1 <html> 2 3 <head> 4 <title>libogg - Decoding</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>libogg documentation</p></td> 12 <td align=right><p class=tiny>libogg release 1.2.0 - 20100325</p></td> 13 </tr> 14 </table> 15 16 <h1>Decoding</h1> 17 <p>Libogg contains a set of functions used in the decoding process. 18 <p> 19 All 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 86 advancing 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 © 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> 101 102 </body> 103 104 </html> 105
