contrib/ogg/doc/libogg/decoding.html


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104

<html>

<head>
<title>libogg - Decoding</title>
<link rel=stylesheet href="style.css" type="text/css">
</head>

<body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
<table border=0 width=100%>
<tr>
<td><p class=tiny>libogg documentation</p></td>
<td align=right><p class=tiny>libogg release 1.3.2 - 20140527</p></td>
</tr>
</table>

<h1>Decoding</h1>
<p>Libogg contains a set of functions used in the decoding process.
<p>
All the <b>libogg</b> specific functions are declared in "ogg/ogg.h".
<p>
<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.
<p>Decoding through the Ogg layer follows a specific logical sequence.  A read loop follows these logical steps:
<ul>
<li>Expose a buffer using <a href="ogg_sync_buffer.html">ogg_sync_buffer()</a>.
<li>Read data into the buffer, using fread() or a similar function.
<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.
<li>Write out the data using <a href="ogg_sync_pageout.html">ogg_sync_pageout</a>.
<li>Submit the completed page to the streaming layer with <a href="ogg_stream_pagein.html">ogg_stream_pagein</a>.
<li>Output a packet of data to the codec-specific decoding layer using <a href="ogg_stream_packetout.html">ogg_stream_packetout</a>.
</ul>
<p>In practice, streams are more complex, and Ogg also must handle headers, incomplete or dropped pages, and other errors in input.
<br><br>

<table border=1 color=black width=50% cellspacing=0 cellpadding=7>
<tr bgcolor=#cccccc>
	<td><b>function</b></td>
	<td><b>purpose</b></td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_init.html">ogg_sync_init</a></td>
	<td>Initializes an Ogg bitstream.</td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_clear.html">ogg_sync_clear</a></td>
	<td>Clears the status information from the synchronization struct.<td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_reset.html">ogg_sync_reset</a></td>
	<td>Resets the synchronization status to initial values.</td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_destroy.html">ogg_sync_destroy</a></td>
	<td>Frees the synchronization struct.</td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_check.html">ogg_sync_check</a></td>
	<td>Check for asynchronous errors.</td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_buffer.html">ogg_sync_buffer</a></td>
	<td>Exposes a buffer from the synchronization layer in order to read data.</td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_wrote.html">ogg_sync_wrote</a></td>
	<td>Tells the synchronization layer how many bytes were written into the buffer.</td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_pageseek.html">ogg_sync_pageseek</a></td>
	<td>Finds the borders of pages and resynchronizes the stream.</td>
</tr>
<tr valign=top>
<td><a href="ogg_sync_pageout.html">ogg_sync_pageout</a></td>
	<td>Outputs a page from the synchronization layer.</td>
</tr>
<tr valign=top>
<td><a href="ogg_stream_pagein.html">ogg_stream_pagein</a></td>
	<td>Submits a complete page to the stream layer.</td>
</tr>
<tr valign=top>
<td><a href="ogg_stream_packetout.html">ogg_stream_packetout</a></td>
	<td>Outputs a packet to the codec-specific decoding engine.</td>
</tr>
<tr valign=top>
<td><a href="ogg_stream_packetpeek.html">ogg_stream_packetpeek</a></td>
	<td>Provides access to the next packet in the bitstream without
advancing decoding.</td>
</tr>
</table>

<br><br>
<hr noshade>
<table border=0 width=100%>
<tr valign=top>
<td><p class=tiny>copyright &copy; 2000-2014 Xiph.Org</p></td>
<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/">Ogg Container Format</a></p></td>
</tr><tr>
<td><p class=tiny>libogg documentation</p></td>
<td align=right><p class=tiny>libogg release 1.3.2 - 20140527</p></td>
</tr>
</table>

</body>

</html>