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Adding Motion Lower Thirds/Backgrounds-problem with alpha??
I tried to add a lower third from digital juice the other day and it renders out black.
The file is a motion .mov background which I pan/cropped down to a rectangle with feathered edges.
I placed it over my video track, then placed text over it.All was transparent and looked excellent in the preview window.
When I rendered it, it comes out gray/black. I tried playing with different alpha channel settings, but cannot figure out what is going on.
Can anybody help??Eric.
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4 Replies
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The bit below is from the DJ website. There is another tutorial type thing on using DJ poducts with Vegas but I couldn’t find it.
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Vegas doesn’t automatically detect the alpha channel, so the background behind overlays, lower thirds, transitions and motion design elements are not transparent and appear black.To get Vegas to detect the alpha:
1. Drop the overlay into a track above your video.
2. Right-click the overlay and select Properties.
3. From the Alpha channel drop down (or on the Media tab), select Straight (unmatted).
****************************Hope this helps.
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Mike, Your answer has raised another question that I have wondered about. What is the difference between ‘straight’ and ‘dirty’??
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I’m not an expert on this one but the differences are basically between ‘straight’ and ‘premultiplied’ alpha channels. Premultiplied applies the alpha information to each color individually as opposed to using the straight alpha channel value for each pixel. If you google ‘premultiplied alpha’ you can find lots of explanations on it’s effects and use.
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I am using a jumbacks .mov file and tried all options for alpha channel, and they all render out black. Prior to rendering, it shows up fine in the preview window with straight-unmatted, but as soon as i go to avi, it comes up black.
???
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