mirror of
https://github.com/dhewm/dhewm3-libs.git
synced 2024-11-29 07:12:01 +00:00
a0e5fcd6c5
CFLAGS="-I$HOME/devel/games/doom3-libs/i686-w64-mingw32/include" \ LDFLAGS="-L$HOME/devel/games/doom3-libs/i686-w64-mingw32/lib" \ ./configure --host=i686-w64-mingw32 \ --prefix=$HOME/devel/games/doom3-libs/i686-w64-mingw32 \ --with-ogg=$HOME/devel/games/doom3-libs/i686-w64-mingw32 \ --disable-examples --disable-oggtest
234 lines
8 KiB
HTML
234 lines
8 KiB
HTML
<!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>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/>
|
|
|
|
These pages © 1994 - 2005 Xiph.Org. All rights reserved.
|
|
</div>
|
|
|
|
</body>
|
|
</html>
|