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-<!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 I format specification: comment field and header specification</h1>
-
-<h1 id="overview">Overview</h1>
-
-<p>The Vorbis text comment header is the second (of three) header
-packets that begin a Vorbis bitstream. It is meant for short, text
-comments, not arbitrary metadata; arbitrary metadata belongs in a
-separate logical bitstream (usually an XML stream type) that provides
-greater structure and machine parseability.</p>
-
-<p>The comment field is meant to be used much like someone jotting a
-quick note on the bottom of a CDR. It should be a little information to
-remember the disc by and explain it to others; a short, to-the-point
-text note that need not only be a couple words, but isn't going to be
-more than a short paragraph. The essentials, in other words, whatever
-they turn out to be, eg:</p>
-
-<blockquote><p>
-"Honest Bob and the Factory-to-Dealer-Incentives, _I'm Still Around_,
-opening for Moxy Fr&uuml;vous, 1997"
-</p></blockquote>
-
-<h1 id="commentencoding">Comment encoding</h1>
-
-<h2 id="structure">Structure</h2>
-
-<p>The comment header logically is a list of eight-bit-clean vectors; the
-number of vectors is bounded to 2^32-1 and the length of each vector
-is limited to 2^32-1 bytes. The vector length is encoded; the vector
-contents themselves are not null terminated. In addition to the vector
-list, there is a single vector for vendor name (also 8 bit clean,
-length encoded in 32 bits). For example, the 1.0 release of libvorbis
-set the vendor string to "Xiph.Org libVorbis I 20020717".</p>
-
-<p>The comment header is decoded as follows:</p>
-
-<pre>
- 1) [vendor_length] = read an unsigned integer of 32 bits
- 2) [vendor_string] = read a UTF-8 vector as [vendor_length] octets
- 3) [user_comment_list_length] = read an unsigned integer of 32 bits
- 4) iterate [user_comment_list_length] times {
-
- 5) [length] = read an unsigned integer of 32 bits
- 6) this iteration's user comment = read a UTF-8 vector as [length] octets
-
- }
-
- 7) [framing_bit] = read a single bit as boolean
- 8) if ( [framing_bit] unset or end of packet ) then ERROR
- 9) done.
-</pre>
-
-<h2 id="vectorformat">Content vector format</h2>
-
-<p>The comment vectors are structured similarly to a UNIX environment variable.
-That is, comment fields consist of a field name and a corresponding value and
-look like:</p>
-
-<pre>
-comment[0]="ARTIST=me";
-comment[1]="TITLE=the sound of Vorbis";
-</pre>
-
-<ul>
-<li>A case-insensitive field name that may consist of ASCII 0x20 through
-0x7D, 0x3D ('=') excluded. ASCII 0x41 through 0x5A inclusive (A-Z) is
-to be considered equivalent to ASCII 0x61 through 0x7A inclusive
-(a-z).</li>
-<li>The field name is immediately followed by ASCII 0x3D ('=');
-this equals sign is used to terminate the field name.</li>
-<li>0x3D is followed by the 8 bit clean UTF-8 encoded value of the
-field contents to the end of the field.</li>
-</ul>
-
-<h3 id="fieldnames">Field names</h3>
-
-<p>Below is a proposed, minimal list of standard field names with a
-description of intended use. No single or group of field names is
-mandatory; a comment header may contain one, all or none of the names
-in this list.</p>
-
-<dl>
-
-<dt>TITLE</dt>
-<dd>Track/Work name</dd>
-
-<dt>VERSION</dt>
-<dd>The version field may be used to differentiate multiple
-versions of the same track title in a single collection.
-(e.g. remix info)</dd>
-
-<dt>ALBUM</dt>
-<dd>The collection name to which this track belongs</dd>
-
-<dt>TRACKNUMBER</dt>
-<dd>The track number of this piece if part of a specific larger collection or album</dd>
-
-<dt>ARTIST</dt>
-<dd>The artist generally considered responsible for the work. In popular music
-this is usually the performing band or singer. For classical music it would be
-the composer. For an audio book it would be the author of the original text.</dd>
-
-<dt>PERFORMER</dt>
-<dd>The artist(s) who performed the work. In classical music this would be the
-conductor, orchestra, soloists. In an audio book it would be the actor who did
-the reading. In popular music this is typically the same as the ARTIST and
-is omitted.</dd>
-
-<dt>COPYRIGHT</dt>
-<dd>Copyright attribution, e.g., '2001 Nobody's Band' or '1999 Jack Moffitt'</dd>
-
-<dt>LICENSE</dt>
-<dd>License information, eg, 'All Rights Reserved', 'Any
-Use Permitted', a URL to a license such as a Creative Commons license
-("www.creativecommons.org/blahblah/license.html") or the EFF Open
-Audio License ('distributed under the terms of the Open Audio
-License. see http://www.eff.org/IP/Open_licenses/eff_oal.html for
-details'), etc.</dd>
-
-<dt>ORGANIZATION</dt>
-<dd>Name of the organization producing the track (i.e.
