[vlc-devel] Re: [bmpx] Re: Proposal for a common D-Bus interface for media players

Milosz Derezynski internalerror at gmail.com
Wed Dec 6 05:57:12 CET 2006

Yeah it would basically mean that one player can run at a time, but going
with what Diego said earlier, i'd concur that it could be very well
something that is not directly at the core of the application, and it can be
started without exposing itself through DBus. BMPx can do this in fact if
you start it with the -bin binary and pass --no-remote to it.

(For those unfamiliar with what i mean with -bin binary: BMPx implements a
single-application-instance/application-as-service [1] mechanism using DBus
activation. There is a 'remote' binary which is for all intents and purposes
for the user just like the main application binary, and a "-bin" binary
(similar to firefox-bin for firefox/comparable) in libexec)

Furthermore, and i'm aware i might be digging up probably unpleasant stuff i
see the problem with XMMS2+DBus the one that there is no "real" reason for
XMMS2 to not switch to DBus (yeah i know about tru's technical explanations
and the don't-broadcast and no TCP/IP transport stuff but that will appear,
well anyway back to the main sentence), so, basically, once XMMS2 implements
a DBus interface using this common spec, there would be no _real_ reason to
not to switch to DBus entirely for server<->client messaging (XMMS2 to
clients for those not in the know).

So either this will happen (you switch entirely), or you guys will just not
switch to DBus at all; everything else is just unfeasible if not at the very
least from a maintenance point of view, and it would be obviously also
hilarious because of other reasons to implement 2 very similar systems of
which either could replace the other (except that without DBus, there will
be hardly a common interface implemented.)

I just want to point this out right now and bring it to the surface, before
we all start a chanty dance around an empty pot.


As for the table, it's something Sham has done some good while ago and it's
a good starting point to see how common the current interfaces are.

Sham (again):

Can you wiki-fy the table and make it editable (perhaps only on request and
only for people you approve for, well, namely the media player developers or
the players listed there at the least, so we can quickly amend it, etc.. ?


[1] http://live.gnome.org/DesktopAppsAsDBusServices (NOTE: We actually
deployed this mechanism 1 year before Alex proposed it in his form, so our
implementation differs in details, but is essentially the same; it doesn't
go -as- far as putting stuff into .desktop files that could be regarded as
bogus until really accepted as a spec/way to do things)

On 12/6/06, Sham Chukoury <eleusis at xmms.org> wrote:
> Hello world.
> Seb Ruiz wrote:
> > Actually, whilst I was in san francisco, I spoke with the xmms2 folks
> > about the same thing. we totally agreed on the necessity for it.
> Indeed, this was discussed a bit during a meeting: [1]
> (full transcript at [2])
> >> I've been working recently of a D-Bus [2] control interface for VLC,
> >> to permit other applications to interact with VLC.
> >> This implements basic functions such as:
> >>         - playback control (Play/Pause/Next..)
> >>         - information on medias (Meta-data/Length)
> >>         - playlist editing (Add new elements to play)
> >>
> >> I've been looking at how other media players already implemented that,
> >> and I thought all their interfaces were highly redundant, and could
> >> benefit of implementing a single, common, shared interface.
> >>
> >> That would let developers use this interface in their programs, and
> >> let their users decide of which media player they wanna use. All about
> I've done a bit of work on this, though in the form of a Python library
> (Chalyx
> - for XMMS2 [3] and MPD [4] clients), not an open spec or interface of any
> kind.
> You can see the class defining the methods to be used at [5]
> It's a bit of a compromise between the interfaces provided by XMMS2 [6]
> and MPD
> [7] (though biased a bit towards XMMS2). You can see a table comparing the
> interfaces at [8] (Some MPRIS/BMP/BMPx calls are included, but they've
> never
> been implemented in Chalyx)
> >> I've copied this specification on the videolan wiki [6], and modified
> >> it to my needs. I tried to keep it as general as possible. However
> >> this still needs more work, and comments.
> >>
> >> This is why i'm reaching you, developers of some media players, to
> >> comment what i've done or work with me, until that specification
> >> fulfills your needs, and can be used in a real world.
> >>
> >> This specification should stay as generic as possible, because media
> >> players that want to make specific methods available with D-Bus can do
> >> it through their specific interface.
> >>
> >> For example, basic methods would be available on the service
> >> org.freedesktop.MediaPlayer and VLC would make streaming methods
> >> available on the service org.videolan.vlc. So, a basic control applet
> >> for the KDE panel originally written for amarok would be able to
> >> control VLC, and a complex pygtk script would control streaming
> >> features of VLC.
> Re: 'The Service' on the DBus-spec page, am I to understand that only one
> player
> supporting the spec may be running at any one time? That makes sense from
> the
> point of view that the user might want a single 'default' player to
> control, but
> what if the user wants 2 such players running at a time? For example,
> listening
> to music using VLC while debugging XMMS2? ;)
> Re: generic interface, does that mean there could be standard interface
> extensions? For example, players with access to a media library could have
> an
> extended interface 'org.freedesktop.MediaPlayer.Library'.
> Cheers.
> -S
> [1]
> http://wiki.xmms2.xmms.se/index.php/IRC_Meeting/2006-11-27/Minutes#Amarok_and_XMMS2_Collaboration
> [2] http://dan.chokola.com/files/xmms2-meeting/2006-11-27/transcript.txt
> [3] http://xmms2.xmms.se/epydoc/public/xmmsclient.XMMS-class.html
> [4] http://mpd.wikia.com/wiki/MusicPlayerDaemonCommands
> [5]
> http://git.xmms.se/?p=chalyx-eleusis.git;a=blob;f=src/Chalyx/services/service.py
> [6]
> http://git.xmms.se/?p=chalyx-eleusis.git;a=blob;f=src/Chalyx/services/xmms2.py
> [7]
> http://git.xmms.se/?p=chalyx-eleusis.git;a=blob;f=src/Chalyx/services/mpd.py
> [8] http://xmms2.xmms.se/~eleusis/misc/client-api-table.html
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