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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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cannam@86 1 <html>
cannam@86 2
cannam@86 3 <head>
cannam@86 4 <title>libogg - Decoding</title>
cannam@86 5 <link rel=stylesheet href="style.css" type="text/css">
cannam@86 6 </head>
cannam@86 7
cannam@86 8 <body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff">
cannam@86 9 <table border=0 width=100%>
cannam@86 10 <tr>
cannam@86 11 <td><p class=tiny>libogg documentation</p></td>
cannam@86 12 <td align=right><p class=tiny>libogg release 1.3.0 - 20110804</p></td>
cannam@86 13 </tr>
cannam@86 14 </table>
cannam@86 15
cannam@86 16 <h1>Decoding</h1>
cannam@86 17 <p>Libogg contains a set of functions used in the decoding process.
cannam@86 18 <p>
cannam@86 19 All the <b>libogg</b> specific functions are declared in "ogg/ogg.h".
cannam@86 20 <p>
cannam@86 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.
cannam@86 22 <p>Decoding through the Ogg layer follows a specific logical sequence. A read loop follows these logical steps:
cannam@86 23 <ul>
cannam@86 24 <li>Expose a buffer using <a href="ogg_sync_buffer.html">ogg_sync_buffer()</a>.
cannam@86 25 <li>Read data into the buffer, using fread() or a similar function.
cannam@86 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.
cannam@86 27 <li>Write out the data using <a href="ogg_sync_pageout.html">ogg_sync_pageout</a>.
cannam@86 28 <li>Submit the completed page to the streaming layer with <a href="ogg_stream_pagein.html">ogg_stream_pagein</a>.
cannam@86 29 <li>Output a packet of data to the codec-specific decoding layer using <a href="ogg_stream_packetout.html">ogg_stream_packetout</a>.
cannam@86 30 </ul>
cannam@86 31 <p>In practice, streams are more complex, and Ogg also must handle headers, incomplete or dropped pages, and other errors in input.
cannam@86 32 <br><br>
cannam@86 33
cannam@86 34 <table border=1 color=black width=50% cellspacing=0 cellpadding=7>
cannam@86 35 <tr bgcolor=#cccccc>
cannam@86 36 <td><b>function</b></td>
cannam@86 37 <td><b>purpose</b></td>
cannam@86 38 </tr>
cannam@86 39 <tr valign=top>
cannam@86 40 <td><a href="ogg_sync_init.html">ogg_sync_init</a></td>
cannam@86 41 <td>Initializes an Ogg bitstream.</td>
cannam@86 42 </tr>
cannam@86 43 <tr valign=top>
cannam@86 44 <td><a href="ogg_sync_clear.html">ogg_sync_clear</a></td>
cannam@86 45 <td>Clears the status information from the synchronization struct.<td>
cannam@86 46 </tr>
cannam@86 47 <tr valign=top>
cannam@86 48 <td><a href="ogg_sync_reset.html">ogg_sync_reset</a></td>
cannam@86 49 <td>Resets the synchronization status to initial values.</td>
cannam@86 50 </tr>
cannam@86 51 <tr valign=top>
cannam@86 52 <td><a href="ogg_sync_destroy.html">ogg_sync_destroy</a></td>
cannam@86 53 <td>Frees the synchronization struct.</td>
cannam@86 54 </tr>
cannam@86 55 <tr valign=top>
cannam@86 56 <td><a href="ogg_sync_check.html">ogg_sync_check</a></td>
cannam@86 57 <td>Check for asynchronous errors.</td>
cannam@86 58 </tr>
cannam@86 59 <tr valign=top>
cannam@86 60 <td><a href="ogg_sync_buffer.html">ogg_sync_buffer</a></td>
cannam@86 61 <td>Exposes a buffer from the synchronization layer in order to read data.</td>
cannam@86 62 </tr>
cannam@86 63 <tr valign=top>
cannam@86 64 <td><a href="ogg_sync_wrote.html">ogg_sync_wrote</a></td>
cannam@86 65 <td>Tells the synchronization layer how many bytes were written into the buffer.</td>
cannam@86 66 </tr>
cannam@86 67 <tr valign=top>
cannam@86 68 <td><a href="ogg_sync_pageseek.html">ogg_sync_pageseek</a></td>
cannam@86 69 <td>Finds the borders of pages and resynchronizes the stream.</td>
cannam@86 70 </tr>
cannam@86 71 <tr valign=top>
cannam@86 72 <td><a href="ogg_sync_pageout.html">ogg_sync_pageout</a></td>
cannam@86 73 <td>Outputs a page from the synchronization layer.</td>
cannam@86 74 </tr>
cannam@86 75 <tr valign=top>
cannam@86 76 <td><a href="ogg_stream_pagein.html">ogg_stream_pagein</a></td>
cannam@86 77 <td>Submits a complete page to the stream layer.</td>
cannam@86 78 </tr>
cannam@86 79 <tr valign=top>
cannam@86 80 <td><a href="ogg_stream_packetout.html">ogg_stream_packetout</a></td>
cannam@86 81 <td>Outputs a packet to the codec-specific decoding engine.</td>
cannam@86 82 </tr>
cannam@86 83 <tr valign=top>
cannam@86 84 <td><a href="ogg_stream_packetpeek.html">ogg_stream_packetpeek</a></td>
cannam@86 85 <td>Provides access to the next packet in the bitstream without
cannam@86 86 advancing decoding.</td>
cannam@86 87 </tr>
cannam@86 88 </table>
cannam@86 89
cannam@86 90 <br><br>
cannam@86 91 <hr noshade>
cannam@86 92 <table border=0 width=100%>
cannam@86 93 <tr valign=top>
cannam@86 94 <td><p class=tiny>copyright &copy; 2000-2011 Xiph.Org</p></td>
cannam@86 95 <td align=right><p class=tiny><a href="http://www.xiph.org/ogg/">Ogg Container Format</a></p></td>
cannam@86 96 </tr><tr>
cannam@86 97 <td><p class=tiny>libogg documentation</p></td>
cannam@86 98 <td align=right><p class=tiny>libogg release 1.3.0 - 20110804</p></td>
cannam@86 99 </tr>
cannam@86 100 </table>
cannam@86 101
cannam@86 102 </body>
cannam@86 103
cannam@86 104 </html>