First off, it might help to look at the similar process in photo editors like Gimp.
(Hope you’re not insulted by this background on backgrounding)
Usually in an app like Gimp if you select some part of a photo, say a “background” sky area
and “delete” it you just get the area replaced by
the background painting color.
But if you add an alpha channel to the photo then when you “delete” a selected area
you create a “transparent area” in the photo. Nothing is “there” in the photo.
So then all you need to do is add a new picture (new background)
behind the first original photo (compost 2 photos)
and the new background picture will show through the
transparent area - giving the photo a new “background”.
The idea of “greenscreening” videos is similar. Except the “selection” is done by
selecting the color instead of some region - usually selecting all “green” areas and "making them “transparent.”
This of course can make the results problematic… If the “green” background is full of
various shadowy areas or off-color-greens then not all the background is transparent.
And if the person or “foreground” phoptp object contains little bits of green then then can become “transparent” - a see-through person.
And sometimes the border of the object needs to be adjusted - when green hits the fan all
s can fly…
So with that bit of introduction… let’s look at Shotcut greenscreening.
(1) first bring in the original video you want to work on
(the one for which you want to replace the background)
and drag it onto the timeline. If you know how to greenscreen (chroma key)
you filmed that video so it has a “pure” green background that you want to replace with some other background.
That is, you filmed yourself talking in front of a green background - green board, green wall, green fabric curtain.
This green area in YOUR video is the one you want to “select” and make “transparent.”
(2) Now with your video on the timeline in Shotcut, click on the Filters tab (to left above timeline) to see the Filters area, then click the + button
to add in a filter (this button is upper left part of Filters area. From the dropdown list there will be lots of Filters - including some for
"alpha" channel. Remember in photo editors like Gimp, adding “alpha” channels is what you do to get transparent background regions. The Chroma Key
works the same way - but color selects green as the “transparent” area.
(3) choose the ChromaKeySimple from the list of filters - to select green areas for transparency.
You can play with the slider to make the “green” background area more or
Don’t be afraid to play with things. Be scientific. Be an explorer. Have fun. Be brave. Try things on your own. If you “destroy” your video you can always Undo. And you do have a backup file of your video anyway… don’t you. So the best advice to anyone is “no fears.” Try things.
(4) So far all you have done is made “green” areas of your original video transparent.
(5) Now drag in the video that you want to be the new background. the scene you want as a replacement for the green.
You probably went out and filmed the sky, or a forest, or the city … or whatever… a film of what you want as a new background.
6)Place this film of background on the timeline… BELOW your original video.
You should see your old video with the new background showing through the transparent areas, replacing the original green areas.
(7) Play some more with the slider controls till you get something you like… no funny green fluff left over etc. only the new background video showing through your original video.
(8) If you want (or not) play some more with adding other filters in… to improve the alpha channel “transparency” effects.
(9) For example add in the Filter… alpha channel adjust… to adjust the alpha channel (transparency) .
Remember with green screening you have made a “selection” by color. turning anything green into a transparent area. So you may not at first like the results you see.
(10) On the alpha channel adjust filter, try settings like Shrink Soft (or any other setting) Don’t be afraid to play. Undo is your best friend. The whole object is to make sure all green are transparent — all transparent areas are where you want them to be.
Now that you have the basic idea, remember to enjoy working with Shotcut. It is fun. Never be afraid to try this and try that. Experiment. (of course help from others helps us to start).
Finally… export the video. Or play, play, play away with other filter settings.
Oh. And welcome to Shotcut.