Reference Manual
CHAPTER 22. MIDI AND KEY REMOTE CONTROL 307
22.2.4 Mapping to Relative MIDI Controllers
Some MIDI controllers can send value increment and value decrement messages instead
of absolute values. These controls prevent parameter jumps when the state of a control in
Live and the corresponding control on the hardware MIDI controller differ. For example,
imagine that you have assigned the pan knob on your control surface to the pan parameter
of a track in Live. If the hardware control is panned hard right, and the Live control is panned
hard left, a slight movement in a hardware pan knob that sends absolute values would tell
Live to pan right, causing an abrupt jump in the track's panning. A pan knob sending relative
messages would prevent this, since its incremental message to Live would simply say, Pan
slightly to the left of your current position.
There are four types of relative controllers: Signed Bit, Signed Bit 2, Bin Offset and Twos
Complement.
Convention (Mode) Increment Decrement
Relative (Signed Bit) 001064 065127
Relative (Signed Bit 2) 065127 001064
Relative (Bin Offset) 065127 063001
Relative (2's Comp.) 001064 127065
Each of these are also available in a linear mode; Some MIDI encoders use acceleration
internally, generating larger changes in value when they are turned quickly. For control
surfaces that are not natively supported, Live tries to detect the controller type and whether
acceleration is being used or not.
You can improve the detection process by moving the relative controller slowly to the left
when you make an assignment. Live will offer its suggestion in the Status Bar's mode
chooser, but if you happen to know the relative controller type, you can manually select it.
Live will do the following with relative MIDI controller messages:
Session View Slots Value increment messages are treated like Note On messages.
Value decrement messages are treated like Note Off messages.
Switches Increment messages turn the switch on. Decrement messages turn it off.
Radio Buttons Increment messages make the radio button jump forward to the next