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diff --git a/vorbis/doc/programming.html b/vorbis/doc/programming.html deleted file mode 100644 index 4b54347..0000000 --- a/vorbis/doc/programming.html +++ /dev/null @@ -1,554 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> -<html> -<head> - -<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-15"/> -<title>Ogg Vorbis Documentation</title> - -<style type="text/css"> -body { - margin: 0 18px 0 18px; - padding-bottom: 30px; - font-family: Verdana, Arial, Helvetica, sans-serif; - color: #333333; - font-size: .8em; -} - -a { - color: #3366cc; -} - -img { - border: 0; -} - -#xiphlogo { - margin: 30px 0 16px 0; -} - -#content p { - line-height: 1.4; -} - -h1, h1 a, h2, h2 a, h3, h3 a { - font-weight: bold; - color: #ff9900; - margin: 1.3em 0 8px 0; -} - -h1 { - font-size: 1.3em; -} - -h2 { - font-size: 1.2em; -} - -h3 { - font-size: 1.1em; -} - -li { - line-height: 1.4; -} - -#copyright { - margin-top: 30px; - line-height: 1.5em; - text-align: center; - font-size: .8em; - color: #888888; - clear: both; -} -</style> - -</head> - -<body> - -<div id="xiphlogo"> - <a href="http://www.xiph.org/"><img src="fish_xiph_org.png" alt="Fish Logo and Xiph.Org"/></a> -</div> - -<h1>Programming with Xiph.Org <tt>libvorbis</tt></h1> - -<h2>Description</h2> - -<p>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> - -<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.</p> - -<h2>Encoding Overview</h2> - -<h2>Decoding Overview</h2> - -<p>Decoding a bitstream with libvorbis follows roughly the following -steps:</p> - -<ol> -<li>Frame the incoming bitstream into pages</li> -<li>Sort the pages by logical bitstream and buffer then into logical streams</li> -<li>Decompose the logical streams into raw packets</li> -<li>Reconstruct segments of the original data from each packet</li> -<li>Glue the reconstructed segments back into a decoded stream</li> -</ol> - -<h3>Framing</h3> - -<p>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> - -<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> - -<p>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).</p> - -<h3>Extracting packets</h3> - -<p>After submitting page[s] to a logical stream, read available packets -using <tt>ogg_stream_packetout</tt>.</p> - -<h3>Decoding packets</h3> - -<h3>Reassembling data segments</h3> - -<h2>Ogg Bitstream Manipulation Structures</h2> - -<p>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:</dt> -<dd>a pointer to the byte data of the raw packet</dd> -<dt>bytes:</dt> -<dd>the size of the packet' raw data</dd> -<dt>b_o_s:</dt> -<dd>beginning of stream; nonzero if this is the first packet of - the logical bitstream</dd> -<dt>e_o_s:</dt> -<dd>end of stream; nonzero if this is the last packet of the - logical bitstream</dd> -<dt>granulepos:</dt> -<dd>the absolute position of this packet in the original - uncompressed data stream.</dd> -</dl> - -<h4>encoding notes</h4> - -<p>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.</p> - -<h4>decoding notes</h4> - -<p><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.</p> - -<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:</dt> -<dd>pointer to the page header data</dd> -<dt>header_len:</dt> -<dd>length of the page header in bytes</dd> -<dt>body:</dt> -<dd>pointer to the page body</dd> -<dt>body_len:</dt> -<dd>length of the page body</dd> -</dl> - -<p>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</h2> - -<h3> -int ogg_page_bos(ogg_page *og); -</h3> - -<p>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> - -<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> - -<p>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> - -<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.</p> - -<h3> -int ogg_page_eos(ogg_page *og); -</h3> - -<p>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> - -<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> - -<p>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> - -<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> - -<p>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> - -<p>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> - -<p>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> - -<p>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> - -<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> - -<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> - -<p>Clears and deallocates the internal storage of the given Ogg stream, -then frees the storage associated with the pointer <tt>os</tt>.</p> - -<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> - -<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> - -<p>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> - -<p>Returns zero on success, nonzero on failure.</p> - -<h3> -int ogg_stream_packetin(ogg_stream_state *os, ogg_packet *op); -</h3> - -<p>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> - -<p>Returns zero on success, nonzero on failure.</p> - -<h3> -int ogg_stream_packetout(ogg_stream_state *os,ogg_packet *op); -</h3> - -<p>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> - -<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> - -<p>If the return value is positive, <tt>ogg_stream_packetout</tt> placed -a packet in <tt>op</tt>. The data in <tt>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> - -<p>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> - -<p>Returns zero on success and non-zero on failure.</p> - -<h3> -int ogg_stream_pageout(ogg_stream_state *os, ogg_page *og); -</h3> - -<p>Used during encode to read complete pages from the stream buffer. The -returned page is ready for sending out to the real world.</p> - -<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>.</p> - -<h3> -int ogg_stream_reset(ogg_stream_state *os); -</h3> - -<p>Resets the given stream's state to that of a blank, unused stream; -this may be used during encode or decode.</p> - -<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> - -<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> - -<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> - -<p>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> - -<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> - -<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> - -<p><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> - -<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> - -<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> - -<p>Clears and deallocates the internal storage of the given Ogg sync -buffer, then frees the storage associated with the pointer -<tt>oy</tt>.</p> - -<p>An alternative function,<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> - -<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> - -<p>Initializes the sync buffer <tt>oy</tt> for use.</p> - -<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> - -<p>Reads complete, framed, verified Ogg pages from the sync buffer, -placing the page data in <tt>og</tt>.</p> - -<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>.</p> - -<h3> -int ogg_sync_reset(ogg_sync_state *oy); -</h3> - -<p><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> - -<p>Returns zero on success, nonzero on failure.</p> - -<h3> -int ogg_sync_wrote(ogg_sync_state *oy, long bytes); -</h3> - -<p>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> - -<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> - -<div id="copyright"> - The Xiph Fish Logo is a - trademark (™) of Xiph.Org.<br/> - - These pages © 1994 - 2005 Xiph.Org. All rights reserved. -</div> - -</body> -</html> |