The VideoBass is an unique hardware/software-combination for controlling live-visuals. Shaped like a electric bass-guitar, it relies on the guitar-paradigm where, basically speaking, the left hand chooses between a wide variety of possible notes, and the right hand triggers them.
About this Document
Author
Michael Egger
[ a n y m a ]
Route de la Fonderie 8c
1700 Fribourg
Switzerland
me (at) anyma.ch
+41 79 278 31 39
Version
Version 1.0
– Last modified: 18.06.2004
Copyright
© 2004 Michael Egger
URL
The VideoBass – project is maintained by [ a n y m a ].
For latest sources, documentation, feedback etc. visit
http://www.anyma.ch/videobass
Abstract
The VideoBass is an unique hardware/software-combination for controlling live-visuals. Shaped like a electric bass-guitar, it relies on the guitar-paradigm where, basically speaking, the left hand chooses between a wide variety of possible notes, and the right hand triggers them.
On the VideoBass, the user selects video-clips with his/her left hand by means of rotary buttons (like tuning keys on a guitar). Once a clip selected, every single frame of video becomes accessible on the instrument’s strings. By moving one’s finger up and down the frettless neck, you can choose any particular image in the clip. With ones right hand, one can trigger the clip by slapping a TactBall, a sensitive sphere located on the instrument’s body.
Additionally the TactBall lets you dissolve between different videos and control their playback speed (by means of slightly moving the ball). Other controls for image parameters can be located on the instrument’s body (for saturation, contrast, color balance etc..), as well as a mode switch for different play modes.
The instrument serves as a Human-Computer-Interface for the VideoBass software, where the actual image processing takes place.
For the time being, it uses MIDI as its communication protocol because of its large distribution and simplicity – other (open-) protocols could be adopted in the future…
License
The VideoBass is free hardware (as in "free speech" not "free beer"). This document as well as all documentation on the project (hardware designs, source code, ...) is published under GNU GPL; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; (where "source code" shall be replaced with "this document" and "program" with "any device built or manufactured according to this document") either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this document; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. http://www.gnu.org
Preamble
Finding new ways to interact with computers is crucial for pushing further computer-assisted performing arts. Mice are nice tools in a non-realtime environment, but pointing and clicking has very little emotional/expressive value.
The VideoBass is an unique custom made hardware/software combination destined to play visuals like on a musical instrument. It consists primarily of a guitar-shaped do-it-yourself MIDI-controller and a piece of software written in MAX/MSP and softVNS. Invented in summer 2003 by Michael Egger, it permits the visual artist to play with his stock of clips and with live recorded material in a musician’s way, concentrating on rhythm and expression. The VideoBass allows for the instrumentalist to step back from the computer, to move freely on stage and to focus on the final output and on the interaction with other performers (rather than sitting autistically behind a computer screen and keyboard, clicking and typing his way through menus and presets…).
The VideoBass – like it’s musical counterpart, the electric bass – is primordially used for visual rhythm and groove. But, as it is finally just a MIDI controller and a bunch of software, one might think of many other possible uses… experiment!
Technical Description
Note
This is a technical description of an early prototype, for a functional description please refer to the abstract. Actual proportions, choice of materials, assembly and electronics may change in the future.
Hardware (see Fig 1 & 2)
The headstock contains four Rotary Encoders [1,2] for selecting clips and a button to initiate the sensor calibration routines, as well as supporting electronics (circuit schematic: see Fig 3)
Four strings [3 thru 6], tightly wound with resistance wire, spanned over a conductive, frettless fingerboard [7]. This results in four very long linear potentiometers (at ~ 1.8k each). The whole fingerboard is at Vcc (+5V) and has a persistent connection to the strings at the nut [8], whereas the saddle [9] is isolating. Inverted voltage drop of each string is measured at the bridge [10] (see also Fig 4 for schematics). This way, open (= not played) strings keep a fixed high voltage drop (~ 4V), whereas fingered strings present voltage drops relative to the distance of the finger to the bridge. Best of all, if one presses several fingers on the same string, only the finger press nearest to the bridge is relevant (like on a traditional guitar).
String tension is not really an issue, as no sound needs to be produced. For convenience one can regulate overall tension of all four strings by means of a tension adjuster [11]
A TactBall [12] on the body serves as a multipurpose sensor for triggering and controlling dissolve and speed (see http://www.anyma.ch/tactball for a detailed technical description)
Additional controls on the body include some general purpose rotary potentiometers [13] and a mode switch [14].
Electronics for converting analog sensor data are located inside the body, a small microprocessor (BasicStamp 2sx) generates MIDI-data which is sent to the plug [15] and further on to the computer…
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Fig 3 |
Fig 4 |
Software
Firmware
For a commented source of the VideoBass firmware (BasicStamp), see videobass_firmware.bsx
Video source folder structure
There can be up to 16 banks with up to 16 clips each. (16 folders, their names will be the bank names, 16 files per folder). The whole folder must be indexed to a movie of 256 frames, with 1 frame of each clip
The VideoBass software
The VideoBass software is based on MAX/MSP, softVNS and jitter. It is very simple, basically just a two-channel mixer without any image manipulation.
There are two main video sources (which can be either a movie file on the hard disk, or a live buffer in RAM), they function identically, so for simplicity’s sake I will focus on one channel for a moment:
Basic Operations
Selecting a bank/clip with the rotary encoders on the VideoBass shows a preview thumbnail on the leftmost screen (these must be able to change very quickly, hence the index movie) but doesn’t change the clip actually playing.
As soon there is a change on the string concerned (string 1 for channel 1, string 3 for channel 2), the selected movie file gets loaded in the preview window (the middle one) – but the clip actually playing still isn’t affected.
Moving your finger on the string lets you scrub through the movie – low notes are at the beginning of the clip.
Slapping the TactBall (from the top for string 1, from the bottom for string 3) loads the new clip into the playing movie (if needed), starts playing the clip from the frame selected on the string, and cuts to the corresponding channel on the mixer.
Subsequent slappings restart the clip from the frame selected on the string. Otherwise the clip loops from the selected frame to the end.
Tilting the TactBall to the top/bottom starts a cross dissolve to the other movie, the amount of tilting controls the amount of crossfading
Tilting the TactBall towards the strings accelerates both movies, tilting in the opposite direction slows down and reverses the speed.
Final output of the VideoBass software is recorded continuously in a 20 second looping buffer. Pulling the TactBall away from the body lets you control the amount of buffer fed back to the output. String 2 lets you adjust the feedback’s delay, low notes being a long delay…
String 4 remains unused for the time being
Acknowledgments
Above all, thanks to Maïté Colin for her neverending patience & support, for intense testing of sometimes completely unusable and terrifying prototypes, for finding hundreds of bugs!
Thanks to Max Egger for help with transistors and the (abandoned) graphite idea
Thanks to Martin Saxer for the idea of the bicycle tubing
Thanks to Fri-Son for numerous testing opportunities under live conditions
Version History
Documentation
- 2004/06/17 updated version for new design, added illustrations and circuit schematics
- 2004/01/27 First draft version
Design
- 2004/06 neck plate replaced with 3 mm aluminum & custom built strings, wound with resistance wire
- 2004/04 even better TactBall with bicycle tubing
- 2004/02 developed a new version of the TactBall
- 2004/11 first presented to the public on Nov. 7th 2003 at Fri-Son in Fribourg, Switzerland.
- 2003/10 first prototype, neck coated with graphite as resistive material, ordinary guitar strings
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