-<HTML><HEAD><TITLE>xiph.org: Ogg Vorbis documentation</TITLE>
-<BODY bgcolor="#ffffff" text="#202020" link="#006666" vlink="#000000">
-<nobr><img src="white-ogg.png"><img src="vorbisword2.png"></nobr><p>
-
-
-<h1><font color=#000070>
-Programming with Xiph.org <tt>libvorbis</tt>
-</font></h1>
-
-<em>Last update to this document: July 22, 1999</em><br>
-
-<h2>Description</h2>
-
-Libvorbis is the Xiph.org Foundation's portable Ogg Vorbis CODEC
-implemented as a programmatic library. Libvorbis provides primitives
-to handle framing and manipulation of Ogg bitstreams (used by the
-Vorbis for streaming), a full analysis (encoding) interface as well as
-packet decoding and synthesis for playback. <p>
-
-The libvorbis library does not provide any system interface; a
-full-featured demonstration player included with the library
-distribtion provides example code for a variety of system interfaces
-as well as a working example of using libvorbis in production code.
-
-<h2>Encoding Overview</h2>
-
-
-
-<h2>Decoding Overview</h2>
-
-Decoding a bitstream with libvorbis follows roughly the following
-steps:
-
-<ol>
-<li>Frame the incoming bitstream into pages
-<li>Sort the pages by logical bitstream and buffer then into logical streams
-<li>Decompose the logical streams into raw packets
-<li>Reconstruct segments of the original data from each packet
-<li>Glue the reconstructed segments back into a decoded stream
-</ol>
-
-<h3>Framing</h3>
-
-An Ogg bitstream is logically arranged into pages, but to decode
-the pages, we have to find them first. The raw bitstream is first fed
-into an <tt>ogg_sync_state</tt> buffer using <tt>ogg_sync_buffer()</tt>
-and <tt>ogg_sync_wrote()</tt>. After each block we submit to the sync
-buffer, we should check to see if we can frame and extract a complete
-page or pages using <tt>ogg_sync_pageout()</tt>. Extra pages are
-buffered; allowing them to build up in the <tt>ogg_sync_state</tt>
-buffer will eventually exhaust memory.<p>
-
-The Ogg pages returned from <tt>ogg_sync_pageout</tt> need not be
-decoded further to be used as landmarks in seeking; seeking can be
-either a rough process of simply jumping to approximately intuited
-portions of the bitstream, or it can be a precise bisection process
-that captures pages and inspects data position. When seeking,
-however, sequential multiplexing (chaining) must be accounted for;
-beginning play in a new logical bitstream requires initializing a
-synthesis engine with the headers from that bitstream. Vorbis
-bitstreams do not make use of concurent multiplexing (grouping).<p>
-
-<h3>Sorting</h3>
-
-The pages produced by <tt>ogg_sync_pageout</tt> are then sorted by
-serial number to seperate logical bitstreams. Initialize logical
-bitstream buffers (<tt>og_stream_state</tt>) using
-<tt>ogg_stream_init()</tt>. Pages are submitted to the matching
-logical bitstream buffer using <tt>ogg_stream_pagein</tt>; the serial
-number of the page and the stream buffer must match, or the page will
-be rejected. A page submitted out of sequence will simply be noted,
-and in the course of outputting packets, the hole will be flagged
-(<tt>ogg_sync_pageout</tt> and <tt>ogg_stream_packetout</tt> will
-return a negative value at positions where they had to recapture the
-stream).
-
-<h3>Extracting packets</h3>
-
-After submitting page[s] to a logical stream, read available packets
-using <tt>ogg_stream_packetout</tt>.
-
-<h3>Decoding packets</h3>
-
-<h3>Reassembling data segments</h3>
-
-
-<h2>Ogg Bitstream Manipulation Structures</h3>
-
-Two of the Ogg bitstream data structures are intended to be
-transparent to the developer; the fields should be used directly.<p>
-
-<h3>ogg_packet</h3>
-
-<pre>
-typedef struct {
- unsigned char *packet;
- long bytes;
- long b_o_s;
- long e_o_s;
-
- size64 granulepos;
-
-} ogg_packet;
-</pre>
-
-<dl>
-<dt>packet: <dd>a pointer to the byte data of the raw packet
-<dt>bytes: <dd>the size of the packet' raw data
-<dt>b_o_s: <dd>beginning of stream; nonzero if this is the first packet of
- the logical bitstream
-<dt>e_o_s: <dd>end of stream; nonzero if this is the last packet of the
- logical bitstream
-<dt>granulepos: <dd>the absolute position of this packet in the original
- uncompressed data stream.
-</dl>
-
-<h4>encoding notes</h4> The encoder is responsible for setting all of
-the fields of the packet to appropriate values before submission to
-<tt>ogg_stream_packetin()</tt>; however, it is noted that the value in
-<tt>b_o_s</tt> is ignored; the first page produced from a given
-<tt>ogg_stream_state</tt> structure will be stamped as the initial
-page. <tt>e_o_s</tt>, however, must be set; this is the means by
-which the stream encoding primitives handle end of stream and cleanup.
-
-<h4>decoding notes</h4><tt>ogg_stream_packetout()</tt> sets the fields
-to appropriate values. Note that granulepos will be >= 0 only in the
-case that the given packet actually represents that position (ie, only
-the last packet completed on any page will have a meaningful
-<tt>granulepos</tt>). Intervening frames will see <tt>granulepos</tt> set
-to -1.
