2) Here's a 5s clip showing the flashes I have to put almost all long the video. I'll keep the second one (the flash which fades out like a wave) but I want to make something else for the first one (which is just a faded white frame) -- done, see #6.
3) I can't use clips instead of flashes because it's already done further in the vid but it needs something more (a flash).
4) Don't tell me about red or green frame flashes

5) Thanks for the lens flare idea. Doesn't really fit the first flash I want to change but I used it for another part of my AMV.
6) Thanks a lot to OmniStrata ^_^. The level effect set to 0->255 over three frames looks quite like a white frame fading out but with a little something more... I'll use that.
7) Here's a part of my vid using both white frame and level flashes. The first serie of flashes uses white frames and the second one level effect. Tell me which you prefer.
I like level flashes more because a white frame is already used for the lady-in-the-red-ball clip (I can't use level effect there because I made the scene black&white).