Blue screen techniques

Kdenlive forum,

I'm using the "blue screen" filter to make a an area of color in the background transparent. In other words, exactly what a bluescreen is for,

The blue screen filter in Kdenlive seems kind of harsh, however. So far as I can tell, if a pixel matches the specified range of color, and makes the pixel completely transparent.

This of course leads to rather jagged edges with lots of noise.

I'm kind of expecting that it's "just the way it is" with this filter.

But I wondered if maybe there was either another filter that could be used in combination, or some other approach to getting a presentable blue-screen or green-screen effect.

Any advice would be much appreciated. Thank you.

For anyone brave, take a look at the following paper, that neatly summarises a number of blue/green screen patents from the 70's that have long since expired and produce very nice keys (the kind that can maintain hair detail and reduce blue spill) and are computationally cheap.

http://portal.acm.org/citation.cfm?id=237263