Masking out the video background in Sony Vegas

Question

I have a video and I need to mask out the background for it.

^{A screenshot from the original video, credits to The Muppets Studio}

The video has been shot with a still camera on a steady background. My goal is to mask out the background (e.g., everything not related to moving objects).
I don't have the original sources, of course.
It is also hard to recreate the background (I mean, to precisely match colors).

My approach, in theory, is the following:

1. Collect a series of screenshots where different parts of background are visible (when objects move away);
2. Glue those parts into a background image (see image below for a partial result);
3. Place the background into a layer and compute the color difference between the original video and the background;
4. Build a set of pixels for which:
   • the difference is nearly zero (within a certain color threshold occurring due to rounding/compression problems);
   • and within a certain minimal area (so that individual pixels did not occasionally appear);
5. Wrap those pixels into a key mask.

Still, I'm stuck with building a proper structure of layers within Sony Vegas to accomplish my goal.

How this can be done?

^{My backround attempt}

My environment is:

• Sony Vegas 12.0/x64, I'm not considering another software;
• Basic set of plugins/filters, but I will also appreciate references to 3rd-party plugins, even the commercial ones;
• Still, I would prefer a "clean" approach based on masking.

Thanks a lot!

Answer 1

chroma key choose a colour*drag) then take eye dropper and select background in the preview window