[maemo-developers] Query about audio management inside Maemo

From: Jyri.Sarha at nokia.com Jyri.Sarha at nokia.com
Date: Tue Jan 12 18:09:12 EET 2010
I am a Maemo audio developer and your questions are mostly
policy related, but I should more or less know the answers...

	From: ext Zheng, Huan [mailto:johan.hedberg at gmail.com] 
	Sent: 12 January, 2010 08:47
	To: maemo-developers at maemo.org
	Subject: Query about audio management inside Maemo

	How maemo handle below two scenario?

	1, voice call comes in while music is played

	2, BT device attached while music is played


	My guessing is

	Voice call use libplayback informs its coming, music player get a notification from OHM daemon to pause, right?

Yes, this is basically right. But in addition to OHM
notification policy enforcement will reroute media
player stream to null sink. So the music playback 
will be muted even if the media player ignores the OHM 

	The 2nd scenario, I can't guess out the flow, but the result should be music flow to BT automatically.

	Could someone explain a more detailed flow for the 2 scenarios above?

The sequence of events may change a bit depending on the used
BT-device etc., but in general it should go like this:
1. bluez notifies about new bluetooth device
2. pulseaudio BT-discovery module loads BT-device module for 
   the new device
3. pulseaudio BT-device module creates card-profile and audio 
   sink for the new device
4. policy notices the new device and routes all audio there

	Thanks a lot!


	And, is libplayback and the maemo component for Pulseaudio opensource?

Maemo pulseaudio is open source but some of the Nokia specific 
pulseaudio modules are not. See: http://repository.maemo.org/pool/maemo5.0beta/free/p/pulseaudio/

As far as I know there should be no reason why libplayback
should be closed, but I could not find it from Maemo SDK...
Anyway you should not rely too much on libplayback's internal
implementation, because it is likely to change in the future.

Jyri Sarha

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