mkvtoolnix is a set of tools that allow users to display information about, extract streams from, merge several streams into, and split Matroska media files. Supported video stream types include streams from AVIs, Ogg/OGM, RealVideo, MP4 files, and MPEG program streams as well as verious elementary streams (h264/AVC, MPEG1/2, VC1, Dirac). Supported audio formats include AAC, (E)AC3, DTS/DTS-HD, FLAC, MP2, MP3, RealAudio, and Vorbis. Several subtitle formats are supported, including SRT, SSA, ASS, VobSub, and many others.
libmidixx is a C++ library to manipulate MIDI sequences. It is intended for a multimedia application that handles playback, recording, and editing of MIDI sequences, though the current version just implements playback only. libmidixx supports OSS, ALSA, and serial (tty) MIDI ports, and also comes with a user-space sequencer implementation, which does a fair job on a lightly-loaded machine.
VLC media player is a multimedia player, framework, streamer, and encoder. It can play inputs like files, network streams, DVDs, audio CDs, Blu-Rays, capture devices, and screens. It can play most audio and video codecs and formats (MPEG 1/2/4, H264, VC-1, DivX, WMV, Vorbis, AC3, AAC, MKV, etc.), but can also be used to convert to different formats and/or send streams through the network.
libSap is linux port of windows' SAP Library which is a software emulation of CPU 6502 microprocessor and Pokey chip. Those two chips are used in Atari XL/XE computers. SAP Library is used to run programs written in 6502 machine language that are using the Pokey chip to play tunes and sounds.