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Timewarp vs Expressions?

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Jochen Knüller
Timewarp vs Expressions?
on Sep 24, 2013 at 10:22:21 pm

I converted an audio file to keyframes and would like the video to speed up accordingly to the resulting slider. Hence I'm trying to get the Speed-Parameter of the Timewarp-Effect hooked up with a slider via an expression (having the Speed equal 100 + the Slider-Value) - However, this results in extremely long render-time.

I figured it could be down to the slider containing a complicated value, so I had it rounded to full numbers, but this doesn't change a thing. I deactivated all frame-generating parameters too, and the effect does render super-fast when I manually enter a value, no matter how precise (e.g. 112,43 or 56,79 or whatever). But once it gets connected to the slider, it slows down immensely (like 0,1 fps render-speed)

What could cause the extreme render time using the expression, and is there a way to avoid it or achieve the desired effect some other way?


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Jochen Knüller
Re: Timewarp vs Expressions?
on Sep 25, 2013 at 11:47:45 am

Alright I'm ditching the Timewarp-effect and trying to use Time Remapping instead - This renders fast.

I did this with adding an expression to the Time Remapping parameter of my video and have that calculate time + slider value. The video now jumps according to the music. Only problem: It skips back once the slider value decreases again on the next frame, and I don't want it to do that. I want the video to "fast forward" once the slider value adds an extra boost the the speed, and then continue from that point onwards once the slider is at 0 again.

Is there a way to "store" a value calculated on the previous frame and then continue from that onwards on the next one?

e.g. Frame 30 calculates time (1) + slider-value (5) resulting in 6. So the time-factor for the next frame should still be 6 + slider-value, not go back to 1.1 + slider-value or whatever. Is this possible at all?


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Walter Soyka
Re: Timewarp vs Expressions?
on Sep 25, 2013 at 5:21:23 pm

[Jochen Knüller] "Is there a way to "store" a value calculated on the previous frame and then continue from that onwards on the next one?"

No. Expressions are instantaneous, not cumulative. Every expression is calculated anew at every frame -- it has no memory of what has come before.

I'd suggest you convert your expression to keyframes (Animation > Keyframe Assistant > Convert expression to keyframes), then copy the time-remapping keyframes to the clipboard and paste them in Excel. Modify the values in Excel (it's much easier to do cumulative math here), then copy and paste them back into Ae.

Walter Soyka
Principal & Designer at Keen Live
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Jochen Knüller
Re: Timewarp vs Expressions?
on Sep 28, 2013 at 5:34:47 pm

Alright, that's not what I wanted to hear, but it's a good idea anyway!

I found an easy fix for my initial problem though - Since the Speed-Parameter of the Timewarp-Effect does exactly what I want, I ended up using that one after all. The solution was to convert the expression to keyframes, which - for whatever reasons - ends up rendering super-fast. No idea why, since the values are all the same and the conversion itself didn't take long at all either - but I'm not gonna ask since it works now!


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