I have a wooded-path scene (DV-avi, NTSC) which needs to have a powdering of snow on the ground. I used the secondary color corrector in Vegas 4 and selected the light brown color of the leaves carpeting the ground as a mask, then sampled the grey sky above. It created a perfect mask of scattered "snow" by turning all leaves within the selection range the near-white of the sky. HOWEVER: The "snow leaves" flicker like crazy as the video runs.

Then I tried saving one frame of the snow effect, where no one is on the path yet (stationary camera), as a jpeg file and put it above the video track. That created an unflickering snow effect but I should have realized that the video underneath is obscured--and by dragging down the fade effect on the overlay, the people in the video underneath only appear in proportion to my fade--so they are like ghosts unless I fade down the effect to zero, which sends me straight back to the drawing board.

Wonder if there is a way to save the mask itself as an alpha channel, or even a jpeg of the alpha channel, which I might put over the video track? Anyone know how I can avoid having to spend hundreds of dollars on software just to get this one effect?