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Slowing down audio keyframe recovery in After Effects

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Jacek Ignaszak
Slowing down audio keyframe recovery in After Effects
on Jul 3, 2020 at 10:15:20 am

Hi,
This might sound a bit confusing since I am not sure how to correctly describe the terminology - I make beat videos that mostly rely on my Kick drum converted into keyframes from audio in After Effects CC 2018 which are then used to control the movement of visual elements using Magnify. Basically - this is a simple audio visualizer that gives a "pumping" effect of a layer in the composition controlled by the audio.

This works fine but since the keyframes created from a quick, transient Kick track are very sudden, the subsequent movement of the visual layers in After Effects is a bit too quick and sudden for the eyes. My question is - how do I slow down the recovery of each burst from the peak keyframe value back to 0 for each hit? I've opened up the keyframe graph editor and I can see the curve of each hit so basically I'd like it to rise to the peak suddenly like it does now, but go back to 0 more gradually so that each final movement does not look so fast when played in real time.

I am aware that I can change this for each individual hit in the graph editor but I am sure there must be a way to do this for all of them at once perhaps using an expression?

Thanks in advance for the help <3


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Filip Vandueren
Re: Slowing down audio keyframe recovery in After Effects
on Jul 3, 2020 at 3:12:33 pm

Hi Jacek,
the word you're looking for is Decay or Release (in audio-terms)

If you use TrapCode SoundKeys, you can use its built-in Fall-off Time settings.

An expression to do this could be kinda slow, but I'll try to come up with something…



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Filip Vandueren
Re: Slowing down audio keyframe recovery in After Effects
on Jul 3, 2020 at 3:37:48 pm

Something like this:


signal=thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider");
fd=thisComp.frameDuration;

sv=signal.value;

decay_time = 1.5;
output=0;

for (t=time; t>time-decay_time; t-=fd) {
st=signal.valueAtTime(t);

decay = easeOut(time, t, t+decay_time, st, 0);
if ( decay > output) {
output = decay
}
}

output;




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Jacek Ignaszak
Re: Slowing down audio keyframe recovery in After Effects
on Jul 6, 2020 at 12:31:38 pm

Hi Filip!
Thank you so much for your reply, it was extremely useful! I have not previously heard of Trapcode Sound Keys but now I realize just how much it would improve my workflow for this kind of work! I have downloaded the trial and will most likely purchase it now to use for my videos. Thanks again for the help and for taking the time to find a solution. Hope you are staying safe, take care.

/Jacek


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