Revision as of 14:13, 17 April 2012

UMMS Architecture

Introduction

This page describes the architecture of umms-0.1, you can get the code from: git://gitorious.org:meego-middleware/umms.git
UMMS general description can found on its main page

Class Diagram

• UmmsAudioManager

Class to implement com.UMMS.AudioManager interface which provide client with audio output control service.

• UmmsVideoOutput

Class to implement com.UMMS.VideoOutput interface which provide client with video output control service.

• UmmsPlayingContentMetadataViewer

Class to implement com.UMMS.PlayingContentMetadataViewer interface which allow the client to query the current playing content on server side.

• UmmsObjectManager

Class to manage MediaPlayer objects, including create/destory, register/unregister MediaPlayer objects.

• UmmsMediaPlayer

Class to implement the com.UMMS.MediaPlayer interface which provide media playback service for client.

• UmmsPlayerBackend

A base class which defined internal interface for media playback. UmmsMediaPlayer uses this class to handle the service request. Backend developer need to subclass it.

• UmmsAudioManagerBackend

A base class which defined internal interface for controlling audio output. UmmsAudioManager uses this class to handle the service request. Backend developer need to subclass it.

• UmmsVideoOutputBackend

A base class which defined internal interface for controlling video output. UmmsVideoOutput uses this class to handle the service request. Backend developer need to subclass it.

• UmmsPlugin

A class which defined the plugin mechanism. All backend should be implemented as a UmmsPlugin.

• Player

An implementation of UmmsPlayerBackend.

• AudioManger

An implementation of UmmsAudioBackend.

• VideoOutput

An implementation of UmmsVideoOutput.

Note that, Player,AudioManger,VideoOutput are plugins and will not provide by umms-1.0.

How to develop a backend

Suppose you are going to develop a player backend.

• Step 1: Subclass UmmsPlayerBackend

The UmmsPlayerBackend is internal interface to abstract all the media playback control. Backend developer should subclass this class and implement its vmethods. Of cause, you can just implement a subset of the virtual methods defined in UmmsPlayerBackendClass struct, e.g. For dvb player backend, it is optional to implement the "pause" method. If you want to add time-shifting feature for DVB playback, implementing "pause" method is a choice.

• Step 2: Fill the UmmsPlugin struct in your PlayerBackend.c file and export it

The definition of struct UmmsPlugin:

typedef struct _UmmsPlugin {
  gint major_version;//the major version number of umms core that plugin was compiled for
  gint minor_version;//the minor version number of core that plugin was compiled for
  UmmsPluginType type;
  const gchar *filename;//set by "plugin loader" when this plugin loaded.
  const gchar *name;
  const gchar *description;

  /*
   * Used for plugins of UMMS_PLUGIN_TYPE_PLAYER_BACKEND type.
   * If supported_uri_protocols is empty, unsupported_uri_protocols is respected
   * as a "black list" of uri. If supported_uri_protocols is not empty, ignore
   * unsupported_uri_protocols.
   * e.g. The implementor can create a black list for its plugin like this:
   * supported_uri_protocols = {NULL};
   * unsupported_uri_protocols = {"dvb"};
   * that means the plugin can handle all uri protocols unless "dvb".
   */
  const gchar **supported_uri_protocols;
  const gchar **unsupported_uri_protocols;

  /*vmethod to create the instance of backend.*/
  gpointer (*backend_new_func) (void);
}UmmsPlugin;

The most important fields are supported_uri_protocols, unsupported_uri_protocols and backend_new_func. For details, ref this