[LAD] MIDI in jack

Flávio Schiavoni fls at rendera.com.br
Mon Jul 7 03:58:39 UTC 2014

It sounds to me like a keylogger as the input + MIDI (Jack or ALSA) as 
output. Maybe a ring buffer or something in between.

If a keylogger is the kind of input you wish:

Trying to guess a naive code implementation, I foresee two problems:
- If one press a key and keep it pressed, the computer keyboard 
repeeeeeeeeeeeeeeeeeeeeat the key, generating several NOTE_ON midi 
- Without a high level API I don´t know if you will have a KEY_RELEASE 
event to generate a NOTE_OFF event. If you have it you can solve the 
former problem.



Em 06-07-2014 12:57, Len Ovens escreveu:
> Hello new to this list but realized I was asking a lot of development
> questions in LAU that would probably be better here.
> I am writing a program that takes some system input from the keyboard
> and redirects it as midi. This is to allow:
> - a second keyboard to be used as a midi control
> - switching the system keyboard back and forth between normal and midi 
> controler
> - using a potion of the system keyboard as a midi controler (the
> numeric pad for example)
> The advantage of this over keyboard short cuts is that this will work
> the same no matter what the desktop focus may be.
> I am (as many people do) writing this for my own use, but will make it
> available for others who may have similar needs.
> My question:
> Where and how is the best place to put the MIDI port?
> My first thought was to get it to create a jack midi port as this
> would be the most direct. The problems I see with this are, 1) my
> program will run as a different user than Jackd, 2) my program will
> run before and perhaps after jackd.
> SO then I thought I guess I have to use ALSA for my midi port. I need
> to know if I do this, will jackd that is running a different backend
> than alsa (firewire for example) still see the alsa midi ports? I am
> guessing that a2jmidid would still work in any case, but not everyone
> uses that.
> Assuming I have to use alsa midi (unless some one can suggest how to
> make this work with jack midi), I have noticed that some aplications
> that use alsa midi do not leave a visible port in alsa and do all
> connections internally which would be useless in this case. There are
> some examples of code at http://www.tldp.org/HOWTO/MIDI-HOWTO-9.html
> and I was wondering if this method will leave visible midi ports. I am
> also noticing it 2004 ish, is the info still valid, or is there a
> better place to look?
> The keyboard input and grabbing will be based on the code from actkbd
> as it seems to already do all that stuff and is gpl2 (and besides the
> code looks understandable to me)
> --
> Len Ovens
> www.ovenwerks.net
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> Linux-audio-dev at lists.linuxaudio.org
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