[PlanetCCRMA] aRts and alsa

[Fernando Pablo Lopez-Lezcano]

On Sun, 2004-08-15 at 08:45, Bruce Elliott wrote:
> I run KDE, and I believe I also run the artsd sound server, although not 
> for any reason beyond my not knowing how to turn it off.  I have also 
> successfully gotten alsa working with my soundcard, can start JACK, and 
> have managed to launch Ardour, although I haven't been able to record 
> just yet.
> 
> My question is how does the native sound system of KDE (aRts, I assume) 
> interact with alsa and jack?  Should I be attempting to disable all of 
> the arts processing in favor of equivalent jack-aware processes?
> 
> Something else, which I believe is related, is that I currently have 
> some .wav sounds that are set to play in response to certain KDE window 
> management events.  They work just fine until I start jack, after which 
> they stop, until I log off and then back on again.  It's not important 
> to me that I hear a noise when I minimize a window, but I'd like to 
> understand why this happens.

Jack "monopolizes" the sound device, so no other processes will be able
to use it while Jack is running, and that includes other sound servers
like artsd. 

> Note: under the KDE Control Center | Sound & Multimedia | System 
> Notifications | Player Settings ... , I have *not* selected to use an 
> external player.  Should I set this to a jack-aware player, if jack is 
> running and I insist on hearing system notifications? 

I don't think there is currently a solution to this problem. You can run
artsd or jack, but not both at the same time. Jack is designed for low
latency work and does not match very well the requirements for a general
purpose sound server (or rather, the expectations of what a general
purpose sound server should be). One solution would be a custom version
of artsd that would connect to jack as a sound server. But keep in mind
that for the kind of usage that Jack was designed for, a random sound
coming from a desktop operation and mixed with the mixdown of your audio
session would be unacceptable. 

> One final thing, which again I think is related - so far I have only a 
> generic cheap soundcard, into which I've plugged a similarly generic and 
> cheap microphone, just for testing.  The mike picks up sounds, which I 
> can hear being echoed through the speakers, but I don't seem to get any 
> signals that make it to Ardour.  In fact, if I run the aRts Control 
> Tool, it doesn't show any signal being passed through at all.  Is my 
> soundcard simply passing the analog signal directly to the speakers?  
> I've made connections from "alsa_pcm | capture_1" and "alsa_pcm | 
> capture_2" to Ardour, but I still don't see any signal.

What you need to tweak changes from card to card. You could start up
gamix (an ALSA gui soundcard mixer) to look at the controls that are
available for your card. There must be something there for recording
(selecting the source, enabling it and changing the input level at
least). 

-- Fernando