Lower File Size for RGB + Alpha videos

[Alexa25883289kqcj]

I'm exporting video files that are about 2-3 seconds and have an important alpha channel for transparency to be used as a transition for streaming. The completed file size is always 641 megs when I want it be under 10 mb. 

When I choose h264 in the export settings, it lowers the size but doesn't include the RGB + Alpha option. I only find that when I choose AVI.

What else can I try?

[Rick Gerard]

High Quality with Alpha is a preset in the Output module. That's much better than any other option. You have to live with the file size or change the frame rate or frame size. Media players do not support Alpha Channel, and none of the MPEG formats, like H.264 or H.265, do.

[Alexa25883289kqcj]

Okayyy ... what about maybe replacing that alpha channel with a green screen in premiere or AE? Any ideas on how I could do that?

[ShiveringCactus]

Adding a green solid at the bottom of your timeline would be the simplest way to add green for the alpha channel.  But if your streaming software handle a separate file for transparency, I'm think a better approach would be to generate a luma matte (white and black values) which should give a better end result.  

[Alexa25883289kqcj]

Brilliant! Thank you folks!