[Fedora-music-list] Jack and pulse on the Spin

[Brendan Jones]

On 06/01/2012 06:58 PM, Fernando Lopez-Lezcano wrote:
> On 05/31/2012 07:10 AM, Brendan Jones wrote:
>> On 05/31/2012 03:25 PM, David Sommerseth wrote:
>>> -----BEGIN PGP SIGNED MESSAGE-----
>>> Hash: SHA1
>>>
>>> On 31/05/12 08:43, Brendan Jones wrote:
>>>> Just a note that the default F17 pulseaudio configuration supports
>>>> jack bridging via dbus (/etc/pulse/default.pa).
>>>>
>>>> ### Automatically connect sink and source if JACK server is
>>>> present .ifexists module-jackdbus-detect.so .nofail load-module
>>>> module-jackdbus-detect .fail .endif
>>>>
>>>> This is different to again to
>>>> module-jack-sink.so/module-jack-source.so which is what some of us
>>>> have been using up until now.
>>>>
>>>> What that means is if jack-audio-connection-kit-dbus is on the spin
>>>> by default, bridging is set up automatically.
>>>>
>>>> This is something that needs to be considered carefully and I'd be
>>>> interested in how well jackdbus is working for people. I was
>>>> having random errors in the past with jackdbus hogging CPU with
>>>> pulse. I will perform some more monitoring here, but it would be
>>>> great to hear what others have experienced.
>>>
>>> Throwing in a large torch at fire here now ... do we really need
>>> pulseaudio? I mean, this is a multi-media production spin, filled
>>> with applications where Jack has become the standard - at least among
>>> the audio based applications.
>>>
>>> I don't know how that jack/pulse bridge really works ... but if pulse
>>> really is needed, wouldn't it be better to write something which can
>>> completely replace the pulse libraries, and rather re-use just the API
>>> ... so that pulse based applications appears as those in/out sinks in
>>> Jack directly? This might be a rather long-term goal though.
>>
>> With pulseaudio-jack bridging, both are running. Pulseaudio simply
>> redirects its output to jack's default system input ports.
>>
>> This means applications which are not jack enabled will in most cases
>> simply work. I regularly need to run applications for work (such as
>> skype) and this seems to be a really stable solution.
>>
>> Having said that, I'd really like one of the aims of the Spin be
>> focussed on ease of configuration, and providing an easy way to disable
>> pulseaudio completely should be considered.
>
> I think pulseaudio is here to stay and if there is still stuff that does
> not work correctly it should be fixed (as opposed to gutting the whole
> thing).
>
> I would be opposed to having the pulse to jack bridge automatically kick
> in.
>
> This should be certainly an option and would be very useful, but there
> should be an easy to use configuration setup where I can choose whether
> pulse automatically goes to jack or not (and for the Fedora Jam spin it
> should be off by default, I think). In the usage cases I manage you do
> not want that to be "on" by default. If you are in the middle of a
> mixing session or in a concert performance you do not want a random
> application that you forgot to turn off suddenly decide it is a good
> idea to warn the user about something with a nice chime sound...
>

Sure. There's a bunch of stuff we can do the %post section of the 
install to tweak configuration. $HOME/.pulse is also somewhere where we 
can override these settings, but I'm still unsure of the limits of what 
we can and can't do in the kickstart.

Ideally something like this [1] that sits in the system tray would be 
awesome (this is from kxstudio's cadence program, not sure if ready  for 
primetime - if not perhaps we can create something similar. I might set 
up a repo for evalution of kxstudio in any case)

[1] http://bsjones.fedorapeople.org/cadence-audio-config.png

Brendan