to <a
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href="ov_read.html">ov_read</a> (incrementing the buffer pointer)
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until the original buffer is filled.
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<h2>file cursor position</h2>
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Vorbis files do not necessarily start at a sample number or time offset
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of zero. Do not be surprised if a file begins at a positive offset of
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several minutes or hours, such as would happen if a large stream (such
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as a concert recording) is chopped into multiple seperate files.
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<p>
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<table border=1 color=black width=50% cellspacing=0 cellpadding=7>
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<tr bgcolor=#cccccc>
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<td><b>function</b></td>
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<td><b>purpose</b></td>
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</tr>
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<tr valign=top>
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<td><a href="ov_read.html">ov_read</a></td>
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<td>This function makes up the main chunk of a decode loop. It takes an
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OggVorbis_File structure, which must have been initialized by a previous
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call to <a href="ov_open.html"><tt>ov_open()</tt></a>, <a href="ov_fopen.html"><tt>ov_fopen()</tt></a>,
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or <a href="ov_open_callbacks.html"><tt>ov_open_callbacks()</tt></a>.</td>
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</tr>
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<tr valign=top>
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<td><a href="ov_read_float.html">ov_read_float</a></td>
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<td>This function decodes to floats instead of integer samples.</td>
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</tr>
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<tr valign=top>
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<td><a href="ov_read_filter.html">ov_read_filter</a></td>
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<td>This function works like <a href="ov_read.html">ov_read</a>, but passes the PCM data through the provided filter before converting to integer sample data.</td>
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</tr>
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</table>
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<br><br>
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<hr noshade>
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<table border=0 width=100%>
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<tr valign=top>
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<td><p class=tiny>copyright © 2000-2010 Xiph.Org</p></td>
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<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td>
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</tr><tr>
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<td><p class=tiny>Vorbisfile documentation</p></td>
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<td align=right><p class=tiny>vorbisfile version 1.3.2 - 20101101</p></td>
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</tr>
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</table>
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</body>
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</html>
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