After Effects - trouble setting up an audio-driven expression-animated numbers counter

Question

I'm trying to animate a numbers counter showing the historical progress of time 1834 to 1934 where the counting up is driven by audio ticks. To do this,

[1] I added an mp3 audio file to my timeline

[2] Converted the audio file to keyframes and noted the audio threshold as "3"

[3] Added a text layer and option clicked Source Text

[4] Pickwhipped Source Text to Audio Amplitude

I'm not sure what I need to do next, but I have two major problems:

[A] I'm seeing single digits instead of the yearly counting up that should be going from 1834 to 1920.

[B] And I have a huge set of decimals when I entered these two integer numbers.

Thank you very much in advance to anyone who can help me resolve this.

ShiveringCactus · Accepted Answer

I was copying that from memory, the square brackets at the end of line 1 needed to be regular ones.

But I've had a chance to play now, try this:

var p = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider");
var txt = 1833;
if(p.numKeys > 0){
    n = p.nearestKey(time).index;
    if(n > 0){
		txt += n;
    } 
}
txt

ShiveringCactus · Answer

By pick whiping the audio levels to the text layer, you are telling the text to display the value of the audio level, not the next year.

What I think you are trying to do is use the click track to generate a change in the audio.

You probably need something like this code from Dan Ebberts to trigger the change based on keyframes:

p = thisComp.layer("Audio Amplitude").effect("Both Channels")["Slider"];
n = 0;
if (p.numKeys > 0){
n = p.nearestKey(time).index;
if (p.key(n).time > time) n--;
}
n > 0 ? time - p.key(n).time : 0;

Now that's to drive opacity, so instead you might need an array of years and use n as the counter, something like:

var yearArray = [];
yearArray[0] = "1836";
yearArray[1] = "1837";

yearArray[n]

I'm not in front of After Effects at the moment, but that's the gist anyway.

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