-
-<h3>ogg_page</h3>
-
-<pre>
-typedef struct {
- unsigned char *header;
- long header_len;
- unsigned char *body;
- long body_len;
-} ogg_page;
-</pre>
-
-<dl>
-<dt>header: <dd>pointer to the page header data
-<dt>header_len: <dd>length of the page header in bytes
-<dt>body: <dd>pointer to the page body
-<dt>body_len: <dd>length of the page body
-</dl>
-
-Note that although the <tt>header</tt> and <tt>body</tt> pointers do
-not necessarily point into a single contiguous page vector, the page
-body must immediately follow the header in the bitstream.<p>
-
-<h2>Ogg Bitstream Manipulation Functions</h3>
-
-<h3>
-int ogg_page_bos(ogg_page *og);
-</h3>
-
-Returns the 'beginning of stream' flag for the given Ogg page. The
-beginning of stream flag is set on the initial page of a logical
-bitstream.<P>
-
-Zero indicates the flag is cleared (this is not the initial page of a
-logical bitstream). Nonzero indicates the flag is set (this is the
-initial page of a logical bitstream).<p>
-
-<h3>
-int ogg_page_continued(ogg_page *og);
-</h3>
-
-Returns the 'packet continued' flag for the given Ogg page. The packet
-continued flag indicates whether or not the body data of this page
-begins with packet continued from a preceeding page.<p>
-Zero (unset) indicates that the body data begins with a new packet.
-Nonzero (set) indicates that the first packet data on the page is a
-continuation from the preceeding page.
-
-<h3>
-int ogg_page_eos(ogg_page *og);
-</h3>
-
-Returns the 'end of stream' flag for a give Ogg page. The end of page
-flag is set on the last (terminal) page of a logical bitstream.<p>
-
-Zero (unset) indicates that this is not the last page of a logical
-bitstream. Nonzero (set) indicates that this is the last page of a
-logical bitstream and that no addiitonal pages belonging to this
-bitstream may follow.<p>
-
-<h3>
-size64 ogg_page_granulepos(ogg_page *og);
-</h3>
-
-Returns the position of this page as an absolute position within the
-original uncompressed data. The position, as returned, is 'frames
-encoded to date up to and including the last whole packet on this
-page'. Partial packets begun on this page but continued to the
-following page are not included. If no packet ends on this page, the
-frame position value will be equal to the frame position value of the
-preceeding page. If none of the original uncompressed data is yet
-represented in the logical bitstream (for example, the first page of a
-bitstream consists only of a header packet; this packet encodes only
-metadata), the value shall be zero.<p>
-
-The units of the framenumber are determined by media mapping. A
-vorbis audio bitstream, for example, defines one frame to be the
-channel values from a single sampling period (eg, a 16 bit stereo
-bitstream consists of two samples of two bytes for a total of four
-bytes, thus a frame would be four bytes). A video stream defines one
-frame to be a single frame of video.<p>
-
-<h3>
-int ogg_page_pageno(ogg_page *og);
-</h3>
-
-Returns the sequential page number of the given Ogg page. The first
-page in a logical bitstream is numbered zero; following pages are
-numbered in increasing monotonic order.<p>
-
-<h3>
-int ogg_page_serialno(ogg_page *og);
-</h3>
-
-Returns the serial number of the given Ogg page. The serial number is
-used as a handle to distinguish various logical bitstreams in a
-physical Ogg bitstresm. Every logical bitstream within a
-physical bitstream must use a unique (within the scope of the physical
-bitstream) serial number, which is stamped on all bitstream pages.<p>
-
-<h3>
-int ogg_page_version(ogg_page *og);
-</h3>
-
-Returns the revision of the Ogg bitstream structure of the given page.
-Currently, the only permitted number is zero. Later revisions of the
-bitstream spec will increment this version should any changes be
-incompatable.</p>
-
-<h3>
-int ogg_stream_clear(ogg_stream_state *os);
-</h3>
-
-Clears and deallocates the internal storage of the given Ogg stream.
-After clearing, the stream structure is not initialized for use;
-<tt>ogg_stream_init</tt> must be called to reinitialize for use.
