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.

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.

GNU Speex is a patent-free audio compression codec specially designed for speech. It is well-adapted to internet applications, such as VoIP. It features compression of different bands in the same bitstream, intensity stereo encoding, and voice activity detection.

RNNoise is a noise suppression library based on a recurrent neural network. The algorithm is described in Jean-Marc Valin's paper A Hybrid DSP/Deep Learning Approach to Real-Time Full-Band Speech Enhancement.

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.

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

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.

SpeexDSP is a DSP (Digital Signal Processing) library based on work from the speex codec.

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.

The libtheora library implements the ogg theora video format, a fully open, non-proprietary, patent-and-royalty-free, general-purpose compressed video format.

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.

Icecast is a streaming media server which currently supports Ogg (Vorbis and Theora), Opus, WebM and MP3 audio streams. It can be used to create an Internet radio station or a privately running jukebox and many things in between.

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.

The conventional models for parsing XML are either DOM (a data structure representing the entire document tree is created) or SAX (callbacks are issued for each element in the XML).

XML grammar is recursive - so it's nice to be able to write recursive parsers for it. XML::Descent allows such parsers to be created.

This package provides methods to cache compiled XML translators.

Libxml2 is the XML C parser and toolkit developed for the Gnome project (but it is usable outside of the Gnome platform).

XML::Feed is a syndication feed parser for both RSS and Atom feeds. It also implements feed auto-discovery for finding feeds, given a URI. XML::Feed supports the following syndication feed formats: RSS 0.91, RSS 1.0, RSS 2.0, Atom

This package provides a Cleaner for cleaning up HTML pages. It supports removing embedded or script content, special tags and CSS style annotations among other features. Its main purpose is removing superfluous content, it is not appropriate for security sensitive environments.

pugixml is a C++ XML processing library, which consists of a DOM-like interface with rich traversal/modification capabilities, a fast XML parser which constructs the DOM tree from an XML file/buffer, and an XPath 1.0 implementation for complex data-driven tree queries. Full Unicode support is also available, with Unicode interface variants and conversions between different Unicode encodings which happen automatically during parsing/saving.

XMLStarlet is a set of command line utilities which can be used to transform, query, validate, and edit XML documents. XPath is used to match and extract data, and elements can be added, deleted or modified using XSLT and EXSLT.

Xmlto is a front-end to an XSL toolchain. It chooses an appropriate stylesheet for the conversion you want and applies it using an external XSL-T processor. It also performs any necessary post-processing.

The XML::Simple module provides a simple API layer on top of an underlying XML parsing module (either XML::Parser or one of the SAX2 parser modules).

This module implements a Perl interface to the libxml2 library which provides interfaces for parsing and manipulating XML files. This module allows Perl programmers to make use of the highly capable validating XML parser and the high performance DOM implementation.