[temp,temp] not generating in Expressions field when using Pick Whip for Audio Amplitude

Question

Adobe fam,

I am working on a Halloween project for someone and I am trying to make a visualizer/react overlay and I have made MILLIONS of visualizers and overlays for channels/streams/content over the years and I have recently come across this issue where when I want to add an expression by using the pick whip and selecting the slider on my Audio Amplitude keyframes, it used to generate an expression immediately that included [temp. temp] and now for some reason [temp, temp] is not showing up in the expression section and if I add it, I am getting expression errors. I cannot for the life of me figure out what has changed or why [temp,temp] isn't generating the same way it used to when I used the pick whip on my audio amplitude layer. I am trying to control the opacity of my jack-o-lantern face and have it react to the beat/audio in the timeline. I attached a video to show this issue a bit easier so maybe someone could point me in the right direction and I can get these projects out the door. Cheers! VIDEO BELOW:

Mike_Abbott · Accepted Answer

Because it is not needed : )Opacity is a one dimensional property - it is driven by one number.[temp, temp] is used where you are taking a one dimensional property and need to apply it to a two dimensional property such as scale, which has (typically) two values - x scale and y scale.

Mike_Abbott · Answer

I thought you might be about to ask that ; ) Yes there is... you want to use a 'linear interpolation' expression. It maps one range of values to another. You can find it under the expression language reference menu - the black triangle in the white circle just to the right of the pickwhip. Go to interpolation > and the second entry. You'll get:

linear(t, tMin, tMax, value1, value2)

in common written form: "As 'something' goes from min value to max value, I want to go from value 1 to value 2"

You need to replace these placeholder values. So look at your audio levels in the graph editor and decide on the min and max values you want to use. From your video maybe 5 min and 25 max.

So here's your expression:

audioAmp = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider");
linear(audioAmp, 5, 25, 40, 100)

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