-Use <tt>ogg_stream_reset</tt> to reset the stream state
-to a fresh, intiialized state.<p>
-
-<tt>ogg_stream_clear</tt> does not call <tt>free()</tt> on the pointer
-<tt>os</tt>, allowing use of this call on stream structures in static
-or automatic storage. <tt>ogg_stream_destroy</tt>is a complimentary
-function that frees the pointer as well.<p>
-
-Returns zero on success and non-zero on failure. This function always
-succeeds.<p>
-
-<h3>
-int ogg_stream_destroy(ogg_stream_state *os);
-</h3>
-
-Clears and deallocates the internal storage of the given Ogg stream,
-then frees the storage associated with the pointer <tt>os</tt>.<p>
-
-<tt>ogg_stream_clear</tt> does not call <tt>free()</tt> on the pointer
-<tt>os</tt>, allowing use of that call on stream structures in static
-or automatic storage.<p>
-
-Returns zero on success and non-zero on failure. This function always
-succeeds.<p>
-
-<h3>
-int ogg_stream_init(ogg_stream_state *os,int serialno);
-</h3>
-
-Initialize the storage associated with <tt>os</tt> for use as an Ogg
-stream. This call is used to initialize a stream for both encode and
-decode. The given serial number is the serial number that will be
-stamped on pages of the produced bitstream (during encode), or used as
-a check that pages match (during decode).<p>
-
-Returns zero on success, nonzero on failure.<p>
-
-<h3>
-int ogg_stream_packetin(ogg_stream_state *os, ogg_packet *op);
-</h3>
-
-Used during encoding to add the given raw packet to the given Ogg
-bitstream. The contents of <tt>op</tt> are copied;
-<tt>ogg_stream_packetin</tt> does not retain any pointers into
-<tt>op</tt>'s storage. The encoding proccess buffers incoming packets
-until enough packets have been assembled to form an entire page;
-<tt>ogg_stream_pageout</tt> is used to read complete pages.<p>
-
-Returns zero on success, nonzero on failure.<p>
-
-<h3>
-int ogg_stream_packetout(ogg_stream_state *os,ogg_packet *op);
-</h3>
-
-Used during decoding to read raw packets from the given logical
-bitstream. <tt>ogg_stream_packetout</tt> will only return complete
-packets for which checksumming indicates no corruption. The size and
-contents of the packet exactly match those given in the encoding
-process. <p>
-
-Returns zero if the next packet is not ready to be read (not buffered
-or incomplete), positive if it returned a complete packet in
-<tt>op</tt> and negative if there is a gap, extra bytes or corruption
-at this position in the bitstream (essentially that the bitstream had
-to be recaptured). A negative value is not necessarily an error. It
-would be a common occurence when seeking, for example, which requires
-recapture of the bitstream at the position decoding continued.<p>
-
-Iff the return value is positive, <tt>ogg_stream_packetout</tt> placed
-a packet in <tt>op</tt>. The data in <t>op</tt> points to static
-storage that is valid until the next call to
-<tt>ogg_stream_pagein</tt>, <tt>ogg_stream_clear</tt>,
-<tt>ogg_stream_reset</tt>, or <tt>ogg_stream_destroy</tt>. The
-pointers are not invalidated by more calls to
-<tt>ogg_stream_packetout</tt>.<p>
-
-<h3>
-int ogg_stream_pagein(ogg_stream_state *os, ogg_page *og);
-</h3>
-
-Used during decoding to buffer the given complete, pre-verified page
-for decoding into raw Ogg packets. The given page must be framed,
-normally produced by <tt>ogg_sync_pageout</tt>, and from the logical
-bitstream associated with <tt>os</tt> (the serial numbers must match).
-The contents of the given page are copied; <tt>ogg_stream_pagein</tt>
-retains no pointers into <tt>og</tt> storage.<p>
-
-Returns zero on success and non-zero on failure.<p>
-
-<h3>
-int ogg_stream_pageout(ogg_stream_state *os, ogg_page *og);
-</h3>
-
-Used during encode to read complete pages from the stream buffer. The
-returned page is ready for sending out to the real world.<p>
-
-Returns zero if there is no complete page ready for reading. Returns
-nonzero when it has placed data for a complete page into
-<tt>og</tt>. Note that the storage returned in og points into internal
-storage; the pointers in <tt>og</tt> are valid until the next call to
-<tt>ogg_stream_pageout</tt>, <tt>ogg_stream_packetin</tt>,
-<tt>ogg_stream_reset</tt>, <tt>ogg_stream_clear</tt> or
-<tt>ogg_stream_destroy</tt>.
-
-<h3>
-int ogg_stream_reset(ogg_stream_state *os);
-</h3>
-
-Resets the given stream's state to that of a blank, unused stream;
-this may be used during encode or decode. <p>
-
-Note that if used during encode, it does not alter the stream's serial
-number. In addition, the next page produced during encoding will be
-marked as the 'initial' page of the logical bitstream.<p>
-
-When used during decode, this simply clears the data buffer of any
-pending pages. Beginning and end of stream cues are read from the
-bitstream and are unaffected by reset.<p>
-
-Returns zero on success and non-zero on failure. This function always
-succeeds.<p>
-
-<h3>
-char *ogg_sync_buffer(ogg_sync_state *oy, long size);
-</h3>
-
-This call is used to buffer a raw bitstream for framing and
-verification. <tt>ogg_sync_buffer</tt> handles stream capture and
-recapture, checksumming, and division into Ogg pages (as required by
-<tt>ogg_stream_pagein</tt>).<p>
-
-<tt>ogg_sync_buffer</tt> exposes a buffer area into which the decoder
-copies the next (up to) <tt>size</tt> bytes. We expose the buffer
-(rather than taking a buffer) in order to avoid an extra copy many
-uses; this way, for example, <tt>read()</tt> can transfer data
-directly into the stream buffer without first needing to place it in
-temporary storage.<p>
-
-Returns a pointer into <tt>oy</tt>'s internal bitstream sync buffer;
-the remaining space in the sync buffer is at least <tt>size</tt>
-bytes. The decoder need not write all of <tt>size</tt> bytes;
-<tt>ogg_sync_wrote</tt> is used to inform the engine how many bytes
-were actually written. Use of <tt>ogg_sync_wrote</tt> after writing
-into the exposed buffer is mandantory.<p>
-
-<h3>
-int ogg_sync_clear(ogg_sync_state *oy);
-</h3>
-
-<tt>ogg_sync_clear</tt>
-
-Clears and deallocates the internal storage of the given Ogg sync
-buffer. After clearing, the sync structure is not initialized for
-use; <tt>ogg_sync_init</tt> must be called to reinitialize for use.
