X Render extension library

http://www.freedesktop.org/Software/xlibs

X Resource usage library

http://www.freedesktop.org/Software/xlibs

X Toolkit library

https://www.freedesktop.org/wiki/Software/xlibs/

X Test extension

https://www.freedesktop.org/Software/xorg

X Video Extension library

http://www.freedesktop.org/Software/xlibs

X Video Extension Motion Compensation library

https://www.freedesktop.org/wiki/Software/xlibs/

X DGA Extension

https://www.freedesktop.org/Software/xorg

X Vidmode Extension

http://www.freedesktop.org/Software/xorg

Free library for decoding ATSC A/52 streams, aka AC-3

https://git.adelielinux.org/community/a52dec/

HE-AAC+ Codec as Shared Library

http://tipok.org.ua/node/17/

Advanced Access Content System implementation

https://www.videolan.org/developers/libaacs.html

3GPP Adaptive Multi-Rate - Wideband (AMR-WB) Speech Codec

http://www.penguin.cz/~utx/amr

Portable audio output library

https://www.xiph.org/ao/

Library to create and read several streaming archive formats

https://libarchive.org/

Memory hard password hashing program and library

https://github.com/P-H-C/phc-winner-argon2

Library for high-performance 2D graphics

http://www.levien.com/libart/

Portable ASS/SSA subtitle renderer

https://github.com/libass/libass

IPC library used by GnuPG and gpgme

https://gnupg.org/related_software/libassuan/index.en.html

Atomic operations access library

https://github.com/ivmai/libatomic_ops

Sound library for SGI audio file

https://www.68k.org/~michael/audiofile/

BD+ System research implementation

https://www.videolan.org/developers/libbdplus.html

Standard C resolver library

https://www.isc.org/software/libbind

Blu-Ray discs playback library for media players

https://www.videolan.org/developers/libbluray.html

Component and compound document system for GNOME2

http://www.gnome.org/

Libburnia library to read/write optical discs

https://dev.lovelyhq.com/libburnia/web/wikis/home

Graphics library that outputs text instead of pixels

http://caca.zoy.org/

Implementation of the Freedesktop sound theme spec

https://0pointer.de/lennart/projects/libcanberra/

Implementation of the Freedesktop sound theme spec

https://0pointer.de/lennart/projects/libcanberra/

Generic driver for USB CCID and ICCD

https://ccid.apdu.fr/

Library for playing audio CDs

https://libcdaudio.sourceforge.net/

Library to access data on a CDDB server

https://libcddb.sourceforge.net/

Compact Disc Input and Control Library

https://www.gnu.org/software/libcdio/

Read audio from the CDROM directly as data

https://www.gnu.org/software/libcdio/

C library aimed to provide a Gtk+ widget to display rasterized maps and markers

http://projects.gnome.org/libchamplain/

Tool to check shared library links

http://svn.idaemons.org/cgi-bin/viewvc.cgi/trunk/?root=libchk

Required library functions for OpenCL C programming language

https://libclc.llvm.org/

Alternative configuration system for Compiz

Simple library for manipulating structured configuration files

https://www.hyperrealm.com/libconfig/libconfig.html

Configuration file parsing library

http://savannah.nongnu.org/projects/confuse/

CSS2 parsing library

http://www.freespiders.org/projects/libcroco/

GNOME application for managing encryption keys (PGP, SSH)

https://gitlab.gnome.org/GNOME/libcryptui

Cascading Style Sheets library

https://www.netsurf-browser.org/projects/libcss/

CUE Sheet Parser Library

https://github.com/lipnitsk/libcue

Lightweight C library that eases the writing of UNIX daemons

http://0pointer.de/lennart/projects/libdaemon/

Double-array trie implementation library

https://linux.thai.net/projects/datrie/

Companion library to GObject and GTK

https://gitlab.gnome.org/GNOME/libdazzle

Free DTS Coherent Acoustics decoder

https://www.videolan.org/developers/libdca.html

Generic Device Query and Monitor interface

https://github.com/freebsd/libdevq

Library to generate arbitrary sequence diffs

https://github.com/kristapsdz/libdiff

Library for creating MusicBrainz DiscIDs

http://musicbrainz.org/doc/libdiscid