overlaying an image to a video

[videolearner1234]

hi all

just hoping for some help or hoping someone can point me in the right direction.

First ill paint the scenario:

Lets say i have a video, the main character in the video is wearing a green (whatever colour works) balaclava with those sensor dots on it. lets say the video runs for 90 minutes.

I want to know how difficult it would be to overlay someone elses face on the character wearing the green balaclava.

I guess what im trying to determine is how long it would take to do and roughly what would someone in the industry charge for something like that? Is it possible to do it yourself? If so, would you need years of training or months?

The character in the video wouldnt be moving too much, if that makes a difference.

If more info is needed please ask and ill try and explain what it is i want!

If anyone can help that would be great!

[Snakebyte1]

This can be fairly easily done using something like Premiere or After Effects or any other software that uses masks. You take your footage with the face you want and mask out everything but the face, then position the face where you need it on the background layer.

Its simple in concept but there are several factors to keep in mind. Is the face you want to composite in a still image or live video? How much movement does your "main character" do? If you are looking for a comic effect that looks like a picture of a face pasted on then that is not overly difficult, and you could use maybe 2 or 3 different angles of the face.

If you are looking at trying to blend the face with the video of the body so they look real, then that is much more difficult as you will need to have footage of the face that somewhat matches the movements of the main character and matches lighting conditions etc.

Regardless, editing this over 90min of someone jumping around would be time consuming.

[guns1inger]

Is this a simple, cartoonish, 2D replacement, or a full 3D replacement ?

If is it a 2D replacement, and realism isn't key, then Snakebyte1 is right - it can be done pretty easily by simple tracking or hand-tracking in After Effects or even in a good editor.

if it is a full 3D replacement then you are looking at a complex project. You will have to track the actors head in 3D space with something like Mokey, model a replacement head in a 3D program such as Maya or XSI, mapping the new face onto it. Preferably the owner of the replacement head should be digitally scanned to get an accurate model, and high quality photographs used to create the maps for it. The 3D tracking data is imported into the 3D tool so the replacement head can be manipulated to follow the original actors movements, often with hand animation being added so the head isn't a lifeless lump of pixels. Once you have the 3D head movements correct, multiple render passes are done, and these are passed to the compositor. The compositor will then bring these into the original footage to replace the actors real head, often with quite a bit of hand rotoscoping and tweaking to get an exact fit and clean edges.

It is a complex process usually done by a team of experts, not one guy on a PC.

[Chemikilla]

In premiere you can do color keying. which is what i think your looking for.