Sansa Clip

These are my notes for using the Clip (V02.01.16A) in UMS mode (USB mass storage device class). They are mostly gleaned from tinkering and from the Clip forum. Most of this is independent of the host platform and so applies to Windows as well as Linux.

Audio books
Files placed in the AUDIOBOOKS directory appear under the Audiobooks menu.
Decoder support
Audible, FLAC, MP3, WMA, WMA-DRM.
Jack (audio-out)
The audio output jack is a ⅛-inch or 3.5mm TRS connector.
Music menus
The Clip apparently builds most of its Music menus (Artists, Albums, Songs, Genres, Podcasts) from the metadata in the files under its MUSIC and PODCAST directories (at least). It scans the metadata (tags) of all files after it is disconnected from the host computer ("Refresh Database") and stores its results in the file MTABLE.SYS in its root directory. Although it permits users to further organize files by adding sub-directories, its menus do not reflect this organization.
Playlists

The Clip uses M3U playlists (cf. Sansa FAQ). In compiling the collection of playlists, it apparently searches the MUSIC directory and its sub-directories for files with the m3u extension. The base name of each M3U file found appears as an item under the Playlist menu. For example:

   #EXTM3U
   Easy Rider\10 - Ballad of Easy Rider.flac
   Born in the U.S.A\07 - No Surrender.flac
   Easy Rider\03 - The Weight.flac
   Born in the U.S.A\03 - Darlington County.flac

File paths are relative to the directory containing the M3U file. To include an audio file residing in the same directory as the playlist, the playlist simply uses the name of the file, without any path information (e.g. "Born to Be Wild.mp3"). For an audio file in a sub-directory, the playlist must use the relative path prepending the sub-directory to the file name (e.g. "Easy Rider\Born to Be Wild.mp3"). The path separator is the backslash character ("\") of FAT file systems. Each filename in a playlist must specify the file's extension.

Playlists do not support absolute path names. A side effect is that playlists can only refer to songs within the MUSIC directory hierarchy. (Peaking into MTABLSE.SYS suggests that an absolute path looks like mmc:0:\PODCASTS\Radio Times\AlphabetJuice.mp3.)

Podcasts
To make a file appear under the Podcast menu, set the file's "Genre" field to "Podcast" (using a tag editor), then copy the file into the Clip's PODCAST (or MUSIC) directory.
Rhythmbox
To get Clip noticed by Rhythmbox, create empty file .is_audio_player in Clip's root directory.
Version
The Clip's version information can also be read from the text file version.sdk in the root directory.