Particles opacity react to audio AE

[AndrewL32]

Hello, I have a little problem and I can not figure out how to do this effect, i want to make the particles(downloaded from youtube, not made in AE) to react to the audio(audio amplitude), like when the song units are down, the particles to stay at 30% opacity, something like this, and when the units are up, the opacity to stay at 100%. The same thing like here:  BOXINLION - Now (ft. Lexie) [Lyrics] - YouTube (min 0:50).

Thank you!

[Mylenium]

Look up any "audio reaction" tutorial and apply the principles to the layer's opacity.

Mylenium

[AndrewL32]

I already tried that, and unfortunetly it works but a little bit.

I set the opacity of the particles video to 30%, after that I typed in the expresion field '30+' and connected the opacity to slider.

This isn't the result wich i want.

[Kyle Hamrick]

On your audio layer, you can right-click > Keyframe Assistant > Convert Audio to Keyframes.
This will give you a numerical value for the left/right/combined channels' amplitudes. You can use these values to drive any property you like using expressions (easily done via the new property pickwhip, if you're in the latest version of AE). Depending on the look you're after, you may need to add a little math to get the exact look you want. We can help you fine-tune a bit if you get stuck.

Agree with Mylenium that there should be quite a few tutorials out there on this and similar techniques.

[AndrewL32]

I explained before (for Mylenium), I know the basics and I watched at many videos on Youtube for the 'audio reaction', but i think that i need some help at the math, as you mentioned.

Thanks for the help btw guys!

[Kyle Hamrick · Accepted solution]

Sorry, I think you actually responded between the time I first opened this thread and when I submitted my response.

The linear function might be helpful here. In the opacity property of your particle layer (or within the particle effect you're using, depending on the exact look you're after), try adding this expression:

audio = pickwhip this to the "Both Channels" value of your created Audio Amplitude ;
audioMin = make this the minimum value of the audio amplitude you want the expression to "see" ;
audioMax = make this the maximum value of the audio amplitude you want the expression to "see" ;
opacityMin = 30;
opacityMax = 100;

linear ( audio, audioMin, audioMax, opacityMin, opacityMax)

This will align the values more precisely, so when the audio dips to whatever the minimum value is (we'll say 0, for the sake of discussion here), the opacity will be 30. When it hits the maximum level (just scrub through the timeline and see where it looks like it's maxing out), it'll be 100.

Let me know if this doesn't seem to be what you're after.

[AndrewL32]

It gives me an expression error, I modified it as you can see here:

audio = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider")

audioMin = 0;

audioMax = 75;

opacityMin = 30;

opacityMax = 100;

linear ( audio, audioMin, audioMax, opacityMin, opacityMax)

Totally wrong i think...

[Kyle Hamrick]

You're missing a semicolon on the first line.

[AndrewL32]

I put it, but unfortunately the expression gives me the same error.

'Object of type Group found where a Number, Array, or Property is needed'.

[Kyle Hamrick]

Can you share some screenshots of what you're trying to do?
This expression works correctly when applied to an Opacity property. Are you applying it to a property with more than one value, like Position, Scale, etc.?

[AndrewL32]

Here is: Imgur: The magic of the Internet

For the Particles I dont use any effect, just the opacity.

I'm using some effects like position, scale but for the text. Which is in a pre-compose group.

[Kyle Hamrick]

Well, I'm not sure what you're encountering here. I copy/pasted the exact expression from your post, and it works correctly.

Are you applying your particle effect to this .wmv? Or just using that for testing purposes?

[AndrewL32]

I made a video to see how I edit the audio reaction and particles, I hope to be helpful.

Example - YouTube

Yes, i want to apply that to a video, not to this, this is just an example for me to learn much more things about the audio react.

I did the particles  reaction in a different way, as you can see in the video. But here is a problem, this works just with songs like this(with bass boosted), for normal songs it's not good, it react too much when it's not needed.

[Kyle Hamrick]

At 3:50, when you pasted in the expression, you're still missing the semicolon at the end of the first line, which is why it gave you the error.

It looks like you have at least an ok comfort level with expressions. Learning linear would be a powerful tool. Jake Bartlett has a great explanation of it here: linear(); - After Effects Expressions - YouTube and another here from Animoplex: After Effects Expressions 205 - Linear & Ease - YouTube . (They both have some great expressions-related stuff here - I highly recommend both.)

With linear, you have control to map those values however you want, so you could tighten the audioMin and audioMax to be watching a bigger/smaller area of the dynamic range, or tweak the other values to allow for less change in the visual. Having a track with a lot of dynamic range will get you the best results, but you could just have it be "watching" a bigger/smaller range of values. Keep in mind, it's just "listening" to the overall amplitude of the track. Having stems (isolated tracks for each instrument) would be ideal, but you could always do some processing of your audio track in Audition to try to isolate the frequencies you want the visuals to be driven by.

From a workflow perspective, you're doing some unnecessary steps/burying of things. Everything you did in that precomp certainly could have happened on one layer in that main comp (and with live text, vs an imported image), for what it's worth.

[AndrewL32]

The semicolon is 0, if I put or not the semicolon at the end of the first line is the same thing, as example, you too didn't used it, I get the error in every case.

Thanks for the help anyway with the linear, keep up the good work.