ogg/doc/libogg/decoding.html

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   4 <title>libogg - Decoding</title>
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  11 <td><p class=tiny>libogg documentation</p></td>
  12 <td align=right><p class=tiny>libogg release 1.3.3 - 20171107</p></td>
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  14 </table>
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  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>
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  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>
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  92 <table border=0 width=100%>
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  94 <td><p class=tiny>copyright &copy; 2000-2017 Xiph.Org Foundation</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 1.3.3 - 20171107</p></td>
  99 </tr>
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