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One of the cool features in both Compressor 3 and Compressor 4 is the ability to add video watermarks to your compressed video. (Adding watermarks during compression saves time compared to adding them during editing.) You see these animated watermarks every day with animated logos embedded in a lower corner of television programming.
[ Here’s an earlier article that describes how to add a text watermark using Compressor. While written for Compressor 3, this technique also works the same for for Compressor 4. ]
However, in order to composite a video clip during compression it needs to contain a transparent background, also called “an alpha channel.”
So, this article illustrates two concepts:
CREATING A TRANSPARENT BACKGROUND
Here’s our star – a dancing heart (courtesy: Pond5 – www.pond5.com).
In this case, the heart is composited into a white background. Before we can use this as an animated watermark in Compressor, we need to replace the white background with a transparent background.
This can be done in Photoshop or any video editing application. Here’s how to do it in Final Cut Pro X.
Open Final Cut Pro X, import the image and edit it into the Timeline as the only image in that project.
The goal is to make the white background transparent.
Go to the Effects Browser and apply Keying > Luma Keyer. By default, the Luma Keyer is designed to remove black backgrounds, which is the opposite of what we want here.
Open the Inspector and click the Video tab at the top. Click the Invert checkbox near the top. Instantly, most of the white background is replaced with black, which in this case means the clip background is transparent.
Whenever we create a matte, which is something that is keyed over something else – like a green-screen image over a background – we need to adjust the foreground image so that it is solid white. To do this, click the Matte icon next to View in the Inspector.
The dancing heart is shades of gray. This means it is translucent, rather than opaque. Time to tweak.
Slide the top slider for Luma to the right. This adjusts the opacity of the foreground image. Slide this until the foreground image is solid white.
Next, slide the bottom slider for Luma to the left. This adjusts the transparency of the background image. Adjust this until the background is solid black.
In both cases, you are looking for as few shades of gray as possible. The perfect key contains areas of solid white and solid black with no shades of gray.
Tweak until this is as good as you can get it.
To see the results of your work, click the Composite icon next to View. (I’m going to leave the small shadows under the feet because to get rid of them I would need to rotoscope them frame by frame, which isn’t necessary for this example.)
EXPORTING A CLIP WITH A TRANSPARENT BACKGROUND
Now we need to export the file with the alpha channel in it. Switch back to the Project Library and select the project you want to export.
Go to Share > Export and set the Video Codec to Apple ProRes 4444. This is the only export codec that supports alpha channels. This is a critical step, because if you select any other codec, the transparent background won’t be included in the clip. (This process of saving transparency information with a clip is called “saving a clip with an alpha channel;” where “alpha channel” means “transparency information.”) The rest of the settings are self-evident.
Click Next, give the file a name, pick a location and click Save.
NOTE: The Luma Keyer is only necessary if you need to create a transparent background where the image is in front of a black or white background. If you have already created a clip with a transparent background, make sure to save it using either Animation or Apple ProRes 4444 codecs – as these are the only two video codecs that support alpha channels.
SECOND NOTE: For software that allows you to select a pre-multiplied export option when saving an alpha channel, both “Straight/Unmatted” and “Pre-multiplied Black” work equally well in Compressor.
ADDING THE WATERMARK
In Compressor, import your file and assign a compression setting (Watermarks can be added to any compression setting, even the presets supplied by Apple. The process is the same.)
Click the compression setting in the Task window (top left) so that the compression setting is loaded into the Inspector.
Click the Filters button near the top of the Inspector.
Scroll down the list of filters to the bottom, where you’ll find Watermark. Check it to turn it on.
Then, at the bottom of the Inspector, click the Choose button to select the movie you just exported from Final Cut Pro X. Don’t panic, you won’t see anything, yet.
Change the Position popup menu to Center and, in the Preview window, you’ll see at least a portion of your video. This Position popup works the best when the animation you want to position is in the center of the frame. (Here, the dancing heart fills the entire frame.)
Depending upon the size of your image – the dancing heart is 1280 x 720 – you will need to scale it.
Here are the settings I used to position the heart:
NOTE: Checking Repeat means that the animated heart will loop in the event that the heart animation isn’t as long as my project.
SECOND NOTE: I have sometimes found that placing the watermark animation exactly where I want it during editing – rather than in the center of the frame – simplifies positioning in Compressor. Most of the time, though, the Position popup menu works well enough. As with all things, experiment to see what works best for you.
And that’s it. All you have left to do is compress your video and your animated logo will be composited right along with everything else.
NOTE: Here’s a video tutorial that shows the step-by-step techniques you can use to compress video for the web using Compressor 4 to get the best quality.
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