03 April 2017

Midi keyboard AKAI LPK25 velocity problem

I have a cheap AKAI LPK25 MIDI keyboard. I it nice, but unusable due to unreliable sensibility. There is a utility: aseqdump that will dump MIDI messages. aseqdump -l will list the Midi client connected ; "-p client" will dump the specific client MIDI messages
  • ON PC, the plugin "MIDI velocity adjust" by Robin Gareus is excellent to compensate the poor physical MIDI keyboard.
  • Android does not seem to feature such filter. Neither does Caustic: http://singlecellsoftware.com/node/13935
To measure the problem:
$ aseqdump -p24 | tee lpk25.txt | sed --quiet -e 's/^.*Note on .*elocity //p'
 # Type some random string on the keyboard ...
$ cat lpk25.txt | sed --quiet -e 's/^.*Note on .*elocity //p' > lpk25.dat
$ cat lpk25.gp   
  n=127 #number of intervals  
  max=128. #max value  
  min=1. #min value  
  width=(max-min)/n #interval width  
  #function used to map a value to the intervals  
  hist(x,width)=width*floor(x/width)+width/2.0  set boxwidth width*0.9  
  #count and plot  
  plot "lpk25.dat" u (hist($1,width)):(1.0) smooth freq w boxes lc rgb"green" notitle

Finally plot the thing:
$ gnuplot -pc lpk25.gp
Velocity goes from 1 to 127. hitting the keys randomly for a while shows that it is not well balanced. There is a huge spike at 1. The aim is to set a minimum value somehow.
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