| 1 | <html> |
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| 2 | |
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| 3 | <head> |
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| 4 | <title>Vorbisfile - function - ov_read</title> |
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| 5 | <link rel=stylesheet href="style.css" type="text/css"> |
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| 6 | </head> |
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| 7 | |
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| 8 | <body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff"> |
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| 9 | <table border=0 width=100%> |
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| 10 | <tr> |
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| 11 | <td><p class=tiny>Vorbisfile documentation</p></td> |
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| 12 | <td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td> |
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| 13 | </tr> |
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| 14 | </table> |
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| 15 | |
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| 16 | <h1>ov_read()</h1> |
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| 17 | |
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| 18 | <p><i>declared in "vorbis/vorbisfile.h";</i></p> |
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| 19 | |
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| 20 | <p> |
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| 21 | This is the main function used to decode a Vorbis file within a |
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| 22 | loop. It returns up to the specified number of bytes of decoded PCM audio |
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| 23 | in the requested endianness, signedness, and word size. If the audio is |
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| 24 | multichannel, the channels are interleaved in the output buffer. |
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| 25 | If the passed in buffer is large, <tt>ov_read()</tt> will not fill |
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| 26 | it; the passed in buffer size is treated as a <em>limit</em> and |
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| 27 | not a request. |
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| 28 | <p> |
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| 29 | |
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| 30 | Note that up to this point, the Vorbisfile API could more or less hide the |
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| 31 | multiple logical bitstream nature of chaining from the toplevel |
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| 32 | application if the toplevel application didn't particularly care. |
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| 33 | However, when reading audio back, the application must be aware |
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| 34 | that multiple bitstream sections do not necessarily use the same |
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| 35 | number of channels or sampling rate. <p> <tt>ov_read()</tt> passes |
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| 36 | back the index of the sequential logical bitstream currently being |
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| 37 | decoded (in <tt>*bitstream</tt>) along with the PCM data in order |
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| 38 | that the toplevel application can handle channel and/or sample |
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| 39 | rate changes. This number will be incremented at chaining |
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| 40 | boundaries even for non-seekable streams. For seekable streams, it |
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| 41 | represents the actual chaining index within the physical bitstream. |
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| 42 | <p> |
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| 43 | |
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| 44 | <br><br> |
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| 45 | <table border=0 color=black cellspacing=0 cellpadding=7> |
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| 46 | <tr bgcolor=#cccccc> |
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| 47 | <td> |
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| 48 | <pre><b> |
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| 49 | long ov_read(<a href="OggVorbis_File.html">OggVorbis_File</a> *vf, char *buffer, int length, int bigendianp, int word, int sgned, int *bitstream); |
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| 50 | </b></pre> |
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| 51 | </td> |
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| 52 | </tr> |
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| 53 | </table> |
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| 54 | |
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| 55 | <h3>Parameters</h3> |
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| 56 | <dl> |
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| 57 | <dt><i>vf</i></dt> |
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| 58 | <dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisfile |
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| 59 | functions.</dd> |
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| 60 | <dt><i>buffer</i></dt> |
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| 61 | <dd>A pointer to an output buffer. The decoded output is inserted into this buffer.</dd> |
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| 62 | <dt><i>length</i></dt> |
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| 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> |
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| 64 | <dt><i>bigendianp</i></dt> |
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| 65 | <dd>Specifies big or little endian byte packing. 0 for little endian, 1 for b |
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| 66 | ig endian. Typical value is 0.</dd> |
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| 67 | <dt><i>word</i></dt> |
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| 68 | <dd>Specifies word size. Possible arguments are 1 for 8-bit samples, or 2 or |
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| 69 | 16-bit samples. Typical value is 2.</dd> |
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| 70 | <dt><i>sgned</i></dt> |
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| 71 | <dd>Signed or unsigned data. 0 for unsigned, 1 for signed. Typically 1.</dd> |
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| 72 | <dt><i>bitstream</i></dt> |
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| 73 | <dd>A pointer to the number of the current logical bitstream.</dd> |
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| 74 | </dl> |
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| 75 | |
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| 76 | |
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| 77 | <h3>Return Values</h3> |
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| 78 | <blockquote> |
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| 79 | <dl> |
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| 80 | <dt>OV_HOLE</dt> |
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| 81 | <dd>indicates there was an interruption in the data. |
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| 82 | <br>(one of: garbage between pages, loss of sync followed by |
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| 83 | recapture, or a corrupt page)</dd> |
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| 84 | <dt>OV_EBADLINK</dt> |
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| 85 | <dd>indicates that an invalid stream section was supplied to |
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| 86 | libvorbisfile, or the requested link is corrupt.</dd> |
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| 87 | <dt>0</dt> |
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| 88 | <dd>indicates EOF</dd> |
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| 89 | <dt><i>n</i></dt> |
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| 90 | <dd>indicates actual number of bytes read. <tt>ov_read()</tt> will |
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| 91 | decode at most one vorbis packet per invocation, so the value |
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| 92 | returned will generally be less than <tt>length</tt>. |
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| 93 | </dl> |
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| 94 | </blockquote> |
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| 95 | |
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| 96 | <h3>Notes</h3> |
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| 97 | <p><b>Typical usage:</b> |
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| 98 | <blockquote> |
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| 99 | <tt>bytes_read = ov_read(&vf, |
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| 100 | buffer, 4096,0,2,1,&current_section)</tt> |
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| 101 | </blockquote> |
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| 102 | |
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| 103 | This reads up to 4096 bytes into a buffer, with signed 16-bit |
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| 104 | little-endian samples. |
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| 105 | </p> |
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| 106 | |
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| 107 | |
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| 108 | |
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| 109 | <br><br> |
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| 110 | <hr noshade> |
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| 111 | <table border=0 width=100%> |
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| 112 | <tr valign=top> |
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| 113 | <td><p class=tiny>copyright © 2007 Xiph.org</p></td> |
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| 114 | <td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td> |
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| 115 | </tr><tr> |
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| 116 | <td><p class=tiny>Vorbisfile documentation</p></td> |
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| 117 | <td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td> |
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| 118 | </tr> |
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| 119 | </table> |
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| 120 | |
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| 121 | </body> |
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| 122 | |
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| 123 | </html> |
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