-Use <tt>ogg_sync_reset</tt> to reset the sync state and buffer to a
-fresh, intiialized state.<p>
-
-<tt>ogg_sync_clear</tt> does not call <tt>free()</tt> on the pointer
-<tt>oy</tt>, allowing use of this call on sync structures in static
-or automatic storage. <tt>ogg_sync_destroy</tt>is a complimentary
-function that frees the pointer as well.<p>
-
-Returns zero on success and non-zero on failure. This function always
-succeeds.<p>
-
-<h3>
-int ogg_sync_destroy(ogg_sync_state *oy);
-</h3>
-
-Clears and deallocates the internal storage of the given Ogg sync
-buffer, then frees the storage associated with the pointer
-<tt>oy</tt>.<p>
-
-<tt>ogg_sync_clear</tt> does not call <tt>free()</tt> on the pointer
-<tt>oy</tt>, allowing use of that call on stream structures in static
-or automatic storage.<p>
-
-Returns zero on success and non-zero on failure. This function always
-succeeds.<p>
-
-<h3>
-int ogg_sync_init(ogg_sync_state *oy);
-</h3>
-
-Initializes the sync buffer <tt>oy</tt> for use.<p>
-Returns zero on success and non-zero on failure. This function always
-succeeds.<p>
-
-<h3>
-int ogg_sync_pageout(ogg_sync_state *oy, ogg_page *og);
-</h3>
-
-Reads complete, framed, verified Ogg pages from the sync buffer,
-placing the page data in <tt>og</tt>.<p>
-
-Returns zero when there's no complete pages buffered for
-retrieval. Returns negative when a loss of sync or recapture occurred
-(this is not necessarily an error; recapture would be required after
-seeking, for example). Returns positive when a page is returned in
-<tt>og</tt>. Note that the data in <tt>og</tt> points into the sync
-buffer storage; the pointers are valid until the next call to
-<tt>ogg_sync_buffer</tt>, <tt>ogg_sync_clear</tt>,
-<tt>ogg_sync_destroy</tt> or <tt>ogg_sync_reset</tt>.
-
-
-<h3>
-int ogg_sync_reset(ogg_sync_state *oy);
-</h3>
-
-<tt>ogg_sync_reset</tt> resets the sync state in <tt>oy</tt> to a
-clean, empty state. This is useful, for example, when seeking to a
-new location in a bitstream.<p>
-
-Returns zero on success, nonzero on failure.<p>
-
-<h3>
-int ogg_sync_wrote(ogg_sync_state *oy, long bytes);
-</h3>
-
-Used to inform the sync state as to how many bytes were actually
-written into the exposed sync buffer. It must be equal to or less
-than the size of the buffer requested.<p>
-
-Returns zero on success and non-zero on failure; failure occurs only
-when the number of bytes written were larger than the buffer.<p>
-
-<hr>
-<a href="http://www.xiph.org/">
-<img src="white-xifish.png" align=left border=0>
-</a>
-<font size=-2 color=#505050>
-
-Ogg is a <a href="http://www.xiph.org"></a> effort to
-protect essential tenets of Internet multimedia from corporate
-hostage-taking; Open Source is the net's greatest tool to keep
-everyone honest. See <a href="http://www.xiph.org/about.html">About
-</a> for details.
-<p>
-
-Ogg Vorbis is the first Ogg audio CODEC. Anyone may freely use and
-distribute the Ogg and Vorbis specification, whether in a private,
-public or corporate capacity. However, the Xiph.org Foundation and
-the Ogg project (xiph.org) reserve the right to set the Ogg Vorbis
-specification and certify specification compliance.<p>
-
-Xiph.org's Vorbis software CODEC implementation is distributed under a
-BSD-like license. This does not restrict third parties from
-distributing independent implementations of Vorbis software under
-other licenses.<p>
-
-Ogg, Vorbis, Xiph.org Foundation and their logos are trademarks (tm)
-of the <a href="http://www.xiph.org/">Xiph.org Foundation</a>. These
-pages are copyright (C) 1994-2002 Xiph.org Foundation. All rights
-reserved.<p>
-
-</body>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">\r
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+<head>\r
+\r
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+<title>Ogg Vorbis Documentation</title>\r
+\r
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+ margin-top: 30px;\r
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+ color: #888888;\r
+ clear: both;\r
+}\r
+</style>\r
+\r
+</head>\r
+\r
+<body>\r
+\r
+<div id="xiphlogo">\r
+ <a href="http://www.xiph.org/"><img src="fish_xiph_org.png" alt="Fish Logo and Xiph.org"/></a>\r
+</div>\r
+\r
+<h1>Programming with Xiph.org <tt>libvorbis</tt></h1>\r
+\r
+<h2>Description</h2> \r
+\r
+<p>Libvorbis is the Xiph.org Foundation's portable Ogg Vorbis CODEC\r
+implemented as a programmatic library. Libvorbis provides primitives\r
+to handle framing and manipulation of Ogg bitstreams (used by the\r
+Vorbis for streaming), a full analysis (encoding) interface as well as\r
+packet decoding and synthesis for playback.</p>\r
+\r
