DBus-spec

Specification for a Common, Desktop neutral, Media Player D-Bus interface

THIS IS A DRAFT

VLC DOES NOT USE THAT AT THIS MOMENT ALTHOUGH IT IS PLANNED

What follows has been largely stolen from http://bmpx.beep-media-player.org/site/MPRIS_Interfacing_Specification

This is an attempt to create a specification for media players to use, for YOUR applications to be able to interact with ANY Media Player YOU want to use on ANY desktop YOU want to use.

This is in the spirit of http://www.freedesktop.org and uses code and ideas from this project, most notably D-Bus : http://dbus.freedesktop.org

Definitions

"Media Player"

An application, either with GUI or GUI-less (or which allows for both modes of operation) which is capable of playing back audio streams. The means by which it does accomplish that (e.g. which audio backend to use, and which output method) is completely up to the application, like MPRIS or VLC, or Rhythmbox, or mplayer, or xine, or Totem, or anything YOU like.

The "Media Player" must:

• Be able to play back at least local storage file streams.
• Be able to play back at least one stream at a time (as in, without having a concept of a "Tracklists", and possibly even being capable of holding several at the same time)

The "Media Player" can, but does not need to:

• Be capable of holding one or more "Tracklists" at a time.

"Client"

The Client is an unspecified application that will interact with the "Media Player" using D-Bus protocol. For example a Client could be a softphone, that pauses, or step the volume down, when a call is being received. A Client could be an applet that nicely integrates in YOUR desktop environment, and let YOU control YOUR' "Media Player".

"Tracklist"

A list of media files which resides within the "Media Player", and whose implementation is opaque to the remote interface.

The "Tracklist" must:

• Hold an ordered list of locations of the media files as URIs (e.g. file:// or http://). The implementation of this can be opaque, which means, it does not neccesarily need to store URIs, but upon remote request, it must be able to return an URI for a given media file.
• Keep the list in an ordered fashion. The order can be changed at any time trough e.g. sorting algorithms, in which case the "Media Player" must send information about the reordering trough it's remote interface

The "Tracklist" can, but does not need to:

• Hold "Metadata" about media files

"Metadata"

"Metadata" is data that the files carry within themselves as a means of self-identification (commonly known as "tags"), or data that has been retrieved about the files trough other means, e.g. an internet service that provides additional data about particular media files.

Furthermore, "Metadata" can be split into two categories:

1) Technical metadata:

• Length in seconds
• (seekable?) (the management of unseekable should go in error management of SetStreamPos)
• codec defined as a fourcc (http://www.fourcc.org has only video codecs)
• bitrate
• samplerate
• (filesize?)

2) Informational metadata (as in, artist, album, title, genre etc)

• Name
• Artist
• Compilation/Album
• Unique Identifier as on http://musicbrainz.org
• Genre
• Comments specific to the "Media Player", like vorbis comments. On the base

D-Bus

The Service

org.freedesktop.MediaPlayer

The Object Hierarchy

• / : Media Player identification

• /Player : Playback control

• /TrackList : TrackList management

• /Extended : Unspecified. Clients should use this path only if the Media Player has been correctly identified.

The Methods

  <method name="Identity">
    <arg type="s" direction="out"/>
  </method>

  <method name="GetMetadataForUri">
    <arg type="s" direction="in" />
    <arg type="a{sv}" direction="out" />
  </method>

  <method name="GetCurrentUri">
    <arg type="s" direction="out" />
  </method>

  <method name="GetCurrentTitle">
    <arg type="s" direction="out" />
  </method>

  <method name="GetCurrentTrack">
    <arg type="i" direction="out" />
  </method>

  <method name="PlayNext">
  </method>

  <method name="PlayPrev">
  </method>

  <method name="PlayPause">
  </method>

  <method name="PlayStop">
  </method>

  <method name="PlayCurrent">
  </method>

  <method name="SendStatus">
  </method>

  <method name="VolumeSet">
  <arg type="i"/>
  </method>

  <method name="VolumeGet">
  <arg type="i" direction="out"/>
  </method>

  <method name="Quit">
  </method>

The signals

  <signal name="TrackChange">
  </signal>

  <signal name="SetPlaystatus">
   <arg type="i"/>
  </signal>

  <signal name="SetVolume">
   <arg type="i"/>
  </signal>

  <signal name="SetStreamPos">
   <arg type="i"/>
  </signal>