Client MIDI with Alsa or Jack

Programming applications for making music on Linux.

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Siv
Established Member
Posts: 4
Joined: Mon May 10, 2010 6:08 pm

Client MIDI with Alsa or Jack

Post by Siv »

Hi all,

I have created a MIDI pedal with an Arduino and a sustain pedal from an old keyboard, and now the Arduino itself is sending MIDI CC messages to the computer.
I also have a software which receives input from the Arduino (through serial port communication) and routes the MIDI messages to Alsa; I have tried it with Jack and SooperLooper, and I am able to activate the recording functionality by pressing the pedal.

My question is: currently, the software client interfaces with Alsa, should it use Jack instead? I have seen that Jack can connect to Alsa software, too (in the third tab of QJackCtl connection panel), but I don't know if this can introduce latency or performance problems.
Opinions?
thorgal
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Posts: 739
Joined: Mon Apr 07, 2008 6:04 pm

Re: Client MIDI with Alsa or Jack

Post by thorgal »

jack and ALSA midi are rather two separate things unless you use -Xseq as an option to jackd.
The ALSA tab in qjackctl is more of a legacy convenience from the time jack did not handle MIDI ports and routing. At the time, the route was ALSA. Since then, jack evolved to handle MIDI as well, since ALSA midi handling was suffering from a few drawbacks (jitter, complicated API, etc). So I would use jack-midi if I were you (use -Xraw as an option to jack but then, keep in mind that with this option, you will fail to see legacy ALSA midi app in the jack midi graph. Only the -Xseq option allows the latter for non native jack-midi apps.

you can of course always use the external bridge a2jmidid (improved by Paul Davis, ardour's main dev). Just google it.
Siv
Established Member
Posts: 4
Joined: Mon May 10, 2010 6:08 pm

Re: Client MIDI with Alsa or Jack

Post by Siv »

Thanks for your reply; the only thing is, I have just found out that SooperLooper (the looping program I want to connect to my pedal) does not use jack-midi, but only the Alsa way; anyway, I will take a look at a2jmidid :)
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