Alpha Channel - how to ...?

[Superully]

Hi guys, I'm pretty new to this video editing stuff, so I really hope my questions doesn't sound too stupid!
I've got a coloured animation (with lots of white in it) which is going to run against an animated background. I want the background to be seen at the points where the white is in the foreground animation.
I understand that in order to achive this I have to use the alpha channel to make the white transparent. However, if I activate the alpha channel on the coloured animation, not only the white becomes transparent, but also the other colours like red, grey or yellow - although not THAT much as the white. Can you follow me?
I also understand that in order to make this work perfectly I would need an EXACT copy of the coloured foreground animation in black and white (no grey) which I could use as the alpha channel animation, right?
Here's my question: how do I create an alpha channel b/w animation which allows me to filter out only the white parts of the coloured foreground animation?
Or is there some easier way to do all this?
Looking forward to your respondes, thx a lot in advance!

[Gees]

I'd love to try and help but.............. you don't tell us a single program you are using to do any of this.

But........... with any - It'd be good practice to make the bg color something completely unique to the rest of the graphic. If you use white and then have grey or light yellow areas, you lose control that you'd have with something like magenta.

Because (at least in the video editing prog I use) you need to work with a combination of alpha channels as well as blending away edges*.

Alpha channels alone might work well for a stationary image, but with anything moving you'd need to be able to set and adjust transparency.

*For instance - I tried a bluescreen-type vid with myself as the subject only to find that -as well as removing the background- my eyes also disappeared. They happen to be the same blue.

[Superully]

thx for your reply. you're right, forgot to mention the progs i'm using.
for cutting and edition i'm using pinnacle studio 8 (which gives me only one video track, so nothing with blending and transparency there).
for overlaying two videos i'm using heroglyph (www.heroglyph.de) which also allows me to use an alpha channel, but no settings like transparency
as i told you, i'm pretty new to this stuff, so progs like pinnacle edition 5 or adobe premiere (which are both too difficult and too expensive for me) are out of the question - unfortunately!
as for the two files i want to "merge" together: the background movie has lots of reds and yellows in it, as does (unfortunately) the movie playing in the foreground, therefore i'd definitely would need an alpha channel image of the foreground movie, but i don't know how to turn it into black & white ...

[Gees]

Well, I don't think you can accomplish what you want, as you've said. Alpha channels are fine for a still image, but you'd need a much more powerful (and expensive I'm sure) prog.

Sorry :c(

Read up about alpha channels and their uses/limitations while you consider what to try next. I think you may be using the wrong terms for what you are trying to do.