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-
-<h1>Ogg Vorbis encoding format documentation</h1>
-
-<p><img src="wait.png" alt="wait"/>As of writing, not all the below document
-links are live. They will be populated as we complete the documents.</p>
-
-<h2>Documents</h2>
-
-<ul>
-<li><a href="packet.html">Vorbis packet structure</a></li>
-<li><a href="envelope.html">Temporal envelope shaping and blocksize</a></li>
-<li><a href="mdct.html">Time domain segmentation and MDCT transform</a></li>
-<li><a href="resolution.html">The resolution floor</a></li>
-<li><a href="residuals.html">MDCT-domain fine structure</a></li>
-</ul>
-
-<ul>
-<li><a href="probmodel.html">The Vorbis probability model</a></li>
-<li><a href="bitpack.html">The Vorbis bitpacker</a></li>
-</ul>
-
-<ul>
-<li><a href="oggstream.html">Ogg bitstream overview</a></li>
-<li><a href="framing.html">Ogg logical bitstream and framing spec</a></li>
-<li><a href="vorbis-stream.html">Vorbis packet->Ogg bitstream mapping</a></li>
-</ul>
-
-<ul>
-<li><a href="programming.html">Programming with libvorbis</a></li>
-</ul>
-
-<h2>Description</h2>
-
-<p>Ogg Vorbis is a general purpose compressed audio format
-for high quality (44.1-48.0kHz, 16+ bit, polyphonic) audio and music
-at moderate fixed and variable bitrates (40-80 kb/s/channel). This
-places Vorbis in the same class as audio representations including
-MPEG-1 audio layer 3, MPEG-4 audio (AAC and TwinVQ), and PAC.</p>
-
-<p>Vorbis is the first of a planned family of Ogg multimedia coding
-formats being developed as part of the Xiph.Org Foundation's Ogg multimedia
-project. See <a href="http://www.xiph.org/">http://www.xiph.org/</a>
-for more information.</p>
-
-<h2>Vorbis technical documents</h2>
-
-<p>A Vorbis encoder takes in overlapping (but contiguous) short-time
-segments of audio data. The encoder analyzes the content of the audio
-to determine an optimal compact representation; this phase of encoding
-is known as <em>analysis</em>. For each short-time block of sound,
-the encoder then packs an efficient representation of the signal, as
-determined by analysis, into a raw packet much smaller than the size
-required by the original signal; this phase is <em>coding</em>.
-Lastly, in a streaming environment, the raw packets are then
-structured into a continuous stream of octets; this last phase is
-<em>streaming</em>. Note that the stream of octets is referred to both
-as a 'byte-' and 'bit-'stream; the latter usage is acceptible as the
-stream of octets is a physical representation of a true logical
-bit-by-bit stream.</p>
-
-<p>A Vorbis decoder performs a mirror image process of extracting the
-original sequence of raw packets from an Ogg stream (<em>stream
-decomposition</em>), reconstructing the signal representation from the
-raw data in the packet (<em>decoding</em>) and them reconstituting an
-audio signal from the decoded representation (<em>synthesis</em>).</p>
-
-<p>The <a href="programming.html">Programming with libvorbis</a>
-documents discuss use of the reference Vorbis codec library
-(libvorbis) produced by the Xiph.Org Foundation.</p>
-
-<p>The data representations and algorithms necessary at each step to
-encode and decode Ogg Vorbis bitstreams are described by the below
-documents in sufficient detail to construct a complete Vorbis codec.
-Note that at the time of writing, Vorbis is still in a 'Request For
-Comments' stage of development; despite being in advanced stages of
-development, input from the multimedia community is welcome.</p>
-
-<h3>Vorbis analysis and synthesis</h3>
-
-<p>Analysis begins by seperating an input audio stream into individual,
-overlapping short-time segments of audio data. These segments are
-then transformed into an alternate representation, seeking to
-represent the original signal in a more efficient form that codes into
-a smaller number of bytes. The analysis and transformation stage is
-the most complex element of producing a Vorbis bitstream.</p>
-
-<p>The corresponding synthesis step in the decoder is simpler; there is
-no analysis to perform, merely a mechanical, deterministic
-reconstruction of the original audio data from the transform-domain
-representation.</p>
-
-<ul>
-<li><a href="packet.html">Vorbis packet structure</a>:
-Describes the basic analysis components necessary to produce Vorbis
-packets and the structure of the packet itself.</li>
-<li><a href="envelope.html">Temporal envelope shaping and blocksize</a>:
-Use of temporal envelope shaping and variable blocksize to minimize
-time-domain energy leakage during wide dynamic range and spectral energy
-swings. Also discusses time-related principles of psychoacoustics.</li>
-<li><a href="mdct.html">Time domain segmentation and MDCT transform</a>:
-Division of time domain data into individual overlapped, windowed
-short-time vectors and transformation using the MDCT</li>
-<li><a href="resolution.html">The resolution floor</a>: Use of frequency
-doamin psychoacoustics, and the MDCT-domain noise, masking and resolution
-floors</li>
-<li><a href="residuals.html">MDCT-domain fine structure</a>: Production,
-quantization and massaging of MDCT-spectrum fine structure</li>
-</ul>
-
-<h3>Vorbis coding and decoding</h3>
-
-<p>Coding and decoding converts the transform-domain representation of
-the original audio produced by analysis to and from a bitwise packed
-raw data packet. Coding and decoding consist of two logically
-orthogonal concepts, <em>back-end coding</em> and <em>bitpacking</em>.</p>
-
-<p><em>Back-end coding</em> uses a probability model to represent the raw numbers
-of the audio representation in as few physical bits as possible;
-familiar examples of back-end coding include Huffman coding and Vector
-Quantization.</p>
-
-<p><em>Bitpacking</em> arranges the variable sized words of the back-end
-coding into a vector of octets without wasting space. The octets
-produced by coding a single short-time audio segment is one raw Vorbis
-packet.</p>
-
-<ul>
-<li><a href="probmodel.html">The Vorbis probability model</a></li>
-<li><a href="bitpack.html">The Vorbis bitpacker</a>: Arrangement of
-variable bit-length words into an octet-aligned packet.</li>
-</ul>
-
-<h3>Vorbis streaming and stream decomposition</h3>
-
-<p>Vorbis packets contain the raw, bitwise-compressed representation of a
-snippet of audio. These packets contain no structure and cannot be
-strung together directly into a stream; for streamed transmission and
-storage, Vorbis packets are encoded into an Ogg bitstream.</p>
-
-<ul>
-<li><a href="oggstream.html">Ogg bitstream overview</a>: High-level
-description of Ogg logical bitstreams, how logical bitstreams
-(of mixed media types) can be combined into physical bitstreams, and
-restrictions on logical-to-physical mapping. Note that this document is
-not specific only to Ogg Vorbis.</li>
-<li><a href="framing.html">Ogg logical bitstream and framing
-spec</a>: Low level, complete specification of Ogg logical
-bitstream pages. Note that this document is not specific only to Ogg
-Vorbis.</li>
-<li><a href="vorbis-stream.html">Vorbis bitstream mapping</a>:
-Specifically describes mapping Vorbis data into an
-Ogg physical bitstream.</li>
-</ul>
-
-<div id="copyright">
- The Xiph Fish Logo is a
- trademark (™) of Xiph.Org.<br/>
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- These pages © 1994 - 2005 Xiph.Org. All rights reserved.
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projects / platform / upstream / libvorbis.git / commitdiff
