DeaDBeeF is a cross-platform desktop music player with a modular plugin architecture. It supports a vast array of audio formats including MP3, AAC, FLAC, Ogg Vorbis, Opus, WavPack, Musepack, DTS, and numerous chiptune and video game music formats (SID, NSF, VGM, MOD, S3M, XM, IT, PSF, etc.) through bundled emulation libraries. The core player handles playlist management, metadata caching, replaygain, DSP chain processing, and streaming. Two native GUI implementations exist: a GTK2/GTK3 interface for Linux and a Cocoa interface for macOS, both offering full-featured playback controls, media library browsing, cover art display, and visualization (scope, spectrum analyzer). The player also includes a converter plugin, MPRIS integration, and extensive keyboard shortcut customization. The architecture is centered around a lightweight plugin API (DB_plugin_t) that decouples decoders, outputs, DSP effects, and UI components. The core library (libdeadbeef) provides threading, file I/O, configuration, and message passing. Plugins are loaded dynamically and register themselves via a factory pattern. The media library plugin uses SQLite for indexing and file system watchers (inotify on Linux) for automatic updates. Artwork is fetched from embedded tags and online services (Last.fm, MusicBrainz) with a local cache. The build system uses autotools, premake5, and Xcode projects, with Docker-based CI for Linux, macOS, and Windows. Key data flows include: file opening via VFS abstraction → decoder plugin → decoded audio blocks (ring buffer) → DSP chain → output plugin. Metadata flows from file tags through a caching layer to the UI and media library. The player supports CUE sheets, gapless playback, and crossfading. External dependencies include GTK2/GTK3, libcurl, libsamplerate, and various codec libraries (libmpg123, libmad, libvorbis, libFLAC, etc.), many of which are bundled as source for portability.