MoonShell is a homebrew multimedia player for the Nintendo DS dual-screen handheld videogame system. It is one of the most well known pieces of Nintendo DS homebrew software, and as of December 2006, one of the few ways to play video on the DS.
The player supports DPG video files, MP3 / OGG / MOD / SPC / MDX (no PCM) / GBS / HES / NSF / XM / MIDI / low bit rate AAC audio / non-progressive JPEG / BMP / GIF / PNG images, and text files. MoonShell plays fullscreen videos at 20fps and widescreen videos at 24fps, with joint stereo sound at a samplerate of 32.768KHz. Both screens on the DS are used, with the bottom screen allowing file selection and control via touchscreen. The integrated plug-in system provides extensibility of program features. To add a feature, the plug-in files are simply copied to the appropriate folder. In order to function as a media player, several plug-in files are distributed with the software.
MoonShell is included as the default multimedia player for the commercial products N-Card, R4, CycloDS, i-cheat XTRA and M3 DS Simply. The EZFlash V Flash Card and SuperCard One has modified Moonshell source code for firmware use which can be used for booting NDS files. Another modification made for the product M3 Real is the DSM Player.
It can also be loaded onto TTDS/DSTT carts by following this faq - GBATemp.net