Different MDPs support different file types and metadata fields. When requesting metadata fields, you must state the metadata categories and the attributes (which map to individual fields); see mmmd_get() for more details. The libmd library combines a category (the prefix) with each of its listed attributes (the suffixes) to form the full names of the metadata fields.
The MDPs shipped with libmd and the file types and metadata fields (expressed as category and attribute combinations) that each MDP supports is as follows:
| MDP | Files | Metadata categories | Attributes |
|---|---|---|---|
| CDDA | CD audio tracks | md_title | album, artist, genre, name, composer, track, bitrate, samplerate, duration, format |
| MMF | MMF files accessible from either a network source (e.g., an HTTP server) or a POSIX device | md_title | name, artist, album, albumartist, composer, genre, comment, duration, track, disc, year, seekable, pausable, samplerate, bitrate, protected, mediatype (see 1), width, height, art, compilation, rating |
| md_video | width, height, pixel_width, pixel_height, frame, fourcc | ||
| md_audio | fourcc | ||
| md_artwork | image, description, type, mimetype, count, size | ||
| Exif | POSIX files on mass storage devices (e.g., USB sticks) | md_title | width, height, date_time_original, shutter_speed, fnumber, iso_speed_ratings, focal_length, orientation, description, latitude, longitude, keywords |
| Extart | External artwork such as cover images for albums and thumbnail graphics for tracks | md_title | art |
| md_artwork | image, count, size, urls | ||
| MediaFS | Files on MTP devices | md_title | name, artist, album, composer, genre, year, duration, comment, protected, track, art |
| md_artwork | image, width, height, size, mimetype, count | ||
| iPod | iPod media files | md_title | art |
| md_artwork | image, mimetype, width, height, size, count |