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| <title>Tremor - function - ov_read</title> |
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| <td><p class=tiny>Tremor documentation</p></td> |
| <td align=right><p class=tiny>Tremor version 1.0 - 20020403</p></td> |
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| </table> |
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| <h1>ov_read()</h1> |
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| <p><i>declared in "ivorbisfile.h";</i></p> |
| |
| <p> |
| This is the main function used to decode a Vorbis file within a |
| loop. It returns up to the specified number of bytes of decoded audio |
| in host-endian, signed 16 bit PCM format. If the audio is |
| multichannel, the channels are interleaved in the output buffer. |
| If the passed in buffer is large, <tt>ov_read()</tt> will not fill |
| it; the passed in buffer size is treated as a <em>limit</em> and |
| not a request. |
| <p> |
| |
| Note that up to this point, the Tremor API could more or less hide the |
| multiple logical bitstream nature of chaining from the toplevel |
| application if the toplevel application didn't particularly care. |
| However, when reading audio back, the application must be aware |
| that multiple bitstream sections do not necessarily use the same |
| number of channels or sampling rate. <p> <tt>ov_read()</tt> passes |
| back the index of the sequential logical bitstream currently being |
| decoded (in <tt>*bitstream</tt>) along with the PCM data in order |
| that the toplevel application can handle channel and/or sample |
| rate changes. This number will be incremented at chaining |
| boundaries even for non-seekable streams. For seekable streams, it |
| represents the actual chaining index within the physical bitstream. |
| <p> |
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| <pre><b> |
| long ov_read(<a href="OggVorbis_File.html">OggVorbis_File</a> *vf, char *buffer, int length, int *bitstream); |
| </b></pre> |
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| <h3>Parameters</h3> |
| <dl> |
| <dt><i>vf</i></dt> |
| <dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisidec |
| functions.</dd> |
| <dt><i>buffer</i></dt> |
| <dd>A pointer to an output buffer. The decoded output is inserted into this buffer.</dd> |
| <dt><i>length</i></dt> |
| <dd>Number of bytes to be read into the buffer. Should be the same size as the buffer. A typical value is 4096.</dd> |
| <dt><i>bitstream</i></dt> |
| <dd>A pointer to the number of the current logical bitstream.</dd> |
| </dl> |
| |
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| <h3>Return Values</h3> |
| <blockquote> |
| <dl> |
| <dt>OV_HOLE</dt> |
| <dd>indicates there was an interruption in the data. |
| <br>(one of: garbage between pages, loss of sync followed by |
| recapture, or a corrupt page)</dd> |
| <dt>OV_EBADLINK</dt> |
| <dd>indicates that an invalid stream section was supplied to |
| libvorbisidec, or the requested link is corrupt.</dd> |
| <dt>0</dt> |
| <dd>indicates EOF</dd> |
| <dt><i>n</i></dt> |
| <dd>indicates actual number of bytes read. <tt>ov_read()</tt> will |
| decode at most one vorbis packet per invocation, so the value |
| returned will generally be less than <tt>length</tt>. |
| </dl> |
| </blockquote> |
| |
| <h3>Notes</h3> |
| <p><b>Typical usage:</b> |
| <blockquote> |
| <tt>bytes_read = ov_read(&vf, |
| buffer, 4096,&current_section)</tt> |
| </blockquote> |
| |
| This reads up to 4096 bytes into a buffer, with signed 16-bit |
| little-endian samples. |
| </p> |
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| <br><br> |
| <hr noshade> |
| <table border=0 width=100%> |
| <tr valign=top> |
| <td><p class=tiny>copyright © 2002 Xiph.org</p></td> |
| <td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td> |
| </tr><tr> |
| <td><p class=tiny>Tremor documentation</p></td> |
| <td align=right><p class=tiny>Tremor version 1.0 - 20020403</p></td> |
| </tr> |
| </table> |
| |
| </body> |
| |
| </html> |
