Lumen itself lacks a video player internally, but you can process video files by playing them into Lumen using any Syphon-enabled software. VDMX has a non-watermarked free trials that you can use to play videos over Syphon.

Syphon output isn't automatically enabled in VDMX like it is in Lumen, but it's really easy to set up once you know where to look. Here’s a short video that shows how you can enable Syphon output in VDMX, which will allow you to see it in Lumen’s camera menu.

Once you have your Syphon-enabled video player running with your video playing you'll be able to choose that Syphon stream as an input in Lumen. You'll choose it using the same dropdown where you normally select a webcam. Note that in order to see the input in Lumen's output you should make sure you've loaded a patch that uses input -- "Camera Passthrough" is a preset designed specifically for testing input.

After processing the video in Lumen, you can then save the output using Syphon Recorder. You can find details about how to set up Syphon Recorder with Lumen here.

All of this works in Lumen's free demo version, so feel free to try it out!