control surfaces (was Re: [linux-audio-dev] GUI-free ardour)

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Subject: control surfaces (was Re: [linux-audio-dev] GUI-free ardour)
From: Lance Blisters (geoff_AT_ugcs.caltech.edu)
Date: Thu Apr 12 2001 - 01:01:31 EEST


Jussi Laako to PDB:
> Btw. do you have plans to implement support for USB controller pads/audio
> systems? It would be great to have taperecorder-style physical controller
> pad.
>
> I've been also thinking that it would be great to create something like GDAM
> with support for Delta1010's HW mixer and external controller. Mouse is too
> slow and otherwise doesn't fit very well for making "live" DJ-mixes.

  Actually, GDAM supports a variety of hardware input devices. In addition
  to midi events (you can bind events against the contents of sysex messages
  as well as parameters, notes, etc) we support raw data from a secondary
  keyboard plugged into the ps2 port, usb human interface devices via 2.4's
  generic input core and /dev/input/eventx (mouse and keyboard are tested,
  joystick / touchpad / etc. should mostly work), and one custom hardware
  device (ultrasonic rangefinders on the parallel port, drive parameters by
  moving hands through space).

  I use the mouse for loading songs, creating new filters, and loading xml
  files with sets of input event bindings. The system keyboard is used for
  text entry and per-window key bindings. I have a tiny $10 keyboard
  on the ps2 port which gives me an extra 108 buttons to start, stop, seek,
  and synchronize tracks regardless of mouse focus. Buttons toggle effects
  on and off, or an effect is active while a certain button is depressed.
  For variable values, i have the wonderful 'bitstream pro' midi controller,
  which gives me 8 sliders, 32 knobs, 8 toggle switches, and an lfo-driven
  parameter.

  Programming for /dev/input/eventx was very simple, and i look forward to
  converting usb hid devices into control surfaces as my budget allows.
  I'm hoping that cirque will answer my mail, and verify that their
  'easycat' usb touchpad can be made to report absolute position before
  i invest in a few of those. I'd also like to try using a joystick or
  trackball to control position and speed when beatmatching to an unknown
  track.

  I'd be curious what sort of usb data is emitted by a USB control surface
  such as the tascam 428... hid reports to /dev/input/eventx? reports with
  useful usages we could handle with a kernel module? Or a proprietary
  protocol crammed through byte-wise?

  Regarding control of sound card's hardware mixer, GDAM has no support for
  this. One of GDAM's weaknesses is that a song can be moved between
  devices, but a song cannot be played to two devices at once. It would be
  great to use the hardware routing and mixing capabilities of cards like
  trident 4dwave and delta1010, but i haven't looked into it. I use the alsa
  mixer app 'gamix' (or alsactl) to split the sound between 'room' and
  'headphone' channels once after opening the device, and leave them that way.

> I think I will build external control gear for that kind of application with
> my DAQ card. It has 24 digital I/O lines, 8 A/D channels and 2 D/A channels.
> So I could have play/stop/pause/fw/rew etc. buttons and potentiometer
> controls for level/EQ/x-fader. I have already written RT-Linux drivers for
> that board.

  My dream controller be only pitch-bend levers, ribbon pads, and jog wheels!
  This would complement my other gear well.

  -geoff

ps - anyone looking for lots of midi continuous controllers, consider
bitstream pro from waveidea.com - best cc/cost and cc/size of any
device i've found. my only reservation is that the bitstream unit doesn't
feel as solid as a mass-produced controller. nevertheless, it has
withstood lots of travel.


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