FLAC stands for Free Lossless Audio Codec, an audio format that is lossless, meaning that audio is compressed in FLAC without any loss in quality.

Opus is a totally open, royalty-free, highly versatile audio codec. Opus is unmatched for interactive speech and music transmission over the Internet, but is also intended for storage and streaming applications. It is standardized by the Internet Engineering Task Force (IETF) as RFC 6716 which incorporated technology from Skype's SILK codec and Xiph.Org's CELT codec.

Ogg vorbis is a non-proprietary, patent-and-royalty-free, general-purpose compressed audio format.

The package vorbis-tools contains ogg123, an ogg vorbis command line audio player; oggenc, the ogg vorbis encoder; oggdec, a simple, portable command line decoder (to wav and raw); ogginfo, to obtain information (tags, bitrate, length, etc.) about an ogg vorbis file.

Libshout is a library for communicating with and sending data to an icecast server. It handles the socket connection, the timing of the data, and prevents bad data from getting to the icecast server.

Kate is an overlay codec, originally designed for karaoke and text, that can be multiplixed in Ogg. Text and images can be carried by a Kate stream, and animated. Most of the time, this would be multiplexed with audio/video to carry subtitles, song lyrics (with or without karaoke data), etc., but doesn't have to be.

Series of curves (splines, segments, etc.) may be attached to various properties (text position, font size, etc.) to create animated overlays. This allows scrolling or fading text to be defined. This can even be used to draw arbitrary shapes, so hand drawing can also be represented by a Kate stream.

Libao is a cross-platform audio library that allows programs to output audio using a simple API on a wide variety of platforms. It currently supports:

1. Null output (handy for testing without a sound device),

2. WAV files,

3. AU files,

4. RAW files,

5. OSS (Open Sound System, used on Linux and FreeBSD),

6. ALSA (Advanced Linux Sound Architecture),

7. aRts (Analog RealTime Synth, used by KDE),

8. PulseAudio (next generation GNOME sound server),

9. esd (EsounD or Enlightened Sound Daemon),

10. Mac OS X,

11. Windows (98 and later),

12. AIX,

13. Sun/NetBSD/OpenBSD,

14. IRIX,

15. NAS (Network Audio Server),

16. RoarAudio (Modern, multi-OS, networked Sound System),

17. OpenBSD's sndio.

The libogg library manipulates the ogg multimedia container format, which encapsulates raw compressed data and allows the interleaving of audio and video data. In addition to encapsulation and interleaving of multiple data streams, ogg provides packet framing, error detection, and periodic timestamps for seeking.

The libvorbis library implements the ogg vorbis audio format, a fully open, non-proprietary, patent-and-royalty-free, general-purpose compressed audio format for mid to high quality (8kHz-48.0kHz, 16+ bit, polyphonic) audio and music at fixed and variable bitrates from 16 to 128 kbps/channel.

Opus is a royalty-free, highly versatile audio codec. Opus-tools provide command line utilities for creating, inspecting and decoding .opus files.

The libopusenc libraries provide a high-level API for encoding Opus files and streams.

The opusfile library provides seeking, decode, and playback of Opus streams in the Ogg container (.opus files) including over http(s) on posix and windows systems.

Libxslt is an XSLT C library developed for the GNOME project. It is based on libxml for XML parsing, tree manipulation and XPath support.

XML::Twig is an XML transformation module. Its strong points: can be used to process huge documents while still being in tree mode; not bound by DOM or SAX, so it is very perlish and offers a very comprehensive set of methods; simple to use; DWIMs as much as possible.

What it doesn't offer: full SAX support (it can export SAX, but only reads XML), full XPath support (unless you use XML::Twig::XPath), nor DOM support.

This module provides a basic framework for creating and maintaining RDF Site Summary (RSS) files. This distribution also contains many examples that allow you to generate HTML from an RSS, convert between 0.9, 0.91, and 1.0 version, and more.

XML::SAX consists of several framework classes for using and building Perl SAX2 XML parsers, filters, and drivers.

Defusedxml provides XML bomb protection for Python stdlib modules.

TinyXML2 is a small and simple XML parsing library for the C++ programming language.

The xmlschema library is an implementation of XML Schema for Python. It has full support for the XSD 1.0 and 1.1 standards, an XPath-based API for finding schema's elements and attributes; and can encode and decode XML data to JSON and other formats.

The lxml XML toolkit is a Pythonic binding for the C libraries libxml2 and libxslt.

Libxlsxwriter is a C library that can be used to write text, numbers, formulas and hyperlinks to multiple worksheets in an Excel 2007+ XLSX file.

This module has a very simple task - to be a base class for PerlSAX drivers and filters. Its default behaviour is to pass the input directly to the output unchanged. It can be useful to use this module as a base class so you don't have to, for example, implement the characters() callback.

This package provides an XML Schema and its catalog. The schema constrains the syntax of xml:lang, xml:spec, xml:base, and xml:id in the schema language defined by the XML Schema Recommendation Second Edition of 28 October 2004.

This module offers a simple to process namespaced XML names (unames) from within any application that may need them. It also helps maintain a prefix to namespace URI map, and provides a number of basic checks.

A collection of smaller Perl modules, scripts, and documents for working with XML in Perl. libxml-perl software works in combination with XML::Parser, PerlSAX, XML::DOM, XML::Grove, and others.