Sound Keys Expression

[Darby Edelen]

[Mark Woloschuk] “d= 1;
tD = opacity.valueAtTime(time – d);
F= .5;
sk= thisComp.layer(“SK_Avg”).effect(“Sound Keys”)(“Output 1”);
if (sk>=7 && sk<=13) t=100 else t=0 tF= t+ (F*tD); tF "

I think your problem is the d variable in this case. valueAtTime() takes a time value in seconds, so you’re subtracting 1 second from the current time in seconds when you want to be subtracting 1 frame’s duration in seconds (1 / fps).

You need to use the comp property frameDuration to get the duration of a frame in seconds:

d = thisComp.frameDuration;

However, I feel it is my duty to tell you that you’ll get better results by playing with the Range > Falloff property in the SoundKeys effect itself, as you can specify instant, linear or exponential decay without writing a bit of code.

Darby Edelen
Designer
Left Coast Digital
Santa Cruz, CA

[Mark Woloschuk]

Thanks Darby but that still doesn’t fix it. When I access the tD value it still doesn’t return a value that makes sense.

I’m aware of the falloff settings in Sound Keys (and indeed am using an exponential falloff) but in this case I need the fade to happen in the layer not in the sound key data since this piece of audio moves so fast.

Imagine someone playing the piano very fast and every key they hit lit up as soon as they touched it but faded out more slowly.

Unless I’m missing something fundamental about Sound Keys, I think the way to do it is within each layer’s opacity values.

But thanks for the effort!

– Mark

[Dan Ebberts]

I think you’re going to need something like this:

sk= thisComp.layer(“SK_Avg”).effect(“Sound Keys”)(“Output 1”);
decay = 7.5;
gotOne = false;
for (t = time; t > 0; t -= thisComp.frameDuration){
if (sk.valueAtTime(t) >=7 && sk.valueAtTime(t)<=13){ gotOne = true; break; } } if (gotOne) 100/Math.exp((time-t)*decay) else 0; Dan

[Mark Woloschuk]

Oh my… that’s way fancier than I would have imagined. But the important part is that it works quite nicely.

Thanks Dan.

P.S. I’m still first in line for that book/video expression training I just know you’re going to spring on us some day.