+<p>The libvorbis library does not provide any system interface; a\r
+full-featured demonstration player included with the library\r
+distribtion provides example code for a variety of system interfaces\r
+as well as a working example of using libvorbis in production code.</p>\r
+\r
+<h2>Encoding Overview</h2>\r
+\r
+<h2>Decoding Overview</h2>\r
+\r
+<p>Decoding a bitstream with libvorbis follows roughly the following\r
+steps:</p>\r
+\r
+<ol>\r
+<li>Frame the incoming bitstream into pages</li>\r
+<li>Sort the pages by logical bitstream and buffer then into logical streams</li>\r
+<li>Decompose the logical streams into raw packets</li>\r
+<li>Reconstruct segments of the original data from each packet</li>\r
+<li>Glue the reconstructed segments back into a decoded stream</li>\r
+</ol>\r
+\r
+<h3>Framing</h3>\r
+\r
+<p>An Ogg bitstream is logically arranged into pages, but to decode\r
+the pages, we have to find them first. The raw bitstream is first fed\r
+into an <tt>ogg_sync_state</tt> buffer using <tt>ogg_sync_buffer()</tt>\r
+and <tt>ogg_sync_wrote()</tt>. After each block we submit to the sync\r
+buffer, we should check to see if we can frame and extract a complete\r
+page or pages using <tt>ogg_sync_pageout()</tt>. Extra pages are\r
+buffered; allowing them to build up in the <tt>ogg_sync_state</tt>\r
+buffer will eventually exhaust memory.</p>\r
+\r
+<p>The Ogg pages returned from <tt>ogg_sync_pageout</tt> need not be\r
+decoded further to be used as landmarks in seeking; seeking can be\r
+either a rough process of simply jumping to approximately intuited\r
+portions of the bitstream, or it can be a precise bisection process\r
+that captures pages and inspects data position. When seeking,\r
+however, sequential multiplexing (chaining) must be accounted for;\r
+beginning play in a new logical bitstream requires initializing a\r
+synthesis engine with the headers from that bitstream. Vorbis\r
+bitstreams do not make use of concurent multiplexing (grouping).</p>\r
+\r
+<h3>Sorting</h3>\r
+\r
+<p>The pages produced by <tt>ogg_sync_pageout</tt> are then sorted by\r
+serial number to seperate logical bitstreams. Initialize logical\r
+bitstream buffers (<tt>og_stream_state</tt>) using\r
+<tt>ogg_stream_init()</tt>. Pages are submitted to the matching\r
+logical bitstream buffer using <tt>ogg_stream_pagein</tt>; the serial\r
+number of the page and the stream buffer must match, or the page will\r
+be rejected. A page submitted out of sequence will simply be noted,\r
+and in the course of outputting packets, the hole will be flagged\r
+(<tt>ogg_sync_pageout</tt> and <tt>ogg_stream_packetout</tt> will\r
+return a negative value at positions where they had to recapture the\r
+stream).</p>\r
+\r
+<h3>Extracting packets</h3>\r
+\r
+<p>After submitting page[s] to a logical stream, read available packets\r
+using <tt>ogg_stream_packetout</tt>.</p>\r
+\r
+<h3>Decoding packets</h3>\r
+\r
+<h3>Reassembling data segments</h3>\r
+\r
+<h2>Ogg Bitstream Manipulation Structures</h2>\r
+\r
+<p>Two of the Ogg bitstream data structures are intended to be\r
+transparent to the developer; the fields should be used directly.</p>\r
+\r
+<h3>ogg_packet</h3>\r
+\r
+<pre>\r
+typedef struct {\r
+ unsigned char *packet;\r
+ long bytes;\r
+ long b_o_s;\r
+ long e_o_s;\r
+\r
+ size64 granulepos;\r
+\r
+} ogg_packet;\r
+</pre>\r
+\r
+<dl>\r
+<dt>packet:</dt>\r
+<dd>a pointer to the byte data of the raw packet</dd>\r
+<dt>bytes:</dt>\r
+<dd>the size of the packet' raw data</dd>\r
+<dt>b_o_s:</dt>\r
+<dd>beginning of stream; nonzero if this is the first packet of \r
+ the logical bitstream</dd>\r
+<dt>e_o_s:</dt>\r
+<dd>end of stream; nonzero if this is the last packet of the \r
+ logical bitstream</dd>\r
+<dt>granulepos:</dt>\r
+<dd>the absolute position of this packet in the original \r
+ uncompressed data stream.</dd>\r
+</dl>\r
+\r
+<h4>encoding notes</h4>\r
+\r
+<p>The encoder is responsible for setting all of\r
+the fields of the packet to appropriate values before submission to\r
+<tt>ogg_stream_packetin()</tt>; however, it is noted that the value in\r
+<tt>b_o_s</tt> is ignored; the first page produced from a given\r
+<tt>ogg_stream_state</tt> structure will be stamped as the initial\r
+page. <tt>e_o_s</tt>, however, must be set; this is the means by\r
+which the stream encoding primitives handle end of stream and cleanup.</p>\r
+\r
+<h4>decoding notes</h4>\r
+\r
+<p><tt>ogg_stream_packetout()</tt> sets the fields\r
+to appropriate values. Note that granulepos will be >= 0 only in the\r
+case that the given packet actually represents that position (ie, only\r
+the last packet completed on any page will have a meaningful\r
