Telepathy Wiki - Streamed Media

Overview

  ---                  ...
  | | - DBus object    : : - other object
  ---                  '''

  --------------------                      --------------
  |Connection Manager|                      |StreamEngine|
  --------------------                      --------------
     |                                         |
  ----------------------                    ......... 
  |StreamedMediaChannel|                    :Channel:
  ----------------------                    '''''''''
     |                                         |
  ----------------                          .........   .................
  |SessionHandler|           <--->          :Session:---:FarsightSession:
  ----------------                          '''''''''   '''''''''''''''''
     |                                         |
  ---------------                           ........   ................
  |StreamHandler|            <--->          :Stream:---:FarsightStream:
  ---------------                           ''''''''   ''''''''''''''''

Stream Engine

Stream Engine effectively exports Farsight to D-Bus. When it's told to handle a particular streamed media channel, it creates sessions and streams that mirror the channels's session handlers and stream handlers. Singals raised and methods called by the connection manager are translated to Farsight and vice versa.

Stream Engine implements two D-Bus interfaces:

org.freedesktop.Telepathy.ChannelHandler
- HandleChannel (s: bus_name, o: connection, s: channel_type, o: channel, u: handle_type, u: handle) -> nothing
org.freedesktop.Telepathy.StreamEngine
- SetOutputVolume (o: channel_path, u: stream_id, u: volume) -> nothing
- MuteInput (o: channel_path, u: stream_id, b: mute_state) -> nothing
- MuteOutput (o: channel_path, u: stream_id, b: mute_state) -> nothing
- SetOutputWindow (o: channel_path, u: stream_id, u: window) -> nothing
- AddPreviewWindow (u: window) -> nothing
- RemovePreviewWindow (u: window) -> nothing
- Shutdown () -> nothing
- Receiving (o: channel_path, u: stream_id, b: state)

Process

New StreamedMediaChannel gets created.
- For outgoing calls, a client will have called RequestChannel to cause this to happen.
Mission control, or the channel handler, will start stream-engine and call HandleChannel on it
stream-engine calls GetSessionHandlers on the channel
stream-engine binds to NewMediaSessionHandler signal on channel
GetSessionHandlers returns:
- stream-engine creates corresponding sessions
- stream-engine binds to NewMediaStreamHandler
NewMediaSessionHandler raised:
- stream-engine creates corresponding session
- stream-engine binds to NewMediaStreamHandler
stream-engine session created: calls Ready on the corresponding session handler, passing a list of local codecs
- local codecs can also be passed in after the Ready call using the SetLocalCodecs method