-the 'record label')</dd>
-
-<dt>DESCRIPTION</dt>
-<dd>A short text description of the contents</dd>
-
-<dt>GENRE</dt>
-<dd>A short text indication of music genre</dd>
-
-<dt>DATE</dt>
-<dd>Date the track was recorded</dd>
-
-<dt>LOCATION</dt>
-<dd>Location where track was recorded</dd>
-
-<dt>CONTACT</dt>
-<dd>Contact information for the creators or distributors of the track.
-This could be a URL, an email address, the physical address of
-the producing label.</dd>
-
-<dt>ISRC</dt>
-<dd>ISRC number for the track; see <a href="http://www.ifpi.org/isrc/">the
-ISRC intro page</a> for more information on ISRC numbers.</dd>
-
-</dl>
-
-<h3 id="implications">Implications</h3>
-
-<ul>
-<li>Field names should not be 'internationalized'; this is a
-concession to simplicity not an attempt to exclude the majority of
-the world that doesn't speak English. Field <emph>contents</emph>,
-however, use the UTF-8 character encoding to allow easy representation
-of any language.</li>
-<li>We have the length of the entirety of the field and restrictions on
-the field name so that the field name is bounded in a known way. Thus
-we also have the length of the field contents.</li>
-<li>Individual 'vendors' may use non-standard field names within
-reason. The proper use of comment fields should be clear through
-context at this point. Abuse will be discouraged.</li>
-<li>There is no vendor-specific prefix to 'nonstandard' field names.
-Vendors should make some effort to avoid arbitrarily polluting the
-common namespace. We will generally collect the more useful tags
-here to help with standardization.</li>
-<li>Field names are not required to be unique (occur once) within a
-comment header. As an example, assume a track was recorded by three
-well know artists; the following is permissible, and encouraged:
-<pre>
- ARTIST=Dizzy Gillespie
- ARTIST=Sonny Rollins
- ARTIST=Sonny Stitt
-</pre></li>
-</ul>
-
-<h2 id="encoding">Encoding</h2>
-
-<p>The comment header comprises the entirety of the second bitstream
-header packet. Unlike the first bitstream header packet, it is not
-generally the only packet on the second page and may not be restricted
-to within the second bitstream page. The length of the comment header
-packet is (practically) unbounded. The comment header packet is not
-optional; it must be present in the bitstream even if it is
-effectively empty.</p>
-
-<p>The comment header is encoded as follows (as per Ogg's standard
-bitstream mapping which renders least-significant-bit of the word to be
-coded into the least significant available bit of the current
-bitstream octet first):</p>
-
-<ol>
-<li>Vendor string length (32 bit unsigned quantity specifying number of octets)</li>
-<li>Vendor string ([vendor string length] octets coded from beginning of string
-to end of string, not null terminated)</li>
-<li>Number of comment fields (32 bit unsigned quantity specifying number of fields)</li>
-<li>Comment field 0 length (if [Number of comment fields]>0; 32 bit unsigned
-quantity specifying number of octets)</li>
-<li>Comment field 0 ([Comment field 0 length] octets coded from beginning of
-string to end of string, not null terminated)</li>
-<li>Comment field 1 length (if [Number of comment fields]>1...)...</li>
-</ol>
-
-<p>This is actually somewhat easier to describe in code; implementation of the above
-can be found in vorbis/lib/info.c:_vorbis_pack_comment(),_vorbis_unpack_comment()</p>
-
-<div id="copyright">
- The Xiph Fish Logo is a
- trademark (&trade;) of Xiph.Org.<br/>
-
- These pages &copy; 1994 - 2005 Xiph.Org. All rights reserved.
-</div>
-
-</body>
-</html>