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Bring in flac, ogg, vorbis
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 19 Mar 2013 17:37:49 +0000
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1 <html>
2
3 <head>
4 <title>libvorbis - API Overview</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>libvorbis documentation</p></td>
12 <td align=right><p class=tiny>libvorbis version 1.3.2 - 20101101</p></td>
13 </tr>
14 </table>
15
16 <h1>Libvorbis API Overview</h1>
17
18 <p>Libvorbis is the reference implementation of the Vorbis codec. It is
19 the lowest-level interface to the Vorbis encoder and decoder, working
20 with packets directly.</p>
21
22 <p>All libvorbis routines and structures are declared in "vorbis/codec.h".</p>
23
24 <h2>Encoding workflow</h2>
25
26 <ol>
27 <li>Initialize a <a href="vorbis_info.html">vorbis_info</a> structure
28 by calling <a href="vorbis_info_init.html">vorbis_info_init</a> and
29 then functions from <a href="../vorbisenc/index.html">libvorbisenc</a>
30 on it.</li>
31 <li>Initialize a <a href="vorbis_dsp_state.html">vorbis_dsp_state</a>
32 for encoding based on the parameters in the vorbis_info by using <a
33 href="vorbis_analysis_init.html">vorbis_analysis_init</a>.</li>
34 <li>Initialize a <a href="vorbis_comment.html">vorbis_comment</a>
35 structure using <a href="vorbis_comment_init.html">vorbis_comment_init</a>,
36 populate it with any comments you wish to store in the stream, and call
37 <a href="vorbis_analysis_headerout.html">vorbis_analysis_headerout</a> to
38 get the three Vorbis stream header packets. Output the packets.</li>
39 <li>Initialize a <a href="vorbis_block.html">vorbis_block</a> structure
40 using <a href="vorbis_block_init.html">vorbis_block_init</a>.</li>
41 <li>While there is more audio to encode:<ol>
42 <li>Submit a chunk of audio data using <a
43 href="vorbis_analysis_buffer.html">vorbis_analysis_buffer</a> and <a
44 href="vorbis_analysis_wrote.html">vorbis_analysis_wrote</a>.</li>
45 <li>Obtain all available blocks using <a
46 href="vorbis_analysis_blockout.html">vorbis_analysis_blockout</a>
47 in a loop. For each block obtained:<ol>
48 <li>Encode the block into a packet (or prepare it for bitrate management)
49 using <a href="vorbis_analysis.html">vorbis_analysis</a>. (It's a good
50 idea to always pass the blocks through the bitrate
51 management mechanism; more information is on the <a
52 href="vorbis_analysis.html">vorbis_analysis</a> page. It does not affect
53 the resulting packets unless you are actually using a bitrate-managed
54 mode.)</li>
55 <li>If you are using bitrate management, submit the block using <a
56 href="vorbis_bitrate_addblock.html">vorbis_bitrate_addblock</a> and obtain
57 packets using <a
58 href="vorbis_bitrate_flushpacket.html">vorbis_bitrate_flushpacket</a>.</li>
59 <li>Output any obtained packets.</li>
60 </ol></li>
61 </ol></li>
62 <li>Submit an empty buffer to indicate the end of input; this will result
63 in an end-of-stream packet after all encoding steps are done to it.</li>
64 <li>Destroy the structures using the appropriate vorbis_*_clear routines.</li>
65 </ol>
66
67 <h2>Decoding workflow</h2>
68
69 <em>Note: if you do not need to do anything more involved than just
70 decoding the audio from an Ogg Vorbis file, you can use the far simpler
71 <a href="../vorbisfile/index.html">libvorbisfile</a> interface, which
72 will take care of all of the demuxing and low-level decoding operations
73 (and even the I/O, if you want) for you.</em>
74
75 <ol>
76 <li>When reading the header packets of an Ogg stream, you can use <a
77 href="vorbis_synthesis_idheader.html">vorbis_synthesis_idheader</a> to
78 check whether a stream might be Vorbis.</li>
79 <li>Initialize a <a href="vorbis_info.html">vorbis_info</a> and a <a
80 href="vorbis_comment.html">vorbis_comment</a> structure using the
81 appropriate vorbis_*_init routines, then pass the first three packets
82 from the stream (the Vorbis stream header packets) to <a
83 href="vorbis_synthesis_headerin.html">vorbis_synthesis_headerin</a> in
84 order. At this point, you can see the comments and basic parameters of
85 the Vorbis stream.</li>
86 <li>Initialize a <a href="vorbis_dsp_state.html">vorbis_dsp_state</a>
87 for decoding based on the parameters in the vorbis_info by using <a
88 href="vorbis_synthesis_init.html">vorbis_synthesis_init</a>.</li>
89 <li>Initialize a <a href="vorbis_block.html">vorbis_block</a> structure
90 using <a href="vorbis_block_init.html">vorbis_block_init</a>.</li>
91 <li>While there are more packets to decode:<ol>
92 <li>Decode the next packet into a block using <a
93 href="vorbis_synthesis.html">vorbis_synthesis</a>.</li>
94 <li>Submit the block to the reassembly layer using <a
95 href="vorbis_synthesis_blockin.html">vorbis_synthesis_blockin</a>.</li>
96 <li>Obtain some decoded audio using <a
97 href="vorbis_synthesis_pcmout.html">vorbis_synthesis_pcmout</a> and <a
98 href="vorbis_synthesis_read.html">vorbis_synthesis_read</a>. Any audio data
99 returned but not marked as consumed using vorbis_synthesis_read carries
100 over to the next call to vorbis_synthesis_pcmout.</li>
101 </ol></li>
102 <li>Destroy the structures using the appropriate vorbis_*_clear routines.</li>
103 </ol>
104
105 <h2>Metadata workflow</h2>
106
107 <em>Note: if you do not need to do anything more involved than just
108 reading the metadata from an Ogg Vorbis file, <a
109 href="../vorbisfile/index.html">libvorbisfile</a> can do this for you.</em>
110
111 <ol>
112 <li>Follow the decoding workflow above until you have access to the comments
113 and basic parameters of the Vorbis stream.</li>
114 <li>If you want to alter the comments, copy the first packet to the output
115 file, then create a packet for the modified comments using <a
116 href="vorbis_commentheader_out.html">vorbis_commentheader_out</a> and output
117 it, then copy the third packet and all subsequent packets into the output
118 file.</li>
119 </ol>
120
121 <br><br>
122 <hr noshade>
123 <table border=0 width=100%>
124 <tr valign=top>
125 <td><p class=tiny>copyright &copy; 2010 Xiph.Org</p></td>
126 <td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/index.html">Ogg Vorbis</a></p></td>
127 </tr><tr>
128 <td><p class=tiny>libvorbis documentation</p></td>
129 <td align=right><p class=tiny>libvorbis version 1.3.2 - 20101101</p></td>
130 </tr>
131 </table>
132
133 </body>
134
135 </html>
136