[Techtalk] MIdi, QjackCtl etc.

[David Sumbler]

On Tue, 2015-09-08 at 19:20 +0300, Maria Pinjanainen wrote:
> ke, 2015-09-09 kello 01:00 +1000, Miriam English kirjoitti:
> > Hi David,
> > 
> > Have you tried adding a synthesiser in the chain?
> > 
> > The keyboard is commonly used to send MIDI signals to control something. 
> > Jack simply connects things together. Try using Jack to link the 
> > keyboard to a synthesiser program like Qsynth or FluidSynth. Make sure 
> > there are jack graphical connections between the keyboard and the 
> > synthesiser. Jack has 3 different kinds of connections (at least on my 
> > version): Audio, MIDI, and ALSA. It is a bit confusing because the MIDI 
> > inputs and outputs can be in jack's ALSA panel or the MIDI panel. It can 
> > be a bit frustrating at first to get the hang of the logic, but when you 
> > do, it will kinda seem obvious in retrospect.
> > 
> > The synth should let you select different voices (piano, harpsichord, 
> > violin, trumpet, etc). It may take a little while to find your way 
> > around the synth program -- music programmers seem to be a different 
> > breed from other programmers.
> > 
> > Let us know how you go.
> > 
> > Cheers,
> > 
> > 	- Miriam

Yes, ultimately what I want to do is to use a midi keyboard for input
and be able to hear what I am playing on the computer.

But at the moment, all I am attempting to do as a first stage is to play
a midi file in a midi editor - but I can get no sound at all.  In other
contexts the sound on the computer is absolutely fine.  And using
tiMidity or Totem I can play midi files perfectly well.

Your last post at least caused me to realise what the Connections screen
in QjackCtl is all about (I think!).  I now see that within one screen
things can be daisy-chained together - e.g. output A in the left panel
connected to input B in the right panel, and output B connected to input
C etc.  Assuming I am correct, the possibilities seem a bit clearer.
Nevertheless, I have tried all sorts of combinations of connections, and
have never heard anything yet!

Perhaps if I give you a typical setup, you can tell me what is wrong
with it.

First I start QjackCtl.  Maybe the problem is right here: in the
Messages window I see

15:19:35.421 Patchbay deactivated.
15:19:35.427 Statistics reset.
15:19:35.434 ALSA connection change.
15:19:35.448 D-BUS: Service is available (org.jackaudio.service aka jackdbus).
15:19:35.598 D-BUS: JACK server is starting...
Cannot connect to server socket err = No such file or directory
Cannot connect to server socket
jack server is not running or cannot be started
Cannot connect to server socket err = No such file or directory
Cannot connect to server socket
jack server is not running or cannot be started
15:19:35.807 D-BUS: JACK server was started (org.jackaudio.service aka jackdbus).
Sat Sep 12 15:19:35 2015: Starting jack server...
Sat Sep 12 15:19:35 2015: JACK server starting in realtime mode with priority 10
Sat Sep 12 15:19:35 2015: control device hw:0
Sat Sep 12 15:19:35 2015: control device hw:0
Sat Sep 12 15:19:35 2015: Acquired audio card Audio0
Sat Sep 12 15:19:35 2015: creating alsa driver ... hw:0|hw:0|1024|2|44100|0|0|nomon|swmeter|-|32bit
Sat Sep 12 15:19:35 2015: control device hw:0
Sat Sep 12 15:19:35 2015: configuring for 44100Hz, period = 1024 frames (23.2 ms), buffer = 2 periods
Sat Sep 12 15:19:35 2015: ALSA: final selected sample format for capture: 32bit integer little-endian
Sat Sep 12 15:19:35 2015: ALSA: use 2 periods for capture
Sat Sep 12 15:19:35 2015: ALSA: final selected sample format for playback: 32bit integer little-endian
Sat Sep 12 15:19:35 2015: ALSA: use 2 periods for playback
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:capture_1'
Sat Sep 12 15:19:35 2015: New client 'system' with PID 0
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:capture_2'
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:playback_1'
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:playback_2'
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:playback_3'
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:playback_4'
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:playback_5'
Sat Sep 12 15:19:35 2015: graph reorder: new port 'system:playback_6'
Sat Sep 12 15:19:35 2015: New client 'PulseAudio JACK Sink' with PID 2189
Sat Sep 12 15:19:35 2015: Connecting 'PulseAudio JACK Sink:front-left' to 'system:playback_1'
Sat Sep 12 15:19:35 2015: Connecting 'PulseAudio JACK Sink:front-right' to 'system:playback_2'
Sat Sep 12 15:19:35 2015: Connecting 'PulseAudio JACK Sink:rear-left' to 'system:playback_3'
Sat Sep 12 15:19:35 2015: Connecting 'PulseAudio JACK Sink:rear-right' to 'system:playback_4'
Sat Sep 12 15:19:35 2015: Connecting 'PulseAudio JACK Sink:front-center' to 'system:playback_5'
Sat Sep 12 15:19:35 2015: Connecting 'PulseAudio JACK Sink:lfe' to 'system:playback_6'
Sat Sep 12 15:19:35 2015: New client 'PulseAudio JACK Source' with PID 2189
Sat Sep 12 15:19:35 2015: Connecting 'system:capture_1' to 'PulseAudio JACK Source:front-left'
Sat Sep 12 15:19:35 2015: Connecting 'system:capture_2' to 'PulseAudio JACK Source:front-right'
Sat Sep 12 15:19:37 2015: Saving settings to "/home/david/.config/jack/conf.xml" ...
15:19:37.873 JACK connection change.
15:19:37.874 Server configuration saved to "/home/david/.jackdrc".
15:19:37.874 Statistics reset.
15:19:37.884 Client activated.
15:19:37.913 JACK connection graph change.
Sat Sep 12 15:19:37 2015: New client 'qjackctl' with PID 20230
15:19:45.833 XRUN callback (1)

I notice 2 possible problems:

"Patchbay deactivated." - I don't really know what this is: I haven't
touched it, but if I open the Patchbay window in QjackCtl the panes are
blank.

"Cannot connect to server socket err = No such file or directory" - this
sounds like a problem, but I see that eventually it seems to settle down
and connect.  It would be more helpful if it said what file (or device)
it is trying to connect to.

If I now start Qtractor (for instance), import a midi file and play it,
both Qtractor and QjackCtl appear to be working, but there is no sound.

In the QjackCtl Connections window, on the Audio tab I have "PulseAudio
JACK Sink" in the left panel, and "PulseAudio JACK Source" on the right,
together with "Qtractor" and "system" on both sides.  On the ALSA tab I
have "Midi Through" on both sides, together with "TiMidity" on the right
hand side only.  The MIDI tab is blank.

Is something missing?  How would you suggest this should be connected?

David