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Making an expression for a Gain Reduction Meter

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Willie Frazier
Making an expression for a Gain Reduction Meter
on Sep 12, 2012 at 1:19:30 am

Hi everyone,

I am faced with a bit of a conundrum, and would appreciate some help from the collective wisdom here.

Presently I am making an audio compressor animation for instructional purposes. This compressor features a pair of VU meters. One for level, which works the way most folks are accustomed to seeing VU meters operate, where the needle bounces in an arc from left to right, with the left most point representing silence, and the right most point of travel indicating the peak of the audio level. I have written an expression that accomplishes this behavior quite nicely:

r=thisComp.layer("Audio Amplitude 2").effect("Both Channels Smooothed")("Slider")*effect("multiplier")("Slider")+effect("offset")("Slider");

I am not, however, having much luck in making such a setup for the second meter, which is to be a Gain Reduction meter. This meter works differently than a level meter in that the needle instead hovers at a position analogous with 1 o'clock, and moves to the left only when the audio has passed a certain level and the compressor kicks in. The amount of left travel (done via rotation with an anchor point at the bottom of the needle) coincides with the amount of attenuation the signal receives based on the compressor's settings.

This GR meter then, has very little movement, and is only occasionally triggered. I thought the minimal movement would be easy to hand-key, but this has turned out to be a tedious and time-consuming process. I feel there simply must be a way to achieve this with an expression.

Any help is greatly appreciated,

- Will

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John Cuevas
Re: Making an expression for a Gain Reduction Meter
on Sep 12, 2012 at 1:45:10 am

If you don't find an answer here, try the expressions forum, Dan Ebberts is genius when it comes to coming up with solutions for expression problems.

Johnny Cuevas, Editor

"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.

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Cassius Marques
Re: Making an expression for a Gain Reduction Meter
on Sep 12, 2012 at 12:34:13 pm

If it's driven by a single value, can't you use a Linear expression?

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