Overlaying 2 movies on top of each other with one transparent to the other?

[Sniffy]

I need to take 2 different short movies and fuse or overlay them together so that one sees both sets of images on top of each other as it plays. This probably would have to be done by making one more transparent to the other (or both equally transparent). Someone at work suggested using a fade-in tool, but that seems to only work when transitioning from one movie to the next in line. What program or tool would let me do this?

Mike

[edDV]

I need to take 2 different short movies and fuse or overlay them together so that one sees both sets of images on top of each other as it plays. This probably would have to be done by making one more transparent to the other (or both equally transparent). Someone at work suggested using a fade-in tool, but that seems to only work when transitioning from one movie to the next in line. What program or tool would let me do this?

Mike

Premiere or Vegas would allow you to assign an alpha channel to the top layer and then modify the alpha on a pixel basis for for a blend following the formula

A = top layer
B = background

New pixel = A x alpha x (B x (1-alpha))

Where alpha = foreground transparency

If you want both equally transparent, you would set foreground alpha to 0.5.

Separate from alpha, a mask can be applied to restrict the foreground over an area defined by the mask. You can also modify the edge of the mask to be a blend or other.

The mask follows a similar formula of

New foreground = Old foreground x mask x (background x (1 - mask))

All compositing special effects use this technique.

[guns1inger]

Vegas would do this easily. Just drop each on a timeline, line up the start points, then adjust the track opacity of the top track until you are happy with the mix.

[manono]

What program or tool would let me do this?

The Overlay command in AviSynth:

http://www.avisynth.org/Overlay