hardware and software for electronic music 
Friday, July 14, 2017
by Randy Jones

Soundplane 1.5 beta available

For the last few months I've been working on a brand new way of extracting touches from the Soundplane pressure data. I'm very happy to send out the first public demo of that work today, as Soundplane 1.5.0b1.

The new touch tracker algorithm is a fundamentally new approach, and fixes small but annoying inconsistencies that players had to work around with the old one. Some of these showed up as stuck notes, or lingering phantom notes that would follow a touch.

I've been playing my Soundplane a lot while working on this. Now, when the sounds aren't right, I'm finding more often it's a problem with where my fingers are and not the software. So I'm very happy to switch my focus a bit more from algorithm development to practising!

Soft touches are no longer subject to a time-varying rejection filter, and should feel much more stable and less spongy. Positions of touches should be more accurate and consistent. Adjacent touches should maintain their positions better over a range of pressure.

Generally speaking, the new algorithm uses spatial filtering in a lot of places where the old one used temporal filtering. So latency should be much better, and in general it should reflect whatever your fingers are doing right now, which is kinds the point. Read on for details.

Version 1.5 changes

  • new touch tracker algorithm
  • attempted fix for Kyma connection

Installation

I'm sending out this version and any other upcoming betas simply as a compressed file containing the application. You can move it to wherever you currently keep your Soundplane application and run the new one alongside the current one. All data files have the same format, so you can use old zone presets with the new version.

On installing, I recommend that you go to the Expert page of the application and choose "restore defaults." This will set the default parameters for the new tracker and pick carriers.

If you have a carefully made calibration for the old tracker, you may want to back that up. I believe that it will be preserved if you switch to the new version and back, but better safe than sorry. The calibration file is in Library/Application Suppport/Madrona Labs/Soundplane/SoundplaneAppState.txt.

Getting started

This new tracker runs on a new, more robust principle and so a calibration procedure is no longer needed at all. In the future, I may add some form of positional fine tuning to allow for differences between instruments, but for now I think this should perform well without any calibration, and we'll have a more consistent baseline so I can get feedback on how it's working for the beta.

A couple of levels might need to be adjusted, as follows. Run the app and go to the "Touches" page, and pick the "xy" view mode from the view mode menu. If you raise the view scale dial to around 10, you can probably see some gray flickering. This is the sensor background noise. If you touch the surface now, you will see some green pixels, and probably a touch. If you see green pixels when you are not touching the surface, the "lo thresh" dial needs adjustment. To do this, go to the Expert page.

Back on the Touches page the "thresh" dial functions basically as before. The default here is 0.01. If you make this lower, lighter pressure will create touches, but touches will not be as consistent. Please use the default value for now when reporting issues.

Beta testing

Let me know if the new tracker seems like an improvement. If there are some cases where it isn't, the most effective communication to me would be a short written statement about what doesn't work well. I may be seeing the issue too, and already aware of it. After that, screen shots and movies are probably the best way to communicate about issues with tracking.

If you have a Kyma, please get in touch and let me know if this fix solves the connection issue with 1.4. If it does not, I will be sorry, but not too surprised, because I don't have a Kyma for testing. Now that the new tracker is done, and we are in the testing phase for this release, I can work frequently with you to find a fix.

New tracker notes

The new tracker runs in multiple phases, which you can see visualizations of using the various view modes on the Touches page. In short, these are:

  • raw data: as before, raw Soundplane data
  • calibrated: data after calibration and spatial smoothing
  • pings: touch candidates obtained by curvature method
  • pings horiz: horizontal pings only with pressure graphs
  • pings vert: vertical pings only with pressure graphs
  • key states: where a touch may be over each key
  • raw touches: touch candidates derived from key states
  • touches: filtered and matched touches
  • xy: finished touches with position histories, also sensor data

Sustaining touches on adjacent keys should now be possible, with careful playing, as long as the touches are more than a key width apart. In other words,

While single touches can be played very softly, groups of touches may take more pressure.

Touches on the bottom row suffer from positional inaccuracy because the palm of the hand is often close by providing a sink for electrical charge. This is a Soundplane hardware issue, not a tracker thing as such. To see an example, try pushing the lower row keys with a nonconductive pen or pencil instead of a finger. You may see that the positions go more easily to their limits. I have found keeping the bulk of my hand away from the surface, by curling the finger underneath and playing with my nail, to be a useful technique.

Touches never go all the way to the edge of the outer keys. If you think about it, you would have to be poking into the corner with something pointy-shaped in order for the center of a touch to be truly on the edge of the surface. The Soundplane is designed for fingers, which all have some thickness.

Next steps

If you look on the Soundplane issue tracker on Github, you can see the problems I know about or improvements I would like to make. If you have a problem with the software or a feature suggestion that's not on this list, please let me know.

The current state of the software archive is a bit messy, and it's not too clear what versions of libraries to grab to compile your own version. I'll be cleaning things up as I work on the 1.5 release. Meanwhile feel free let me know if you have any questions.

I also look forward to finally updating the manual, now that the software is settling down. I'm having a lot of fun playing now, and I plan to do some more video demonstrations soon.

Finally, all this work sets the stage for the soundplane-to-CV module, and the next model of the Soundplane itself. Stay tuned for developments.