1<html> 2 3<head> 4<title>Vorbisfile - function - ov_read</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_read()</h1> 17 18<p><i>declared in "vorbis/vorbisfile.h";</i></p> 19 20<p> 21 This is the main function used to decode a Vorbis file within a 22 loop. It returns up to the specified number of bytes of decoded PCM audio 23 in the requested endianness, signedness, and word size. If the audio is 24 multichannel, the channels are interleaved in the output buffer. 25 If the passed in buffer is large, <tt>ov_read()</tt> will not fill 26 it; the passed in buffer size is treated as a <em>limit</em> and 27 not a request. 28<p> 29 30Note that up to this point, the Vorbisfile API could more or less hide the 31 multiple logical bitstream nature of chaining from the toplevel 32 application if the toplevel application didn't particularly care. 33 However, when reading audio back, the application must be aware 34 that multiple bitstream sections do not necessarily use the same 35 number of channels or sampling rate. <p> <tt>ov_read()</tt> passes 36 back the index of the sequential logical bitstream currently being 37 decoded (in <tt>*bitstream</tt>) along with the PCM data in order 38 that the toplevel application can handle channel and/or sample 39 rate changes. This number will be incremented at chaining 40 boundaries even for non-seekable streams. For seekable streams, it 41 represents the actual chaining index within the physical bitstream. 42<p> 43 44<br><br> 45<table border=0 color=black cellspacing=0 cellpadding=7> 46<tr bgcolor=#cccccc> 47 <td> 48<pre><b> 49long ov_read(<a href="OggVorbis_File.html">OggVorbis_File</a> *vf, char *buffer, int length, int bigendianp, int word, int sgned, int *bitstream); 50</b></pre> 51 </td> 52</tr> 53</table> 54 55<h3>Parameters</h3> 56<dl> 57<dt><i>vf</i></dt> 58<dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisfile 59functions.</dd> 60<dt><i>buffer</i></dt> 61<dd>A pointer to an output buffer. The decoded output is inserted into this buffer.</dd> 62<dt><i>length</i></dt> 63<dd>Number of bytes to be read into the buffer. Should be the same size as the buffer. A typical value is 4096.</dd> 64<dt><i>bigendianp</i></dt> 65<dd>Specifies big or little endian byte packing. 0 for little endian, 1 for b 66ig endian. Typical value is 0.</dd> 67<dt><i>word</i></dt> 68<dd>Specifies word size. Possible arguments are 1 for 8-bit samples, or 2 or 6916-bit samples. Typical value is 2.</dd> 70<dt><i>sgned</i></dt> 71<dd>Signed or unsigned data. 0 for unsigned, 1 for signed. Typically 1.</dd> 72<dt><i>bitstream</i></dt> 73<dd>A pointer to the number of the current logical bitstream.</dd> 74</dl> 75 76 77<h3>Return Values</h3> 78<blockquote> 79<dl> 80<dt>OV_HOLE</dt> 81 <dd>indicates there was an interruption in the data. 82 <br>(one of: garbage between pages, loss of sync followed by 83 recapture, or a corrupt page)</dd> 84<dt>OV_EBADLINK</dt> 85 <dd>indicates that an invalid stream section was supplied to 86 libvorbisfile, or the requested link is corrupt.</dd> 87<dt>OV_EINVAL</dt> 88 <dd>indicates the initial file headers couldn't be read or 89 are corrupt, or that the initial open call for <i>vf</i> 90 failed.</dd> 91<dt>0</dt> 92 <dd>indicates EOF</dd> 93<dt><i>n</i></dt> 94 <dd>indicates actual number of bytes read. <tt>ov_read()</tt> will 95 decode at most one vorbis packet per invocation, so the value 96 returned will generally be less than <tt>length</tt>. 97</dl> 98</blockquote> 99 100<h3>Notes</h3> 101<p><b>Typical usage:</b> 102<blockquote> 103<tt>bytes_read = ov_read(&vf, 104buffer, 4096,0,2,1,&current_section)</tt> 105</blockquote> 106 107This reads up to 4096 bytes into a buffer, with signed 16-bit 108little-endian samples. 109</p> 110 111 112 113<br><br> 114<hr noshade> 115<table border=0 width=100%> 116<tr valign=top> 117<td><p class=tiny>copyright © 2007 Xiph.org</p></td> 118<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td> 119</tr><tr> 120<td><p class=tiny>Vorbisfile documentation</p></td> 121<td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td> 122</tr> 123</table> 124 125</body> 126 127</html> 128