Fade with configurable time curves?

[shae]

Are there any fade plugins or scripts that allow configuring the fade curve?

Similar to, for example:
https://developer.mozilla.org/en-US/docs/Web/CSS/transition-timing-function#syntax

[johnmeyer]

For something like this, where you want to interact with your video while adjusting, I always use my NLE (Vegas). Here is what an adjustable fade might look like. You can add as many points as you want, and you can make the transition between points linear, or you can curve the transition.

https://i.imgur.com/TEIbuep.png

[coolgit]

http://avisynth.nl/index.php/Dissolve may do what you want.

[shae]

The idea was to have it scriptable, and not have to use external tools.

If nothing exists, the simple way may be to make a script function to calculate the points, then Merge() or Overlay() each frame in the range with pure color.

coolgit, with Dissolve() the only control you have is the number of frames, it seems.

[wonkey_monkey]

You can use Expr. I think the simplest way is to use ConvertBits(32) first for YUV clips so that chroma is offset properly and you don't need to do a complicated Expr, then do something like

Expr("x time *") # linear fade in
Expr("x 1 time - *") # linear fade out
Expr("x time 2 pow *") # quadratic(?) fade in
Expr("x time pi * cos 0.5 * 0.5 + *") # sinusoidal fade out

And so on. Watch out for how Expr deals with limited range video, for example the above examples all fade/to 0 rather than 16.

[Reel.Deel]

Very nice wonkey_monkey.

Would you mind sharing a few more examples for those who are not mathematically inclined? I would like to add these examples on the Expr documentation page.

[shae]

Thanks. Won't Merge or Overlay be faster than Expr?