collaborating on bluetooth audio

Michael 'Mickey' Lauer mickey at
Sun Jan 28 16:09:46 CET 2007

FYI: I have forwarded this from the community-list, since it seems to
be right on the spot for the devel-list.

Lars Hallberg wrote:

> Brad Midgley skrev:
>> Koen
>>     > After reading the LCA slides on pulse-audio it seems to be the
>>     best choice for an
>>     > audiorouting app
>> FYI, I mocked up some diagrams including one that incorporates pulse. 
>> I am hoping to have some of these ideas validated, so let me know if 
>> you have any thoughts on it.
> I like the use of D-bus for finding out whats there and hove to use it.
> But there really should be *one* audio connection manager. Were I can 
> find a headset whether it is connected by usb or blutooth or anything 
> else. And find out hove to connect to it (preferably in many ways, ie:
> hove to build a gst stream, hove to connect by pulse, hove to get a dsp
> interface, hove to get at it with alsa, hove to get at it by some 
> lowlevel interface (eg: by blutooth directly). So an app can choose to
> connect the best way it know.

> For apps that don't care much for latency, it shuld be possible 
> streaming the sound by D-bus, encoded with mimetype, or tell the D-bus
> service to play a file with (optionally?) given mimetype. Record to a 
> file or D-bus stream into given mimetype. Then those apps only need to
> know hove to talk D-bus to get sound support. Don't need to know 
> anything about encoders or conections, just ask the system what is 
> supported.

> That gives a few D-bus services:

> General audio connection mgt, possably xfer agent.

> Blutooth audio device discovery agent.

> USB audio device discovery agent.

> Build audio connection service (possably several different 
> 'protocol'/sources/targets). Support for mixer to?

> D-bus audio sink (passably several different for different formats - 
> destinations). Support volume?

> D-bus audio source (passably several different for different formats -
> source). Support volume?

> This can be implemented in one demon, in several demons, inside other 
> demons (like ones who discover other usb/blutooth devices). D-bus 
> activation should let the app just talk to the D-bus interface the 
> General audio connection manager point it to. Even pulse could be 
> started on demand if we want :-)

> It need not be implemented in one shot ether. It's possably starting out
> supporting, say, only pulse and only main audio and blutooth. But USB 
> shuld be a priority too.

> The D-bus audio sink/source may be left to more advanced media player 
> apps/libs to implement. The audio connection mgr only need interface to
> register services and offer them.

> /LaH

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Best regards,

Michael 'Mickey' Lauer | OpenMoko Software Team

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