How can I use clip A to create a mask for clip B?

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Level 1

8 points

How can I use clip A to create a mask for clip B?

Hello. I am having some trouble with my project.

I have a video with subtitles and a subtitle background at the bottom. The subtitle background is at 50% opacity, so you can still somewhat see through it. I want to make it look slick and apply blur to the main clip, but only the part that is covered by the subtitle background. I can't draw the mask manually, because the actual subtitles and the background are animated, so if I were to draw the mask manually I would have to go frame by frame, which would take me literally days.

I hope I made my explanation clear. If not, basically I need to use one clip's area to create a mask area for another clip. The clip is also animated, so the mask needs to adjust accordingly. I've been trying to find a solution with no luck for hours.

Thank you in advance.

Posted on Jul 10, 2016 9:58 AM

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Answer 1

Jul 11, 2016 3:35 AM in response to AdamJKwiatek

It is not quite clear to me but you seem to be saying that the subtitle background is animated, somehow? Is that so?

Like its size varies depending on the actual size of the subtitles, is that it?

And you want to blur just the area of the main clip that, at any given time, lays behind this subtitle background?

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Answer 2

AdamJKwiatek Author

Level 1

8 points

Jul 11, 2016 4:07 AM in response to Luis Sequeira1

Hi. Sorry for confusing you. The way it looks is a 50% opacity rectangular box moves in from the left side, stays in the center for a few seconds, and moves out to the right. And the main clip is behind it, so you can see through the box. I would like the part portion of the main clip not only to be obstructed by the box, but also blured. I could draw a mask the size of the box, buy like I said it moves in from the left and leaves to the right, so I would have to draw a lot of mask. And there are about 40 clips of the box animation

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Answer 3

Jul 11, 2016 6:17 AM in response to AdamJKwiatek

I have an idea for how you may achieve this.

1) Make a duplicate of the main clip and place this above the main and below the sb (subtitle background); apply the desired blur to this duplicate.

2) Select the Crop tool, and use it to Trim the top and bottom to match the height of the sb.

3) Use keyframes for the left and right trim to match the movement of the sb

Maybe it is too late now, but after trying this I realize that this process would be easier and more precise if the "movement" of the sb had been achieved by keyframing the trim parameters; in this case, rather than trying to match the move as above, one only needed to do command-C to copy on the sb, and command-shift-V to Paste Attributes on the copy of the clip; this would be fairly automatic.

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Answer 4

Jul 11, 2016 8:05 AM in response to AdamJKwiatek

Hi Adam,

something like that?

if you're familiar with Motion5, such a 'moving blur box title' is done in minutes <cough> some minutes 😉

I'm lazy, haven't switched my UI to English, but as a concept:

clone the background, apply blur and mask, link position of mask to pos of text/title, publish parameter esp. x-pos of box, done.

This allows you to set keyframes for the box' position => move in, move out...

Let me know, if you prefer a ready made plugin, tell me what parameter you need in the Inspector, here in my quick welded demo, it's amount of blur, size of box.. anything else? (text format is done via the normal title-settings)

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