+<tt>granulepos</tt>). Intervening frames will see <tt>granulepos</tt> set\r
+to -1.</p>\r
+\r
+<h3>ogg_page</h3>\r
+\r
+<pre>\r
+typedef struct {\r
+ unsigned char *header;\r
+ long header_len;\r
+ unsigned char *body;\r
+ long body_len;\r
+} ogg_page;\r
+</pre>\r
+\r
+<dl>\r
+<dt>header:</dt>\r
+<dd>pointer to the page header data</dd>\r
+<dt>header_len:</dt>\r
+<dd>length of the page header in bytes</dd>\r
+<dt>body:</dt>\r
+<dd>pointer to the page body</dd>\r
+<dt>body_len:</dt>\r
+<dd>length of the page body</dd>\r
+</dl>\r
+\r
+<p>Note that although the <tt>header</tt> and <tt>body</tt> pointers do\r
+not necessarily point into a single contiguous page vector, the page\r
+body must immediately follow the header in the bitstream.</p>\r
+\r
+<h2>Ogg Bitstream Manipulation Functions</h2>\r
+\r
+<h3>\r
+int ogg_page_bos(ogg_page *og);\r
+</h3>\r
+\r
+<p>Returns the 'beginning of stream' flag for the given Ogg page. The\r
+beginning of stream flag is set on the initial page of a logical\r
+bitstream.</p>\r
+\r
+<p>Zero indicates the flag is cleared (this is not the initial page of a\r
+logical bitstream). Nonzero indicates the flag is set (this is the\r
+initial page of a logical bitstream).</p>\r
+\r
+<h3>\r
+int ogg_page_continued(ogg_page *og);\r
+</h3>\r
+\r
+<p>Returns the 'packet continued' flag for the given Ogg page. The packet\r
+continued flag indicates whether or not the body data of this page\r
+begins with packet continued from a preceeding page.</p>\r
+\r
+<p>Zero (unset) indicates that the body data begins with a new packet.\r
+Nonzero (set) indicates that the first packet data on the page is a\r
+continuation from the preceeding page.</p>\r
+\r
+<h3>\r
+int ogg_page_eos(ogg_page *og);\r
+</h3>\r
+\r
+<p>Returns the 'end of stream' flag for a give Ogg page. The end of page\r
+flag is set on the last (terminal) page of a logical bitstream.</p>\r
+\r
+<p>Zero (unset) indicates that this is not the last page of a logical\r
+bitstream. Nonzero (set) indicates that this is the last page of a\r
+logical bitstream and that no addiitonal pages belonging to this\r
+bitstream may follow.</p>\r
+\r
+<h3>\r
+size64 ogg_page_granulepos(ogg_page *og);\r
+</h3>\r
+\r
+<p>Returns the position of this page as an absolute position within the\r
+original uncompressed data. The position, as returned, is 'frames\r
+encoded to date up to and including the last whole packet on this\r
+page'. Partial packets begun on this page but continued to the\r
+following page are not included. If no packet ends on this page, the\r
+frame position value will be equal to the frame position value of the\r
+preceeding page. If none of the original uncompressed data is yet\r
+represented in the logical bitstream (for example, the first page of a\r
+bitstream consists only of a header packet; this packet encodes only\r
+metadata), the value shall be zero.</p>\r
+\r
+<p>The units of the framenumber are determined by media mapping. A\r
+vorbis audio bitstream, for example, defines one frame to be the\r
+channel values from a single sampling period (eg, a 16 bit stereo\r
+bitstream consists of two samples of two bytes for a total of four\r
+bytes, thus a frame would be four bytes). A video stream defines one\r
+frame to be a single frame of video.</p>\r
+\r
+<h3>\r
+int ogg_page_pageno(ogg_page *og);\r
+</h3>\r
+\r
+<p>Returns the sequential page number of the given Ogg page. The first\r
+page in a logical bitstream is numbered zero; following pages are\r
+numbered in increasing monotonic order.</p>\r
+\r
+<h3>\r
+int ogg_page_serialno(ogg_page *og);\r
+</h3>\r
+\r
+<p>Returns the serial number of the given Ogg page. The serial number is\r
+used as a handle to distinguish various logical bitstreams in a\r
+physical Ogg bitstresm. Every logical bitstream within a\r
+physical bitstream must use a unique (within the scope of the physical\r
+bitstream) serial number, which is stamped on all bitstream pages.</p>\r
+\r
+<h3>\r
+int ogg_page_version(ogg_page *og);\r
+</h3>\r
+\r
+<p>Returns the revision of the Ogg bitstream structure of the given page.\r
+Currently, the only permitted number is zero. Later revisions of the\r
+bitstream spec will increment this version should any changes be\r
+incompatable.</p>\r
+\r
+<h3>\r
+int ogg_stream_clear(ogg_stream_state *os);\r
+</h3>\r
+\r
+<p>Clears and deallocates the internal storage of the given Ogg stream.\r
+After clearing, the stream structure is not initialized for use;\r
+<tt>ogg_stream_init</tt> must be called to reinitialize for use.\r
+Use <tt>ogg_stream_reset</tt> to reset the stream state\r
+to a fresh, intiialized state.</p>\r
+\r
