Export Composition Background in After Effects

Question

I made a lower third for someone else. Of course it needs an alpha channel, but rendering RGB+Alpha results in humongous filesizes. Now I was wondering if you can export the whole thing using a chroma key?

Now the Thing is, I could of course export it while putting a green solid behind the whole thing, but I thought, maybe if I change the composition background to green I would not have to fit such a green solid but everything that is transparent would be green by default. However every time I render it, the background defaults to black.

Is there a way to tell AME or AE to use the composition background colour for the rendered output instead of black?

Thanks in advance!

Answer 1

I'd have to back up what has already been said. For best results, you will need to export as a Quicktime Animation using RGB+Alpha. Yes, the file size will be huge.

However, there are things you can do to reduce the overall file size, and these things have to do with how your project is set up and your workflow.

• Make your Composition size the size of the lower third, not the size of the canvas size for the end user. If the video being produced is 1080, the lower third will be at max 1920 wide, but will likely only use a slice of the vertical space. So size the comp to that and let the editor place it where it needs to go.

• Secondly, render the lower third without the name, have them bring up the name in PPro, now he will only need 1 file.

• Having not seen your lower third, I can only assume it animates on and off. Does it continue to have motion while up? If not, render only the build on, and build off. And render 1 frame of the static. Let the editor use the build on, then frame hold the static section, then build off files.

• Last, if your graphic does have consistent motion, you can either animate in a way that loops to reduce the length and allow the editor to repeat the loop. Also, and I have done this, is- break the composition down into multiple outputs of animation files which can be different sizes, or loops. Things like glimmers, flares, etc, they may only be a short duration of the overall graphic animation. You can isolate those out and render as separate files.

Yes, your editor will have to layer. But PPro can handle that. He can create a sequence for the lower third, and use it as a nested sequence inside his main sequence to apply the names.

My suggestion is think hard about workflow and output possibilities, and go with, as others have said, QT Animation with Alpha. Anything else will give you sub par results.

Answer 2

I hope the person receiving your 'green screen' lower third doesn't ever find you in a dark alley. If it was me I'd be looking to bring the hurt. Really, this is not the way to do it.

Firstly there are more space efficient codecs with alpha channels than the default Apple Animation, try proRes 4444 or the newer Cineform

If you really can't afford the bandwidth to send the video with alpha, render out the alpha channel as a separate movie and send them both. I'm old enough to remember that's the way things were done in the days when dinosaurs roamed the earth and when sending a Betacam SP videotape by courier was the highest bandwidth way of sending material. There's no such thing as an alpha channel on analogue tape.

You can achieve that by adding an output module to the render (right click the output module in the render queue and choose add output module). Change the Channels dropdown to Alpha instead of RGB or RGB+. If you want, you can use a compressed codec to save space (or compress after the render, which is what I'd recommend). Just don't compress too much or you'll end up with blockiness in your alpha channel.

Answer 3

For best results, you should use an alpha channel for lower thirds. However, certain situations may require your proposed workaround.

With your composition active in the timeline, hit CMD/CTRL + K to bring up your Composition Settings. Double check your Background Color and ensure it is chroma key green:

#00FF00

Now add the composition to your Render Queue in AE and under Output Module, ensure your Video Output channel is set to RGB. This will output your selected background color in any area that is set to alpha in your composition. For partially opaque areas, there will be a slight green tint behind the content, so keep this in mind when using motion blur or opacity fades as you may run into quality problems down the road.

Hope this helps!