ubuntu studio 10.04 and novation x-station - trying to record audio 1 and 2

jay gallivan jay.gallivan at gmail.com
Mon Jul 19 05:47:23 BST 2010

On Sat, Jul 17, 2010 at 6:34 PM, Pablo <pablo.fbus at gmail.com> wrote:

> jay gallivan escribió:
> > Thanks for your reply. I'm a total newbie to all of this.
> Hi Jay,
Greetings. Long couple of days growing my understanding of audio on Linux.
I've worked with micros since 1981, UNIX since 1988 and Linux since 1996.
I've never had to pay attention to audio before now. Is this what happens
when computer people find themselves in a band? That's how I came to this. I
play bass. It's tough to get the the three of us together. So, the plan was
to record the leader - who does the singing and plays acoustic guitar - so i
could practice. The X-Station was lying around (bought for one of the kids
years ago) and I have 'extra' Linux boxes. So, the adventure began....

> Pulseaudio is a linux sound system (audio server) desktop oriented and
> Jack (Jack Audio Connection Kit) is another one, oriented towards music
> production (low latency, anything to anywhere connections...). Both use
> the alsa drivers (jack can also use the ffado drivers for firewire audio
> devices but this is not your case) but apart from that, they are very
> different beasts.

ALSA had been just another four letter word to me. No more.

> Timidity is a default midi server. It can do jack, but it doesn't by
> default. In a musical environment timidity is not as used as qsynth for
> example, which is "jackified" by default. But you must load a soundfont
> in qsynth.

I'm beginning to get the idea of MIDI. Another protocol. In Rosegarden I can
seen MIDI message flow. That's helpful in the same way that looking at
network packet traces are helpful. "Oh. So that's what's going on."

> In order to use Rosegarden (the audio part) you need the jack audio
> server and forget about pulseaudio interfaces (once jack takes hold of
> your soundcard, pulseaudio is useless, and, hopefully, harmless). You
> launch the server by means of a graphical front-end called qjackctl
> (Jack Control in the sound and video menu). First, you press "setup" to
> configure the jack audio server. In the interface field you select your
> usb audio card (you will see a generic usb-audio or similar, I guess).
> Then press start to activate jack.

Pulseaudio drops out of the picture but the motherboard audio i/o still
seems to be there. This appears to be the path to my external speakers for
monitoring. So that would be something like.... Ardour/Rosegarden -> Jack ->
ALSA -> chips -> speakers?

> If jack does not start, this is the first problem you should solve (more
> below).

I had quite a bit of trouble with Jack. First, a very slow box - eight years
old. I moved to a newer box - maybe three years old - and found i had way to
little ram. 1GB. Went to 2GB today and things are much better - with Jack
grabbing 1.5GB. Ouch! Do i need to get more?

> If it starts, then the jack audio clients, like rosegarden, and many
> more (most music oriented programs are jack-aware by default) will show
> their ports in the connect window, audio tab, when you launch them.
> The MIDI tab stands for jack MIDI which is not used by Rosegarden
> nowadays. The alsa tab refers to alsa  sequencer or alsa MIDI. It has
> nothing to do with jack but it is there for convenience because several
> synths and sequencers use the alsa sequencer for MIDI and jack for
> audio. Some newer ones use jack MIDI and jack audio but not Rosegarden.
This explains that you could capture midi in Rosegarden despite the jack
> server was not active.
So both ALSA and Jack do MIDI? Can you point me to some data flow diagrams?

> Also, take into account that Rosegarden does not make sounds by itself
> and it has not any default synth that makes it work out of the box.. It
> needs either a software synth plugin or an external synth, either
> software (say, qsynth, zynaddsubfx...) or hardware.  But this is a
> second step. The first step is jack setup.
I'm do have Jack running in RT mode. The Ubuntu Studio installation
installed a preemptive kernel. First time I've ever needed that! I did come
across some documentation describing what you outlined. That certainly
caused me concern re memory.

> In order to have jack working in realtime mode (recommended) you need,
> as a user, some priorities that you can check in a terminal with:
> ulimit -r (this is realtime priority for the user)
> ulimit -l (this is memlock limit for the user)
> You need the first one at ninety-something and the second one, unlimited
> or a reasonable amount of your RAM, in kB. In turn, to gain these
> privileges, there must be a file called:
> /etc/security/limits.d/audio.conf
> with the relevant lines. So please, do a:
> cat /etc/security/limits.d/audio.conf
> and you must have something like:
> @audio - rtprio 99
> @audio - memlock unlimited
> Now you (you the user) have to belong to the "audio" group. Check in a
> terminal with:
> groups
> If you see audio (between others) you are done. If you don't, you must do:
> sudo adduser user audio
> where "user" is your login name. Then reboot and you will have the
> system prepared to use jack
> (check again with the ulimit commands)
> >
> > I don't see anything in Patchbay. In PulseAudio Manager I see
> > X-Station analong stero as a sink and the same as sources for stereo
> > and stereo monitor.
> Just don't use pulseaudio.
> >
> > When I connect (via Connect) X-Station to Timidity I am able to play
> > the keyboard and hear the results via my computer's speakers. And I
> > can record and playback via Rosegarden when I connect X-Station to
> > Rosegarden.
> Don't use timidity unless you do it jack-aware.
> >
> > I've tried Audacity on my Windows XP box and I've been able to
> > pickup/record from the X-Station audio ports - though merged into a
> > single track for some reason.
> >
> > So it seems that the X-Station is doing what it's supposed to do. But
> > that (some component of ) Ubuntu Studio is dropping the X-Station
> > audio. Any thoughts on that?
> See above.
> Cheers! Pablo

So here's where things now stand. I bought an Alesis iO2 with a view to
being able to capture the mic and guitar at the same time. I've been able to
demonstrate that to myself by using the Puluseaudio volume controller and
the Sound Recorder application. Sound Recorder created an ogg file which I
then converted to wav. I was able to read the file into Ardour. Then I ran
out of weekend.

Right now I'm in a good place: I can make the recording I need to make. But
I've also discovered a whole new area of interest! I've always like Linux -
and avoided MS and Apple. It's wonderful to see how much amazing work has
been done!

Thanks very much for taking the time to reply.


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