+<p><tt>ogg_stream_clear</tt> does not call <tt>free()</tt> on the pointer\r
+<tt>os</tt>, allowing use of this call on stream structures in static\r
+or automatic storage. <tt>ogg_stream_destroy</tt>is a complimentary\r
+function that frees the pointer as well.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure. This function always\r
+succeeds.</p>\r
+\r
+<h3>\r
+int ogg_stream_destroy(ogg_stream_state *os);\r
+</h3>\r
+\r
+<p>Clears and deallocates the internal storage of the given Ogg stream,\r
+then frees the storage associated with the pointer <tt>os</tt>.</p>\r
+\r
+<p><tt>ogg_stream_clear</tt> does not call <tt>free()</tt> on the pointer\r
+<tt>os</tt>, allowing use of that call on stream structures in static\r
+or automatic storage.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure. This function always\r
+succeeds.</p>\r
+\r
+<h3>\r
+int ogg_stream_init(ogg_stream_state *os,int serialno);\r
+</h3>\r
+\r
+<p>Initialize the storage associated with <tt>os</tt> for use as an Ogg\r
+stream. This call is used to initialize a stream for both encode and\r
+decode. The given serial number is the serial number that will be\r
+stamped on pages of the produced bitstream (during encode), or used as\r
+a check that pages match (during decode).</p>\r
+\r
+<p>Returns zero on success, nonzero on failure.</p>\r
+\r
+<h3>\r
+int ogg_stream_packetin(ogg_stream_state *os, ogg_packet *op);\r
+</h3>\r
+\r
+<p>Used during encoding to add the given raw packet to the given Ogg\r
+bitstream. The contents of <tt>op</tt> are copied;\r
+<tt>ogg_stream_packetin</tt> does not retain any pointers into\r
+<tt>op</tt>'s storage. The encoding proccess buffers incoming packets\r
+until enough packets have been assembled to form an entire page;\r
+<tt>ogg_stream_pageout</tt> is used to read complete pages.</p>\r
+\r
+<p>Returns zero on success, nonzero on failure.</p>\r
+\r
+<h3>\r
+int ogg_stream_packetout(ogg_stream_state *os,ogg_packet *op);\r
+</h3>\r
+\r
+<p>Used during decoding to read raw packets from the given logical\r
+bitstream. <tt>ogg_stream_packetout</tt> will only return complete\r
+packets for which checksumming indicates no corruption. The size and\r
+contents of the packet exactly match those given in the encoding\r
+process. </p>\r
+\r
+<p>Returns zero if the next packet is not ready to be read (not buffered\r
+or incomplete), positive if it returned a complete packet in\r
+<tt>op</tt> and negative if there is a gap, extra bytes or corruption\r
+at this position in the bitstream (essentially that the bitstream had\r
+to be recaptured). A negative value is not necessarily an error. It\r
+would be a common occurence when seeking, for example, which requires\r
+recapture of the bitstream at the position decoding continued.</p>\r
+\r
+<p>If the return value is positive, <tt>ogg_stream_packetout</tt> placed\r
+a packet in <tt>op</tt>. The data in <tt>op</tt> points to static\r
+storage that is valid until the next call to\r
+<tt>ogg_stream_pagein</tt>, <tt>ogg_stream_clear</tt>,\r
+<tt>ogg_stream_reset</tt>, or <tt>ogg_stream_destroy</tt>. The\r
+pointers are not invalidated by more calls to\r
+<tt>ogg_stream_packetout</tt>.</p>\r
+\r
+<h3>\r
+int ogg_stream_pagein(ogg_stream_state *os, ogg_page *og);\r
+</h3>\r
+\r
+<p>Used during decoding to buffer the given complete, pre-verified page\r
+for decoding into raw Ogg packets. The given page must be framed,\r
+normally produced by <tt>ogg_sync_pageout</tt>, and from the logical\r
+bitstream associated with <tt>os</tt> (the serial numbers must match).\r
+The contents of the given page are copied; <tt>ogg_stream_pagein</tt>\r
+retains no pointers into <tt>og</tt> storage.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure.</p>\r
+\r
+<h3>\r
+int ogg_stream_pageout(ogg_stream_state *os, ogg_page *og);\r
+</h3>\r
+\r
+<p>Used during encode to read complete pages from the stream buffer. The\r
+returned page is ready for sending out to the real world.</p>\r
+\r
+<p>Returns zero if there is no complete page ready for reading. Returns\r
+nonzero when it has placed data for a complete page into\r
+<tt>og</tt>. Note that the storage returned in og points into internal\r
+storage; the pointers in <tt>og</tt> are valid until the next call to\r
+<tt>ogg_stream_pageout</tt>, <tt>ogg_stream_packetin</tt>,\r
+<tt>ogg_stream_reset</tt>, <tt>ogg_stream_clear</tt> or\r
+<tt>ogg_stream_destroy</tt>.</p>\r
+\r
+<h3>\r
+int ogg_stream_reset(ogg_stream_state *os);\r
+</h3>\r
+\r
+<p>Resets the given stream's state to that of a blank, unused stream;\r
+this may be used during encode or decode.</p>\r
+\r
+<p>Note that if used during encode, it does not alter the stream's serial\r
