Windowed Averaging

June 18, 2007

Recently I’ve been keeping things very simple – eight frequency bands driving all my graphics. My previous experiments used 64 bands, split into four groups of sixteen with Ess kindly working out the average for these groups. My past methods were based completely on event triggering – when a spectrum band peaks above its group’s average by a certain amount something happens.

I’ll definitely work a feature like this back into the mix. If tamed correctly it finds drum hits (particularly the snare) and highlights big dynamic changes really well.

For now, I’ve stripped things back to find more complex ways of interpreting these spectrum values. The plan is to have these always changing spectrum values controlling movement and speed. Turns out it’s quite tricky – even with audio dampening, getting smooth results will take a bit more work. Until then I’ve been thinking up ways to visually highlight structural change beyond a keyboard or time based trigger.

Here is St. Anthony’s Fire (the song I will be using, right click to download) split into eight frequency bands and averaged every 60 frames (two seconds). Not exactly a sexy piece of data visualisation I know but useful enough.

windowaverage
(right click to see a larger version)

The song is very heavy and a total mess of frequencies but windowed averaging has made the structural changes quite clear to the trained eye. I’ve circled the points in which I could set thresholds or even better link a windowed average to a particular variable to get a nice gradual transition rather than an instant shift. Hopefully I can give these six sections a completely different look/structure and provide smooth transitions to create a clip that’s always flowing and moving. Generative animation’s beauty is its capacity to provide output, shapes and movements beyond the programmer’s initial intention – visuals that are somewhat ‘alive’. I’d like to turn the visuals into a character of sorts, a complex and wild beast that twists, turns and changes with the music. Avoiding hard cuts and instant transitions will help the visuals to live and breathe.

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