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Hi Kemal,<BR>
<BR>
On Sun, 2007-07-29 at 12:26 +0300, ext Kemal Hadimli wrote:
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<FONT COLOR="#000000">I'm looking for info on com.osso.Playback.Manager, libplayback-1-0 and</FONT>
<FONT COLOR="#000000">possibly osso-hss-control. If you have the time, a couple minutes free</FONT>
<FONT COLOR="#000000">on your lunch break, a few words (preferably along with a few sample</FONT>
<FONT COLOR="#000000">dbus calls) would suffice.</FONT>
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It's now lunch time!<BR>
<BR>
In previous maemo releases, the media-server had two methods com.nokia.osso_media_server.disable and .enable in order to "suspend" the player when you made/receive a call. To improve the usability, it was necessary to extend this behavior to any supported player (flash, rhapsody, canola, to name a few) and also other voice applications.<BR>
<BR>
We designed an interface that a player should implement in order to be managed:<BR>
<BR>
Each playback object /com/osso/playback%d has:<BR>
<BR>
<interface name="com.osso.Playback"><BR>
<property name="State" type="s" access="readwrite"/><BR>
<property name="AllowedState" type="as" access="readwrite"/><BR>
<property name="Class" type="s" access="read"/><BR>
</interface><BR>
<BR>
- State property allows the client to declare its current state (from a limited set for now: None,Play,Stop), and a controller change the playback State (it can fail)<BR>
- AllowedState property is a set of state that the user is allowed to ask for (this give us a chance to grey out some UI buttons)<BR>
- Class is the playback object class from Media, VoIP, Event, Background...<BR>
<BR>
Those property are notify when they change (it uses a *non-standard Notify* signal from DBUS_INTERFACE_PROPERTIES).<BR>
<BR>
When a player need to make a state change, it has to kindly request it to the com.osso.Playback.Manager (it could also *override* the permission: this is generally a bad idea) using the RequestState method. The reply is either an error, or the newly permitted state. Meanwhile, the manager take care of changing the state of the other players (and changing the allowed states).<BR>
<BR>
The manager is currently provided by hss-control. And the rule is rather simple: the first VoIP play request stops everything. The last Media player to request "Play" get the "Play" lock. The Background class remains playing, even if a Media is playing (Flash case).
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<FONT COLOR="#000000">I was testing some stuff when I stumbled upon the com.osso.Playback</FONT>
<FONT COLOR="#000000">signal, and followed from there. Tried some dbus calls with no luck.</FONT>
<FONT COLOR="#000000">No reason, I'm just curious. Could help with a media player project</FONT>
<FONT COLOR="#000000">though.</FONT>
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Eh eh, it is not enough to send a call via dbus-send (because the manager need additional information from the requester, especially if the first it asks is a new state...).<BR>
libplayback try to implement the interface the right way. An application needs to worry for a minimal bunch of call/cb. <BR>
<BR>
At some point we wanted to open a specification for this interface and also support the library. But we had to postpone the sharing, because of the lack of a "home" place in the stack. And the high subject-to-change condition. We are thinking of two coming projects to land this proposal: MPRIS (which could replace the client interface) and OHM or PulseAudio for the managing bits.
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<FONT COLOR="#000000">Thanks.</FONT>
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You're welcome!<BR>
<BR>
Note: hss-control is a rather bad name for all its doing (at the beginning it was handling headsets): now this daemon handles audio routing/tuning stuffs, the playback management, a few legacy interfaces, some audio power management, and the sound interactions (click-tap). We are studying how to distribute this work in HAL/OHM and other projects.
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