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How to use alpha channels in video transitions
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grDancer  
#1 Posted : Tuesday, May 15, 2018 11:33:53 AM(UTC)
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I got some title sequence videos created where my logo swooshes in over a black background. I'd like to figure out how to use that as a video transition - I can't figure it out from the vmxix video tutorial here though:
.

I want the black background to be transparent, so that when I hit the stinger1 button, it will overlay the video with the logo swooshing in, and cut to the cued input at a suitable point.

I'm just not sure what settings I should use for the whole "premultiplied alpha" stuff. Are there tutorials that explain that stuff?
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NHT  
#2 Posted : Tuesday, May 15, 2018 11:48:20 AM(UTC)
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It'll only work if the original video has an alpha channel, it doesn't sound like it does.

You can try using the luma key option but it probably wont look all that great.

The best thing is to pull the video into a video edit program, luma key it in the edit program over a transparent layer and then output it as a png image sequence.
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grDancer on 5/15/2018(UTC)
DWAM  
#3 Posted : Tuesday, May 15, 2018 12:28:12 PM(UTC)
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I'll second NHT for this.
One more thing though, if you have After Effects, you can easily create your sequence with alpha (transparent) background and export it as an image sequence for stinger use. It's even easier and better than using Luma.

Guillaume
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grDancer on 5/15/2018(UTC)
rowby  
#4 Posted : Tuesday, May 15, 2018 1:28:46 PM(UTC)
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Regarding Guiluime’s png suggestion. There is a vMix tutorial on “stingers” that shows how to do this step by step. Go to the vMix video tutorials section to see how to do it. Or seatch YouTube for vMix stingers
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