This chapter uses OSC queries to construct a traditional three-band sound-to-light system. The example animates a video image consisting of six sprites, but it is easy to adapt this method to control lighting levels or nearly any parameter of any cue in QLab.
Here it is in action, best viewed full screen:
How it works
A Group cue set to “start all children simultaneously” contains three Audio cues that all target the same audio file. Each cue has an AUBandpass filter appled in the Audio Effects tab of the inspector. In one cue, the bandpass is centered around 4100 Hz, in another it’s set to 768 Hz, and in the third it’s set to 148 Hz.
Another Group cue contains several Network cues, each of which query the Audio
liveAverageLevel to get an instantaneous level reading. Depending
upon which Audio cue they query, they get a reason for the high-, mid-, or
low-frequency content of the target audio. The level is then used to modify
geometry parameters of Text cues which use emoji to make a picture of a weird
face. In an actual show, you’d probably use Video cues displaying PNG images
with alpha transparency, but the example workspace uses emoji for compactness.
Here’s one of the OSC queries used in the workspace:
/cue/LOM/scaleX #/cue/LO/liveAverageLevel/1 1 20#
This message animates the x scale of cue
LOM (the eyeballs) by getting the
average level of the cue numbered
LO (which has a bandpass filter applied to
isolate bass frequencies). The query ends in three numbers; the first is the cue
output that’s measured, and the second and third number represent the minimum
and maximum range that the level is scaled to. Therefore, when the level of cue
output 1 of cue
LO is silent, the query will return
1. When the level is as
loud as is possible, the query will return
Music in Demo Workspace: “Stringed Disco” by Kevin MacLeod (incompetech.com). Licensed under a Creative Commons Attribution 3.0 Unported License.