+number. In addition, the next page produced during encoding will be\r
+marked as the 'initial' page of the logical bitstream.</p>\r
+\r
+<p>When used during decode, this simply clears the data buffer of any\r
+pending pages. Beginning and end of stream cues are read from the\r
+bitstream and are unaffected by reset.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure. This function always\r
+succeeds.</p>\r
+\r
+<h3>\r
+char *ogg_sync_buffer(ogg_sync_state *oy, long size);\r
+</h3>\r
+\r
+<p>This call is used to buffer a raw bitstream for framing and\r
+verification. <tt>ogg_sync_buffer</tt> handles stream capture and\r
+recapture, checksumming, and division into Ogg pages (as required by\r
+<tt>ogg_stream_pagein</tt>).</p>\r
+\r
+<p><tt>ogg_sync_buffer</tt> exposes a buffer area into which the decoder\r
+copies the next (up to) <tt>size</tt> bytes. We expose the buffer\r
+(rather than taking a buffer) in order to avoid an extra copy many\r
+uses; this way, for example, <tt>read()</tt> can transfer data\r
+directly into the stream buffer without first needing to place it in\r
+temporary storage.</p>\r
+\r
+<p>Returns a pointer into <tt>oy</tt>'s internal bitstream sync buffer;\r
+the remaining space in the sync buffer is at least <tt>size</tt>\r
+bytes. The decoder need not write all of <tt>size</tt> bytes;\r
+<tt>ogg_sync_wrote</tt> is used to inform the engine how many bytes\r
+were actually written. Use of <tt>ogg_sync_wrote</tt> after writing\r
+into the exposed buffer is mandantory.</p>\r
+\r
+<h3>\r
+int ogg_sync_clear(ogg_sync_state *oy);\r
+</h3>\r
+\r
+<p><tt>ogg_sync_clear</tt>\r
+clears and deallocates the internal storage of the given Ogg sync\r
+buffer. After clearing, the sync structure is not initialized for\r
+use; <tt>ogg_sync_init</tt> must be called to reinitialize for use.\r
+Use <tt>ogg_sync_reset</tt> to reset the sync state and buffer to a\r
+fresh, intiialized state.</p>\r
+\r
+<p><tt>ogg_sync_clear</tt> does not call <tt>free()</tt> on the pointer\r
+<tt>oy</tt>, allowing use of this call on sync structures in static\r
+or automatic storage. <tt>ogg_sync_destroy</tt>is a complimentary\r
+function that frees the pointer as well.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure. This function always\r
+succeeds.</p>\r
+\r
+<h3>\r
+int ogg_sync_destroy(ogg_sync_state *oy);\r
+</h3>\r
+\r
+<p>Clears and deallocates the internal storage of the given Ogg sync\r
+buffer, then frees the storage associated with the pointer\r
+<tt>oy</tt>.</p>\r
+\r
+<p><tt>ogg_sync_clear</tt> does not call <tt>free()</tt> on the pointer\r
+<tt>oy</tt>, allowing use of that call on stream structures in static\r
+or automatic storage.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure. This function always\r
+succeeds.</p>\r
+\r
+<h3>\r
+int ogg_sync_init(ogg_sync_state *oy);\r
+</h3>\r
+\r
+<p>Initializes the sync buffer <tt>oy</tt> for use.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure. This function always\r
+succeeds.</p>\r
+\r
+<h3>\r
+int ogg_sync_pageout(ogg_sync_state *oy, ogg_page *og);\r
+</h3>\r
+\r
+<p>Reads complete, framed, verified Ogg pages from the sync buffer,\r
+placing the page data in <tt>og</tt>.</p>\r
+\r
+<p>Returns zero when there's no complete pages buffered for\r
+retrieval. Returns negative when a loss of sync or recapture occurred\r
+(this is not necessarily an error; recapture would be required after\r
+seeking, for example). Returns positive when a page is returned in\r
+<tt>og</tt>. Note that the data in <tt>og</tt> points into the sync\r
+buffer storage; the pointers are valid until the next call to\r
+<tt>ogg_sync_buffer</tt>, <tt>ogg_sync_clear</tt>,\r
+<tt>ogg_sync_destroy</tt> or <tt>ogg_sync_reset</tt>.</p>\r
+\r
+<h3>\r
+int ogg_sync_reset(ogg_sync_state *oy);\r
+</h3>\r
+\r
+<p><tt>ogg_sync_reset</tt> resets the sync state in <tt>oy</tt> to a\r
+clean, empty state. This is useful, for example, when seeking to a\r
+new location in a bitstream.</p>\r
+\r
+<p>Returns zero on success, nonzero on failure.</p>\r
+\r
+<h3>\r
+int ogg_sync_wrote(ogg_sync_state *oy, long bytes);\r
+</h3>\r
+\r
+<p>Used to inform the sync state as to how many bytes were actually\r
+written into the exposed sync buffer. It must be equal to or less\r
+than the size of the buffer requested.</p>\r
+\r
+<p>Returns zero on success and non-zero on failure; failure occurs only\r
+when the number of bytes written were larger than the buffer.</p>\r
+\r
+<div id="copyright">\r
+ The Xiph Fish Logo is a\r
+ trademark (™) of Xiph.Org.<br/>\r
+\r
+ These pages © 1994 - 2005 Xiph.Org. All rights reserved.\r
+</div>\r
+\r
+</body>\r
+</html>\r