Fade audio with expressions

[trinitywebdesign]

Ok, I've taken an epxression for automactically fading opacity (which worked wonderfully) and tried to modify it to fade audio the same way.  Now, I get an error that says "After Effects warning: Expression Disabled. Error at line 0 in property....  expression result must be of dimension 2 not 1."

Here is the tweaked expression:

fadeTime = 30;

audio.audioLevelsMin = -50;

audio.audioLevelsMax = 0;

layerDuration = outPoint - inPoint;

singleFrame = thisComp.frameDuration;

animateIn = linear(time, inPoint, (inPoint + framesToTime(fadeTime)), audio.audioLevelsMin, audio.audioLevelsMax);

animateOut = linear(time, (outPoint - framesToTime(fadeTime+1)), (outPoint-singleFrame), audio.audioLevelsMax, audio.audioLevelsMin);

if(time < (layerDuration/2+inPoint)){

animateIn;

}else{

animateOut;

}

Now, opacity is a linear, 1 dimensional characteristic.  Why did that work and the updated expression for audio cause an error?

[Dan Ebberts · Accepted solution]

Try it this way:

fadeTime = 30;

audio.audioLevelsMin = -50;

audio.audioLevelsMax = 0;

layerDuration = outPoint - inPoint;

singleFrame = thisComp.frameDuration;

animateIn = linear(time, inPoint, (inPoint + framesToTime(fadeTime)), audio.audioLevelsMin, audio.audioLevelsMax);

animateOut = linear(time, (outPoint - framesToTime(fadeTime+1)), (outPoint-singleFrame), audio.audioLevelsMax, audio.audioLevelsMin);

if(time < (layerDuration/2+inPoint)){

  [animateIn,animateIn];

}else{

  [animateOut,animateOut];

}

Dan

[trinitywebdesign]

It worked!!  I see the small change that you made at the end with [animateIn,animateIn]; How did that effect the process? Was it like giving it an extra coordinate??

[Dan Ebberts]

Yes, stereo audio level is a two-dimensional property, so you need to provide two values, in array notation.

Dan

[bryan.gough]

I have a similar question (I think)... where I have several pre comps that have different lengths, but use the same .wav file for the background music. The end of the .wav file has a chime timed to the motion at the end of the pre-comp. I'd like to be able to copy/paste the .wav file into my pre-comps, align the chime with the animation at the end, and let an expression handle the fade-up at the beginning of the pre-comp, so I don't have to go in and manually adjust keyframes.

UPDATE:

It works, but only if I trim the layer to the beginning of the comp. If I just slide the layer and don't trim the inPoint of the layer... it doesn't work. Could the above expression be modified to use the comp's In and Out instead?

[Dan Ebberts]

Something like this maybe:

fadeTime = 30;

audio.audioLevelsMin = -50;

audio.audioLevelsMax = 0;

animateIn = linear(time,0,framesToTime(fadeTime), audio.audioLevelsMin, audio.audioLevelsMax);

[animateIn,animateIn];

Dan

[bryan.gough]

Mr. Ebberts... I don't ask for help on here very often. And when I do, I'm always expecting someone to say, "Read the manual." or "Let me Google that for you." But, usually what happens is that—within 24 hours, usually—I get a response from a Dan Ebberts (and a few other regulars) that absolutely sets me on the right path, if not solve my problem directly.

This is another home run. Thank you sir!

Consider the next beer/tab/round that someone else picks up on your behalf as "inspired" by my gratitude! Thank you!

[bryan.gough]

fadeTime = 30;

audio.audioLevelsMin = -50;

audio.audioLevelsMax = 0;

animateIn = linear(time,0,framesToTime(fadeTime), audio.audioLevelsMin, audio.audioLevelsMax);

[animateIn,animateIn];

This expression solved my problem, but then I created another one:

I want to move this expression onto a controller in my main comp so I only have to edit values for audioLevelsMin/Max in one place and have it propagate across all instances of the music track in a variety of pre-comps.

1. I added Slider to my Null object
2. I attached the above expression to the slider by alt+clicking on the slider stopwatch.
3. Then I got an immediate expression error.
   • The property name "audio" is missing...

Am I thinking about this correctly?

[Dan Ebberts]

You could try this on your slider:

fadeTime = 30;

audioLevelsMin = -50;

audioLevelsMax = 0;

linear(time,0,framesToTime(fadeTime), audioLevelsMin, audioLevelsMax);

and then link each audio level to it with something like this:

animateIn = comp("Main Comp").layer("Null 1").effect("Slider Control")("Slider");

[animateIn,animateIn]

Dan

[bryan.gough]

thanks Dan (again)!

I think what was breaking my previous attempt was that I was looking for audio.audioLevelsMin/Max where no audio property existed.

I appreciate the help!

[coolwhiff]

Replying to an ollllld post for posterity:

This expression – specifically the part that creates new properties on the property group 'audio' (audio.audioLevelsMax and audio.audioLevelsMin) – will fail on a royalty-free render-only node (with 2020, at least). It *appears* that the audio property group disallows creation of new properties when in render-only mode. The expression works perfectly fine in the fully-licensed UI but will effectively be ignored during render (leading to Very Loud Audio).

The fix is simple: use top-level variables instead, eg. use 'audioLevelsMin = -50' instead of 'audio.audioLevelsMin = -50'