Making Overlay Video

[MI6]

I want to produce video clip from pictures with black background(moving stars, balloons, lens flares……) which I want to use as overlay video for my main video clip(video mask) but I have problem with making visible when I put the clip on the Vegas timeline.I use sequence of for example 50 JPG or BMB pictures with black background, putting them on the timeline and then render as AVI video clip with uncompressed RGB 32 AVI file wit 32 bit color depth. In Vegas I change the Alpha channel of the video clip from “None” to “Premultiplied(dirty)” but I still can’t get one overlay effect.
So, my main question is how I can get overlay effect from this video clip, how I should render this AVI file from pictures to make it visible with an overlay effect.
Regards.

[guns1inger]

So you want to replace the black with your video ?

How are you generating the sequence of images that you are using ?
Is it possible to use either.png with transparency, or .tga with an alpha channel built-in. This will make masking much simpler.

Your other option is to put the overlay clip on a timeline above the clip you want to have showing through the black. On the overlay clip add the Sony Chromakey effect, select black as the colour, and the adjust the thresholds until you have removed the black, but left enough of everything else.

I would also, if possible, avoid using jpgs for your sequence. There are two main reasons for this. One is that jpeg compression tends to have problems with high contrast borders and creates artifacts along the egdes which will impact the keying. The second is that you can't guarantee consistency of the image compression, which will show up as noise in your sequence when you convert it to avi.