Replacing a computer screen with a still image

[Eric Dumas]

Hi,

I have a short video (5 seconds) of someone talking to the camera.

Behind this person, there is a computer screen turned off (black).

I need to add a still image to fill the screen, even when some of the person's shoulder gets in front of the screen, hiding a small portion of the screen.

I was hoping that the latest version of AE would have a way to help me with that.

What is your easiest recipe?

Thanks

[Mylenium]

No easy answers, especially without seeing the actual footage. most likely you will need to use conventional masking or semi-automated stuff by tracking shapes in mochaAE. The Rotobrush tool is too crude to begin with and tends to not produce good results if the footage doesn't have enough motion it can detect. If the obscuration is only partial it should be easy enough to just hand-animate a bunch of masks. 5 seconds really is nothing and trying to be a sleuth and employing every trick in the box with convoluted tracking will be much mor time-consuming and inefficient.

Mylenium

[dj.summitt]

If it is a tripod shot with no movement a simple corner pin will work to put it on the computer. Experiment with blending modes to get the glare and reflections correct. I disagree with Mylenium. I use rotobrush for this exact thing all the time. It should work great. Just make sure to refine the edge.

If the computer is moving in the frame, like a handheld or Steadicam shot, then you'll go to Animation>Track in mochaAE.
This will help you get started in making the track data. Learn Tracking and Screen Replacement with Mocha for After Effects in only 6 minutes! - YouTube
But basically it's the same process, just a corner pin & rotobrush combination.

[Rick Gerard]

Motion track the footage in Mocha using Corner Pin tracking if there is camera movement then create any needed roto by hand. Something like this but with an additional mask to fix the shoulder problem.

If there is no camera movement you may be able to just scale and align the image, use one mask to carefully match the edges of the monitor, then use a second mask to roto the shoulder of your actor.

It's actually an advantage to have the black screen because you can now play with blend modes to pick up reflections. If the image is a lot lighter than the background you may also want to use one of a dozen or so techniques to apply a light wrap on the shoulder of your actor.

The most efficient and effective technique depends entirely on the shot. There is no magic way to do this that only takes a click or two.

Your experience level also makes a difference. This is pretty basic compositing so I am assuming you may be new. If so, let us know.

[Eric Dumas]

Hi,

Thanks for the feedback, I will check the link to youtube tutorial.

The camera and the screen do not move. The human part is the challenge. I masked the screen but the person swivels on his chair, so part of his shoulder disappears under the fake screen content.

I was hoping there was a photoshop-like magic wand with a dynamic intelligence to it that would replace black with fake screen on a frame-by-frame basis. Yes, I am new to AE (and naive!)

[Rick Gerard · Accepted solution]

If the camera doesn't move then a simple hand roto is probably all you need to mask out the shoulder. The easiest way to createthat track matte is probably with a few keyframes. Follow this procedure for creating the track matte:

Ignore the part about stabilizing the footage and lining up the matte. Pay attention to how the mask is created using a colored solid and a blend mode so you can easily see through the matte, then set keyframes at key points in the motion. Put the roto layer right above the screen replacement. You should only need a few keyframes. Then set the roto layer as a track matte for the screen replacement.

Unless the actor is a nervous type really moving around a lot it should only take you a few minutes to create the roto layer. An alpha inverted Track matte will create your hole. Then it's just a matter of a little finessing of the edges with blur or the matte tools in AE to finish the composite.