To get interesting, flowy moving content for the LEDs, I sample pixels out of video content and store them as JPEGs, with the current state of all LEDs represented as the X axis (regardless of orientation) and time as the Y axis.
This converter:
Uses ffmpeg to decode video to individual frames.
Loads individual frames in RAM.
Applies a mask to each frame, sampling pixels in the order they're represented over USB to the controller.
For each minute of video, generates one 1224x1800 JPEG image, representing the state of 1224 pixels over 1800 frames, and saves it.