I don’t know what a “filmstrip BMP” is. Googling for it brings me back here, it looks like you mean a sprite sheet. I didn’t think of trying that–all of the examples on the SD card were one file per frame.
The main difference is that I used the exact format of the backing store, with the pixel order and zigzag pixel output order baked into the file. This means the loop of reading a row at a time goes away, since I can just do read(strip.getPixels(), 768); strip.show(). The frame delay is embedded per-frame (though I doubt I’ll use anything but a constant value). I have a simple Python script to convert from an image sequence to this format.
Sprite sheets would probably have done the job, but I like the result (INI files go away, and each video is a single file in the top directory), and it only took a few hours to do. (I spent more time getting Arduino to work than actually implementing anything, actually…)