[pulseaudio-discuss] jack soundcard reservation behavior

[Lennart Poettering]

On Fri, 31.07.09 11:01, Fernando Lopez-Lezcano (nando at ccrma.Stanford.EDU) wrote:

> Hi, new on this list... (please keep cc'ing Stephane, he's not in the pa
> list). 
> 
> I'm testing the jack soundcard reservation dbus code with the latest
> release of jackmp (1.9.3) and I'm not sure things are working quite
> right. 
> 
> When starting jackd the soundcard is correctly reserved, pulseaudio
> releases it, and jackd is able to start normally and use the card. A
> stream that was playing through the soundcard at that point in time
> seems to be paused by the reservation code (I'm using rhythmbox to test
> but the same thing seems to happen with other apps). If running
> pulseaudio with -vvv I can see a message re: the successful
> reservation. 
> 
> When quitting jackd, jackd prints a message to the effect that the card
> was released but nothing seems to happen on the pulseaudio side (this is
> being tested on Fedora 11 with the latest pulseaudio package). No
> message is printed and no state changes in the application that was
> playing audio before the reservation took place. In the case of
> rhythmbox I need to press "play" _twice_ to get it to continue playing
> from where it stopped. 

Yes, PA in F11 only resumes the device after a new stream gets started
on the device. PA in the upcoming F12 has been fixed to actively
monitor the reservation logic and automatically resume the device when
jack goes away.

So with F12 you start jack, and rb stops and then you quit jack and rb
continues automatically.

> [*] for example it would allow for currently playing streams to be moved
> to a dynamically loaded jack plugin without missing a beat (or rather,
> with a very short interruption). Part of this is also implemented in my
> current script. 

I'd love to make PA automatically load a jack connectivity module when
JACK is started up. A simple way to implement that would be by
watching for JACK's service name to appear on the bus. But
unfortunately jack doesn't work that way and the running daemon does
not take name on the bus.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4