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1<html>
2
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4<title>libogg - Decoding</title>
5<link rel=stylesheet href="style.css" type="text/css">
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8<body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
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11<td><p class=tiny>libogg documentation</p></td>
12<td align=right><p class=tiny>libogg release 1.2.0 - 20100325</p></td>
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15
16<h1>Decoding</h1>
17<p>Libogg contains a set of functions used in the decoding process.
18<p>
19All the <b>libogg</b> specific functions are declared in "ogg/ogg.h".
20<p>
21<p>Decoding is based around the ogg synchronization layer.  The <a href="ogg_sync_state.html">ogg_sync_state</a> struct coordinates between incoming data and the decoder.  We read data into the synchronization layer, submit the data to the stream, and output raw packets to the decoder.
22<p>Decoding through the Ogg layer follows a specific logical sequence.  A read loop follows these logical steps:
23<ul>
24<li>Expose a buffer using <a href="ogg_sync_buffer.html">ogg_sync_buffer()</a>.
25<li>Read data into the buffer, using fread() or a similar function.
26<li>Call <a href="ogg_sync_wrote.html">ogg_sync_wrote()</a> to tell the synchronization layer how many bytes you wrote into the buffer.
27<li>Write out the data using <a href="ogg_sync_pageout.html">ogg_sync_pageout</a>.
28<li>Submit the completed page to the streaming layer with <a href="ogg_stream_pagein.html">ogg_stream_pagein</a>.
29<li>Output a packet of data to the codec-specific decoding layer using <a href="ogg_stream_packetout.html">ogg_stream_packetout</a>.
30</ul>
31<p>In practice, streams are more complex, and Ogg also must handle headers, incomplete or dropped pages, and other errors in input.
32<br><br>
33
34<table border=1 color=black width=50% cellspacing=0 cellpadding=7>
35<tr bgcolor=#cccccc>
36	<td><b>function</b></td>
37	<td><b>purpose</b></td>
38</tr>
39<tr valign=top>
40<td><a href="ogg_sync_init.html">ogg_sync_init</a></td>
41	<td>Initializes an Ogg bitstream.</td>
42</tr>
43<tr valign=top>
44<td><a href="ogg_sync_clear.html">ogg_sync_clear</a></td>
45	<td>Clears the status information from the synchronization struct.<td>
46</tr>
47<tr valign=top>
48<td><a href="ogg_sync_reset.html">ogg_sync_reset</a></td>
49	<td>Resets the synchronization status to initial values.</td>
50</tr>
51<tr valign=top>
52<td><a href="ogg_sync_destroy.html">ogg_sync_destroy</a></td>
53	<td>Frees the synchronization struct.</td>
54</tr>
55<tr valign=top>
56<td><a href="ogg_sync_check.html">ogg_sync_check</a></td>
57	<td>Check for asynchronous errors.</td>
58</tr>
59<tr valign=top>
60<td><a href="ogg_sync_buffer.html">ogg_sync_buffer</a></td>
61	<td>Exposes a buffer from the synchronization layer in order to read data.</td>
62</tr>
63<tr valign=top>
64<td><a href="ogg_sync_wrote.html">ogg_sync_wrote</a></td>
65	<td>Tells the synchronization layer how many bytes were written into the buffer.</td>
66</tr>
67<tr valign=top>
68<td><a href="ogg_sync_pageseek.html">ogg_sync_pageseek</a></td>
69	<td>Finds the borders of pages and resynchronizes the stream.</td>
70</tr>
71<tr valign=top>
72<td><a href="ogg_sync_pageout.html">ogg_sync_pageout</a></td>
73	<td>Outputs a page from the synchronization layer.</td>
74</tr>
75<tr valign=top>
76<td><a href="ogg_stream_pagein.html">ogg_stream_pagein</a></td>
77	<td>Submits a complete page to the stream layer.</td>
78</tr>
79<tr valign=top>
80<td><a href="ogg_stream_packetout.html">ogg_stream_packetout</a></td>
81	<td>Outputs a packet to the codec-specific decoding engine.</td>
82</tr>
83<tr valign=top>
84<td><a href="ogg_stream_packetpeek.html">ogg_stream_packetpeek</a></td>
85	<td>Provides access to the next packet in the bitstream without
86advancing decoding.</td>
87</tr>
88</table>
89
90<br><br>
91<hr noshade>
92<table border=0 width=100%>
93<tr valign=top>
94<td><p class=tiny>copyright &copy; 2000-2010 Xiph.Org</p></td>
95<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/">Ogg Container Format</a></p></td>
96</tr><tr>
97<td><p class=tiny>libogg documentation</p></td>
98<td align=right><p class=tiny>libogg release 1.2.0 - 20100325</p></td>
99</tr>
100</table>
101
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