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Export overlaid video, add background later


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I'm doing another virtual choir project. I have to export each line in a 4 x 4 box separately and then combine them; doing them all at once causes some videos to flash or disappear. (Hardware issue, I assume.)

Once I have all of the lines, I will overlay them to form a complete grid. Then, I want to add a video on Track 1 so it's behind all the boxes. I can't do this as I go along because the background video isn't ready. Just ran a test with one row of boxes and an image added to Track 1 doesn't show. The boxes are now on a black background.

I should add that the exported test of one row of boxes had nothing on video Track 1.    

I could swear I did this before but it's not working now. Borate, I could use your help again. 


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Thanks, Borate. Still need help.

Here's what I tried: Select clip on timeline, choose green screen effect, change green square to black. Export video. 

When placing that exported video back on the timeline, it still has a black background; an image added on Track 1 does not show through.

I also tried to key out the black on the exported video. Same issue.

I must be doing something wrong but can't figure out what. Help?

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Since you are using a background clip a different approach has to be used when adding your choir clips together. You won't be able to simply add them side by side and displaced to show all the singers which is the way we came up with for creating a multi screen chior.

As noted, the clips containing the first row of videos..(horizontal or vertical), unlike the original split layout which you created, do not now have a transparent background but there may be another problem with what you are wanting to achieve.

As a simple example..

  • Place your background image/clip on Video Track 1......it will fill the frame.
  • bb.jpg
  • Place your exported first clip containing your row of singers on Video Track 2. Because this clip is no longer transparent being an exported split screen clip, it will cover the background clip completely.  You will just see the row of singers (say the left hand vertical row) the right hand side will be black....
  • aa.jpg
  • Initially it is a simple idea.....make the black area transparent so you can see the background clip...... So....
  • Click the FX box for the singers clip (Video Track 2)  and select the Green Screen effect.
  • Use the pipette to select the colour that you want to make transparent. (black - and you can pick it from the sequence preview image if you like) The black area will now be transparent (chequered) You should now see the background clip with the vertical row of singers on the left...
  • ccc.jpg
  • It has worked OK.....But look closely and you will see that the singer at the top has also lost its background as it was black!...... If there is black anywhere in the singer clip it will become transparent. That is the problem.

The way around this is to create a mask around the required black area and make that transparent. There is no need for a Green Screen. As all the singer clips are identical with a row at the left end, the mask can be saved if needed and  used for all the clips but as  it's a simple rectangle it's probably easier to make one for each singer clip.

So try this for each singer clip in turn..

  • Place the background clip on Video Track 1
  • Place the first singer clip on a higher track..It will cover the background clip as mentioned above.
  • Click the FX and then click the Add effect mask. (To the right of the green +) This puts a dotted mask on the clip preview image...
  • dd.jpg
  • Grab the corner blocks and move them to the corners of the black area..
  • ee.jpg
  • In the Effects window make sure the Mask inside box is ticked and then add a Transparency effect. Make the Opacity 0% (Slide to the left)
  • The masked area only will now be transparent (chequered) and the background clip will now be visible....
  • gg.jpg
  • Note the top singer now has its background. Do this for each of the singer clips. You can now move them to different parts of the screen; come in singly; move etc and always see the background clip. The only time the background will be covered is if you place the singers side by side..

Hope this helps


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Thanks, Nat.  I appreciate the step-by-step. Unfortunately, my grid has space between boxes on all sides, so I can't just mask a section. Sigh. 

Looks like I will not be able to use all of the row-by-row projects I've created because there is some black in a few boxes. 

Back to the drawing board. This should teach me not to try to get a jump on a project when I don't have all of the elements in hand! 

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You might play around with masking the black between boxes, then adding a zero TRANSPARENCY opacity effect.  The exported mp4 was the source here.

Individual masks were drawn to isolate two vertical spaces (black) between singers.  The cyan background appears only in the masked areas.

Snapshot - 5.png

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