[PD] problem with MIDI (linux)

Roman Haefeli reduzierer at yahoo.de
Thu Nov 26 09:57:48 CET 2009


Hi Chi


Am 26.11.09 01:49 schrieb "chi ball" unter <c_cb at hotmail.it>:
 
>> iirc, you should use the same user to start jackd and Pd.
>> so if you run Pd as user "chi", than you should also run jackd as user
>> "chi". the same if you use root (which i don't recommend; you should
>> rather fix your /etc/security/limits.conf to be able to run realtime
>> processes as member of the audio-group).
> 
> Thanks..
> 
> I've resolved the problem of "user" adding (as root) those rows in
> /etc/security/limits.conf:
> 
> @audio - rtprio 80
> @audio - memlock 288000
> #288000 because my RAM is 576 MB
> @audio - nice -10
> 
> and I set user in "audio" member group.

You need to make sure, that your user is a member of the group 'audio'.  If
not already done, please do:

sudo adduser <username> audio

whereas <username> should be replaced by your user name. To make sure, that
jackd knows about the new permissions, log out and back in again. Check, if
you're really now a member of the audio group by doing:

group 

in a terminal. 'audio' should be listed in the output.

After having made sure, that you belog to the audio group and after the
changes you made to /etc/security/limits.conf you definitely should be able
to run jack with realtime privileges.

> _______________________
> In JACK setup I set:
> realtime, priority 80
> midi driver: seq
> _______________________
> So now I can open qjackctl and start JACK correctly (play), but give me this
> error:
> 
> cannot use real-time scheduling (FIFO at priority 90) [for thread -1238557840,
> from 
> thread -1238557840] (1: Operation not permitted)
> 

Is jackd really running? Doesn't it say something like: 'killall jackd' and
'Could not connect to JACK Server as client'? However, if everything from
above went well, you shouldn't see this message anymore, when starting
jackd. 

> Now I open pd, and in "media" I select: JACK, and ALSA-MIDI.
> 
> Then I open JACK connections: I see 2 windows: AUDIO and MIDI. Here, in both
> windows,  I connect pd with
> my SB LIVE! sound card.
> ____________________________________________
> Now, running some patch in pd, happen this:
> 
> 1)in a audio patch (for example a simple oscillator with a slide..) *I can
> listen sound correctly* (even if
> with a fastidious background noise) and I can change frequency well with the
> slide.

>From the audio I/O errors you mention below, i can tell you that you're
still running pd with alsa, but not with jackd. After having made sure, that
your jackd is running correctly, try this in a terminal:

pd -rt -jack -channels 2

Usually, you don't need even to manually connect pd to the soundcard in the
connection window of qjackctl, but the connection should happen
automatically.

> 2)in a midi patch (a patch certainly correct, tested in o.s. Windows..!) *I
> can't listen anything*.
> I see numbers change, but *no sound*.

Ok, i think, i kind of understand now, what you mean. If you send in windows
MIDI to your SB Live, it'll produce GeneralMidi synthesizer sounds. I don't
know how this works in details, i guess in some cases it is simply a
software synthesizer in the driver.  Probably some soundcards have this
capability built into the hardware.  The fact, that you don't hear anything
in linux, when sending MIDI from pd, doesn't mean, that your Pd MIDI doesn't
work, it simply means, that you're lacking a similar setup with some kind of
synth. There are a lot of synths available also in linux, you might find
one, that suits your needs. You would then need to connect Pd to 'yourSynth'
in the connection window in the MIDI tab.

BTW: i found this page quite a helpful resource for setting up an audio
system with linux:

https://help.ubuntu.com/community/UbuntuStudioPreparation
 
roman



	
		
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