GBS, HES, KSS, SGC, VGM, and VGZ. The MOD tracker format, and the Yamaha SMAF are also now supported. Some profiles in Monkey's Audio are not real time on all targets due to very high CPU needs. Also, Rockbox will not play files with a digital rights management (DRM) scheme. Rockbox features Beside the ability of playing and recording audio files, Rockbox offers many playback enhancements that other firmware packages may not have implemented yet. Listed below are a handful of these features. Gapless playback Crossfading ReplayGain 10 band fully parametric equalizer Variable speed decoding with pitch correction Crossfeed OTF ("on the fly") playlists True random shuffle (fresh randomly shuffled list every time) Custom UI themes Dynamic Playlists (queue files to play next, or in other parts of a dynamic playlist) Stereo voice/MIC & FM radio recording to WAV/AIFF/WavPack (lossless) and MP3 (limited model/device/target support) Remote control (supporting devices) Digital S/PDIF input/output (supporting devices) Last.fm support (even on players lacking RTC) Cue sheet support Album art Sleep timer Plug-ins Rockbox developers can create plug-ins, which provide the user with other enhancements that may not be available on various firmware modules. Available plug-ins include: JPEG viewer (16 bit color/129 shade greyscale) Rockboy Game Boy emulator (port of Gnuboy) ZXBox ZX Spectrum emulator (port of Spectemu) Doom (port of the PrBoom engine) Duke Nukem 3D, Quake, and Wolfenstein 3D running atop a version of the Simple DirectMedia Layer runtime XWorld, a clone of Another World WAV to MP3 and Wavpack encoder MPEG video player PictureFlow, an album art viewer similar to Apple's Cover Flow Various games including 2048, Sudoku, Solitaire, Chess, Minesweeper, Pong and many others (see https://www.rockbox.org/wiki/PluginIndex for an official list of plug-ins) Musical Instrument Digital Interface (MIDI) player, real-time on some targets. MikMod, used to play multiple module file formats Architecture Rockbox uses a simple kernel, with a flat memory model and single process, letting it run on platforms without a memory management unit. Thin threads run cooperatively, returning control to a scheduler that prioritizes the audio thread; the only form of preemption is through interrupts. The operating system and plug-ins are written in C, with assembly used for code that is device- and platform-specific, and performance sensitive. The simple and lightweight architecture allows Rockbox to run on a variety of targets, with memory ranging from 1 to 64 MB, and CPU speeds ranging 12 to 532 MHz. Rockbox also